2D Neuronal Network Characterization and Omics Analysis of Engineered human patient-derived Medium Spiny Neurons with RARb mutation

MCOPS12 is an ultra-rare and lethal neurodevelopmental disorder that affects the striatum, the eyes and other internal organs. The disease is linked to mutations in the Retinoic Acid Receptor beta (RARb). Microphthalmia, cognitive and progressive motor impairments are the most common symptoms of MCOPS12. The cognitive and developing motor deterioration is linked to striatal circuitry misregulation. 95% of the striatum is composed of two subpopulations of Medium Spiny Neurons (MSNs). The direct Dopamine Receptor 1 positive (DR1+) and indirect Dopamine Receptor 2 positive (DR2+) striatal MSN subpopulations are antagonistic in their action in the control of motor function. It is hypothesized that a misregulation of the precise balance between DR1+ and DR2+ MSN subpopulations in the striatum can lead to cognitive and movement disorders in MCOPS12 patients.
The main aims of this study are: a) To reprogram human MCOPS12 patient- derived somatic cells into iPSCs and generate robust lines, b) To develop a protocol for direct DR1+ and indirect DR2+ MSN differentiation from human iPSCs; valuable tools for the investigation of MCOPS12 biology.
In this study I investigated the effect of MCOPS12 RARbR387C mutation on MSNs. For this, I first reprogramed MCOPS12 patient derived blood cells into iPSC lines. Then, I successfully developed a differentiation protocol that generates direct DR1+ and indirect DR2+ MSNs within D55. I differentiated MCOPS12 Patient Derived (PD) iPSCs and wild type (wt) control iPSCs into a mixed DR1+ and DR2+ MSN subpopulation. I performed transcriptomic analysis of these derived MSNs at D55 of differentiation. I also employed CRISPR/Cas9 to induce the RARbR387C mutation into wt control iPSCs and to repair MCOPS12 RARbR387C PD iPSCs to the wt genotype. These engineered iPSCs are a perfect isogenic control to study the RARbR387C mutation and will benefit further MCOPS12 research. Data from the transcriptomic study will be integrated with existing MCOPS12 mice transcriptomic data and clinical patient data. The data integration will hopefully shed new light on MCOPS12 disease development, progression and could potentially lead to new therapies for people affected by MCOPS12.
Our developed MSN protocol has the potential to become a perfect tool for various striatal disease and disorder investigations and disease modeling. It also could be used as a pharmaceutical drug screenings platform to target striatal neurons negatively affected by Parkinson’s or Huntington’s diseases.