MyoD and the specification of muscle and non-muscle fates during postembryonic development of the C. elegans mesoderm.
Basic-helix-loop helix factors of the myoD/myf5/ myogenin/MRF4 family have been implicated in acquisition and elaboration of muscle cell fates. Here we describe both myogenic and non-myogenic roles for the Caenorhabditis elegans member of this family (CeMyoD) in postembryonic mesodermal patterning. The postembryonic mesodermal lineage in C. elegans provides a paradigm for many of the issues in mesodermal fate specification: a single mesoblast ('M') divides to generate 14 striated muscles, 16 non-striated muscles, and two non-muscle cells. To study CeMyoD function in the M lineage, we needed to circumvent an embryonic requirement for the protein. Two approaches were used: (1) isolation of mutants that decrease CeMyoD levels while retaining viability, and (2) analysis of genetic mosaics that had lost CeMyoD in the M lineage. With either manipulation, we observed a series of cell-fate transformations affecting a subset of both striated muscles and non-muscle cells. In place of these normal fates, the affected lineages produced a number of myoblast-like cells that initially failed to differentiate, instead swelling to acquire a resemblance to sex myoblasts (M-lineage-derived precursors to non-striated uterine and vulval muscles). Like normal sex myoblasts, the ectopic myoblast-like cells were capable of migration and proliferation followed by differentiation of progeny cells into vulval and uterine muscle. Our results demonstrate a cell-intrinsic contribution of CeMyoD to specification of both non-muscle and muscle fates.
Harfe
B D
BD
Carnegie Institution of Washington, Department of Embryology, Baltimore, MD 21210, USA.
Branda
C S
CS
Krause
M
M
Stern
M J
MJ
Fire
A
A
D000818:Animals; D019521:Body Patterning; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000235:genetics; D002454:Cell Differentiation; D003433:Crosses, Genetic; D012734:Disorders of Sex Development; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000502:physiology; D004627:Embryonic Induction; D005260:Female; D018257:Helix-Loop-Helix Motifs; D008297:Male; D008648:Mesoderm / Q000166:cytology / Q000502:physiology*; D009132:Muscles / Q000196:embryology*; D017570:MyoD Protein / Q000096:biosynthesis*
D017570:MyoD Protein