N1-Src kinase is required for primary neurogenesis in Xenopus tropicalis

The presence of the neuronal-specific N1-Src splice variant of the C-Src tyrosine kinase is conserved through vertebrate evolution, suggesting an important role in complex nervous systems. Alternative splicing involving a N1-Src specific microexon leads to a five or six amino acid insertion into the SH3 domain of Src. A prevailing model suggests that N1-Src regulates neuronal differentiation via cytoskeletal dynamics in the growth cone. Here we have investigated the role of n1-src in the early development of the amphibian Xenopus tropicalis, and find that n1-src expression is regulated in embryogenesis, with highest levels detected during the phases of primary and secondary neurogenesis. In situ hybridisation analysis, using locked nucleic acid (LNA) oligo probes complementary to the n1-src microexon indicate that n1-src expression is highly enriched in the open neural plate during neurula stages and in the neural tissue of adult frogs. Given the n1-src expression pattern, we investigated a possible role for n1-src in neurogenesis. Using splice site-specific antisense morpholino oligos, we are able to inhibit n1-src splicing, whilst preserving c-src expression. Differentiation of neurons in the primary nervous system is reduced in n1-src knockdown embryos, accompanied by a severely impaired touch response in later development. These data reveal an essential role for n1-src in amphibian neural development and suggest that alternative splicing of C-Src in the developing vertebrate nervous system evolved to regulate neurogenesis

N1-Src kinase is required for primary neurogenesis in Xenopus tropicalis

The presence of the neuronal-specific N1-Src splice variant of the C-Src tyrosine kinase is conserved through vertebrate evolution, suggesting an important role in complex nervous systems. Alternative splicing involving a N1-Src specific microexon leads to a five or six amino acid insertion into the SH3 domain of Src. A prevailing model suggests that N1-Src regulates neuronal differentiation via cytoskeletal dynamics in the growth cone. Here we have investigated the role of n1-src in the early development of the amphibian Xenopus tropicalis, and find that n1-src expression is regulated in embryogenesis, with highest levels detected during the phases of primary and secondary neurogenesis. In situ hybridisation analysis, using locked nucleic acid (LNA) oligo probes complementary to the n1-src microexon indicate that n1-src expression is highly enriched in the open neural plate during neurula stages and in the neural tissue of adult frogs. Given the n1-src expression pattern, we investigated a possible role for n1-src in neurogenesis. Using splice site-specific antisense morpholino oligos, we are able to inhibit n1-src splicing, whilst preserving c-src expression. Differentiation of neurons in the primary nervous system is reduced in n1-src knockdown embryos, accompanied by a severely impaired touch response in later development. These data reveal an essential role for n1-src in amphibian neural development and suggest that alternative splicing of C-Src in the developing vertebrate nervous system evolved to regulate neurogenesis

Fibronectin supports neurite outgrowth and axonal regeneration of adult brain neurons in vitro

AbstractThe molecular basis of axonal regeneration of central nervous system (CNS) neurons remains to be fully elucidated. In part, this is due to the difficulty in maintaining CNS neurons in vitro. Here, we show that dissociated neurons from the cerebral cortex and hippocampus of adult mice may be maintained in culture for up to 9days in defined medium without added growth factors. Outgrowth of neurites including axons was observed from both CNS sources and was significantly greater on plasma fibronectin than on other substrata such as laminin and merosin. Neurite outgrowth on fibronectin appears to be mediated by α5β1 integrin since a recombinant fibronectin fragment containing binding sites for this receptor was as effective as intact fibronectin in supporting neurite outgrowth. Conversely, function-blocking antibodies to α5 and β1 integrin sub-units inhibited neurite outgrowth on intact fibronectin. These results suggest that the axonal regeneration seen in in vivo studies using fibronectin-based matrices is due to the molecule itself and not a consequence of secondary events such as cellular infiltration. They also indicate the domains of fibronectin that may be responsible for eliciting this response

Prescreening evaluation of a brush-based faecal immunochemical test for haemoglobin

U

Cohabitation in twentieth century England and Wales : law and policy

This article reviews the complex, and sometimes conflicting, policies adopted by the law of England and Wales over the course of the twentieth century. Its aim is to highlight the fact that cohabitation is not merely a modern legal issue, but one with which both the legislature and the courts have had to grapple for decades. It argues that reform has been piecemeal and context-specific because the courts and legislature have not adopted a coherent policy toward cohabiting relationships