Gain of affinity point mutation in the serotonin receptor gene 5‐HT 2Dro accelerates germband extension movements during Drosophila gastrulation

Serotonin (5‐HT) not only works as a neurotransmitter in the nervous system, but also as a morphogenetic factor during early embryogenesis. In Drosophila , a previous report showed that embryos that lack the 5‐HT 2Dro receptor locus, display abnormal gastrulation movements. In this work, we screened for point mutations in the 5‐HT 2Dro receptor gene. We identified one point mutation that generates a gain of serotonin affinity for the receptor and affects germband extension: 5‐HT 2Dro C1644 . Embryos homozygous for this point mutation display a fourfold increase in the maximal speed of ectodermal cell movements during the rapid phase of germband extension. Homozygous 5‐HT 2Dro C1644 embryos present a cuticular phenotype, including a total lack of denticle belt. Identification of this gain of function mutation shows the participation of serotonin in the regulation of the cell speed movements during the germband extension and suggests a role of serotonin in the regulation of cuticular formation during early embryogenesis. Developmental Dynamics 236:991–999, 2007. © 2007 Wiley‐Liss, Inc.