Worm Breeder's Gazette 10(2): 102

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.

Molecular Analysis within the dpy-20 to unc-22 Region of Chromosome IV

S. Prasad, B. Kuchinka and D.L. Baillie

Previously we reported the use of cross-hybridization of C.  
briggsae genomic DNA with cosmid derived probes as a tool to 
efficiently identify coding sequences in the cosmids that were 
positioned to the left of unc-22.  Among the four cosmids analyzed, 
nine regions with homology to C.  briggsae DNA were identified.  Seven 
of the nine cross-hybridizing fragments also hybridized to mRNA 
transcripts on Northern blots.  Probes for these transcripts were 
hybridized to RNA prepared separately from each larval stage and 
adults.  The expression of each of these homologous regions was stage 
specific and surprisingly similar in pattern (abundant at L2 stage).  
Furthermore, the expression profile of each of these seven regions was 
very similar to the expression profile observed with the muscle actin 
probe and was dissimilar to both the hsp-1 or rat Na+ channel probes.  
These observations have led us to speculate that the genes in this 
region may be coregulated for their expression.  Further analysis of 
the regulatory sequences in these genes will address this hypothesis.
We have, so far, isolated (either from B.  Meyer's or J.  Ahringer's 
cDNA libraries) and characterized four different cDNA clones 
corresponding to four of the above mentioned conserved regions.  
Sequence analysis of each cDNA clone showed a long ORF and a poly (A) 
addition site.  Only one of the four cDNA clones represented the full 
length transcript and the sequence analysis of this cDNA revealed a 
trans-spliced leader at the 5' end (Krause et al., 1987; S.  Bektesh, 
personal communication).
We have also screened a charon 4 C.  briggsae genomic library (
constructed by T.  Snutch) using the isolated cDNA clones as probes.  
We are interested in 1) determining the amount of nucleotide 
divergence between C.  elegans and C.  briggsae, and 2) finding if any 
gene order is maintained between C.  elegans and C.  briggsae.  Thus 
far, genomic sequences of one homologous region have been compared and 
our sequence analyses indicate that these genomes are approximately 
82% diverged and these species diverged from a latest common ancestor 
about 40 Myr ago.  Coding sequences were found to be 80% conserved at 
the nucleotide level and 91% at the amino acid level, while the 
introns and the 3' flanking sequences were highly diverged.
This work was supported by grants from the Natural Sciences and 
Engineering Council, and the Muscular Dystrophy Association of Canada 
to DLB.