The
zyg-11 gene, on chromosome II, is required for proper cytoplasmic organization in early embryos. Mutations in the gene have a strict maternal-effect lethal phenotype. In embryos from
zyg-11 mothers, meiosis arrests at metaphase II, there is a delay in the appearance of pronuclei, the position of the first cleavage furrow is abnormal, and P granules fail to segregate properly (Kemphues et al., Dev. Biol. 113, 449 (1986)). We believe that a molecular analysis of this gene will help us to understand the nature and function of maternally-encoded factors in the egg. To identify a
zyg-11 clone, we made use of a 400kb contig from Alan Coulson and John Sulston that we thought likely to contain
zyg-11. We had previously shown that the left-most cosmid of the contig overlapped the left end of mnDf103, and the remainder of the contig extended to the right on the genetic map ( toward
zyg-11). The contig also covered the sites of 2 Tc1 elements identified in a mutator strain by Ikue Mori, Don Moerman and Bob Waterston (WBG 10 #1, p.47). Ikue kindly sent us a worm strain containing the two Tc1 's, and we showed by 3-factor crosses that zyg- 11 mapped to the left of Tc1 #40 (RW#200L). Therefore,
zyg-11 had to be in the contig somewhere. We decided to find the position of
zyg-11 in the contig by using individual cosmids as probes of a Southern blot containing DNA from 2
mut-2 induced
zyg-11 mutants (
it50 and
it65) that we had found earlier. The first cosmid that we tested, DH11, must contain at least part of
zyg-11 since it detected DNA rearrangements in both
it50 and
it65. The rearrangement in
it50 appeared to be a 2.9kb insertion, while the rearrangement in
it65 appeared to be a 1.6kb insertion. Both insertions occurred within a 3. 0kb EcoRI fragment. Additional Southern analysis narrowed down the points of insertion to an 800-base EcoRI-BglII fragment. We are now sequencing that fragment. We will also use the clone as a probe to study transcription of
zyg-11. The cosmid DH11 also seems to cover an endpoint of mnDf104 since it detects a novel restriction fragment when used as a probe against mnDf104 DNA. The figure below shows some clones of the contig, along with some genetic markers. [See Figure 1]