Worm Breeder's Gazette 13(5): 52 (February 1, 1995)
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.
Fundamental Research Laboratories, NEC Corporation, Miyukigaoka, Tsukuba 305, Japan
During hermaphrodite development, the two distal tip cells (DTCs) located on the anterior and the posterior ends of the gonad primodium migrate and make the two U-shaped arms of the gonad in rotational symmetry; the anterior arm to the right and the posterior arm to the left of the intestine. Although the migration of DTCs is just more complicated than the other long range migrations, analysis of the DTC migrations is advantageous because the trajectories of the DTCs can be deduced from the shape of the gonad arms (1). I have isolated four recessive mutations in four different genes affecting the turning frequency of DTCs. DTCs normally turn twice when they change their migrating directions from along the ventral muscles to dorsalward and from dorsalward to along the dorsal muscles. However, DTCs in these mutations often make extra turns once or more after the apparently normal two turns. The extra turned arms usually run to the opposite direction along the unoccupied surface of the dorsal muscles. In addition to DTC, some embryonic (HSNs, CANs, ALMs, coelomocytes) and postembryonic migrations (QRpa and QLpa descendants, excretory canals) were observed in these mutants and summarized below. mig(kl O9) X: Both arms usually made extra turns more than twice; 98percent for anterior and 98percent for posterior. No penetrant abnormality was observed for other migrations. migfkl21) ?: Anterior arms often made one extra turn; 42percent for anterior and 15percent for posterior. No penetrant abnormality was observed for other migrations. mig(kl23) IV: Posterior arms often made one extra turn like kl21; 15percent for anterior and 32percent for posterior. Left embryonic coelomocytes were often positioned too anteriorly. mig(kl24) 11: Posterior arms often made one extra turn like kl21; 3percent for anterior and 35percent for posterior. QL migration was reversed and QRpa descendants (SDQ, AVM) were posteriorly misplaced. HSNs were often too posterior. The mutant often had a protruding vulva or none and was slightly uncoordinated. All of the mutations are likely to affect the turning programs of DTCs. It is interesting that the frequencies of extra turns for anterior (right) and posterior (left) arms are not always the same in spite of the symmetry of the arms. Similar observations are reported for dorsal migrations of DTCs in unc-5 and unc-62. There are three phenotypic classes, I) both arms are affected similarly (k109); 2) anterior or right arms are affected more frequently than posterior or left arms (k121); 3) posterior or left arms are affected more frequently than anterior or right arms (k123, kl24). Because no other migration defect was detected in kl09 and kl21, these genes may function specifically for the DTC migration. On the other hand, kl23 and kl24 showed some other migration defects. kl24 was very pleiotropic. So, these genes seem to define more general functions for cell migration and/or cell type specification. I am presently isolating more mutants with an extra turning phenotype too identify a group of genes responsible for this phenotype. 1. Hedgecock et al. (1987). Development 100, 365-382. (2). Hedgecock; et al. (1990). Neuron 2. 61-85.