HEB-deficient hESCs retained key features of pluripotency, including expression of SOX2 and SSEA-4 and teratoma formation, while NANOG expression was reduced.
Reprogrammed iPSCs were positive for oct3/4, nanog, and sox2, formed embryoid bodies in vitro, and induced teratomas in nonobese diabetic/severe combined immunodeficient mice.
Supplementation with VPA for 5 days further upregulated OCT4, KLF4, and SOX2, and induced expression of NANOG, SSEA3, TRA-1-60, and TRA-1-81, with cells now able to form EBs and teratomas.
These cells also showed typical properties of ESCs (alkaline phosphatase (AP) positive, expressions of Oct4, Sox2, Nanog, and SSEA1, with the capacity to form teratomas and differentiate into various types of cells within three germ layers).
In contrast to skin fibroblasts, melanocytes and melanoma cells did not require ectopic Sox2 expression for conversion into iPSCs. iPSC lines from melanocytic cells expressed pluripotency markers, formed teratomas and contributed to viable chimeric mice with germ line transmission.
Thus, SOX2 is expressed in embryonal carcinoma and primitive neuroectoderm of teratoma, and unlike OCT3/4, not in intra-tubular germ cell neoplasia and seminoma.