Seoul National University Children’s Hospital

Gastroenterology, hepatology and Nutrion

F. Sang hee, Cho

ATP7B mutation in patients with

Wilson disease

Wilson disease (WD) was first described in 1912 by

Kinnear Wilson as “progressive lenticular

degeneration,” a familial, lethal neurological disease

accompanied by chronic liver disease leading to

cirrhosis.

In 1993, the abnormal gene in WD was identified.

ATP7B encodes a metal-transporting P-type

adenosine triphosphatase (ATPase)

Introduction

Critical role in human metabolism as a cofactor of key metabolic enzymes, which are involved in respiration, neurotransmitter biosynthesis, radical detoxification, iron metabolism, and many other physiological processes

Average daily intake of copper : 1-3mg

When intake is less than 1mg/day, more than 50% of the copper is absorbed, when copper intake is more than 5mg/day, less than 20% is absorbed

Liver is the principal storage site for copper and regulates its excretion into the bile

Copper Homeostasis

High-affinity copper transporter (Ctr1) : polytopicmembrane protein involved in the copper uptake at the hepatocyte plasma membrane

Metallothioneins (MT) : a group of cysteine-rich intracellular proteins capable of binding metal ions

Metallochaperones (ATOX1/HAH1, CCS, Cox17) : involved in the transfer of copper to specific cellular targets

Cu-ATPase : ATP7B, ATP7A

Copper transporters

P. Ferenci et al.Pathophysiology and clinical features of Wilson disease 2004;19:229-39

ATPase 7A (ATP7A)

In intestine, choroid plexus, vascular smooth

muscle, adrenal gland

ATPase 7B (ATP7B)

primarily expressed in the liver, and also in the

brain, kidney, placenta.

membrane protein located in the trans-Golgi involved in

incorporation of free copper into apoceruloplasmin and

in transporting the excess copper to secretory vesicles

for excretion into biliary canaliculi.

Copper transporters

Svetlana et.al. Function and Regulation of Human Copper-Transporting ATPase.Physiol Rev

2007;87:1011-46

NML45

Intracellular pathways of copper distribution

Svetlana et.al. Function and Regulation of Human Copper-Transporting ATPase.Physiol Rev

2007;87:1011-46

Localization and function of Cu-ATPases

Svetlana et.al. Function and Regulation of Human Copper-Transporting ATPase.Physiol Rev

2007;87:1011-46

Six N-terminal metal-binding sites (MBS)

Actuator domain (A-domain)

Phosphorylationdomain(amino acid residues 971-1035;containing the highly conserved Asp-Lys-Thr-Gly-Thr motif)

Nucleotide-binding domain(N-domain; amino acid residues 1240-1291)

Eight hydrophobic transmembrane sequences

Gereral Architecture of Cu-ATPases

Svetlana et.al. Function and Regulation of Human Copper-Transporting ATPase.Physiol Rev

2007;87:1011-46

Gereral ATPase catalytic cycle

de Bie, P et al. J Med Genet 2007;44:673-688

Structure of isolated NH2-terminal metal-binding

domain(MBD)

Svetlana et.al. Function and Regulation of Human Copper-Transporting ATPase.Physiol Rev

2007;87:1011-46

Sites of Wilson disease-

causing mutations are in

red.

The bound ATP molecule

is in green.

ATP-binding domain of ATP7B

Svetlana et.al. Function and Regulation of Human Copper-Transporting ATPase.Physiol Rev

2007;87:1011-46

At least 300 distinct mutations :

missence, nonsense, deletions, insertion

WD gene showing the site of common mutations

Peter F. Regional distribution of mutations of the ATP7B gene. Hum Genet

2006;120:151-59

Genotype-to-phenotype correlations in WD are hampered by the high prevalence of compound heterozygotes and the relative paucity of homozygotes.

Studies in homozygotes suggest that mutations affecting critical portions of the protein, including copper-binding domains or the ATPase loop, may lead to early onset of hepatic disease, but strict concordance is difficult to prove.

In general, convincing genotype-phenotype correlations remain elusive.

Genotype-to-phenotype correlations in WD

In the genetically confirmed 92 WD patients,

Common mutations (allele frequency)

R778L (40%),

A874V and N1270S (8.7%)

L1083F and V872X (6.0%)

Fourteen (15%) WD patients were homozygous

and 46(50%) heterozygous for the R778L.

Mutation analysis of ATP7B in 114 WD patients

(SNUCH 2009)

Total R778L

homozygot

es

R778L

heterozygot

es

Other

mutations

P value

Number(n) 92 14 (15.2%) 46 (50%) 32(34.8%) -

Age at

diagnosis(ye

ars)

9.0± 3.8 10.5 ± 3.4 8.4 ± 3.7 9.2 ± 4.1 0.21041)

K-F ring(n) 30 6 (20%) 11 (36.7%) 13 (43.3%) 0.20312)

Neurologic

symptoms(n)

17 4 (23.5%) 6 (35.3%) 7 (41.2%) 0.35102)

Ceruloplasmi

n (mg/dL)

6.9±5.8 9.8 ± 10.1 6.7 ± 5.6 6.0± 2.2 0.11241)

24hr urine

copper(ug/da

y)

345.0±398.

6

320.6±231.6 375.4 ±

484.9

312.1±

316.0

0.76851)

Clinical and laboratory data of 92 WD patients and

correlation with R778L

1) ANOVA2) Chi-square test

THANK YOU~~!!!

THANK YOU~~!!!