Of particular interest is the signal near the PTPRD gene (rs4401971), the most significant found in this study (P=4.13×10−7). PTPRD is a member of the receptor protein tyrosine phosphatase family, which comprises transmembrane signaling molecules that regulate a variety of cellular processes including cell growth and differentiation 39. Pre-synaptic PTPRD promotes the differentiation of glutamatergic synapses 40–43 and interacts with Slit and NTRK-like family member 3 (SLITRK3) which acts as a postsynaptic adhesion molecule. Together both proteins selectively regulate inhibitory GABAergic synapse development 44. This is interesting because molecules in the same family, SLITRK5 and SLITRK1, have been shown to be associated with TS and OCD, the former in a mouse model and the latter in a TS genetic study 45, 46.
