The FCH and double SH3 domains protein 1 (FCHSD1, also known as NWK2) and the related protein FCHSD2 were initially identified in silico as distantly related proteins to FNBP1 and FNBP2. Both share the common domain structure consisting of FCH, FBH, two SH3 and C-terminal proline-rich domains. While little is known of the function of FCHSD1, the related protein NWK is an adaptor protein that is thought to regulate Rho activity downstream of Robo receptors, suggesting that FCHSD1 may be involved in synaptic morphology by regulating actin dynamics in presynaptic terminals.Synonyms: FCH and double SH3 domains protein 1