Genetic Approaches to Genetic Approaches to Understanding Periodontal Understanding Periodontal

Disease Risk & SusceptabilityDisease Risk & Susceptability

Naheed MohamedNaheed Mohamed

IntroductionIntroduction

Periodontal diseases Periodontal diseases are initiated by are initiated by microbial plaque, which microbial plaque, which accumulates in the accumulates in the sulcular region and sulcular region and induces an induces an inflammatory response. inflammatory response. This response may This response may progress in certain progress in certain susceptible individuals susceptible individuals to chronic destructive to chronic destructive inflammatory condition inflammatory condition termed periodontitis.termed periodontitis.

While microbial and other While microbial and other environmental factors are believed environmental factors are believed to initiate and modulate periodontal to initiate and modulate periodontal disease progression, there now disease progression, there now exists strong supporting evidence exists strong supporting evidence that genes play a role in the that genes play a role in the predisposition to and progression of predisposition to and progression of periodontal diseases. periodontal diseases. (Sofaer, 1990; Hart, 1994; (Sofaer, 1990; Hart, 1994; Michalowicz, 1994; Hassel and Harris, 1995; Hodge and Michalowicz, Michalowicz, 1994; Hassel and Harris, 1995; Hodge and Michalowicz, 2001)2001)

Immune ResponseImmune Response Production of inflammatory biochemical mediators, Production of inflammatory biochemical mediators,

collectively known as “cytokines”collectively known as “cytokines” (e.g., IL-1, TNF-alpha)(e.g., IL-1, TNF-alpha)

Cytokines signal other cells, such as fibroblast, to Cytokines signal other cells, such as fibroblast, to produce PGE2 and MMPs, which have been associated produce PGE2 and MMPs, which have been associated with bone destruction and connective tissue degradation, with bone destruction and connective tissue degradation, respectively. respectively.

Host response can be both protective and destructive. Host response can be both protective and destructive.

Specific genes may determine the degree to which an Specific genes may determine the degree to which an individual’s immune response is protective or destructive individual’s immune response is protective or destructive (Malo and Skamene, Trends in Genetics, 1994)(Malo and Skamene, Trends in Genetics, 1994)

Putative pathogens are essential to Putative pathogens are essential to develop periodontitis, however, their develop periodontitis, however, their mere presence is insufficient to initiate mere presence is insufficient to initiate periodontitis. periodontitis. (Haffajee and Socransky, 1994) (Haffajee and Socransky, 1994)

The primary etiology for periodontitis is The primary etiology for periodontitis is bacteria, however the extent and severity bacteria, however the extent and severity of periodontal lesions can be influenced of periodontal lesions can be influenced by environmental factors, acquired by environmental factors, acquired factors, and genetic predispositionfactors, and genetic predisposition. . (Kornman et (Kornman et al., 1997 and Salvi et al., 1997) al., 1997 and Salvi et al., 1997)

Genetic factors influence inflammatory and Genetic factors influence inflammatory and immune responses in general. Individuals immune responses in general. Individuals may respond differently to common may respond differently to common environmental challenges due to their environmental challenges due to their genetic profile. Specifically different forms genetic profile. Specifically different forms of genesof genes(allelic variants(allelic variants), can produce ), can produce variations in tissue structure(innate variations in tissue structure(innate immunity), and inflammatory mediators immunity), and inflammatory mediators (non-specific inflammation). Allelic (non-specific inflammation). Allelic variants at multiple gene loci probably variants at multiple gene loci probably influence periodontitis susceptability. influence periodontitis susceptability. (Kinane 2003).(Kinane 2003).

Introduction to Introduction to GeneticsGenetics

Basic TerminologyBasic Terminology GenomeGenome – refers to all the genes carried by an – refers to all the genes carried by an

individual or cell. The human genome consists of individual or cell. The human genome consists of more than 3 billion pairs of bases contained in 22 more than 3 billion pairs of bases contained in 22 pairs of chromosomes, termed pairs of chromosomes, termed autosomes,autosomes, and two and two sex chromosomes.sex chromosomes.

ChromosomeChromosome – a nuclear structure carrying genetic – a nuclear structure carrying genetic information arranged in a linear sequence. information arranged in a linear sequence.

GeneGene – a functional and physical unit of inheritance – a functional and physical unit of inheritance that occupies a specific position (locus) within that occupies a specific position (locus) within genome or chromosome. In other words, It is a genome or chromosome. In other words, It is a sequence of nucleotides located at a particular sequence of nucleotides located at a particular position on a particular chromosome carrying a set of position on a particular chromosome carrying a set of instructions usually directing the synthesis of proteinsinstructions usually directing the synthesis of proteins

Alternative form of a gene Alternative form of a gene is ALLELEis ALLELE

Humans carry two sets of Humans carry two sets of chromosomes, one from each chromosomes, one from each parent. Single nucleotide parent. Single nucleotide polymorphisms may render two sets polymorphisms may render two sets of equivalent genes different.of equivalent genes different.

AlleleAllele – one of several possible – one of several possible alternative forms of a given gene at alternative forms of a given gene at a particular locus of a chromosome a particular locus of a chromosome differing in DNA sequence differing in DNA sequence

Different alleles are responsible for Different alleles are responsible for variation in inherited characteristics variation in inherited characteristics such as hair color or blood type.such as hair color or blood type.

In an individual, the dominant form In an individual, the dominant form of an allele is expressed of an allele is expressed

HomozygousHomozygous – the presence of – the presence of identical alleles of one or more identical alleles of one or more specific genes (e.g. A/A).specific genes (e.g. A/A).

HeterozygousHeterozygous – the presence of – the presence of differing alleles of one or more differing alleles of one or more specific genes (e.g. A/B).specific genes (e.g. A/B).

More DefinitionsMore Definitions GenotypeGenotype – the genetic makeup of an organism or cell distinct from – the genetic makeup of an organism or cell distinct from

its expressed features or phenotype.its expressed features or phenotype.

PhenotypePhenotype – the observable characteristics displayed by an – the observable characteristics displayed by an organism as influenced by environmental factors and independent of organism as influenced by environmental factors and independent of the genotype of the organism. (Phenotype = genotype x the genotype of the organism. (Phenotype = genotype x environment)environment)

Gene expressionGene expression – the process involving use of the information in a – the process involving use of the information in a gene via transcription and translation leading to production of a gene via transcription and translation leading to production of a protein affecting the phenotype of the organism determined by that protein affecting the phenotype of the organism determined by that gene.gene.

Autosomal dominantAutosomal dominant – the dominant effect of one gene located on – the dominant effect of one gene located on an autosome regardless of the presence of the other normal copy.an autosome regardless of the presence of the other normal copy.

Autosomal recessiveAutosomal recessive – A gene on an autosome that is required in – A gene on an autosome that is required in two copies to be active in an individual. An individual who carries two copies to be active in an individual. An individual who carries two such copies of the same abnormal gene will be subjected to two such copies of the same abnormal gene will be subjected to effects from that geneeffects from that gene..

Genetic VarianceGenetic Variance

Different forms of genes are called Different forms of genes are called allelic allelic variantsvariants..

Allelic variants differ in their nucleotide Allelic variants differ in their nucleotide sequences.sequences.

When a specific allele occurs in at least When a specific allele occurs in at least 1% of the population it is called a 1% of the population it is called a genetic genetic polymorphismpolymorphism..

When a nucleotide change is very rare When a nucleotide change is very rare and not present in many individuals it is and not present in many individuals it is often referred to as a often referred to as a mutationmutation..

Sources of VariationSources of Variation MutationMutation : : alteration of the genomic sequence compared to aalteration of the genomic sequence compared to a

reference state. Not all mutations have harmful reference state. Not all mutations have harmful eventsevents

(silent mutation). (silent mutation). (<1% of population)(<1% of population)

PolymorphismPolymorphism: : a region on the genome that varies betweena region on the genome that varies between individual members of a population present in aindividual members of a population present in a significant number of individuals. significant number of individuals. (>1% of (>1% of

population)population)

Single nucleotide polymorphism (SNP):Single nucleotide polymorphism (SNP): a a polymorphismpolymorphism

caused by the change in a single nucleotide caused by the change in a single nucleotide believed to be the most common genetic variation believed to be the most common genetic variation between individual humans.between individual humans.

Single Nucleotide Single Nucleotide PolymorphismPolymorphism

A A Single Nucleotide Single Nucleotide PolymorphismPolymorphism, or, or SNPSNP, , is a small genetic change, is a small genetic change, or variation, that can or variation, that can occur within a person's occur within a person's DNA sequenceDNA sequence

An example of a SNP is An example of a SNP is the alteration of the DNA the alteration of the DNA segment Asegment AAAGGTTA to GGTTA to AATTGGTTA, where the GGTTA, where the second “A” is replaced by second “A” is replaced by a “T”a “T”

On average, SNPs occur On average, SNPs occur in the human population in the human population > 1 %.> 1 %.

SNPSNP A change in nucleotide that occurs in the population with a A change in nucleotide that occurs in the population with a

frequency of frequency of 1% 1%

Reported Sequence AAGTACGGCTCReported Sequence AAGTACGGCTC

SNP Sequence AAGTSNP Sequence AAGTGGCGGCTCCGGCTC

Occurs approximately every 300 to 1000 bps.Occurs approximately every 300 to 1000 bps.

Coding Region ChangesCoding Region Changes Synonymous TTT=Phe Synonymous TTT=Phe

TTTTCC = = PhePhe

Non-Synonymous GTT = ValNon-Synonymous GTT = Val

GGGGT = T = GlyGly

Stop codon TAC = Stop codon TAC = TyrTyr

TATAAA =Stop=Stop

Changes that occur in the Changes that occur in the promoter regionpromoter region, 5’ and 3’, 5’ and 3’ UTR(untranslated region)UTR(untranslated region), and , and intronintron may alter may alter expressionexpression levels levels

Gene ExpressionGene Expression

Environmental ExposuresEnvironmental Exposures Differences in physiologic functioning of Differences in physiologic functioning of

proteins due to polymorphisms can be proteins due to polymorphisms can be enhanced by certain environmental enhanced by certain environmental exposures (eg smoking, diabetes, microbes).exposures (eg smoking, diabetes, microbes).

If the protein functions in the inflammatory If the protein functions in the inflammatory process then certain polymorphisms can process then certain polymorphisms can increase or decrease risk for disease increase or decrease risk for disease phenotype.phenotype.

Epigenomics (link between environment Epigenomics (link between environment and its effects on gene expression)and its effects on gene expression)

EpigeneticsEpigenetics study of heritable changes in genome function that occur study of heritable changes in genome function that occur

without a change in DNA sequence. This includes; the without a change in DNA sequence. This includes; the study of how patterns of gene expression are passed from study of how patterns of gene expression are passed from one cell to its descendants, how gene expression changes one cell to its descendants, how gene expression changes during the differentiation of one cell type into another, and during the differentiation of one cell type into another, and how environmental factors can change the way genes are how environmental factors can change the way genes are expressed. expressed.

The discovery that enzymes can re-organise chromatin into The discovery that enzymes can re-organise chromatin into accessible and inaccessible configurations revealed accessible and inaccessible configurations revealed epigenetic mechanisms that considerably extend the epigenetic mechanisms that considerably extend the information potential of the genetic code. Thus, one information potential of the genetic code. Thus, one genome can generate many 'epigenomes', as the fertilised genome can generate many 'epigenomes', as the fertilised egg progresses through development and translates its egg progresses through development and translates its information into a multitude of cell fates. information into a multitude of cell fates.

Genetic Basis of DiseaseGenetic Basis of Disease Genetic variance and environmental exposures Genetic variance and environmental exposures

are the key determinants to phenotypic are the key determinants to phenotypic differences.differences.

Simple Mendelian DiseasesSimple Mendelian Diseases follow follow predictable & simple patterns of transmission. predictable & simple patterns of transmission. In most cases a single gene locus is the major In most cases a single gene locus is the major determinant of disease.determinant of disease.

Complex genetic diseaseComplex genetic disease are more prevalent are more prevalent (>1%), do not follow simple pattern of familial (>1%), do not follow simple pattern of familial distribution, and are the result of interaction of distribution, and are the result of interaction of multiple different gene loci as well as multiple different gene loci as well as environmental factors.environmental factors.

Complex Genetic Complex Genetic DiseasesDiseases

No correlation between presence of allele and No correlation between presence of allele and occurrence of disease.occurrence of disease.

Associated polymorphisms not directly causally Associated polymorphisms not directly causally linked. linked.

Each polymorphism contributes to a small part Each polymorphism contributes to a small part of the disease process, sometimes requiring of the disease process, sometimes requiring multiple genes to develop disease phenotype.multiple genes to develop disease phenotype.

Environmental factors are also critical to Environmental factors are also critical to etiology.etiology.

Methods of Genetic Methods of Genetic AnalysisAnalysis

1.1. Familial Familial AggregationAggregation

2.2. Twin StudiesTwin Studies

3.3. Segregation Segregation AnalysisAnalysis

4.4. Linkage StudiesLinkage Studies

5.5. Association Association StudiesStudies

Evidence for the Role of Evidence for the Role of Genetic Variants in Genetic Variants in

PeriodontitisPeriodontitis German studies of familial nature in the German studies of familial nature in the

early 20early 20thth century have shown aggregation century have shown aggregation of chronic forms of periodontitis in of chronic forms of periodontitis in families. This strongly suggested genetic families. This strongly suggested genetic predisposition. predisposition. (Rev’d by Hassell & Harris 1995)(Rev’d by Hassell & Harris 1995)

Note:Note: Important consider shared Important consider shared environment in these types of studies, due environment in these types of studies, due to interaction of genotypic expression and to interaction of genotypic expression and environment.environment.

Evidence StudiesEvidence Studies Michalowicz et al. (1991)Michalowicz et al. (1991) studied dizygous twins studied dizygous twins

reared together and apart and monozygous twins reared together and apart and monozygous twins reared together and apart.reared together and apart.

Mean probing depth and attachment level varied Mean probing depth and attachment level varied less for MZT than DZT.less for MZT than DZT.

Alveolar bone ht. showed significant variations Alveolar bone ht. showed significant variations related to difference in genotype.related to difference in genotype.

Twin groups had similar OH and smoking hx.Twin groups had similar OH and smoking hx.

Concluded genetics plays a role in susceptibility Concluded genetics plays a role in susceptibility to periodontal disease.to periodontal disease.

Evidence StudiesEvidence Studies

Segregation analysis in North American Segregation analysis in North American families performed by families performed by Marazita et al (1994).Marazita et al (1994).

Studied >100 families, segregating Studied >100 families, segregating aggressive forms of periodontitis, and aggressive forms of periodontitis, and found support for autosomal dominant found support for autosomal dominant transmission. Concluded autosomal transmission. Concluded autosomal dominant inheritance with ~70% dominant inheritance with ~70% penetrance occurred in Blacks and non-penetrance occurred in Blacks and non-Blacks.Blacks.

Evidence StudiesEvidence Studies

Boughman et al (1986)Boughman et al (1986) found an autosomal found an autosomal dominant form of LAgP in an extended family dominant form of LAgP in an extended family in Southern Maryland. In this family type III in Southern Maryland. In this family type III dentinogenesis imperfecta and a localized dentinogenesis imperfecta and a localized form of AgP were segregating as dominant form of AgP were segregating as dominant traits.traits.

Gene for DGI-III had been previously Gene for DGI-III had been previously localized to chromosome 4, performed localized to chromosome 4, performed linkage analysis and showed close linkage of linkage analysis and showed close linkage of gene for AgP to this DGI-III gene.gene for AgP to this DGI-III gene.

Evidence StudiesEvidence Studies

Hart et al (1993)Hart et al (1993) evaluated support for evaluated support for linkage of AgP near chromosome 4 in linkage of AgP near chromosome 4 in different population of families (14 AA different population of families (14 AA and 4 caucasian).and 4 caucasian).

Results showed that in these populations Results showed that in these populations no linkage existed . Results could mean no linkage existed . Results could mean that this population had a different form that this population had a different form of AgP than the Maryland kindred. of AgP than the Maryland kindred.

Syndromic Forms of Syndromic Forms of PeriodontitisPeriodontitis

Severe periodontitis presents as part Severe periodontitis presents as part of the clinical manisfestations of of the clinical manisfestations of several monogenetic syndromes.several monogenetic syndromes.

Significance of these conditions is Significance of these conditions is that they clearly demonstrate that a that they clearly demonstrate that a genetic mutation at a single locus genetic mutation at a single locus can impart susceptibility to can impart susceptibility to periodontitis.periodontitis.

Papillon LeFevre Papillon LeFevre SyndromeSyndrome

Clinically characterized by: Clinically characterized by: Palmoplantar Palmoplantar

hyperkeratosishyperkeratosis Severe early onset Severe early onset

periodontitisperiodontitis that results that results in premature loss of the in premature loss of the primary and secondary primary and secondary dentition (distinguishes dentition (distinguishes PLS from other PLS from other plamoplantar keratoderma) plamoplantar keratoderma)

Prevalence 1/ 4millionPrevalence 1/ 4million No gender or racial No gender or racial

predilectionpredilection

CTSC gene encodes for CTSC gene encodes for Cathepsin C proteaseCathepsin C protease

CTSC gene lies on chromosone 11q14-q21; seven CTSC gene lies on chromosone 11q14-q21; seven exons encoding for lysosomal protease cathepsin C.exons encoding for lysosomal protease cathepsin C.

It is expressed at high levels in a variety of immune It is expressed at high levels in a variety of immune cells including polymorphonuclear leucocytes, cells including polymorphonuclear leucocytes, macrophages, and in epithelial regions commonly macrophages, and in epithelial regions commonly affected by PLS, including the palms, soles, knees, affected by PLS, including the palms, soles, knees, and oral keratinized gingiva (RT-PCR) and oral keratinized gingiva (RT-PCR) (Hart et al., (Hart et al., 1999).1999).

Cathepsin C is a protease enzyme that processes and Cathepsin C is a protease enzyme that processes and activates a number of granule serine proteases activates a number of granule serine proteases critical to immune and inflammatory responses of critical to immune and inflammatory responses of myeloid and lymphoid white blood cellsmyeloid and lymphoid white blood cells

Mutations in CTSC geneMutations in CTSC gene Mutations in Cathepsin C (CTSC) gene are implicated for Mutations in Cathepsin C (CTSC) gene are implicated for

PLSPLS

For example: For example: One exon 1 nonsense mutation (856COne exon 1 nonsense mutation (856CT): introduces a T): introduces a

premature stop codon at amino acid 286. premature stop codon at amino acid 286. Three exon 2 mutations: Three exon 2 mutations:

single nucleotide deletion (2692delA) of codon 349: single nucleotide deletion (2692delA) of codon 349: introduces a frameshift and premature termination codon, introduces a frameshift and premature termination codon,

2 bp deletion (2673-2674delCT): introduces a stop codon at 2 bp deletion (2673-2674delCT): introduces a stop codon at amino acid 343, and amino acid 343, and

GGA substitution in codon 429 (2931GA substitution in codon 429 (2931GA): introduces a A): introduces a premature termination codon.premature termination codon.

Truncated or altered conformation of the protein may not Truncated or altered conformation of the protein may not be transported to the organelle and may not be able to be transported to the organelle and may not be able to activate protein kinases activate protein kinases

In other words, Cathepsin C activity in these patients is In other words, Cathepsin C activity in these patients is nearly absentnearly absent

Association between CTSC gene Association between CTSC gene alterations and PLS patient’s alterations and PLS patient’s susceptibility to periodontal susceptibility to periodontal

disease.disease.

Two possible explanations:Two possible explanations:

1.1. CTSC protein is implicated in activation of proteases CTSC protein is implicated in activation of proteases related to phagocytosis, antigen presentation, local related to phagocytosis, antigen presentation, local activation, and deactivation of cytokines and other activation, and deactivation of cytokines and other inflammatory markers inflammatory markers (Toomes et al., Nature Genetics (Toomes et al., Nature Genetics 1999 101:421-424)1999 101:421-424)

2.2. CTSC influences periodontal progression through its CTSC influences periodontal progression through its role in epithelial differentiation or desquamation. role in epithelial differentiation or desquamation. Aberrant differentiation of sulcular and junctional Aberrant differentiation of sulcular and junctional epithelium may alter the mechanical barrier to epithelium may alter the mechanical barrier to periodontal pathogens periodontal pathogens (Toomes et al., Nature Genetics (Toomes et al., Nature Genetics 1999 101:421-424)1999 101:421-424)

Polymorphism Studies on Polymorphism Studies on PeriodontitisPeriodontitis

Host response is predominantly Host response is predominantly influenced by genetic make-up.influenced by genetic make-up.

Several features of host’s innate immune Several features of host’s innate immune response may contribute to susceptibility response may contribute to susceptibility to AgP and include epithelial, connective to AgP and include epithelial, connective tissue, fibroblast, and PMN defects.tissue, fibroblast, and PMN defects.

Aspects of the host inflammatory response Aspects of the host inflammatory response namely cytokines are crucial variants namely cytokines are crucial variants influencing host respone in periodontitis.influencing host respone in periodontitis.

Immunological Immunological PolymorphismsPolymorphisms

MHC or HLA genes determine our response MHC or HLA genes determine our response to particular antigens.to particular antigens.

Japanese study of AgP pts found a Japanese study of AgP pts found a significant association for pts with atypical significant association for pts with atypical BamH1 restriction site in the HLA.DQB BamH1 restriction site in the HLA.DQB gene gene (Takashiba et al. 1994).(Takashiba et al. 1994).

Hodge & Kinane (1999)Hodge & Kinane (1999) found no assoc. in found no assoc. in caucasian AgP pts and this restriction site.caucasian AgP pts and this restriction site.

IL-1 Gene IL-1 Gene PolymorphismsPolymorphisms

In In 1997 Kornman et al1997 Kornman et al found an association found an association between polymorphisms in genes enconding between polymorphisms in genes enconding for IL-1a(-889) and IL-1B(+3953) and an for IL-1a(-889) and IL-1B(+3953) and an increased severity of periodontitis.increased severity of periodontitis.

The specific genotype of the polymorphic IL-The specific genotype of the polymorphic IL-1 cluster (called 1 cluster (called PST-periodontitis PST-periodontitis susceptibility traitsusceptibility trait) was associated with ) was associated with severity of PD in only non-smokers, and severity of PD in only non-smokers, and distinguished individuals with severe distinguished individuals with severe periodontitis from those with mild disease.periodontitis from those with mild disease.

Genetic control of IL-1: Genes and Locus of SNPs associated Genetic control of IL-1: Genes and Locus of SNPs associated with controlling IL-1 biological activitywith controlling IL-1 biological activity

Genes Genes PolymorphisPolymorphism Locusm Locus

Current Locus Current Locus assessed with assessed with testtest

Controlled productControlled product

IL-1A Allele 2 -889 Allele 2 IL-1A +4845

IL-1 alpha

IL-1B Allele 2 +3953

Allele 2 IL-1B +3954

IL-1 beta

IL-1RN Protein receptor antagonist (impedes IL-1 alpha and beta)Genetic Susceptibility Test for periodontitis: tests for the

presence of at least one copy of allele 2 at the IL-1A +4845 loci and at least one copy of allele 2 at the IL-1B +3954 locus.

*IL-1A +4845 is being used because it is easier to identify than IL-1A -889 and it is essentially concordant with it. ** IL-1B +3953 has been now renumbered as IL-1B +3954 because the current convention indicates that the numbering of the transcription should begin at +1 instead of zero.

Interleukin 1Interleukin 1

A proinflammatory multifunctional A proinflammatory multifunctional cytokine.cytokine.

Enables ingress of inflammatory cells Enables ingress of inflammatory cells into sites of infectioninto sites of infection

Promotes bone resoroptionPromotes bone resoroption Stimulates eicosanoid (PGE2) release Stimulates eicosanoid (PGE2) release

by monocytes and fibroblastsby monocytes and fibroblasts Stimulates release of MMP’s that Stimulates release of MMP’s that

degrades proteins of the ECM.degrades proteins of the ECM. Forms IL-1Forms IL-1αα and IL-1B and IL-1B

IL-1IL-1αα

IL-1α is a IL-1α is a pleiotropicpleiotropic cytokine involved in cytokine involved in various various immune responsesimmune responses, , inflammatory processesinflammatory processes, , and and hematopoiesishematopoiesis

This cytokine is produced This cytokine is produced by many cell types but is by many cell types but is only secreted by only secreted by monocytesmonocytes and and macrophagesmacrophages. .

produced as a produced as a proproteinproprotein, , which is cleaved by which is cleaved by calpaincalpain and released in a and released in a mechanism that is still not mechanism that is still not well studied. well studied.

IL-1IL-1ββ

expressed in monocytes and expressed in monocytes and macrophagesmacrophages

Inactive precursor cleaved Inactive precursor cleaved by caspase-1 enzymeby caspase-1 enzyme

Secreted to extracellular Secreted to extracellular compartmentcompartment

Wide spectrum of immune Wide spectrum of immune functionsfunctions

IL-1 as modulator for IL-1 as modulator for PeriodontitisPeriodontitis

Kornman et al. (1997)Kornman et al. (1997) Genotype-positive non-smokersGenotype-positive non-smokers 18.9 times more likely to 18.9 times more likely to

have severe periodontitis (when compared with genotype-have severe periodontitis (when compared with genotype-negative non smokers)negative non smokers)

No significant association between periodontal status and No significant association between periodontal status and genotype detected when genotype detected when smokerssmokers were included in the were included in the statistical analysis.statistical analysis.

86% of the severe periodontitis patients were accounted for by 86% of the severe periodontitis patients were accounted for by either smoking or IL-1 genotypeeither smoking or IL-1 genotype

Presence of allele 2 at IL-1A -889 or IL-1B +3953 did not Presence of allele 2 at IL-1A -889 or IL-1B +3953 did not significantly increase the risk of periodontitis among smokers significantly increase the risk of periodontitis among smokers and non-smokers.and non-smokers.

+IL-1 genotype and IL-1 +IL-1 genotype and IL-1 proteinprotein

The specific periodontitis-associated IL-1 genotype The specific periodontitis-associated IL-1 genotype consists of a variant in the IL-B gene that is associated consists of a variant in the IL-B gene that is associated with high levels of IL-1 productionwith high levels of IL-1 production.(Poiciot et al 1992).(Poiciot et al 1992)

Patients positive for composite IL-1A (+4845) and IL-1B Patients positive for composite IL-1A (+4845) and IL-1B (+3954) periodontitis-associated genotype has higher level (+3954) periodontitis-associated genotype has higher level of IL-1B in GCF, but not in gingival tissue before and after of IL-1B in GCF, but not in gingival tissue before and after treatment treatment (Kornmann et al 1999)(Kornmann et al 1999)

Carriage of allele 2 in the (-889) locus resulted in an Carriage of allele 2 in the (-889) locus resulted in an almost four fold increase of IL-1 protein levels in chronic almost four fold increase of IL-1 protein levels in chronic periodontitis patients periodontitis patients (Shirodaria et al., 2000)(Shirodaria et al., 2000)

Contradictory StudiesContradictory Studies Meisel et al (2002)Meisel et al (2002)

Stated that the composite genotype showed strong Stated that the composite genotype showed strong interaction with smoking, whereas non-smokers,even interaction with smoking, whereas non-smokers,even genotype-positive were not at any increased riskgenotype-positive were not at any increased risk

Papapanou (2001)Papapanou (2001)132 periodontitis pts who were age and sex matched with 132 periodontitis pts who were age and sex matched with controls did not show any association with the composite controls did not show any association with the composite genotype and periodontitis.genotype and periodontitis.

Ehmeke (1999)Ehmeke (1999)Of 33 pts, 16 were genotype positive. Following 2yrs of Of 33 pts, 16 were genotype positive. Following 2yrs of maintanence tx, no difference in tooth or attachment loss maintanence tx, no difference in tooth or attachment loss between the two groups.between the two groups.

Clinical Significance of IL-1 Clinical Significance of IL-1 GenotypeGenotype

Bleeding Upon ProbingBleeding Upon Probing

Lang et al. (2000)Lang et al. (2000) - after periodontal surgery, maintenance patients were after periodontal surgery, maintenance patients were

monitored for BOP and tested for the candidate genotype. monitored for BOP and tested for the candidate genotype.

- no significant relationship between BOP and the candidate no significant relationship between BOP and the candidate

polymorphism when the entire study population was polymorphism when the entire study population was evaluated (N=333). evaluated (N=333).

- - non-smokers genotype positivenon-smokers genotype positive demonstrated significantly demonstrated significantly more bleeding (when compared to non-smokers genotype-more bleeding (when compared to non-smokers genotype-negative).negative).

Attachment lossAttachment lossKornman et al. (1997)Kornman et al. (1997)

Reported 18.9 times greater risk (OR=18.9) Reported 18.9 times greater risk (OR=18.9) of finding severe periodonitis among non-of finding severe periodonitis among non-smokers genotype-positive.smokers genotype-positive.

McDevitt et al. (2000)McDevitt et al. (2000) Among non-smokers or former smokers, Among non-smokers or former smokers,

genotype positive individuals had 3.75 genotype positive individuals had 3.75 greater odds of having moderate to greater odds of having moderate to advanced periodontitis than genotype-advanced periodontitis than genotype-negative.negative.

Genotype and tooth lossGenotype and tooth loss McGuire and Nunn (1999)McGuire and Nunn (1999)

Genotype-positive individuals had a 2.7 greater Genotype-positive individuals had a 2.7 greater chance than genotype-negative patients of losing a chance than genotype-negative patients of losing a tooth.tooth.

Combined effect of being genotype-positive and Combined effect of being genotype-positive and heavy smoker increased the odds of tooth loss to 7.7 heavy smoker increased the odds of tooth loss to 7.7 compared with genotype-negative non-smokers. compared with genotype-negative non-smokers.

PST can be helpful in treatment planning.PST can be helpful in treatment planning.

Genotype and healing after surgeryGenotype and healing after surgery De Sanctis and Zucchelli (2000)De Sanctis and Zucchelli (2000)

Evaluated the impact of patient’s genotype on maintenance of Evaluated the impact of patient’s genotype on maintenance of gained clinical attachment after guided tissue regeneration gained clinical attachment after guided tissue regeneration (GTR)(GTR)

At base line: no difference between genotype-positive (N=14) At base line: no difference between genotype-positive (N=14) and genotype-negative (N=26) with reference to clinical and genotype-negative (N=26) with reference to clinical parameters (BOP, PD, and CAL)parameters (BOP, PD, and CAL)

At At one yearone year: no difference (gain of CAL 5.1 mm vs 5.2 mm; : no difference (gain of CAL 5.1 mm vs 5.2 mm; residual PD 6.3 mm vs 6.4 mm)residual PD 6.3 mm vs 6.4 mm)

At At four yearsfour years: genotype positive patients demostrated a : genotype positive patients demostrated a significantly greater loss of clinical attachment (2.3 mm vs 1.0 significantly greater loss of clinical attachment (2.3 mm vs 1.0 mm) and increased probing depth (2.2 mm vs 0.8 mm)mm) and increased probing depth (2.2 mm vs 0.8 mm)

Periodontal PathogensPeriodontal Pathogens

Socransky et al (2000)Socransky et al (2000)

Found that the mean counts of specific species were Found that the mean counts of specific species were higher in general IL-1 positive genotypes compared to higher in general IL-1 positive genotypes compared to negative subjects. Species detected at higher levels negative subjects. Species detected at higher levels were those frequently detected with periodontal were those frequently detected with periodontal inflammation.inflammation.

Prevalence of genotype positive Prevalence of genotype positive individuals in different ethnic groupsindividuals in different ethnic groups

Frequency of many genetic alleles varies between ethnic groups, therefore, it is Frequency of many genetic alleles varies between ethnic groups, therefore, it is necessary to establish allele frequencies in populations before genetic test can be necessary to establish allele frequencies in populations before genetic test can be evaluated and used. evaluated and used.

Caucasions:Caucasions: 29% of northern european caucasions were genotype positive 29% of northern european caucasions were genotype positive

(Kornman et al., 1997) (Kornman et al., 1997) African Americans: African Americans:

14.5% of non-diseased individuals and 8% of patients with localized 14.5% of non-diseased individuals and 8% of patients with localized form of aggressive periodontitis were genotype-positive. form of aggressive periodontitis were genotype-positive. (Walker et (Walker et al., 2000)al., 2000)

Chinese: Chinese: 2.3% of sample of 132 mod-severe periodontitis cases were 2.3% of sample of 132 mod-severe periodontitis cases were

genotype-positive genotype-positive (Armitage et al., 2000)(Armitage et al., 2000) Hispanics:Hispanics:

26% of hispanic individuals with peridontitis were genotype-26% of hispanic individuals with peridontitis were genotype-positive positive (Lopez et al., 2005)(Lopez et al., 2005)

Take home message: Dissimilarity in the prevalence of genotypes Take home message: Dissimilarity in the prevalence of genotypes in different ethnic groups precludes extrapolating data from one in different ethnic groups precludes extrapolating data from one group to another. group to another.

Summary of IL-1 genotype Summary of IL-1 genotype in Periodontitisin Periodontitis

1.1. Unlikely to be relevant in AgPUnlikely to be relevant in AgP2.2. It is at best in linkage disequilibrium with the gene It is at best in linkage disequilibrium with the gene

contributing susceptibility to chronic periodontitiscontributing susceptibility to chronic periodontitis3.3. It confers risk independent of that due to smokingIt confers risk independent of that due to smoking4.4. The polymorphism is at best one of several involved.The polymorphism is at best one of several involved.5.5. The polymorphism is a useful marker in only defined The polymorphism is a useful marker in only defined

populations, relatively absent in some (Armitage et al populations, relatively absent in some (Armitage et al 2000), and is too prevalent in others (Walker et al 2000), and is too prevalent in others (Walker et al 2000).2000).

6.6. Demonstration of functional significance of this gene Demonstration of functional significance of this gene polymorphism is yet to be confirmed.polymorphism is yet to be confirmed.

7.7. Clinical utilization of these composite genotype Clinical utilization of these composite genotype polymorphisms for risk assessment and prognostic polymorphisms for risk assessment and prognostic determination is currently premature.determination is currently premature.

(Kinane, 2003)(Kinane, 2003)

GENETIC RISK DETERMINATION GENETIC RISK DETERMINATION

WITH GENOTYPE® PST® PLUSWITH GENOTYPE® PST® PLUS

Mutations in the genes for interleukin-1 and its natural antagonist, Mutations in the genes for interleukin-1 and its natural antagonist, the interleukin-1 receptor antagonist, may lead to an overproduction the interleukin-1 receptor antagonist, may lead to an overproduction of interleukin-1, an important mediator of inflammation of the of interleukin-1, an important mediator of inflammation of the immune system. Even if only a few bacteria are present, an over immune system. Even if only a few bacteria are present, an over activation of osteoclasts results in an increased degradation of activation of osteoclasts results in an increased degradation of periodontal soft and bone tissue. Patients with increased interleukin-periodontal soft and bone tissue. Patients with increased interleukin-1 levels require particularly intensive treatment strategies. In such 1 levels require particularly intensive treatment strategies. In such cases, the GenoType PST™ plus test is a valuable tool for the cases, the GenoType PST™ plus test is a valuable tool for the optimization of follow-up and prophylaxis intervals and for the risk optimization of follow-up and prophylaxis intervals and for the risk determination prior to extensive implant restorations.determination prior to extensive implant restorations.

Instructions for UseInstructions for Use

Sample ReportSample Report