Worm Breeder's Gazette 14(1): 53 (October 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.

unc-40-GFP is expressed in cells undergo circumferentially- oriented migrations on the epidermis.

Shirley Chan1, Ming-Wan Su1, Hong Zheng1, Joe Culotti1, Ed Hedgecock2

1 S.Lunenfeld Res. Inst., Mt. Sinai Hospital, Toronto M5G 1X5
2 Biology, Johns Hopkins U., Baltimore, MD 21218 

          unc-40 is required to guide ventrally and dorsally-
     oriented cell and growth cone (GC) migrations in C. elegans.
     These migrations are oriented by graded expression of the UNC-
     6 path cue molecule along the D/V axis (1995 MTG ABS. p.15).
     unc-40 encodes an integral membrane receptor (1995 MTG ABS.
     p.16) related to the human protein DCC (deleted in colorectal
     cancer) and the chick neogenin gene, both of which are
     expressed in growing neurons. We have made transgenic animals
     that express GFP under the control of the unc-40 regulatory
     region to get some idea of where UNC-40 protein may be
     expressed in the nematode.
          The regulatory region used contains 0.7 kb of sequence 5'
     to the initiator methionine in exon 1, plus exons 1-3, introns
     1-2 and part of intron 3 (total 3.5 kb). The 0.7 kb of
     sequence 5' to the initiator codon alone does not appear to
     drive full expression of GFP suggesting that exons 1-3 and/or
     introns 1-3 contain regulatory elements essential for full
     expression.
          The unc-40-GFP transgenic animals express in all neurons
     whose axons are known to be misguided in unc-40 mutants and
     in a number of mesodermal cells whose migrations are affected.
     Expression has been observed in all motorneurons in the
     ventral cord; most intensely in those that grow to the dorsal
     side.  Expression also occurs in a number of sensory neurons
     including several that extend pioneer axons ventrally on the
     epidermis. These include AVM, PVM, HSN, PVD,PHA, PHB (and
     probably ADE and PDE), as well as 2-3 unidentified lumbar
     neurons. The hermaphrodite distal tip cells also stain very
     early in their first phase longitudinal migration, well before
     unc-5-GFP expression occurs (see abstract by Su et al., this
     issue).  Additional glowing cells include CANs, at least one
     neuron in the pharynx, at least one pair of labial neurons
     (IL1, IL2, OLQ and/or OLL), at least one pair of monopolar
     ring interneurons (possibly RIM, RIC, or AVB), phasmid and
     postdeirid sensillar support cells (sheath and socket cells),
     and several yet unidentified neurons in the head and tail. The
     excretory cell also stains in many animals and some body
     muscles stain very faintly and variably. Vulval muscles stain
     intensely and reproducibly.
          The pattern of neuronal staining observed overlaps so
     thoroughly with the spectrum of cells affected by unc-40
     mutations that it is tempting to speculate that it reflects
     the real pattern of unc-40 expression. If this is true, it
     would imply that UNC-40 is a receptor expressed on cells or
     pioneer axon GCs that migrate dorsally or ventrally on the
     epidermis. It may act with UNC-5 receptor in dorsally
     migrating cells and GCs to mediate avoidance responses to
     ventral concentrations of UNC-6 and in ventrally migrating
     cells and GCs to mediate attractive responses to UNC-6.