Worm Breeder's Gazette 9(1): 71

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.

Suppression of dpy-22 Male Inviability By X Duplications

W.B. Wood

XO males carrying the dpy-22(e652) X mutation generally do not 
survive to adulthood; those that do are small and sickly.  We have 
postulated that the low viability is due to apparent under-expression 
of the X chromosome caused by this mutation (Meneely and Wood, 1985 C. 
elegans Meeting Abstracts, p.  90; Meneely et al., in preparation).  
Presence of X duplications generally appears to increase overall X 
expression (Meneely and Wood, 1983, Genetics 106:29; Meneely, this 
issue).  To determine how these two effects interact, we have begun 
testing the viability of dpy-22 XO males that carry X duplications 
derived from either the maternal or the paternal parent.  In N2(male) 
x dpy-22(hermaphrodite) crosses, the progeny male ratio (PMR: 
identifiable Dpy progeny males to total outcross progeny) ranges from 
about 10% to 30%.  For the initial duplication experiments we used 
mnDp25 (X;I), a duplication of about 25% of the X including the unc-3 
locus but not the dpy-22 locus.  The cross mnDp25/+;unc-3/0(male) x 
dpy-22 rodite) gave  PMR of 16% +- 5% (39/244 
in two experiments), compared to 19% +- 6% (31/165) in the control 
cross N2(male) x dpy-22 maphrodite).  Therefore, 
introduction of this duplication paternally has no significant effect. 
To test the effect of introducing it maternally, we crossed N2(male) 
x mnDp25;unc-20 unc-3(hermaphrodite) (rather than 
the simpler mnDp25;dpy-22 maphrodite), which turned 
out to have unexpectedly low viability).  We obtained a PMR of 46% +- 
5% (158/341), compared to 5% +- 2% (21/389) in the control cross N2(
male) x unc-20 unc-3(hermaphrodite).  Similar 
results have been obtained in preliminary experiments with mnDp8 (-15% 
of X) and mnDp9 (-25% of X), neither of which include the dpy-22 locus.
Further experiments with these and additional duplications are in 
progress.  So far it appears that X duplications not including the dpy-
22 locus can suppress the inviability of dpy-22 XO males if supplied 
from the maternal parent, but not if supplied from the paternal parent,
consistent with a maternal effect of X duplications on early X-
chromosome expression in the embryo.