Pattern Formation in Caenorhabditis Elegans

Abstract

This chapter discusses pattern formation in Caenorhabditis elegans ( C. elegans ). C. elegans has two sexes, hermaphrodites and males. Hermaphrodites produce both oocytes and sperm and can reproduce by internal self-fertilization. Alternatively, males can fertilize hermaphrodites. The formation of any pattern specified by cell interactions involves the differentiation of two or more cells with equal developmental potentials. The formation of several developmental patterns can be events of sequential induction and cell interactions. For example, lateral signaling between two gonad precursor cells determines the anchor cell; the anchor cell then induces vulva1 formation; and the formation of the vulva then in turn induces several other developmental events including the branching of ventral cord motor neurons. The gonad of a C. elegans hermaphrodite or male starts to develop at the L1 larval stage from a gonadal primordium. The somatic gonad develops throughout the larval stages; the germ line continues to divide after the animals enter the adult stage. Cell interactions play important roles in the development of both the somatic gonad and germ line. Vulval pattern formation is proposed to be controlled by both inductive and lateral cell signals. An inductive signal from the anchor cell (AC) in the gonad to the ventral hypodermis controls the binary decision of vulval precursor cells (VPCs) between vulval cell types and the hypodermal cell type. Lateral signaling among vulval precursor cells controls the binary decision of the VPCs between two different vulval precursor cell types.