The zebrafish homologue of the ret receptor and its pattern of expression during embryogenesis

Abstract

The c-ret proto-oncogene, a member of the receptor tyrosine kinase gene superfamily, plays a critical role in the development of the excretory system and the enteric and autonomic nervous systems of mammalian embryos. To study the potential function of the c-ret locus in lower vertebrates, we have isolated its zebra®sh homologue, ret1 and established its expression pattern during embryogenesis. Ret1 mRNA ®rst appears during early somitogenesis in the presumptive brain, spinal cord and excretory system. Within the CNS, expression of ret1 is detected in primary motor and sensory (Rohon ± Beard) neurons. Ret1 transcripts are also expressed in subsets of neural crest cells and cranial ganglia as well as in the enteric nervous system. In the excretory system, expression is detected in the developing nephric duct and the pronephros. Our ®ndings reveal a remarkable similarity in the expression pattern of c-ret between higher and lower vertebrates, suggesting that the function of this locus has been conserved throughout vertebrate evolution. Furthermore, the conservation of ret1 expression in cell types which remain una ected by the mammalian c-ret mutations, such as motor and sensory neurons, suggests a function of this receptor in these cell lineages.

Noradrenergic neurons in the zebrafish hindbrain are induced by retinoic acid and requiretfap2afor expression of the neurotransmitter phenotype

“…In mouse embryos, the receptor tyrosine kinase Ret is expressed early together with Phox2a in derivatives of the epibranchial placode (Pachnis et al, 1993;Valarche et al, 1993;Robertson and Mason, 1995;Tiveron et al, 1996). The zebrafish homolog of Ret, ret1, is expressed in the branchial arches (Bisgrove et al, 1997;Marcos-Gutierrez et al, 1997), and we could also detect expression in cranial neural placodes (Fig. 4E).…”

Expression pattern of Drosophila ret suggests a common ancestral origin between the metamorphosis precursors in insect endoderm and the vertebrate enteric neurons

“…4D) and the imaginal retina (Fig. 4I), in keeping with the vertebrate ret expression in the eye (9,11,34).…”

Notch signaling controls the differentiation of transporting epithelia and multiciliated cells in the zebrafish pronephros

“…Expression of jagged and notch genes in the pronephros suggests that they could play an important role in patterning the pronephric nephron (Zecchin et al, 2005). Evidence for nephron patterning in the pronephros is seen in the segment-specific expression of ion transporters Shmukler et al, 2005), in the expression of receptors and transcription factors in discrete segments (Bisgrove et al, 1997;Marcos-Gutierrez et al, 1997;Van Campenhout et al, 2006), and in the disruption of segment-boundary formation in the pax2.1 (also known as pax2a -Zebrafish Information Network) mutant no isthmus (Majumdar et al, 2000). In our examination of cilia function in the kidney (Kramer-Zucker et al, 2005) we have found that two types of ciliated cells exist in the pronephros: single ciliated cells that have the morphology of typical transporting epithelial cells, and multiciliated cells that, by several criteria, appear specialized for fluid propulsion in the pronephros.…”