Mutations in <i>RHOT1</i> Disrupt Endoplasmic Reticulum–Mitochondria Contact Sites Interfering with Calcium Homeostasis and Mitochondrial Dynamics in Parkinson's Disease

Abstract

<b><i>Aims:</i></b> The outer mitochondrial membrane protein Miro1 is a crucial player in mitochondrial dynamics and calcium homeostasis. Recent evidence indicated that Miro1 mediates calcium-induced mitochondrial shape transition, which is a prerequisite for the initiation of mitophagy. Moreover, altered Miro1 protein levels have emerged as a shared feature of monogenic and sporadic Parkinson's disease (PD), but, so far, no disease-associated variants in <i>RHOT1</i> have been identified. Here, we aim to explore the genetic and functional contribution of <i>RHOT1</i> mutations to PD in patient-derived cellular models. <b><i>Results:</i></b> For the first time, we describe heterozygous <i>RHOT1</i> mutations in two PD patients (het c.815G>A; het c.1348C>T) and identified mitochondrial phenotypes with reduced mitochondrial mass in patient fibroblasts. Both mutations led to decreased endoplasmic reticulum-mitochondrial contact sites and calcium dyshomeostasis. As a consequence, energy metabolism was impaired, which in turn caused increased mitophagy. <b><i>Innovation and Conclusion:</i></b> Our study provides functional evidence that <i>ROTH1</i> is a genetic risk factor for PD, further implicating Miro1 in calcium homeostasis and mitochondrial quality control.