Worm Breeder's Gazette 13(5): 28 (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.

The mua-1 Gene encodes a Zinc-finger Transcription Factor.

John Plenefisch and Edward Hedgecock

Johns Hopkins University, Baltimore MD 21218
      We have identified and characterized 12 genes, designated mua  (for
muscle attachment), that are required for maintaining muscle to cuticle
attachments (WBG 12.3).  Phenotypically, these mutations are reminiscent
of the muscular dystrophies of vertebrates.   One intriguing possibility
raised by our studies is that a tension-activated feedback system may
regulate muscle attachment formation in C. elegans.  We have previously
reported the cloning of mua-3  (WBG v13.3), which encodes a novel matrix
receptor protein, and have recently cloned mua-1.
     mua-1(rh160) causes a progressive detachment of the body-wall muscles
from the hypodermis and cuticle during larval growth.  About 20% of L1
larvae, 80% of L2 and over 90% of adults are affected.  The initial
detachment is often in either the head or midbody where intact muscle
bands pull away from a small region of their normal attachments. 
Subsequent larger regions of detachment and occasional breaks between
adjacent muscles within the bands are observed.  There is a ventral bias,
74% of the affected L2s (and 54% of adults) show only ventral detachment.
          rh160 animals often display additional defects, which are 
presumably secondary consequences of the body-wall muscle defect.  These
include aberrant gonadal morphologies, egg laying defects  due to loss of
vulval muscle attachments, and death due to eversion of the uterus through
the vulva.  However, in  rh160 homozygous adults with intact body-wall
muscles anal depressor muscle and pharyngeal musculature are unaffected. 
These observations suggest that mua-1 activity is specific to the body-
wall muscles. 
       We have cloned mua-1 by genetic mapping and microinjection rescue.
Rescuing activity is contained within an 8 kb SpeI to HindIII fragment of
cosmid F54H5.  Deleting DNA on either side of a KpnI site within the
fragment abolishes its activity.  We sequenced outwards from this KpnI
site, and aligned our sequence with the genomic sequence of F54H5 obtained
from the Sequencing Project.   The predicted MUA1 protein (246 aa)
comprises a potential N terminal activating region and three C terminal C2
H2 zinc-fingers. The KpnI site lies between the N terminal and the zinc-
finger portions of the protein.
       MUA1 is most closely related to human BTEB2 and mouse
erythroid Krupple-like factor (EKLF), members of sub-family of GC box
binding transcriptional regulators.  An analysis of the zinc-finger
domains of these proteins, and the closely related Sp1 and the Wilms-Tumor
WT1 , shows MUA1 to be more distantly related to BTEB2 and EKLF than they
are to each other. Both these proteins show organ specific expression
patterns but neither is expressed in muscle, raising the possibility that
a vertebrate MUA1 remains to be
identified. If such a gene exists, we predict mutations in it might result
in a dystrophic muscle phenotype.

Sp1 rat...................*I*HIQ**G*V*G*T***R**L*W*T**R**M*N*SY*GKR*T  
WT1 rat.............TSEKRPFM*A****N*R*F*L***QM*S*K*T****YQ*DFKD*ERR*S