RMDN3 and frontotemporal dementia: We therefore studied how VAPB/PTPIP51 expression affects damage to ER-mitochondria Ca2+ delivery induced by two familial FTD/ALS mutants, TDP43-Q331K or TDP43-A382T; both of these mutants have been shown to damage the VAPB-PTPIP51 interaction, ER-mitochondria contacts and IP3 receptor delivery of Ca2+ to mitochondria [47].