Dynamic expression of the osmosensory channel trpv4 in multiple developing organs in zebrafish.

Transient receptor potential channels function in a wide spectrum of tissues and transduce sensory stimuli. The vanilloid (capsaicin) channel TRPV4 is sensitive to osmotic changes and plays a central role in osmoregulatory responses in a variety of organisms. We cloned a zebrafish trpv4 cDNA and assayed its expression during embryogenesis. trpv4 is expressed as maternal mRNA in 4-cell embryos and later zygotic expression is first observed in the forming notochord at the one somite stage. Notochord expression persists to 24 hpf when broad expression in the brain is observed. At 32 hpf trpv4 expression is observed in the endocardium, restricted primarily to the ventricular endothelium. Low level expression of trpv4 is also seen from 32-48 hpf in the pronephric kidney with strongest expression in the most distal nephron segment and in the cloaca. Expression is also observed in lateral line organs starting at 32 hpf, primarily in the hair cells. At 72 hpf, expression of trpv4 in heart, kidney, brain, and lateral line organs persists while expression in the notochord is down-regulated.