Serotonin 2B receptor signaling is required for craniofacial and ocular morphogenesis in Xenopus

Serotonin (5-HT) is a neuromodulator that plays many roles in adult and embryonic life. Among the 5-HT receptors, 5-HT2B is one of the key mediators of 5-HT functions during development. We demonstrated that 5-HT2B modulates postmigratory skeletogenic cranial neural crest cell (NCC) behavior. 5-HT2B overexpression induced the formation of an ectopic visceral skeletal element and altered the dorsoventral patterning of the branchial arches. Loss-of-function experiments revealed that 5-HT2B signaling is necessary for jaw joint formation (Reisoli et al., 2010). Moreover, 5-HT2B morphants have defective eyes with the loss of the ventral optic fissure closure (coloboma). Interestingly, the 5-HT2B gene is expressed in periocular mesenchyme (POM), a key signaling center required for eye morphogenesis. It is composed by cranial NCC and cranial paraxial mesoderm derived cells. In 5-HT2B morphants the expression of key genes involved in POM development, such as Pitx2, FoxC1 and Raldh3 is affected. NCCs remain gathered in the ventral part of the eye failing to conclude their migration within the optic fissure. POM also participate to the morphogenesis of the periocular muscles that result not properly organized in 5-HT2B morphants. These results contribute to the understanding of the interactive networks of patterning signals that are involved in the development of the vertebrate craniofacial and ocular structures. Reisoli E., et al., 2010 Development 137(17): 2927-37.