Worm Breeder's Gazette 8(3): 25
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.
The single ace-1+ gene present on a free duplication in an otherwise homozygous ace-2 I;ace-1 X genetic background is responsible for coordinated animal movement and acetylcholinesterase activity in the regions of the nerve ring and ventral and dorsal nerve cords. We have found that gentle squashing of these animals followed by freezing in liquid nitrogen, popping off of the coverslip and then fixing and staining according to Culotti et al.(1981 Genetics 97: 281) gives reliable staining of both cords and the ring. We have used animals of genotype ace-2 I; unc-93 III; unc-3 sup-10 f) (where the duplication carries the wild-type alleles of all four X linked markers) to select specifically for genetic mosaics in which mnDp14 was lost at P1. These animals are non-Unc-3 and non-Daf (normal FITC staining) because the duplication is retained in the AB lineage; they are non-Unc-93 in movement and egg laying because all muscle cells but one lack sup-10+; and all of their progeny are Unc-3 because the duplication is not present in the germ line. They also show the Ace-Unc phenotype and the absence of histochemical staining for acetylcholinesterase characteristic of the homozygous ace-2; This indicates that one or more descendants of P1 are primarily responsible for both properties of ace-1+ that we have followed. We have used animals of genotype ace-2 I; unc-3 ace-1 X; mnDp14(X;f) to select for Ace-Unc non-Unc- 3 progeny produced through somatic duplication loss. (This method precludes the possibility of detecting losses occurring at either AB or ABp because duplication loss by either of these cells generates an Unc-3 phenotype, which is epistatic to Ace-Unc.) Ten were found and all were missing the duplication from their germ lines. This result indicates that in order to produce an Ace-Unc phenotype by a single event of duplication loss, the loss must usually occur in a germ line precursor cell, i.e., P1-P4. We have also looked at the consequences of losing ace-1+ from cells of the AB lineage and obtained results consistent with the above experiments. First, we were unable to find Ace-Unc progeny of ace-2 I; daf-6 odites that had retained the duplication in their germ lines. Such animals should have been found if duplication loss at AB, for example, gave an Ace-Unc phenotype. We have also used the daf-6 marker to select specifically for loss of the duplication at either ABp or AB in ace-2; ace-1; The results showed that an animal in which ace-1+ is missing from all descendants of ABp (which is precursor to 74 of 75 cord motor neurons) has normal movement and normal enzyme activity in the ring and cords. When the above results are considered in light of the known cell lineages, it is difficult to escape the conclusion that the effects of ace-1+ on coordinated movement and acetylcholinesterase appearance in these animals are very likely due, at least primarily, to gene expression in muscle cells. Since it is likely that ace-1 is a structural gene for the enzyme (Johnson et al. 1981 Genetics 97: 261), the obvious suggestion is that the enzyme is synthesized by the muscle cells and is then localized in the regions of the muscle arms that make neuromuscular junctions (which are in the nerve ring and the cords).