Worm Breeder's Gazette 9(3): 39

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.

Progress in Mapping a Gene Affecting Adult Surface Antigen Expression

S.M. Politz and S. Savely

We are mapping a gene defined by adult-specific antigenic 
differences between Bristol (N2) and the varietal strain PA-l. These 
phenotypic differences were described previously (WBG V. 9, #1, p. 52).
Stage-specific surface antigens may play a role in the host immune 
response to medically important parasitic nematodes. In addition, 
genes directly and specifically affecting adult surface antigen 
expression may respond to the action of major regulatory genes and may 
therefore provide specific genetic markers for heterochrony besides 
morphological characters already in use such as the adult alae and 
Adults of strain PA-l do not bind adult-specific rabbit antibodies 
prepared against N2 cuticle proteins. We analyzed the genetic 
differences that account for the observed surface antigen difference 
by performing hybrid crosses between N2 and PA-l. First, we determined 
that the N2 (antigen-positive) phenotype is dominant in Fl hybrids. N2 
males were crossed with PA-l hermaphrodites or vice versa. Fl hybrid 
males were tested for adult-specific antibody binding. Individuals 
were scored for immunofluorescence; 97-100% of the Fl males in either 
cross were positive. N2 and PA-l male control samples showed 100% and 
4% positive males, respectively. The similarity in results of the two 
reciprocal hybrid crosses further suggests that the phenotype is not 
determined in a sex-linked fashion. 
In similar crosses between N2 visibly marked (dpy or unc) strains 
and PA-l, we isolated outcross F2 segregants that were antigen-
negative and bred true, like the PA-l parental strain. Their relative 
frequency suggested that the phenotype might be determined by a small 
number of genes. We therefore pursued linkage analysis in hybrid 
crosses using linkage markers on all 5 autosomes. 
dpy/+ or unc/+ males in the Bristol genetic background were crossed 
with PA-l. Outcross clones were identified as those segregating for 
the marker phenotype. Homozygous wild-type (nonmarker) segregant 
clones were established, and about twelve of these were screened for 
antibody binding by immunofluorescence. In the case of close linkage, 
most or all homozygous non-marker clones should show the non-
recombinant, antigen-negative phenotype. Of all the markers tested, 
only unc-4(e120)II,  and rol-1(e91)II showed 
linkage, with about 80% of clones in each case showing the antigen-
negative phenotype. Thus, only linkage group II markers showed 
significant linkage. 
We have apparently identified a gene or cluster of genes on linkage 
group II that specifies the N2 adult surface antigen phenotype. Do 
strains such as PA-l carry allelic alternatives to the N2 antigen gene,
or do they carry null alleles of the N2 gene? This is an intriguing 
question for further investigation.