Worm Breeder's Gazette 8(3): 28

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.

An unc-22 Mutant With Temperature-Dependent Paralysis Phenotype

S.L. Wilson, L. Jacobson

The unc-52 allele su250 was described by Mackenzie et al.  [Cell 
15:751-762 (1978)] as a derivative of the e669 allele which, when 
homozygous, produced only a mildly uncoordinated phenotype as compared 
with the total paralysis produced by allele e669.  Both sarcomere 
organization and myosin heavy chain B accumulation in su250 
homozygotes were reported to be intermediate between wild-type and 
animals homozygous for more severe unc-52 alleles [Zengel & Epstein, 
PNAS 77:852-856 (1980)].
In our hands, strain HE250 unc-52(su250)II, obtained from CGC, shows 
a temperature-dependent paralyzed phenotype.  When grown at 16 C, the 
worms are nearly wild-type in size and movement rate, paralysis sets 
in late in adulthood (late egg-laying uncoordination sets in earlier, 
becoming complete paralysis around the beginning of egg-laying.  Worms 
grown at 20 C show an intermediate phenotype: partial paralysis is 
evident by early egg-laying and total paralysis occurs only late in 
Outcross results with HE250 indicate that the ts phenotype does not 
result from extragenic suppression.  Furthermore, when su250 is placed 
over an unc-52 null (e669) or a deficiency (jDf02), the animals are 
completely paralyzed even at 16 C.  We infer that a single copy of the 
su250 allele produces insufficient functional gene product to sustain 
Temperature shift experiments indicate that muscle function, rather 
than muscle morphogenesis alone, may be temperature-dependent.  Adult 
su250 homozygotes grown at 16 C become noticeably impaired within 8 
hrs.  after an upshift to 25 C, and totally paralyzed in less than 240 
hrs.  Conversely, larvae or adults downshifted from 25 C to 16 C 
retain whatever degree of motor impairment they had at the time of the 
downshift.  Thus, the phenotypic effect of high temperature is not 
We had previously reported (Worm Meetings, 1983) that unc-52 mutants 
are deficient in lysosomal cathepsin D.  Both enzyme activity and 
cathepsin D protein (measured by quantitative immunoblots) are near-
normal (50-75% of wt) in HE250 grown at 16 C, and are reduced (15-20% 
of wt) in paralyzed HE250 grown at 25 C.  This matter is still under 
investigation, but we believe now that the cathepsin D deficiency is 
an indirect effect of underfeeding in paralyzed animals (see Clokey & 
Jacobson, this issue).