The function and expression of sproutin, a novel neurite outgrowth factor

TA20 cDNA was previously cloned as a neurite outgrowth factor from a hybridoma of mouse and rat cells, NG108-15. To clarify the detailed function and tissue distribution of this gene, homologous sequences of rat and mouse were identified. The cloned sequences had no homology with known genes, and was designated as sproutin. A predicted open reading frame of rat sproutin was transfected into human SK-N-SH cells. The over-expressed protein was distributed in cytoplasm and neurites, and caused an increase in the levels of microtuble associated proteins, but not that of phosphorylated neurofilament-H. The percentage of cells with neurites, the length of neurites and the number of neurites per cell were increased by sproutin transfection. Sproutin mRNA was brain specific. These results suggest that an increase in sproutin promotes dendritic extension.