Aberrant CHCHD2-Associated Mitochondrial Abnormality in Kii ALS/PDC Astrocytes

The Amyotrophic Lateral Sclerosis/Parkinsonism-Dementia Complex (Kii ALS/PDC), a rare and complex neurological disorder, is predominantly observed in the Western Pacific islands, including regions of Japan, Guam, and Papua. This enigmatic condition continues to capture medical attention due to patients displaying symptoms that parallel those seen in either classical amyotrophic lateral sclerosis (ALS) or Parkinson's Disease (PD). Distinctly, post-mortem examinations of the brains of affected individuals have shown concurrent hallmarks: the presence of α-synuclein aggregates, which are a signature of PD, and TDP-43, associated with classical ALS. These observations are further complicated by the detection of phosphorylated tau, accentuating the multifaceted proteinopathic nature of Kii ALS/PDC. The etiological foundations of this disease remain undetermined, and genetic investigations have yet to provide conclusive answers. However, emerging evidence has cast a spotlight on astrocytes, cells pivotal for maintaining brain health. These astrocytes are likely to play a significant role in the pathogenesis of Kii ALS/PDC. Leveraging advanced iPSC technology, our team cultivated multiple astrocyte lines to probe the disease further. CHCHD2 emerged as asignificantly dysregulated gene when disease astrocytes were compared to healthy controls. Our analyses also unveiled imbalances in specific pathways: those associated with astrocytic cilium dysfunction, known to have ties with neurodegeneration, and those related to major neurological disorders, including classical ALS and PD. Further in-depth examinations revealed abnormalities in the mitochondrial morphology and metabolic processes of the affected astrocytes. A particularly striking observation was the reduced expression of CHCHD2 in a patient’s spinal cord. In sum, our findings suggest a potential compromise in the support Kii ALS/PDC astrocytes provide to neurons, emphasizing the need to explore the role of CHCHD2 in maintaining mitochondrial health and its implications for the disease.