PTPRD is expressed in brain, and displays prominent hippocampal expression. Its extracellular ligands have not been elucidated, though it can bind to liprin [185]. PTPRD knockout mice display altered hippocampal long-term potentiation and spatial learning [186], which fit well with the human phenotypes related to cognitive function. Mice with deletions of both PTPRD and a related PRP sigma (but not with either knockout alone) die at birth due to failure to innervate appropriately [187]. SCGZ participates in protein complexes with cell adhesion-like [188]. High levels of SGCZ expression in the brain are confirmed by Allen brain atlas images [172]. Biochemical studies identify expression in schwann cells of peripheral nerves [188]. SCGZ can be found in complexes with αδ or with εβδ sarcoglycans, demonstrating specificity of the context of its function in brain [189].
