Worm Breeder's Gazette 9(2): 77

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.

An Embryonic Lethal Mutation Affecting Pharynx Development

H. Schnabel and R. Schnabel

sot-1 (e2123) ('sore-throat') is a zygotic embryonic lethal mutation 
preventing differentiation of the pharynx.  At 25 C, e2123 embryos 
arrest at the pretzel stage and fail to form a functional pharynx.  
Pharyngeal cells are formed and are surrounded by a basement membrane. 
The only defects outside of the pharynx detected by Nomarski 
microscopy are lumps and dumpiness in the head, possibly caused by 
improper pharyngeal differentiation.  Some mutant embryos hatch and 
die as L1's.  Immunofluorescence with monoclonal antibodies shows that 
pharyngeal differentiation arrests at the plum to twofold stage (e.g.  
no expression of pharynx-specific myosin), whereas differentiation 
outside of the pharynx appears to proceed as in wild type embryos.  
sot-1 maps to a locus on LGIII between vab-7 and tra-1.  It is a 
zygotic embryonic lethal, completely penetrant at 20 C and 25 C, wild 
type at 15 C.  The ts period is near the end of proliferation/early 
morphogenesis in the embryo.  Further evidence for a pharynx-specific 
differentiation function comes from the phenotypes of e2123/eDf2 and 
e1855 embryos.  eDf2 is a large deficiency including sot-1.  e1855 (
obtained from J.  Hodgkin) fails to complement tra-1 and e2123 and is 
probably a small deficiency.  The phenotypes of both e2123/eDf2 and 
e1855 embryos are very similar to that of e2123, however, the 
phenotype of e1855 embryos is slightly less severe than that of e2123. 
Also, recombination was observed between e2123 and e1855.  This 
suggests either that e1855 has a breakpoint within sot-1, retaining 
some sot-1 activity, or that the failure of e1855 to complement e2123 
may be due to a position effect.  Attempts to obtain new alleles and 
to define the null phenotype are in progress.