GENETICS OF MUSCLE PATTERN FORMATION IN C. ELEGANS

Abstract

As part of a general study of genes specifying a pattern of muscle attachments, I have identified and genetically characterised two genes, mup-1 and mup-2. The body wall muscles of early stage mup-1 embryos have a wild-type myofilament pattern but may extend ectopic processes. Later in embryogenesis, some body wall muscles detach from the epidermis. Genetic analysis suggests that mup-1 has both a maternal and a zygotic component and is not required for postembryonic muscle growth and attachment. mup-1 mutants are suppressed by mutations in several genes which encode extracellular matrix components. I propose that mup-1 may encode a cell surface/extracellular matrix molecule required both for the positioning of body wall muscle attachments in early embryogenesis and the subsequent maintenance of these attachments to the epidermis until after cuticle synthesis. The only existing mup-2 allele is a temperature sensitive allele and has a terminal muscle phenotype similar to that of mup-1 mutants, as well as a gonad phenotype. The temperature sensitive period of the muscle phenotype suggests that the mup-2 gene is required in the late three-quarters of the threefold stage during embryonic development. mup-2 was cloned by microinjecting cosmids around its locus to obtain transformation rescue. Further delineation by transformation rescue of subclones has narrowed down the smallest rescuing genomic region to 8.6kb. The translated product of a cDNA that is mapped within this rescuing fragment shows homology to the troponin T (TnT) protein. The putative mup-2 product is therefore a TnT-like protein.