Worm Breeder's Gazette 14(1): 37 (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.

Characterization of the ceh-24 vulval enhancer and m8 UAS

Brian Harfe1,2, Andy Fire1

1 Carnegie Institution of Washington, Department of Embryology
2 Biology Graduate Program, The Johns Hopkins University

     We have been studying the regulation of a gene, ceh-24, which encodes
a novel homeodomain of the NK2 class. We are particularly interested in
the ceh-24 expression pattern, since lacZ and gfp fusion experiments
indicate that the promoter acts in specific subsets of muscle cells:
muscle m8 of the pharynx and the vulval muscles (expression is also seen
in 9-10 neurons in the head). We hope that precise identification of the
signals responsible for expression in different muscle types will aid us
in the identification of the mechanism responsible for setting muscle type
during determination and differentiation.
     Translational fusions containing 2.85 kb of upstream ceh-24 sequence
are sufficient for the complete expression pattern described above. The
sequences responsible for both vulval and m8 reporter gene expression have
been tentatively identified. The vulval signal has been narrowed down to
a 83 bp fragment located 2 kb upstream of the ceh-24 start codon. This 83
bp fragment can activate a #198#pes-10::lacZ  construct in vulval muscle
(starting vector pPD95.18 - Fire Lab Vector Kit 1995). This occurs
independent of any other ceh-24 sequence and works in either orientation.
Deletion of this sequence in a complete ceh-24::gfp construct results in
total loss of vulval gfp expression. This 83 bp fragment contains two
identical E-boxes (CATATG) that have diverged from known E-boxes. E-boxes
serve as binding sites for the helix-loop-helix (HLH) family of
transcription factors. However, the C. elegans  HLH-1 protein is not
expressed in vulval muscle cells.
      The sequence responsible for m8 reporter expression has been
narrowed down to a 270 bp fragment located 1.8 kb upstream of the ceh-24
start codon. This fragment can also work independent of any other ceh-24
sequence [assayed in a #198#myo-2 promoter construct (pPD95.62 - Fire Lab
Vector Kit 1995)].