Worm Breeder's Gazette 10(3): 58

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.

Identification of a Transposon Insertion in lon-2

Gwen Freyd and Bob Horvitz

Mutants of the gene lon-2 cause worms to grow to one-and-a-half 
times their normal length.  Since cell lineages appear normal, we 
hypothesize that the gene either could be directly lengthening all 
cells in the animal, or that it could be affecting the structure of 
the cuticle, which is known to be important in maintaining the worm's 
body shape.
A powerful approach to characterizing this gene would be its 
molecular cloning.  We isolated a lon-2 allele (n1630) in TR679, a mut-
2 strain with a high frequency of transposon transposition.  The 
unbackcrossed strain reverts at a high frequency, whereas the 10X 
backcrossed strain does not, leading us to believe a transposon has 
inserted into lon-2.  We have subsequently identified an approximately 
20kb HindIII restriction fragment that is likely to include at least 
part of the lon-2 gene.
We used three-factor crosses with nearby markers, unc-78 and dpy-8, 
and subsequent Southern blot analysis with Tc1 probes to identify the 
band.  We have analyzed six recombinants in the interval between unc-
78 and lon-2 (approximately 4.5 map units) and six recombinants 
between dpy-8 and lon-2 (approximately 0.5 map units).  A band of 
about 20 kb is present in 6/6 recombinants that show the lon-2 
phenotype and in 0/6 recombinants that are wild-type, mapping the band 
to within 0.2 map units on one side and 1.8 map units on the other 
side of lon-2.In addition, we have analyzed a spontaneous dominant 
revertant of this lon-2 allele.  The mutation causing the reversion is 
tightly linked to lon-2 and is lacking the 20kb Tc1-hybridizing band 
present in the lon-2(n1630) mutant strains.  These results suggest 
that a transposon excision event caused the reversion.  Two other lon-
2 alleles (cgl1 and u383) have been isolated in mutator backgrounds in 
the laboratories of Jim Kramer and Marty Chalfie that we have not