Abstract 1481 Biochemical identification of proteins disrupted by dysregulated nuclear LMNB1 in DYT1 induced pluripotent stem cells-derived motor neurons

The childhood-onset DYT1 dystonia is a neurodevelopmental disorder and it is caused by a heterozygous mutation (ΔE) in the TOR1A gene, responsible for encoding a membrane-embedded AAA+ (ATPase Associated with diverse cellular Activities) ATPase. The exact mechanism by which ΔE causes dystonia remains poorly understood. Previously, we discovered prominent cellular deficits using DYT1 patient-derived motor neurons (MNs), including nuclear Lamin B1 (LMNB1) dysregulation in terms of expression and subcellular distribution. However, the molecular mechanisms underlying nuclear LMNB1 dysregulation and how dysregulated nuclear LMNB1 contributes to the pathogenesis of DYT1 dystonia remain unknown. In this study, we converted human induced pluripotent stem cells (hiPSC) into motor neurons using lentiviral delivery of transcription factors and ectopically expressed the full length LMNB1 and its truncated mutation (LMNB1_N409). The truncated LMNB1 mutation lacks the nuclear localization sequence (NLS) and mislocalized in the cytoplasm, mimicking the subcellular distribution of dysregulated nuclear LMNB1 in DYT1 patient-specific motor neurons. Using co-immunoprecipitation coupled with Mass spectrometry (Co-IP/MS) analysis, we identified that mislocalized nuclear LMNB1 extensively disrupted critical factors and signaling pathways involved in various biological processes and neuronal functions. The 14-3-3 proteins, which are highly expressed in the central nervous system (CNS) and play critical roles in neurodevelopment, showed the strongest interactions with mislocalized LMNB1. These findings shed light on the molecular mechanisms of how LMNB1 dysregulation alters neuronal functions and advance our understanding of the pathophysiology of childhood-onset DYT1 dystonia. This work was supported by NIH National Institute of Neurological Disorders and Stroke (NINDS) (NS112910 and NS133252 to B.D.), Department of Defense (DoD) Peer Reviewed Medical Research Program (PRMRP) Discovery Award (W81XWH2010186 to B.D), and LSU Health Shreveport Center for Brain Health (CBH) Grant in Aid and Chancellor's Pathways Research Award (to B.D.).