[
International C. elegans Meeting,
1999]
Dermatomyositis is an autoimmune inflammatory disease. Antibodies against Mi-2 are regarded as a specific marker in dermatomyositis. Mi-2 is a 218 kd protein of 1912 amino acids belonging to the SNF2/RAD54 helicase family. It contains 2 PHD-zinc finger domains, 2 chromodomains and a helicase/ATPase domain. Biochemical studies demonstrated that Mi-2 is a component of a complex that has histone deacetylase and nucleosome remodeling activities. Homozygous mutants of Drosophila dMi-2 die as first or second instar larva. We identified two Mi-2 homologs in the C. elegans genome, F26F12.7 and T14G8.1. Mi-2 and F26F12.7 are 44% identical; Mi-2 and T14G8.1 are 44.8% identical. The helicase/ATPase domain is most highly conserved. To study the in vivo functions of these two C. elegans Mi-2 homologs, we screened for gene knockouts. We identified a deletion of 1616 bp between the third exon and the forth exon of F26f12.7, which creates a stop codon. The encoded truncated protein is 528 amino acids truncated between the two chromodomains. Homozygous mutants (derived from heterozygotes) can develop into adults but are completely sterile. We are further characterizing the mutant phenotypes and screening for a T14G8.1 deletion. We are also characterizing the human Mi-2 protein by biochemical approaches.
[
East Coast Worm Meeting,
2000]
Dermatomyositis is an autoimmune inflammatory disease. Antibodies against Mi-2 are a specific marker for dermatomyositis. Mi-2 is a 218 kd protein of 1912 amino acids belonging to the SNF2/RAD54 helicase family. It contains 2 PHD-zinc finger domains, 2 chromodomains and a helicase/ATPase domain. Biochemical studies demonstrated that Mi-2 is a component of a complex that has histone deacetylase and nucleosome remodeling activities. Homozygous mutants of Drosophila dMi-2 die as first or second instar larva. We identified two Mi-2 homologs in the C. elegans genome, F26F12.7 and T14G8.1. Mi-2 and F26F12.7 are 44% identical; Mi-2 and T14G8.1 are 44.8% identical. The helicase/ATPase domain is the most highly conserved region in these proteins. To study the in vivo function of these twoC. elegans Mi-2 homologs, we screened for gene knockouts. We isolated a deletion of 1616 bp between the third exon and the forth exon of F26f12.7, that also generates a premature stop codon. The truncated protein is only 528 amino acids and terminates between the two chromodomains. Homozygous mutants (derived from heterozygotes) can develop into adults but are completely sterile. 80% of homozygous mutant worms are defective in vulval morphogenesis such that the vulva extrudes and uterus is deformed. There is a low percentage of multi-vulva worms (1-2%) observed. The gonads of homozygous mutants turn prematurely and the DTC appears abnormal. In vivo RNAi experiments showed that the loss-of-function mutant worms of T14G8.1 gene arrest at L1 stage. Both genes are expressed from the egg to adult. F26F12.7 is expressed in hypodermis and in uterus at L4 stage specifically. In adult worms, the expression in the uterus is greatly decreased. T14G8.1 is expressed strongly in the pharynx and also in hypodermis, intestine and some neurons. Biochemical studies demonstrated that the human Mi-2 has DNA dependent ATPase activity.