※ Ryk family introduction

    Ryks are atypical receptor tyrosine kinases. One member have been found in human genome, known as Ryk. Ryk contains a Wnt inhibitory factor domain in its extracellular region, an intracellular kinase catalytic domain and a PDZ motif. However, as several mutations have been found on critical conserved tyrosine residue in kinase domain, Ryk might loss the kinase catalytic activity. The Drosophila Ryk was originally identified to be associated with learning and memory. Lin-18, the C.elegans homolog, is essential for establishing the secondary vulval cell linage polarity. Lin-18 also has a genetic interaction of Frizzled durning vulval development. Ryk knockout on mice will cause the rapid death after birth and display a cleft of the secondary palate with a abnormal craniofacial appearance. In addition, Ryk is also involved in Wnt signaling pathway, in which Ryk can bind Wnt-1 and Wnt-3a and is required for the activation of TCF. Active TCF will subsequently lead to Wnt-3a activation which is important in induce neurite outgrowth (1).

Reference
1. Lu, W., Yamamoto, V., Ortega, B. and Baltimore, D. (2004) Mammalian Ryk is a Wnt coreceptor required for stimulation of neurite outgrowth. Cell, 119, 97-108. PMID: 15454084