Generation of Neural Progenitor Cells from human iPS cells for the study of Huntington Disease

Huntington disease (HD), also known as Huntington's chorea, is an autosomal dominant inherited neurological disorder caused by a trinucleotide repeat expansion in the huntingtin gene (HTT) which leads to a mutant form of HTT protein. Mutant HTT misfolding causes accumulation of aggregates causing severe alterations such as impairment of calcium signaling in the cell, altered gene transcription and mitochondrial dysfunction. HD patients present degeneration of specific types of neurons, with consequent severe brain atrophy which leads to motor dysfunction, dementia and other psychiatric symptoms. After a genome-wide screening on mouse Embryonic Stem (mES) cells performed in my hosting laboratory, promising potential suppressor genes for toxic effects caused by mutant HTT were identified and tested in vitro, in mES cells, and in vivo, in zebrafish and mouse. Nevertheless, at the moment we do not know if our candidate suppressor genes are also effective in human neuronal cells. Consequently, we wanted to generate a human in vitro model from induced Pluripotent Stem Cells (hiPSCs) obtained from HD patients, with the aim of resembling the human cellular target in HD, recapitulating some of the disease hallmarks, like increased ROS production. Using two previously published protocols, we successfully differentiated two kinds of Neural Progenitor Cells (NPCs) from hiPSCs: forebrain and caudal NPCs which show expression of early neural marker SOX1 and Nestin. Typical anterior markers PAX6 and OTX2 were detected in forebrain NPCs, confirming their anterior fate. Oxidative state of forebrain and caudal NPCs in the cytosolic and mitochondrial compartments was assessed. Results showed increased ROS production in NPCs obtained from hiPSCs line carrying HD mutation, which exhibits 109 CAG repetitions in HTT gene, in comparison with the healthy control line hiPSCs Q21. Besides, it is also possible to maintain caudal NPCs after differentiation, for a higher number of passages. These results indicate that human caudal NPCs are valid in vitro model for testing novel HD therapeutic approaches.