Reprogramming competence of POU factors is linked to the donor-cell epigenome

Octamer-binding Pit-Oct-Unc (POU) family members have distinct reprogramming competences. OCT4 induces pluripotency, whereas POU III factors (OCT6, OCT7, OCT8, and OCT9) lack this ability, but are prone to inducing neural identities. However, which specific features of these proteins render the distinct reprograming competences remains unknown. Here, we present that OCT6 can also induce pluripotency. But, it works only with human cells, indicating its species-dependent reprogramming activity. Functional readouts with a series of reciprocal mutants uncover that the central role of OCT4 and its strong reprogramming competence to pluripotency arise from its C-terminal transactivation domain. Furthermore, we identify intrinsic properties of OCT7, OCT8, and OCT9 that are detrimental for inducing pluripotency. A chemical screen reveals that their persistent deficiency for inducing pluripotency can be surmounted by reducing H3K79 methylation in donor cells. Our findings delineate that intrinsic properties of POU factors and their responsive donor-cell epigenome state are tightly linked to the reprogramming competence. 28 human samples were analyzed: Fibs1, Human fibroblast, 2 replicates Fibs2, Human fibroblast, 2 replicates O4 iPS#1, Human induced Pluripotent Stem (iPS) cells with OCT4, SOX2 KLF4, MYC, clon 1, 2 replicates O4 iPS#2, Human induced Pluripotent Stem (iPS) cells with OCT4, SOX2 KLF4, MYC, clon 2, 2 replicates O6 iPS#1, Human induced Pluripotent Stem (iPS) cells with OCT6, SOX2 KLF4, MYC, clon 1, 2 replicates O6 iPS#2, Human induced Pluripotent Stem (iPS) cells with OCT6, SOX2 KLF4, MYC, clon 2, 2 replicates O7 iPS#1, Human induced Pluripotent Stem (iPS) cells with OCT7, SOX2 KLF4, MYC, clon 1, 2 replicates O7 iPS#4, Human induced Pluripotent Stem (iPS) cells with OCT7, SOX2 KLF4, MYC, clon 4, 2 replicates O8 iPS#1, Human induced Pluripotent Stem (iPS) cells with OCT8, SOX2 KLF4, MYC, clon 1, 2 replicates O8 iPS#3, Human induced Pluripotent Stem (iPS) cells with OCT8, SOX2 KLF4, MYC, clon 3, 2 replicates O9 iPS#3, Human induced Pluripotent Stem (iPS) cells with OCT9, SOX2 KLF4, MYC, clon 3, 2 replicates O9 iPS#4, Human induced Pluripotent Stem (iPS) cells with OCT9, SOX2 KLF4, MYC, clon 4, 2 replicates H1, Human Embryonic Stem Cell (ESC) line H1, 2 replicates H9, Human Embryonic Stem Cell (ESC) line H9, 2 replicates 14 mouse samples were analyzed: O4 iPS, Mouse induced Pluripotent Stem (iPS) cells with Oct4, Sox2 Klf4, Myc, 2 replicates O6 iPS, Mouse induced Pluripotent Stem (iPS) cells with Oct6, Sox2 Klf4, Myc, 2 replicates O7 iPS, Mouse induced Pluripotent Stem (iPS) cells with Oct7, Sox2 Klf4, Myc, 2 replicates O8 iPS, Mouse induced Pluripotent Stem (iPS) cells with Oct8, Sox2 Klf4, Myc, 2 replicates O9 iPS, Mouse induced Pluripotent Stem (iPS) cells with Oct9, Sox2 Klf4, Myc, 2 replicates O11 iPS, Mouse induced Pluripotent Stem (iPS) cells with Oct11, Sox2 Klf4, Myc, 2 replicates ESC, Mouse Embryonic Stem Cell (ESC), 1 replicate MEF, Mouse Embryonic Fibroblast (MEF), 1 replicate