Worm Breeder's Gazette 10(2): 127

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.

Reconstruction of Nervous System of Another unc-13 Mutant

I. Maruyama and L. Nawrocki

As previously reported, we have found that in unc-13(e450) the 
largest pair of interneurons in the ventral cord, AVAL and AVAR, make 
wrong gap junctions to the excitatory motoneurons of the classes VB 
and DB as a major lesion [WBG (Vol.  9, No.  3)].  In this report, we 
describe the results of another mutant, unc-13(e1091) which is also an 
amber mutant allele and is located about 0.0004 map units to the left 
of e450 allele on the genetic map [Rose & Baillie,(1980) Genetics, 96, 
Our reconstruction started from just VA2 cell body, which is the 
most posterior cell body in RVG, and continued to include one repeat 
of motoneurons in the ventral cord.  The lesions we uncovered in the 
region were as 
1) VD3 cell body shifted further posteriorly beyond DB3 and DA2 cell 
bodies, and had gap junctions to VD4 neuron.  This is consistent with 
the result in e450 allele.
2) AS2 cell had neither axon nor commissure.  This was not seen in 
e450 allele.
The major lesions that we found in e450 allele, that is wrong gap 
junctions between AVA interneurons and B class motoneurons, were not 
found in e1091 allele.  Taken together, the unc-13 gene is not 
specifically relevant to the neural connectivity.  It may even 
dramatically affect nervous system development throughout the body 
because in the previous reconstruction of e450, the position of cell 
bodies in RVG shifted further down to the ventral cord and were rather 
messy although we have not identified all of the cells in the region.  
Furthermore, some, not all, muscle cells show a bizarre filament 
orientation.  The direction of filament in one cell is not parallel to 
that in the next-door cell.  This may also be the result of unc-13 
mutation, or may be due to some other reasons like hypercontraction 
and so on.  In order to elucidate the primary function of unc-13 gene, 
it is important to identify the cell(s) expressing unc-13 gene product.