BACKGROUND:Some studies have shown that more copy number variations are present in early passage human induced pluripotent stem cells than later passage human human induced pluripotent stem cells, their parental somatic fibroblasts or human embryonic stem cells. OBJECTIVE:To investigate whether the reprogramming process itself compromises genomic stability and further explore the efficiency of induced pluripotent stem cellestablishment. METHODS:Using high-resolution Affymetrix CytoScan HD array, we compared copy number variations and loss of heterozygosity in early passage induced pluripotent stem cells with their fibroblast cellorigins from genetic epilepsy patients. RESULTS AND CONCLUSION:Compared with somatic fibroblasts from genetic epilepsy patient, there was no difference in the loss of heterozygosity between the two types of cells, but more copy number variations were present in early passage human induced pluripotent stem cells which were characterized as microduplication and involved oncogenic genes. Results demonstrate the dynamic nature of genomic abnormalities during reprogramming process and the necessity of frequent monitoring human induced pluripotent stem cells to assure their genomic stability and clinical safety.

The correct differentiation of oligodendrocyte precursor cells (OPCs) is essential for the myelination and remyelination processes in the central nervous system. Determining the regulatory mechanism is fundamental to the treatment of demyelinating diseases. By analyzing the RNA sequencing data of different neural cells, we found that cyclin-dependent kinase 18 (CDK18) is exclusively expressed in oligodendrocytes. In vivo studies showed that the expression level of CDK18 gradually increased along with myelin formation during development and in the remyelination phase in a lysophosphatidylcholine-induced demyelination model, and was distinctively highly expressed in oligodendrocytes. In vitro overexpression and interference experiments revealed that CDK18 directly promotes the differentiation of OPCs, without affecting their proliferation or apoptosis. Mechanistically, CDK18 activated the RAS/mitogen-activated protein kinase kinase 1/extracellular signal-regulated kinase pathway, thus promoting OPC differentiation. The results of the present study suggest that CDK18 is a promising cell-type specific target to treat demyelinating disease.