Worm Breeder's Gazette 1(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.

Studies on the Structures of the Ventral Cords of Developmental Mutants

J.G. White, E. Southgate, M. Anness, J.E. Sulston

We have been studying the ventral cords of two mutants which fail at 
different stages in the period of post-embryonic development which 
occurs just prior to the L1 moult.  In one mutant, E1348 isolated by J.
E.  Sulston, the precursors, which would normally give rise to 5 
neurones and one hypodermal cell, do not divide while in the second, 
E1414, isolated by H. R.  Horvitz, only the last rounds of division 
are variably blocked.
In both these mutants the structure and organization of the juvenile 
set of motor neurones is the same as that in the wild-type adults.  
The 'precursor' cells in H86 generally turn out to be motor neurones, 
although one case has been seen where one had become a hypodermal cell 
which had fused with the hypodermal syncytium.  The neurone-like cells 
have many more branches than normal motor neurones and show some of 
the characteristics of the individual neurones that would normally be 
produced from these cells, such as the characteristic dendritic spines 
of the class D motor neurones.
In the case of E1414, some of the neuroblasts that would normally 
give rise to a type A and a B or an AS and a VD motor neurone fail in 
this terminal division.  These cells take on the characteristics of 
their posterior daughters i.e.  a class B and a class VD, both in 
terms of their morphology and synaptic input.  Those neuroblasts that 
divide normally produce normal looking progeny cells.