Worm Breeder's Gazette 10(3): 104

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.

A Story of Two Kinky Mup's

Phuay Yee Goh and Thierry Bogaert

We looked for mutants in which the pattern of body wall muscles is 
disrupted and muscle cells are inappropriately attached (i.e.  in more 
than one quadrant).
600 F1 of mutagenized daf-2 (e1368) were shifted to 25 C and 
screened for the presence of larval lethals which do not move and 
contain bends and kinks with a constant position in the animal (a 
phenotype which Ed Hedgecock named 'mup').  Candidates were screened 
by polarized light microscopy for the presence of muscles which attach 
across quadrants.  The candidates picked had a normal pharynx and a 
smooth, non-blistered cuticle.  Three mutants were 
- e2346 is a ts larval lethal on the left arm of X close to and 
probably to the left of dpy-7.  It complements dpy-(e14),  & 
ev400), unc-18(e81) and dpy-8(e130).  It has not yet been complemented 
to unc-97 and unc-98.- e2347 is a non-ts larval lethal and is on the 
left arm of II.  It is not balanced by mnC1 and is not under mnDf30.- 
e2348 is a larval lethal allele of unc-15 (paramyosin).
Phenotypes of e2346 and 
e2346 and e2347 embryos hatch as curled up L1's with many muscles 
detached and some attached across quadrants.  Most die as L1 or L2.  
e2347 larvae are dpy.  Antibody staining with NE8/4C6.3 (a muscle 
specific antibody from the LMB) indicates that at the 1.25-1.5 fold 
stage of embryogenesis, when in wild type myoblasts are already 
arranged in quadrants, some muscles extend processes across quadrants 
and some cells are displaced from the quadrants of muscle cells.  In 
further elongated embryos more inappropriately attached and possibly 
detached muscles are observed.  These cells extend processes 
containing muscle filaments in many directions.  These ectopic 
processes contain contracting muscle filaments which have nice muscle 
attachments as seen on E.M.  sections of larvae (courtesy N.  Thompson)
.  In three fold stage embryos the arrangement of body wall muscles 
becomes very disorganized.  In e2346 the arrangement of overlying 
hypodermal cells is normal as seen by the anti-desmosome antibody MH27 
(courtesy of Francis & Waterston) and an anti-seam antibody (courtesy 
of H.  & R.  Schnabel).
At 15 C e2346 is viable but most hermaphrodites are sterile or 
produce only a few eggs (males are quite fertile).  e2346 embryos 
shifted from 15 C to 25 C before the 2.5 fold stage invariably develop 
into mup L1's.  Later embryos have not yet been shifted.  This 
together with the fact that ectopic muscle processes are already 
observed at the 1.5 fold stage indicates that e2346 may be required 
throughout morphogenesis.  A more detailed analysis of the temperature 
sensitive period of e2346 is in progress.  L2's shifted to 25 C 
invariably develop into sterile (non unc) hermaphrodites.  At the 
junction of the spermatheca and oviduct the spermatocytes and oocytes 
are extruded into the pseudocoelomic cavity.  The vulva, uterus and 
oviduct appear normal.  These sterile hermaphrodites produce only a 
few oocytes.
e2347 is suppressed by dpy 2, dpy-10 and dpy-11:e2347/mnC1(dpy-10 
unc-52) produced some dpy's (F1) which gave offspring consisting 
mainly of mup's, partially suppressed but fertile dpy's with one or 
two kinks in the body and some dpy's (F2) which have normal body wall 
muscles.  These F2 dpy's were e2347/e2347 (determined by outcrossing 
to wt males and checking for segregation of mnC1).  The suppressed dpy 
F2 daughters gave only mup offspring (F3).  e2347 dpy-10 / e2347 dpy-
10 are strong dpy's or partially suppressed mup's.  The dominant 
suppression by mnC1 therefore is likely to be due to the maternal 
product of the dpy-10 mutation on mnC1.  We are now determining the 
genotype of F1 dpy's (e2347/e2347 or e2347 mnC1/ e2347 ) to find out 
whether the F2's are suppressed by dpy-10 product from the parent or 
Dpy-11(e224) also suppresses e2347 to give a viable strain.  About 
10% of the offspring of e2347;e224 are fertile piggy dpy's but most 
are mup's suppressed to different extents and die as later stage 
larvae than e2347/e2347.  The (partially) suppressed dpy e2347 have 
muscle filaments crossing quadrants and muscle cells attaching nicely 
in both quadrants.  Some muscles have ragged edges.  We do not know 
whether there is a dominant or maternal component to the suppression 
of dpy-11.  e2347 dpy-2 (e8) / e2347 dpy-2 are (like e2347 dpy-10) 
strong dpy's or partially suppressed mup's but dpy-2 rescues a higher 
proportion of mup's than dpy-10.  Dpy-5(e61) does not suppress e2347, 
indicating that not all dpy's suppress e2347.
We have isolated two mutants e2346 and e2347 required for 
appropriate body wall muscle development.  The mutations appear not to 
affect the pharynx nor the ultrastructure of the muscle filaments (
from EM sections, courtesy N.  Thomson).  The observation of 
inappropriately placed myoblasts and myoblasts sending processes in 
several directions in early embryos (1.25-1.5 fold) of e2346 and e2347 
suggests an early function of these genes in the development (possibly 
attachment) of body wall muscles.  The phenotypes of myo-3 (Bob 
Waterston, WBG, 9(2), 30) and e2348, a lethal allele of unc-15 
indicate that the inappropriate attachment or detachment of body wall 
muscles could also be due to a failure to lay down appropriate (or 
appropriately patterned) muscle filaments in the body wall muscles.  
The suppression of e2347 by several dpy's which are mutations of genes 
of the collagen family are known to suppress various dpy's, bli's, 
rol's, or sqt's which are also collagen genes (Schuyler et al.  WBG 10(
1), 23; Cox.  et al., Genetics, 95:317-339), may indicate a basement 
membrane/cuticle defect in e2347.
A more detailed phenotypic analysis and further mapping of e2346 and 
e2347 are in progress.