The ELAV-Type RNA-binding protein, ETR-1, is one of two CELF-family RNA-binding proteins that exist in C. elegans. Our studies have previously shown that ETR-1 depletion via RNAi results in defects in muscle development, an increased number of germline apoptotic corpses in hermaphrodites, and an overall reduction in hermaphrodite reproductive capacity. We will show here that ETR-1 also plays a significant role in spermatogenesis both in hermaphrodite and male animals. Our expression data will show that ETR-1 is expressed throughout the male somatic gonad and germline tissue. ETR-1 exhibits cytoplasmic expression in spermatids and upon activation localizes to the pseudopod of the spermatozoa where it colocalizes with Major Sperm Program (MSP). Spermatogenesis genes in C. elegans are typically resistant to RNAi, therefore most researchers study spermatogenesis defects using mutant alleles. Only a few genes, such as the
gsp-3/4genes, have been shown to result in a penetrant male sterility phenotype when depleted via RNAi in an enhanced sensitivity to RNAi worm strain [
rrf-3(
pk1426)] (Chu et al., 2006). We will show that RNAi depletion of ETR-1 in L4
rrf-3male animals results in a strong male fertility defect. Males depleted of
etr-1via RNAi are 64% less fertile that control(RNAi)animals when mated to
fog-2(
q71) feminized animals. These ETR-1-depleted males exhibit sperm activation defects, including both the presence of prematurely activated spermatids, similar to
spe-47(
hc198)mutants, and delayed activation of spermatids. Some of the spermatids have "rod-like" and "spike-like" projections, similar to phenotypes observed in
spe-15(
ok153)spermatids, and suggestive of defects in Major Sperm Protein polymerization and sorting of cellular components respectively. Interestingly, depleting ETR-1 earlier during development at the L1 stage results in a significant percentage of males with deformed tails, including gross abnormalities in overall tail shape and either fused or missing tail rays. As we begin to elucidate how ETR-1 might be functioning in C. elegans, including during spermatogenesis, we performed RIP-seq to identify the mRNA targets of ETR-1. Initial analysis of our RIP-seq data indicates an enrichment of calcium binding genes and Major Sperm Protein genes, both of which are involved in sperm activation. Knowledge of themRNA targets of ETR-1 in conjunction with the phenotypes observed upon ETR-1 depletion will enable us to start to deduce the mechanism of ETR-1 in spermatogenesis.