Practice question

Induced pluripotent stem cells are produced by transient overexpression of embryonic transcription factors that epigenetically reset somatic genome toward embryonic state. Yamanaka factors Oct4, Sox2, Klf4, and c-Myc disrupt fibroblast transcriptional program, induce mesenchymal to epithelial transition, demethylate pluripotency enhancers, and reactivate endogenous Oct4, Nanog, Esrrb circuitry necessary for self-renewal. Klf4 and c-Myc facilitate proliferation and chromatin opening. Protocols employ retroviral, Sendai virus, mRNA, or episomal delivery with varying efficiency. Resulting iPSCs are molecularly and functionally similar to embryonic stem cells, offering isogenic models without embryo destruction.