Impaired lipid metabolism in astrocytes underlies degeneration of cortical projection neurons in hereditary spastic paraplegia

• Published in: Acta neuropathologica communications Vol. 8; no. 1; pp. 214 - 20
• Main Authors: Mou, Yongchao, Dong, Yi, Chen, Zhenyu, Denton, Kyle R., Duff, Michael O., Blackstone, Craig, Zhang, Su-Chun, Li, Xue-Jun
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 07.12.2020; BioMed Central; BMC
• Subjects: Astrocytes; Axonal degeneration; Cholesterol; Cholesterol homeostasis; Cortical projection neurons; Gene expression; Genetic aspects; Hereditary spastic paraplegia; Human pluripotent stem cells; Lipids; Metabolism; Mutation; Neurons; Paralysis; Paralysis, Spastic; Proteins; Spasticity; Stem cells; Fiji; Hereditary spastic paraplegia; Human pluripotent stem cells; Astrocytes; Axonal degeneration; Cholesterol homeostasis; Cortical projection neurons
• DOI: 10.1186/s40478-020-01088-0
• ISSN: 2051-5960

Hereditary spastic paraplegias (HSPs) are caused by a length-dependent axonopathy of long corticospinal neurons, but how axons of these cortical projection neurons (PNs) degenerate remains elusive. We generated isogenic human pluripotent stem cell (hPSC) lines for two ATL1 missense mutations associated with SPG3A, the most common early-onset autosomal dominant HSP. In hPSC-derived cortical PNs, ATL1 mutations resulted in reduced axonal outgrowth, impaired axonal transport, and accumulated axonal swellings, recapitulating disease-specific phenotypes. Importantly, ATL1 mutations dysregulated proteolipid gene expression, reduced lipid droplet size in astrocytes, and unexpectedly disrupted cholesterol transfer from glia to neurons, leading to cholesterol deficiency in SPG3A cortical PNs. Applying cholesterol or conditioned medium from control astrocytes, a major source of cholesterol in the brain, rescued aberrant axonal transport and swellings in SPG3A cortical PNs. Furthermore, treatment with the NR1H2 agonist GW3965 corrected lipid droplet defects in SPG3A astrocytes and promoted cholesterol efflux from astrocytes, leading to restoration of cholesterol levels and rescue of axonal degeneration in SPG3A cortical PNs. These results reveal a non-cell autonomous mechanism underlying axonal degeneration of cortical PNs mediated by impaired cholesterol homeostasis in glia.