Worm Breeder's Gazette 10(3): 91

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.

Cod and Mab Mutants

Cheng Song, Leslie Barber and Paul Sternberg

To identify genes necessary for normal male tail development we are 
screening for mutants defective in male tail morphology or mating 
behavior using the screen developed by J.  Hodgkin [Genetics 103:43-64 
(1983)].  From examination of the males produced by 834 independent F2 
clones derived from mutagenized him-5(e1490) grandparents, we have 
obtained 27 mutant strains with abnormal male tail morphology (Mab).  (
An additional 15 strains have abnormal males, but also have 
hermaphrodite defects such as uncoordinated movement or dumpy body 
shape and thus are probably alleles of known genes).  We have examined 
the gross anatomy of males of these strains and found that six mutants 
have tail defects reflecting abnormalities in epidermal development; 
sixteen have defects primarily in the proctodeum; and five have 
defects in gonadogenesis such that the gonad does not connect to the 
proctodeum.  We are particularly interested in mutants with defects in 
spicule formation (M & B lineages) or gonadogenesis (Z1 & Z4 lineages).

A second class of mutants obtained in this screen are anatomically 
normal yet defective in copulation (we call these Cod for 'copulation 
defective').  Each of the four Cod mutants mate with <1% of wild-type 
efficiency.  Because a major class of mutants defective in a variety 
of behaviors including male mating fail to avoid high osmotic strength 
media, we tested the Cod mutants for this behavior using J.  Thomas' 
assay [WBG10(1)89-90].  All mutants displayed wild-type behavior as 
compared to him-5 and osm-3; , indicating 
that we have not just reisolated alleles of known genes.  To better 
characterize these Cod mutants, we have started to develop assays for 
various steps in copulation.  We have developed an assay for the 
attraction of males to hermaphrodites based on the original 
observations of J.  Sulston and R.  Horvitz.  In this assay, paralyzed 
hermaphrodites [unc-52(e444)] are placed in the center of a dry 5cm 
plate with full bacterial lawn ( The dryness of the plate is crucial) 
and allowed to incubate for six hours.  Following this time, a male is 
placed on the edge of the plate.  Examination of the tracks made on 
the lawn indicates whether tracking occurred.  In a typical assay, 
10/12 him-5(e1490) males reach the hermaphrodites within 25 minutes.  
Once a male reaches the hermaphrodites, it stays nearby (Jim Thomas' 
'accumulation').  Both of the Cod mutants tested, sy38 and sy48, were 
essentially wildtype for this behavior,with 20/36 and 24/36 males 
tracking, respectively.  In these experiments, N2 hermaphrodites 
served as a negative control, with 0/10 hermaphrodites tracking 
Some mutants first identified on the basis of mating defects, on 
closer examination, turned out to have anatomical defects; these have 
been included in the Mab category.  For example, sy56 III, which has a 
male-specific defect in germ line proliferation, was picked up as a 
Cod mutant.  This observation indicates the efficacy of the behavioral 
screen, as we would have missed such subtle anatomical defects looking 
only at low magnification.