A Zinc-Finger Protein family Required for Pairing and Synapsis

in C. elegans

杨茹& 岳云欢

Review

• Pairing: side-by-side alignment of homologs• Synapsis: intimate association of

chromosomes specifically in the context of the synaptonemal complex (SC)

Details of Prophase I

细线期 偶线期

双线期 终变期 中期 I

粗线期Condensation: chromosomes become visible

Pairing: telomere bouquet Synapsis is complete

Chiasma formation

p610

Former investigation

The wild-type haploid karyotype of C. elegans

HIM-8 protein

• HIM:high incidence of males

• HIM-8 binds to the X chromosome pairing center and mediates chromosome-specific meiotic synapsis. Cell 123, 1051–1063. [Phillips, C.M., Wong, C., Bhalla, N., Carlton, P.M., Weiser, P.,Meneely, P.M., and Dernburg, A.F. (2005).]

The HIM-8 Protein

Localizes to the PC Region of

the X Chromoso

me

New Results

• The Gene cluster of the Family of Zinc-Finger Proteins

ZIM: zinc-finger protein in meiosis

SC incomplete ： Mutations in the zim Genes Result in Meiotic Defects

Results of Mutation of Each zim Gene

Each zim Gene Is Responsible for Synapsis of Specific Autosome Pairs

1.Premeiotic 2.Pairing and Synapsis3. 4. &5.pachtene

Diagram of a hermaphrodite gonad

Pairing of Chromosome V Is Disruptedin the zim-2 Mutant

Diagram of a hermaphrodite gonadGenomic locations of FISH

Wild-type gonad

Wild-type gonad

premeioticTransition

zone Pachytene region

ZIM-2 mutation

Each chromosome relies on a specific member of the family

ZIM Proteins Bind to the Pairing Centersof the Chromosomes They Control

Pairing Centers Associate with the Nuclear Envelopebut Do Not Cluster

Multiple foci dispersed along the nuclear periphery

•Schematic of the ZIM/HIM-8 gene cluster in C. elegans, C. briggsae, and C. remanei. Predicted orthologs based on sequence comparisons are linked by gray shading.

Evolution of the ZIM/HIM-8 Protein Family

Questions

• The relationship between zim/him and telomeres?

• Recognition of the homolog chromosome

Conclusion & ReviewIs the result important?The first effort to find a family of protein

working in pairing and synapsisWhy could they succeed?The good model animal: C.elegansThe former research : SC 、 PC 、 HIM-8……