Worm Breeder's Gazette 15(1): 71 (October 1, 1997)

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.

Characterization of duf-1: C. elegans first Hypofusion Mutant.

Tammar Gattegno, Benjamin Podbilewicz

Department of Biology, Technion-Israel Institute of Technology Haifa 32000, Israel.

We are interested in mechanisms of cell adhesion and cell fusion. Cell
fusion in humans occurs during fertilization and during the development
of  multinucleate cells that are contained in bones, muscles and
placenta. In C. elegans  there are cell fusions during the formation of
the vulva, pharynx, uterus, excretory gland and in the hypodermis.
There are 46 multinucleate cells (1) of which hyp7 is the largest (133
nuclei).Hpy 7 is part of the hypodermal envelope that surround the
adult worm. In a screen for mutations that are affected in the process
of cell fusion many mutants were found and analyzed. The mutations were
sorted into two main groups: hyperfusion and disordered hypodermis (1).
No mutants with fewer fusions in the hypodermis were identified
        duf-1(zu316cs) is a dorsal unfused zygotic lethal mutation that
was isolated in a screen for mutants affected in the process of
elongation (2). The phenotype was analyzed by immunofluoresence using
the MH27 antibody. The MH27 protein is expressed in the adherens
junctions at the apical domain of the hypodermis and it  enable us to
follow the fusions between hypodermal cells.
        After outcrossing we found that zu316cs  is a cold sensitive
mutation, at 15!C embryonic elongation arrests between 1.5 to 2 fold
with fewer fusions in the dorsal hypodermis (hyp6 and hyp7) compared to
the wild type and the tail is twisted (3).  At 25!C some embryos arrest
at 1.5 to 2 fold with fewer dorsal fusions, most embryos arrest at 3
fold and many hatch with normally fused hyp7 and variable posterior
defects. duf-1 was mapped to the X chromosome, 10 centiM away from
        Viral induced cell fusion and invasion by enveloped viruses are
cold-sensitive processes. Many cold-sensitive mutations in different
fusogenic viral proteins have been analyzed. Our characterization of
duf-1(zu316) is consistent with the idea that membrane fusion is a
cold-sensitive process.

The future plans are to further characterize the phenotypes at the
permissive and restrictive temperatures, find the cold sensitive period
and to continue the mapping.

1. Podbilewicz B.(1997) Worm Meeting Abstract, p.300
2. Costa M. and Priess J.(1995) Worm Meeting Abstract, p.165
3. Gattegno T. and Podbilewicz B.(1997) Worm Meeting Abstract, p.546
We thank Mike Costa and Jim Priess for sending zu316 to us.