Worm Breeder's Gazette 11(5): 78

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 mab-5 Complex?

Bruce Wang and Cynthia Kenyon

The Antennapedia and Bithorax complexes in Drosophila consist of 
homeobox containing genes that specify segmental identity.  The order 
of these homeotic genes along the chromosome correlates with the order 
of expression along the anterior-posterior axis of the embryo.  
Vertebrate homologues to these genes have been described: they are 
also arranged in clusters and, as shown in the mouse, the chromosomal 
organization also correlates with their domains of expression.  We are 
interested in determining whether C.  elegans contains a similar 
complex of homeotic selector genes.  Previous work in our lab on mab-5,
an Antp-like homeobox gene responsible for pattern formation in one 
posterior body region, and more recent work by several labs on egl-5 
and lin-39 suggest that such a complex may exist.
Andrew Chisholm has been analyzing egl-5, a gene required for-normal 
fates of several cells in the tail region (WBG 10:2).  He has shown 
that egl-5 maps 0.03 m.u.  to the right of mab-5 and that the cosmid 
C08C3 rescues egl-5 mutants.  C08C3 contains both mab-5 and the 
homeobox gene ceh-11, described by Schaller, et al.  (Nuc.  Acids Res. 
18:2033).  We have noticed that ceh-11 has some homology to 
Drosophila AbdB, consistent with the chromosomal organization in 
vertebrate clusters and in Drosophila.  We are continuing Andrew's 
rescue experiments, and have now narrowed down the rescuing activity 
to a 13 kb fragment containing ceh-11.Sasha Kamb in our lab previously 
identified a new homeobox gene (ceh-15) in a PCR screen for more Antp-
like homeoboxes.  Alan Coulson has recently found that ceh-15 is 
positioned to the left of mab-5 across a gap in the contig map.  This 
is the map position of lin-39, a good candidate for a gene that 
functions in the central body region, which Scott Clark has 
characterized.  In lin-39 hermaphrodites P(3-8) cells do not form a 
vulval equivalence group and VC neurons but instead behave like P 
cells in other body regions (S.  Clark and B.  Horvitz, WBG 11:2).  
Based on the map position of lin-39 that Scott provided us, both we 
and Scott have rescued lin-39 mutants using cosmids containing Sasha's 
homeobox, ceh-15.  For our rescue experiments, we injected lin-39(mu26)
, a new allele isolated recently by Judith Austin in the lab in a 
screen for Q migration mutants.  We have now narrowed down the 
rescuing activity to a 10 kb fragment that contains ceh-15.  The ceh-
15 homeobox exhibits homology to Drosophila Dfd, again consistent with 
the organization in flies.  We are currently continuing rescue 
experiments with ceh-11 and ceh-15 to determine whether these genes do 
in fact correspond to egl-5 and lin-39 respectively.
If there is a 'mab-5 complex' evolutionarily related to the 
Drosophila clusters, other homeobox genes might be located in the 
region.  In fact, another homeobox gene which has lab-like homology, 
ceh-13, is located near ceh-15.  (Schaller, et al., op cit.)) We are 
now probing about 20 overlapping cosmids spanning the mab-5 region (
mec-14 to egl-45) with degenerate homeobox-specific oligos described 
by Burglin, et al.  (Nature 341: 239).  Preliminary data suggest that 
there are several additional Antp-like homeobox genes in this region.