Worm Breeder's Gazette 9(1): 72

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.

Mosaicism For Expression Of A Single-Copy Vitellogenin Gene In Intestines Of Triploid Intersexes

P. Schedin and W.B. Wood

We showed previously that vitellogenin gene transcripts can be 
easily detected in intestinal cells of hermaphrodites but not males, 
by in situ hybridization to dissected intestines using a cloned vit-5 
probe (from T.  Blumenthal), which cross-hybridizes to four other 
members of a multigene family in addition to vit-5.  Among triploid 
intersex animals (3A;2X plus a large X duplication), about twenty 
percent show mosaic intestines, with some cells that hybridize and 
some that do not.  The patterns of positive and negative cells are 
nonrandom and inconsistent with a lineage-related mechanism of 
intestinal-cell sex determination based on patterns predicted from the 
known E lineage.  Instead, all mosaics show eight to sixteen 
contiguous positive cells at the anterior end and negative cells 
throughout the remaining observable portion of the intestine, implying 
positional influences on the decision to express or not to express 
vitellogenin genes (Schedin and Wood, 1985 C.  elegans Meeting 
Abstracts, p. 102).  In some mosaic intestines the vit-5 hybridization 
level is not uniform in all positive cells, but shows a gradient of 
intensity, with anterior positive cells hybridizing more strongly than 
posterior positive cells.  The variable hybridization could be due to 
more individual members of the vit-5 gene family being expressed 
anteriorly, or to variable levels of expression for one or more 
members of the family.  Probes specific for individual family members 
are not available.  Therefore, to ask whether a single vitellogenin 
gene could show variable expression, we analyzed intestines of 
intersexes using a single-gene vit-6 probe (from T.  Blumenthal), 
which does not crosshybridize with the vit-5 gene family under our 
conditions.  We found that vit-6 expression shows patterns similar to 
those seen for expression of the vit-5 gene family.  Animals with 
mosaic intestines all show an anterior region of contiguous positive 
cells, and a posterior region of contiguous negative cells.  The 
hybridization sometimes appears uniform over the positive cells and 
sometimes shows the same sort of anterior-posterior gradient of 
intensity seen with the vit-5 probe.  We conclude that the level of 
expression of vit-6, a single-copy gene, can be variable in mosaic 
intestines.  To determine whether the vit genes are coordinately 
regulated in intersex mosaics, we are currently doing double labelling 
experiments with a biotin-labelled vit-5 probe and a 35S-labelled vit-
6 probe.