摘要: During development and homeostasis, individual cells must divide, differentiate, migrate, adapt to the environment, or die at appropriate times places. A key deciphering molecular mechanisms by which make these decisions is characterize regulation function of proteins that regulate important changes in gene expression. The family transcription factors contain basic-helix-loop-helix PAS motifs has been shown control many critical developmental events mediate responses certain environmental stimuli. For example, bHLH-PAS play central roles specific neural tissues vasculature, they are core components clock govern circadian rhythms. also integral pathways sense respond hypoxia (low oxygen) xenobiotics (1). Phylogenetic analyses suggest genes arose early animal development, some cases, functions largely conserved across phyla. This review describes a genetic model organism, nematode Caenorhabditis elegans.