Worm Breeder's Gazette 2(2): 15

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.

Genetic Control of Sexual Dimorphism in C. elegans

M. Klass

Gonadogenesis in C.  elegans provides an excellent system for the 
study of cellular differentiation.  In C.  elegans, male and 
hermaphrodite gonads develop from morphologically identical primordia. 
The small primordial gonad lies on the ventral side of the worm in 
the coelomic cavity and contains four nuclei at hatching.  In the 
hermaphrodite, the primordium develops into a double-armed gonad 
encased by a cellular sheath displaying two-fold rotational symmetry.  
The hermaphrodite gonad produces first sperm and then oocytes.  In the 
male, however, the primordium develops into an asymmetrical structure 
that lacks a cellular sheath and continuously produces sperm.  
A temperature-sensitive sex transformer mutant, tsB202 has been 
isolated (Devel.  Biol.  52:1-18).  tsB202 carries an autosomal 
recessive mutation in linkage group II that at restrictive temperature 
transforms an XX hermaphrodite into a phenotypic male, complete with a 
normal male gonad and vestigial external genitalia.  Proper 
manipulation of the temperature regimen causes the production of 
intersexes.  The transformed males and intersexes have been analyzed 
by electron microscopy and polyacrylamide gel electrophoresis.  By EM 
analysis the gonads of the transformed males produced at 25.5 C are 
essentially identical to N2 male gonads, showing no cellular sheath in 
either the distal or proximal arms, normal spermatogenesis, limited 
core region in the distal arm, and a vas deferens.  The gonads of the 
intersex forms predictably have characteristics of both male and 
hermaphrodite gonads depending upon the specific time of the 
temperature shift.  The tsB202 male intersex produced by 9 hrs at 25.5 
C followed by 80 hrs at 16 C has a male gonad with normal 
spermatogenesis and lacking a well-developed cellular sheath.  Yet 
this male gonad shows oocyte differentiation similar to the N2 
hermaphrodite.  These oocytes are never fertilized and accumulate 
large quantities of DNA, yolk, and membranous material characteristic 
of unfertilized eggs of N2 hermaphrodites.  The complementary 
hermaphrodite intersex, produced by 36 hrs at 16 C followed by 42 hrs 
at 25.5 C, has a hermaphrodite gonad with a cellular sheath similar to 
N2 hermaphrodites.  Germ cells of the hermaphrodite intersex undergo 
normal spermatogenesis but fail to undergo oogenesis and oocytes are 
never produced.  Sperm is overproduced (> 700 per arm) and a mature 
spermatheca does not form.
One dimensional polyacrylamide gel electrophoretic patterns obtained 
from tsB202 transformed males are identical to those obtained from N2 
males.  Four major protein bands specific to eggs and oocytes are not 
present in tsB202 transformed males, tsB202 hermaphrodite intersexes, 
or N2 males.  These four oocyte-specific bands are present in tsB202 
male intersexes as well as N2 hermaphrodites.
An EMS-induced revertant of tsB202 has been isolated and is 
currently being investigated.