Genetic and phenotypic analyses of
gld-1 mutants have revealed several germline specific functions for the wildtype
gld-1 gene product. These include a major role in progression through female meiotic prophase, a sex non-specific role in pre-meiotic proliferation, and a nonessential role in hermaphrodite spermatogenesis.
gld-1 produces two 2.5 kb transcripts that differ by 9 nt. These transcripts are most abundant in L4, adult, and embryo RNA on developmental Northern blots. The encoded GLD-1 proteins are similar to the mammalian protein Sam68 (a.k.a. GAPap62), and suggest a biochemical function of RNA binding for GLD 1. We have raised antibodies to GLD-1 and have begun to analyze RNA and protein expression. Somewhat surprisingly,
gld-1 RNA and GLD-1 protein do not have identical expression patterns. In the adult hermaphrodite germ line,
gld-1 RNA and protein are detectable within the mitotic region but not in the most distal portion of the gonad. Both RNA and protein are abundant throughout the region containing germ cells in the early stages of meiosis (through pachytene).
gld-1 RNA remains detectable at apparently high levels throughout the later stages of meiotic progression including in mature oocytes. However, protein staining decreases after the pachytene region, reaching background levels in mature oocytes. We have determined experimentally that
gld-1 RNA is maternally contributed to embryos, and in situ localization shows that it is present in early stage embryos but is not detectable after the 16-20 cell stage. We have not, however, been able to detect GLD-1 protein in embryos, either in situ or on immunoblots. In L4 hermaphrodites, RNA and protein expression pattern is similar to adults distally, but the most proximal germ cells in pachytene (presumptive male) and differentiating sperm no longer express
gld-1 RNA or protein.
gld-1 RNA and protein are also present within the male germ line, but at qualitatively lower levels than hermaphrodites. Within the regions of the gonad that GLD-1 protein is expressed, we have analyzed its cellular localization by confocal microscopy. We find intense staining within the core region of the gonad with diffuse cytoplasmic staining throughout. We do not find nuclear staining, although there does appear to be some punctate peri-nuclear staining. We have begun to analyze GLD-1 protein expression in various
gld-1 mutant backgrounds.