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.

Mutations With Extra Turning Phenotype of DTCs.

Kiyoji Nishiwaki

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
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
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
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.