C. elegans PAT-9 is a nuclear zinc finger protein critical for the assembly of muscle attachments

Positional cloning, reverse genetics, and plasmid rescue experiments were used to identify the predicted C. elegans gene T27B1.2 (recently named ztf-19) as the pat-9 gene. Analysis of pat-9 showed it is expressed early in development and within body wall muscle lineages, consistent with a role in muscle development and producing a Pat phenotype. However, unlike most of the other known Pat gene family members, which encode structural components of muscle attachment sites, PAT-9 is an exclusively nuclear protein. Analysis of the predicted PAT-9 amino acid sequence identified one putative nuclear localization domain and three C2H2 zinc finger domains. Both immunocytochemistry and PAT-9::GFP fusion expression confirm that PAT-9 is primarily a nuclear protein and chromatin immunoprecipitation (ChIP) experiments showed that PAT-9 is present on certain gene promoters.We have shown that the T27B1.2 gene is pat-9. Considering the Pat-9 mutant phenotype shows severely disrupted muscle attachment sites despite PAT-9 being a nuclear zinc finger protein and not a structural component of muscle attachment sites, we propose that PAT-9 likely functions in the regulation of gene expression for some necessary structural or regulatory component(s) of the muscle attachment sites.The nematode C. elegans provides an established, developmentally well-documented, and evolutionarily conserved system to study muscle structure, development, and function [1,2]. The C. elegans sarcomere, the basic muscle contraction unit, has been studied for decades revealing a highly organized structure consisting of several hundred proteins, yet new components are still being identified [2-6]. In C. elegans sarcomeres, myosin thick filaments are organized around M-lines and actin thin filaments are anchored to the dense bodies, structures analogous to the vertebrate Z-disk. The dense bodies and M-lines are sites of attachment for body wall muscle cells to the basement membrane, thus transmitting the force of