Worm Breeder's Gazette 15(1): 65 (October 1, 1997)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

A C. elegans homologue of DAZ/boule is involved in progression through meiosis during oogenesis

Takeshi Karashima, Asako Sugimoto, Masayuki Yamamoto

Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Tokyo 113, Japan

        Human DAZ (Deleted in Azoospermia), mouse Dazla, and Drosophila
boule encode a family of proteins with a single RNP-type RNA-binding
motif and are thought to be essential for meiosis during
spermatogenesis (Nature, 381: 783-785, 1996).  The C.elegans cDNA
project identified a putative homologue of DAZ/boule.  This cDNA
(yk62b4, kindly supplied by Yuji Kohara) appears to contain the
complete open reading frame for the gene and its predicted amino acid
sequence contains a putative RNA-binding domain most similar to Boule,
as well as a motif found in all DAZ family members (see figure).  We
tentatively call this gene Ce-boule .  Ce-boule maps close to clr-1 on
Chromosome II.
        To examine whether Ce-boule is involved in meiosis in C.
elegans, antisense Ce-boule RNA was injected into gonads of wildtype L4
hermaphrodites.  F1 hermaphrodite progeny derived from the injected P0s
were sterile at high penetrance.  The sterile F1s had normal somatic
gonads and normal-looking sperm (by both Nomarski and DAPI staining),
but oogenesis was severely affected: with Nomarski microscopy, gonad
arms were filled with mostly small nuclei, and none of the cells
displayed the characteristic morphology of developing or mature
oocytes.  By DAPI staining, majority of the nuclei looked similar to
mitotic cells.  Possible pachytene nuclei were occasionally observed in
the proximal arms, but no diplotene-diakinesis nuclei were found.
Although the morphology of the nuclei appears mitotic, the phenotype is
not tumorous (unlike gld-1(null) or glp-1(gf)), judging from the
density of the nuclei in the gonad.  The injected P0s themselves showed
a similar phenotype after they laid approximately 30 fertilized eggs.
Thus, antisense Ce-boule  injection seems to affect either the
transition from mitosis to meiosis or the early stage of meiosis during
        The expression pattern of Ce-boule in the adult hermaphrodite
germ line was studied by in situ hybridization and it was found that
Ce-boule mRNA shows a graded pattern in the gonad.  The signal was
detected starting at the mitosis/meiosis transition zone and increased
in intensity toward the pachytene region.The strong signal was
maintained through the proximal arm except in mature oocytes, where the
signal was distinctly weaker.  No signal was seen in mature sperm.
This expression pattern is consistent with the hypothesis that Ce-boule
is required during oogenesis, for the meiotic entry and/or the prophase
of meiosis I.
        It is surprising that DAZ/boule's possible counterpart in
C.elegans appears to be essential for oogenesis and dispensable for
spermatogenesis, as both DAZ and boule seem to be mainly associated
with male sterility.  For further characterization, we are currently
screening for mutants of Ce-boule by a PCR-based method and by looking
for sterile mutants in the corresponding chromosomal region.

        We are grateful to Tim Schedl and Lisa Kadyk for helpful
suggestions and guidance.