Loss-of-function mutations in thefem-l gene transforrn animals of both chromosomal sexes into fertile females, indicating thatfem-l function is essential for male development in both soma and gerrnline( l) . The DNA sequence of the gene predicts that its product is an intracellular protein containing six tandemly arranged 33 arnino acid cdclO/SWI6 motifs near its N-terminus(2) . Northern analysis shows that the 2.4 kb fem-l mRNA is expressed throughout hermaphrodite development at approximately constant levels. Althoughfem-l acts in hermaphrodites only to influence the sexual fate of the germline, its mRNA is present in mutant hermaphrodites lacking a germline [glp-l(
e2144) or SS104
(bn2)] suggesting that in contrast to
fem-3(3), the gene is expressed in herrnaphrodite somatic tissues. Reduced levels offem-l transcripts in animals lacking germ cells suggest that the gerrn line is however a major site offem-l expression. In adult males, a sub-population of transcripts slightly larger than lhose seen in hermaphrodites is evident. Whether the change in size is due to regulation of polyadenylation as has recently been observed infem-3(gf) mutants(4) is under investigation.