Although insulin is the defining protein of a cell, we found that it was dispensable for differentiation, as we were able to obtain insulin-negative cells expressing key ?cell markers, including PDX1, MAFA, and NKX6.1. homeostasis, including at night, and the stem cell-derived grafts adapted insulin secretion to metabolic changes. Our study provides proof of principle for the generation of genetically corrected cells autologous to a patient with non-autoimmune insulin-dependent diabetes. These cases should be readily amenable to autologous cell therapy. Mutation Can Be Corrected by CRISPR/Cas9 in Human Induced Pluripotent Stem Cells We obtained a skin biopsy from the patient after parental informed consent and derived fibroblast cultures and reprogrammed the somatic skin cells to iPSCs using mRNA-mediated reprogramming. Two iPSC lines were derived, and one of the two was differentiation competent. This is consistent with the variable differentiation competence of iPSC lines (Sui et?al., 2017). Stem cells contained the mutation as determined by Sanger sequencing (Figure?1A). A guide RNA was designed against the INS locus close to the mutation site, along with a correction template with both the normal ATG and a neutral SNP. This neutral SNP prevented Cas9 activity on the corrected alleles and allowed CCT251236 us to distinguish the corrected allele from a wild-type allele (Figure?1C). Two days post transfection, Cas9-GFP-positive cells were sorted and clonally expanded. Genomic DNA was isolated to amplify and sequence the?insulin ATG region. Sixty-one of 72 colonies were sequenced, with three showing the desired gene correction. Since the homozygous mutation originates from a consanguineous marriage, we were unable to test for heterozygosity in the vicinity of the insulin gene, which would have confirmed the correction of both alleles. Such testing can exclude the presence of a wild-type copy on one allele and a large deletion removing the primer-binding site on another allele (Egli et?al., 2018). The possibility of introducing larger deletions has been addressed by others (Kosicki et?al., 2018). Three top off-target sites were examined by PCR and Sanger sequencing. One cell line showed an off-target effect 1.7 kb upstream of the locus (Figure?S1), a gene involved in nervous system development. To control for possible inadvertent changes to the genome through CRISPR/Cas9, three gene-corrected lines were utilized for experimentation in subsequent experiments. No differences were seen with regard to insulin expression. Last, to confirm the pluripotency of the gene-corrected stem cells, both mutant and corrected patient iPSCs were used for karyotyping and immune staining. All cell lines expressed pluripotent marker genes, OCT4 and SOX2, and had normal karyotypes (46/XY), including two copies of chromosome 11 (Figures 1B and 1D), where the gene resides, which excluded the possibility of chromosome loss or large chromosome abnormalities that might result in detection of only corrected alleles. Open in a separate window Figure?1 Genotyping at the Insulin Locus of a Patient with PNDM, and Gene CCT251236 Correction in Patient-Derived Stem Cells Using CRISPR/Cas9 (A) Sanger sequencing results at the start codon of the gene. (B) Immunostaining for pluripotency genes OCT4 and SOX2 in mutant and corrected cells. Scale bar, 50?m. (C) Correction of mutation in patient iPSCs by CRISPR/Cas9 using a single-stranded DNA (ssDNA) repair Rabbit Polyclonal to TCF7 template. The neutral nucleotide polymorphism introduced is indicated by the red arrowhead. gRNA, CCT251236 guide RNA. (D) Karyotypes of patient and gene-edited iPSCs (46/XY). See also Figure?S1. Mutant Stem Cells Efficiently Differentiate to Insulin-Negative CCT251236 Endocrine Cells To determine whether the mutant and the gene-corrected cells could differentiate to -like cells, we used a stepwise differentiation protocol (Figure?2A) (Pagliuca et?al., 2014, Rezania et?al., 2014, Sui et?al., 2017). There was no detectable difference in differentiation efficiency among mutant and corrected iPSCs. Both the insulin mutant and the corrected cells differentiated efficiently to the definitive endoderm (DE) stage, with 96% of cells positive for both SOX17 and FOXA2 (Figures 2B, S2A, and S2B). At the pancreatic progenitor (PP) stage, more than 40% of cells in both populations CCT251236 were double positive for PDX1 and NKX6.1 (Figures 2C, S2C, and S2D). Open in a separate window Figure?2 Stem Cells Differentiate to Endocrine Cells without Insulin (A) Schematic of cell differentiation. Markers for specific stages of differentiation are indicated. DE, definitive endoderm;.