Novel genetic features of human and mouse Purkinje cell differentiation defined by comparative transcriptomics.

Abstract

Comparative transcriptomics between differentiating human pluripotent stem cells (hPSC) and developing mouse neurons offers a powerful approach to compare genetic and epigenetic pathways in human and mouse neurons. To analyze human Purkinje cell (PC) differentiation, we optimized a protocol to generate hPSC-PCs that formed synapses when cultured with mouse cerebellar glia and granule cells and fired large calcium currents, measured with the genetically encoded calcium indicator jRGECO1a. To directly compare global gene expression of hPSC-PCs with developing mouse PCs, we used translating ribosomal affinity purification (TRAP). As a first step, we used Tg(Pcp2-L10a-Egfp) TRAP mice to profile actively transcribed genes in developing postnatal mouse PCs, and used metagene projection to identify the most salient patterns of PC gene expression over time. We then created a transgenic Pcp2-L10a-Egfp TRAP hESC line to profile gene expression in differentiating hPSC-PCs, finding that the key gene expression pathways of differentiated hPSC-PCs most closely matched those of late juvenile, mouse PCs (P21). Comparative bioinformatics identified classical PC gene signatures as well as novel mitochondrial and autophagy gene pathways during the differentiation of both mouse and human PCs. In addition, we identified genes expressed in hPSC-PCs but not mouse PCs and confirmed protein expression of a novel human PC gene, CD40LG, expressed in both hPSC-PCs and native human cerebellar tissue. This study therefore provides the first direct comparison of hPSC-PC and mouse PC gene expression and a robust method for generating differentiated hPSC-PCs with human-specific gene expression for modeling developmental and degenerative cerebellar disorders. Significance StatementTo compare global gene expression features of differentiating human pluripotent stem cell-derived Purkinje cells (hPSC-PC) and developing mouse Purkinje cells (PC) we derived hPSC-PCs and compared gene expression datasets from human and mouse PCs. We optimized a differentiation protocol that generated hPSC-PCs most similar in gene expression to mouse P21 PCs. Metagene projection analysis of mouse PC gene expression over postnatal development identified both classical PC marker genes as well as novel mitochondrial and autophagy gene pathways. These key gene expression patterns were conserved in differentiating hPSC-PCs. We further identified differences in timing and expression of key gene sets between mouse and hPSC-PCs and confirmed expression of a novel human PC marker, CD40LG, in human cerebellar tissue.