Huntington’s Disease Human Lateral Ganglionic Eminence Precursors Differentiate into Functionally Mature Medium Spiny Neurons Exhibiting Pathology

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease characterised by the loss of GABAergic medium spiny neurons (MSNs). Cellular models of HD are mainly derived from human embryonic stem cells or induced pluripotent stem cells. These models are limited by their DNA embryonic age, low neuronal yields and limited disease pathology. We propose direct reprogramming, which maintains the aging signature of the cells, to human induced lateral ganglionic eminence precursors (hiLGEP) results in the generation of high yields of functionally mature MSNs exhibiting pathological hallmarks of HD. hiLGEPs were derived from normal and HD fibroblasts by direct reprogramming and differentiated to MSNs. hiLGEP and MSN fate acquisition was compared between normal and HD through gene and protein expression. Known pathological hallmarks of HD were investigated within the hiLGEP-derived MSNs. The formation of functional synapses was investigated using live cell calcium imaging. We demonstrate that HD fibroblasts can be reprogrammed to hiLGEPs expressing key linage markers and displaying disease-related changes in expression of FOXP1 and FOXP2. HD hiLGEPs can be differentiated to high yields of MSNs co-expressing DARPP32, GABA, or GAD65/67, and SYN1 and PSD-95. HD MSNs show a reduced expression of BDNF, HAP1, TRKB, Rhes and PGC1α, exhibit MW8+ mHTT aggregates and display smaller cell somas, reduced total neurite length and reduced branched neurites when compared to normal MSNs. An administration of 100 µM dopamine was necessary to generate a calcium response in HD MSNs. This study establishes a directly reprogrammed hiLGEP-derived MSN model of HD which recapitulates pathological signatures.