Robust and highly efficient hiPSC generation from patient non-mobilized peripheral blood-derived CD34+ cells using the auto-erasable Sendai virus vector.

BACKGROUND: Disease modeling with patient-derived induced pluripotent stem cells (iPSCs) is a powerful tool for elucidating the mechanisms underlying disease pathogenesis and developing safe and effective treatments. Patient peripheral blood (PB) cells are used for iPSC generation in many cases since they can be collected with minimum invasiveness. To derive iPSCs that lack immunoreceptor gene rearrangements, hematopoietic stem and progenitor cells (HSPCs) are often targeted as the reprogramming source. However, the current protocols generally require HSPC mobilization and/or ex vivo expansion owing to their sparsity at the steady state and low reprogramming efficiencies, making the overall procedure costly, laborious, and time-consuming. METHODS: We have established a highly efficient method for generating iPSCs from non-mobilized PB-derived CD34+ HSPCs. The source PB mononuclear cells were obtained from 1 healthy donor and 15 patients and were kept frozen until the scheduled iPSC generation. CD34+ HSPC enrichment was done using immunomagnetic beads, with no ex vivo expansion culture. To reprogram the CD34+-rich cells to pluripotency, the Sendai virus vector SeVdp-302L was used to transfer four transcription factors: KLF4, OCT4, SOX2, and c-MYC. In this iPSC generation series, the reprogramming efficiencies, success rates of iPSC line establishment, and progression time were recorded. After generating the iPSC frozen stocks, the cell recovery and their residual transgenes, karyotypes, T cell receptor gene rearrangement, pluripotency markers, and differentiation capability were examined. RESULTS: We succeeded in establishing 223 iPSC lines with high reprogramming efficiencies from 15 patients with 8 different disease types. Our method allowed the rapid appearance of primary colonies (~ 8 days), all of which were expandable under feeder-free conditions, enabling robust establishment steps with less workload. After thawing, the established iPSC lines were verified to be pluripotency marker-positive and of non-T cell origin. A majority of the iPSC lines were confirmed to be transgene-free, with normal karyotypes. Their trilineage differentiation capability was also verified in a defined in vitro assay. CONCLUSION: This robust and highly efficient method enables the rapid and cost-effective establishment of transgene-free iPSC lines from a small volume of PB, thus facilitating the biobanking of patient-derived iPSCs and their use for the modeling of various diseases.

Atypical SIFD with novel TRNT1 mutations: a case study on the pathogenesis of B-cell deficiency.

Mutation in the gene encoding tRNA nucleotidyl transferase, CCA-adding 1 (TRNT1), an enzyme essential for the synthesis of the 3'-terminal CCA sequence in tRNA molecules, results in a disorder that features sideroblastic anemia, B-cell immunodeficiency, periodic fever, and developmental delay. Mutations in TRNT1 are also linked to phenotypes including retinitis pigmentosa, cataracts, and cardiomyopathy. To date, it has remained unclear how defective TRNT1 is linked to B-cell deficiency. Here we report the case of a 12-year-old boy without sideroblastic anemia who harbors novel compound heterozygous mutations in TRNT1. Immunophenotypic analysis revealed severely decreased levels of B cells and follicular helper T cells. In the bone marrow, B-cell maturation stopped at the CD19+CD10+CD20+/- pre-B-cell stage. Severe combined immunodeficiency mice transplanted with bone marrow hematopoietic stem cells from the patient showed largely normal B-cell engraftment and differentiation in the bone marrow and periphery at 24 weeks post-transplantation, comparable to those in mouse transplanted with healthy hematopoietic stem cells. Biochemical analysis revealed augmented endoplasmic reticulum (ER) stress response in activated T cells. Peripheral B-cell deficiency of TRNT1 deficiency may be associated with augmented ER stress in immature B cells in the bone marrow.