RESUMO
OBJECTIVE: F-spondin is part of a group of evolutionarily conserved extracellular matrix proteins in vertebrates. It is highly expressed in the embryonic floor plate, and it can bind to the ECM and promote neuronal outgrowth. A characterization of F-spondin expression patterns in the adult zebrafish brain was previously reported by our group. However, given its importance during development, we aimed to obtain a detailed description of green fluorescent protein (GFP) expression driven by the spon1b promotor, in the developing zebrafish brain of the transgenic Tg(spon1b:GFP) line, using light sheet fluorescence microscopy (LSFM). RESULTS: Images obtained in live embryos from 22 to 96 h post fertilization confirmed our earlier reports on the presence of spon1b:GFP expressing cells in the telencephalon and diencephalon (olfactory bulbs, habenula, optic tectum, nuclei of the medial longitudinal fasciculus), and revealed new spon1b:GFP populations in the pituitary anlage, dorso-rostral cluster, and ventro-rostral cluster. LSFM made it possible to follow the dynamics of cellular migration patterns during development. CONCLUSIONS: spon1b:GFP larval expression patterns starts in early development in specific neuronal structures of the developing brain associated with sensory-motor modulation. LSFM evaluation of the transgenic Tg(spon1b:GFP) line provides an effective approach to characterize GFP expression patterns in vivo.
Assuntos
Encéfalo/embriologia , Encéfalo/metabolismo , Proteínas da Matriz Extracelular/genética , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Fluorescência Verde/genética , Proteínas de Peixe-Zebra/genética , Peixe-Zebra/embriologia , Peixe-Zebra/crescimento & desenvolvimento , Animais , Embrião não Mamífero/metabolismo , Proteínas da Matriz Extracelular/metabolismo , Fertilização , Proteínas de Fluorescência Verde/metabolismo , Habenula/embriologia , Habenula/metabolismo , Proteínas de Peixe-Zebra/metabolismoRESUMO
Although progress has been made in resolving the genetic pathways that specify neuronal asymmetries in the brain, little is known about genes that mediate the development of structural asymmetries between neurons on left and right. In this study, we identify daam1a as an asymmetric component of the signalling pathways leading to asymmetric morphogenesis of the habenulae in zebrafish. Daam1a is a member of the Formin family of actin-binding proteins and the extent of Daam1a expression in habenular neuron dendrites mirrors the asymmetric growth of habenular neuropil between left and right. Local loss and gain of Daam1a function affects neither cell number nor subtype organisation but leads to a decrease or increase of neuropil, respectively. Daam1a therefore plays a key role in the asymmetric growth of habenular neuropil downstream of the pathways that specify asymmetric cellular domains in the habenulae. In addition, Daam1a mediates the development of habenular efferent connectivity as local loss and gain of Daam1a function impairs or enhances, respectively, the growth of habenular neuron terminals in the interpeduncular nucleus. Abrogation of Daam1a disrupts the growth of both dendritic and axonal processes and results in disorganised filamentous actin and α-tubulin. Our results indicate that Daam1a plays a key role in asymmetric habenular morphogenesis mediating the growth of dendritic and axonal processes in dorsal habenular neurons.