Overcoming the effect of ASH1L haploinsufficiency on stem cells amenability to genome editing and differentiation into the neuronal lineage - a technical report

Genome editing and neuronal differentiation protocols have proliferated in the last decade. Mutations in genes that control pluripotency could lead to a potential obstacle with regards to the survival and differentiation potential of the genome-edited cell lines. Here we describe a protocol for the generation, and differentiation, of cell lines containing CRISPR/Cas9 induced mutations in the histone methyl transferase ASH1L. This chromatin modifier was previously implicated in hematopoietic stem cell pluripotency and is a major genetic risk factor for autism spectrum disorders (ASD). We find that haploinsufficiency of ASH1L leads to decreased NANOG gene expression leading to reduce cell survival and increased spontaneous differentiation. We report a method that provides improved single-cell survival with higher colony formation efficiency in ASH1L mutant stem cells. Additionally, we describe a modified dual-SMAD inhibition neuronal induction methodology that permits the successful generation of human neurons with mutations in ASH1L, in a smaller scale than previously reported methods. With our modified CRISPR-genome editing and neuronal differentiation protocols, it is possible to generate genome-edited stem cells containing mutations in genes that impact pluripotency and could affect subsequent cell lineage specific differentiation. Our detailed technical report presents cost-effective strategies that will benefit researchers focusing on both translational and basic science using stem cell experimental systems.