Abstract
The Wilms tumor suppressor gene Wt1 encodes a zinc finger transcription factor, which is highly conserved among vertebrates. It is a key regulator of urogenital development and homeostasis but also plays a role in other organs including the spleen and the heart. More recently additional functions for Wt1 in the mammalian central nervous system have been described. In contrast to mammals, bony fish possess two paralogous Wt1 genes, namely wt1a and wt1b. By performing detailed in situ hybridization analyses during zebrafish development, we discovered new expression domains for wt1a in the dorsal hindbrain, the caudal medulla and the spinal cord. Marker analysis identified wt1a expressing cells of the dorsal hindbrain as ependymal cells of the choroid plexus in the myelencephalic ventricle. The choroid plexus acts as a blood-cerebrospinal fluid barrier and thus is crucial for brain homeostasis. By employing wt1a mutant larvae and a dye accumulation assay with fluorescent tracers we demonstrate that Wt1a is required for proper choroid plexus formation and function. Thus, Wt1a contributes to the barrier properties of the choroid plexus in zebrafish, revealing an unexpected role for Wt1 in the zebrafish brain.
Highlights
The choroid plexus (CP) is a cellular structure within each ventricle of the vertebrate brain
We performed a detailed expression analysis of wt1a in zebrafish larvae using in situ hybridization and discovered three prominent sites of expression within the central nervous system, namely in the dorsal hindbrain, the caudal medulla and the spinal cord
In this work we show that one of the two paralogs of the Wilms tumor transcription factor Wt1, namely Wt1a, has a role in formation and function of the choroid plexus of the myelencephalic ventricle in zebrafish
Summary
The choroid plexus (CP) is a cellular structure within each ventricle of the vertebrate brain. It constitutes a barrier between the blood and the cerebrospinal fluid (CSF) and consists of epithelial cells, fenestrated blood vessels, stromal cells and extracellular matrix (Wolburg and Paulus, 2010). The cuboid epithelial cells of the CP, called ependymal cells are connected by tight junctions and are highly polarized. They harbor cilia and microvilli on their apical surface that projects into the ventricle and face the Soma with their basal side (Lun et al, 2015). It is not surprising that the CP is associated with a number of diseases including hydrocephalus (Wolburg and Paulus, 2010), Wt1a Regulates Choroid Plexus Development neurodegenerative diseases (Alvira-Botero and Carro, 2010), multiple sclerosis (Vercellino et al, 2008) as well as tumors (Tong et al, 2015)
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