In vitro restoration of Friedreich's Ataxia defect with novel Cas9-edited hiPSC-derived Dorsal Root Ganglion-like Organoids (DRGOs) and Microfluidic System

Friedreich's ataxia (FRDA) is an autosomal-recessive neurodegenerative and cardiac disorder which occurs when transcription of the frataxin (FXN) gene is silenced due to the expansion of GAA·TTC repeats in intron 1 of the same gene, leading loss of the essential mitochondrial protein frataxin with several impairment in iron metabolism and respiration, primarily affects the sensory DRG neurons. A major limitation in the study of FRDA is the lack of robust animal and cellular models. To fill this gap, this study presents a novel 3D protocol to generate dorsal root ganglia-like organoids (DRGOs) from human iPSCs in which to model Friedreich's ataxia. DRGOs show a robust expression pattern of peripheral markers, are electro-physiologically active and out-perform peripheral sensory neurons generated with a traditional 2D protocol. Furthermore, when co-cultured with human stretch receptor intrafusal muscle fibers, DRGOs contact their peripheral target and form an in vitro muscle spindle. DRGOs generated from FRDA patient-derived iPSCs recapitulate several aspects of FRDA pathology including reduced expression of FXN and TCA-cycle components and mitochondrial fragmentation. We present also the recovery of this pathological signs, achieved by a new CRISPR-Cas9 mediated deletion of the GAA·TTC tract along with the majority of the affected intron. FRDA patient edited DRGOs with the long deletion boast normalized markers of oxidative stress, as well as recovered mitochondrial defect, particularly in the axonal compartment. Overall design: 3x Dorsal Root Ganglia Organoids