   Sci. Signal., 7 April 2009 Vol. 2, Issue 65, p. ec120 [DOI:
10.1126/scisignal.265ec120]   Nuclear Receptors Translating
Hormone Cues Tissue-Specifically  Annalisa M. VanHook  Science
Signaling, AAAS, Washington, DC 20005, USA  In insects and
nematodes, global hormone signals coordinate tissue-specific
morphological and physiological changes to affect developmental
transitions such as progression from one larval stage to
another. In the nematode Caenorhabditis elegans, mutations in
genes encoding microRNAs (miRNAs) often yield heterochronic
phenotypes in which the developmental progression of specific
tissues fails. In the absence of the steroid hormone {Delta}4-DA
(dafachronic acid), animals enter diapause at the third larval
stage (L3), but in the absence of the {Delta}4-DA receptor
DAF-12, animals show heterochronic phenotype in which there are
extra hypodermal seam cells, specialized epithelial cells that
exhibit stage-specific patterns of proliferation, due to
repetition of the L1 cell division program