Hierarchical mechanisms for direct reprogramming of fibroblasts to neurons.
Direct lineage reprogramming is a promising approach for human disease modeling and regenerative medicine, with poorly understood mechanisms. Here, we reveal a hierarchical mechanism in the direct conversion of fibroblasts into induced neuronal (iN) cells mediated by the transcription factors Ascl1, Brn2, and Myt1l. Ascl1 acts as an "on-target" pioneer factor by immediately occupying most cognate genomic sites in fibroblasts. In contrast, Brn2 and Myt1l do not access fibroblast chromatin productively on their own; instead, Ascl1 recruits Brn2 to Ascl1 sites genome wide. A unique trivalent chromatin signature in the host cells predicts the permissiveness for Ascl1 pioneering activity among different cell types. Finally, we identified Zfp238 as a key Ascl1 target gene that can partially substitute for Ascl1 during iN cell reprogramming. Thus, a precise match between pioneer factors and the chromatin context at key target genes is determinative for transdifferentiation to neurons and likely other cell types.
Howard Hughes Medical Institute and Program in Epithelial Biology, Stanford University, Stanford, CA 94305, USA; Program in Cancer Biology, Stanford University, Stanford, CA 94305, USA.
Orly L
OL
Wapinski
Thomas
T
Vierbuchen
Kun
K
Qu
Qian Yi
QY
Lee
Soham
S
Chanda
Daniel R
DR
Fuentes
Paul G
PG
Giresi
Yi Han
YH
Ng
Samuele
S
Marro
Norma F
NF
Neff
Daniela
D
Drechsel
Ben
B
Martynoga
Diogo S
DS
Castro
Ashley E
AE
Webb
Thomas C
TC
Südhof
Anne
A
Brunet
Francois
F
Guillemot
Howard Y
HY
Chang
Marius
M
Wernig
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D002454:Cell Differentiation; D065150:Cellular Reprogramming; D002843:Chromatin / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology*; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism; D053263:Gene Regulatory Networks; D055106:Genome-Wide Association Study; D006801:Humans; D051379:Mice; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000166:cytology* / Q000378:metabolism; D050809:POU Domain Factors / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism
D051792:Basic Helix-Loop-Helix Proteins; D002843:Chromatin; D009419:Nerve Tissue Proteins; D050809:POU Domain Factors; D012097:Repressor Proteins; D014157:Transcription Factors; C499317:Ascl1 protein, mouse; C561019:Myt1l protein, mouse; C520669:Zbtb18 protein, mouse; C074066:Pou3f2 protein, mouse