Worm Breeder's Gazette 13(5): 68 (February 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.

A Nob Allele at the unc-62 Locus

Daniel C. Weaver, Lois Edgar, and William B. Wood

University of Colorado - Boulder, Campus Box 347, Boulder, CO 80309

        The ct344 mutation, isolated by Lois Edgar, results in  nonviable
embryos, some of which hatch and die as L1's with disorganized posteriors. 
In this way ct344 resembles other nob mutations being  characterized in
this laboratory (1) and as a result, it was previously referred to as
nob-5(ct344).  It is unique, however, in that it displays a partial
maternal effect.  Heterozygous hermaphrodites  give rise to phenotypically
wild-type homozygous mutant progeny, which produce 100% Nob animals and
dead eggs, unless mated with a wild-type male.  This mutation was mapped
to LGV(L) near unc-62.  Complementation tests showed that it fails to
complement either the  Unc phenotype resulting from unc-62(e644) or the
non-maternal effect  embryonic lethal phenotype resulting from
unc-62(s472).  Examination  of e644 homozygous mutant animals reveals that
about 19% of their progeny display the Nob phenotype, though neither this
nor the Unc  phenotype show the maternal effect described for ct344.
        Results of dosage experiments shown in the table below suggest
that  s472 is a nearly complete loss-of-function mutation, and that ct344
is completely recessive.  In addition, e644/s472 trans-heterozygotes
display a maternal effect that is not seen in the homozygous e644  mutant
animals.  Further dosage experiments and phenotypic
characterization of the embryonic lethal phenotypes resulting from  ct344
and s472 are in progress.

                    F1 homozygotes                    F2 homozygotes     
            or trans-heterozygotes            or trans-heterozygotes
Genotype    %Nob   %dead eggs    %viable     %Nob   %dead eggs   %viable 
---------  -----   ----------    -------     ----   ----------   ------- 
e644/e644    19         5           76         19        5         76
ct344/ct344  12        nd           87         42       57         <1
e644/sDf26    8        51           40         No F1 animals survive     
                                                  to produce progeny
ct344/sDf26   9        56           33         No F1 animals survive     
                                                 to produce progeny
e644/s472    25        30           45          6       82         11
ct344/s472   23        30           47         No F1 animals survive     
                                                 to produce progeny
ct344/ct344/yDp1 <2    <2           >95 *

* These percentages are estimates.  Good brood counts have not yet been

        We used the e644 mutation to identify the region of the physical
map  that includes unc-62.  Using polymorphisms between the Bristol and
Bergerac  strains as reference points, we mapped this mutation to the
region between  stP3 and another polymorphism associated with the cosmid
RW#L63.  Two  deficiency break points fall in this region: the right end
of sDf50 and the right end of sDf27.  PCR mapping experiments of these
deficiencies performed by A. Scouras and M.F. Wakarchuk in David Baillie's
laboratory further limit the candidate physical region. These compiled
results leave two candidate cosmids and the surrounding cosmid gaps.  The
candidate cosmids are being injected into the ct344  and s472 mutant

(1) Edgar, L.G., N. Wolfe, S.H. Carr, and W.B. Wood. "The Nog genes and
pal-1 are involved in embryonic posterior morphogenesis." 1993 Worm
Meeting Abstracts: p.10.