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.
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.