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.
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, 639-648]. 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 follows: 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.