A BMP homolog acts as a dose-dependent regulator of body size and male tail patterning in Caenorhabditis elegans

We cloned the dbl-1 gene, a C. elegans homolog of Drosophila decapentaptegi c and vertebrate BMP genes. Loss-of-function mutations in dbl-1 cause reduc ed body size and defective male copulatory structures. Conversely, dbl-1 ov erexpression causes markedly increased body size and partly complementary m ale tail phenotypes, indicating that DBL-1 acts as a dose-dependent regulat or of these processes. Evidence from genetic interactions indicates that th ese effects are mediated by a Smad signaling pathway, for which DBL-1 is a previously unidentified ligand, Our study of the dbl-1 expression pattern s uggests a role for neuronal cells in global size regulation as well as male tail patterning.