The C. elegans gene lin-9,which acts in an Rb-related pathway, is required for gonadal sheath cell development and encodes a novel protein.

The Caenorhabditis elegans gene lin-9 functions in an Rb-related pathway that acts antagonistically to a receptor tyrosine kinase/Ras signal transduction pathway controlling vulval induction. We show that lin-9 is also required for the development of the sheath cells in the hermaphrodite gonad and for the development of the male spicule, rays and gonad. lin-9 is transcribed as two alternatively spliced 2.4kb messages, which use two distinct polyadenylation sites and are SL1 trans-spliced. The conceptual translation of lin-9 cDNA sequences predicts proteins of 642 and 644 amino acids with a significant similarity to predicted Drosophila and vertebrate proteins. We suggest that lin-9 is the founding member of a new protein family that functions in Rb-related pathways in many species.