Worm Breeder's Gazette 6(1): 43
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The previous report by Ambros et. al. suggests that mutants altered in the genes lin-4 and lin-14 may have major alterations in changes that occur at post-embryonic molts. We report here a few preliminary observations concerning e912 and some speculations. Cox and Staprans (Newsletter vol 5, no. 2, p. 15) have found a number of major differences in the gel patterns of proteins extracted from L1, L4, adult and dauer cuticles. We have now examined extractable cuticle proteins from L2 and L3 juveniles and find they yield a pattern on SDS-PAGE indistinguishable from the L4. We have examined the extractable proteins from sexually mature e912 and find they give the L2-L3-L4 gel pattern. This result is consistent with the notion that e912 is arrested at the L1 stage since it is in the L1 stage that the L2 cuticle materials are synthesized. We have constructed double mutants containing e912 and several cuticle defective mutations that are phenotypically expressed only at the adult stage, a roller, rol-1 (e 91) and two blisters, bli-1(SC73) and bli-2 (e768) In none of these doubles is the cuticle defective phenotype expressed, e912 behaves as suppressor of these mutations, consistent with its neotenic phenotype. It seems to us conceivable that lin-4 and lin-14 are not, strictly speaking lineage genes but rather are genes that control switching from one post embryonic stage to another. It may be useful to think of postembryonic development as metamorpic rather than continuous,with molting being more concerned with metamorphic change than with growth. It is interesting (and fortunate) that while some major aspects of postembryonic development are modified (regulated?) by mutations in these two genes, others (sexual maturation, the molting cycle) appear little affected. We believe it is worth pointing out that in parasitic nematodes shift in habitat (eg. lung to gut) is coincident with molting and with major changes in behavior, nutrition, cuticle anatomy etc. While C. elegans may not be parasitic, many of its relatives are. It may have retained residual aspects (cuticle changes?) of a parasitic ancestor. We are now about to renew attempts to identify more Heterochronic mutations using stage specific cuticle mutants to aid in their detection.