Worm Breeder's Gazette 14(1): 62 (October 1, 1995)

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.

Pos-1 (=skn-2 ?), a gene which shows localization of its mRNA to the P lineage during early cleavage of C.elegans embryo.

Hiroaki Tabara1, Tomoko Motohashi2, Craig Mello3, Jim Priess4, Yuji Kohara5

1 Gene Library Lab, National Institute of Genetics, Mishima 411, Japan
2 Gene Library Lab, National Institute of Genetics, Mishima 411, Japan
3 Cancer Center, University of Massachusetts, Worcester, MA 01605
4 Fred Hutchinson Cancer Research Center, Seattle, WA 98195
5 Gene Library Lab, National Institute of Genetics, Mishima 411, Japan 

      We have long been searching for localized maternal mRNA in early
embryos of the worm by a range of approaches of differential screening.

In the course of the systematic analysis of in situ hybridization with
a set of classified cDNA clones which have been generated by our cDNA
project (see '95 IWM abstract #2), we found that the clone, yk61h1, of
the cDNA group CELK01662 (= YK1662 in ACEDB) showed an asymmetric
distribution of its mRNA at 2-cell stage embryos.   Closer examinations
on behavior of the mRNA in gonads and embryos by in situ hybridization
showed that (1) the mRNA started to appear at the turn of gonad, (2) it
was distributed evenly in oocytes, (3) it was segregated posteriorly as
the first cleavage proceeded, (4) the mRNA remained in P4 but
disappeared in other somatic blastmeres (perhaps by a mechanism of
degradation).   In situ analysis using nop-1 embryos which lacked
pseudo-cleavage suggested that the segregation of the mRNA occurred
during the first cleavage.   Northern hybridization showed that the
mRNA (1.3 Kb) was detected in embryos and adults but not in L1 larva.
We named this gene pos-1 (posterior segregation), and have analyzed it
further.
      Full sequencing of the cDNA clone showed that the pos-1 mRNA has
the trans-spliced leader SL1 and strong homology to the zinc-finger
region of the mammalian Tsi11 growth factor inducible genes.   This
zinc- finger motif is also found in the maternally expressed C.elegans
gene pie-1.   Interestingly, the position of pos-1 turned out to be very
close to a second maternal gene, skn-2.   The skn-2 gene like pie-1 is
required for proper development of the P lineage and skn-2 and pie-1
mutants exhibit dominant genetic interactions (see '95 IWM abstract #215
and 441).   These genetic interactions and the physical and genetic
proximity of pos-1 and skn-2 led us to invetigate the possibility that
pos-1 = skn-2.   Preliminary evidence supports this hypothesis:
(1) injection experiments using pos-1 anitsense RNA caused phenocopies
of skn-2,  and (2) a missense mutation was found in the zinc finger
region of pos-1 in a skn-2 mutant (zu148).   Injection-rescue
experiments and genomic sequencing of pos-1 region in more skn-2 mutant
alleles are in progress.   We are also raising antibodies against pos-1
protein and continuing our analysis of the skn-2 mutant phenotype.