CROSSTALK BETWEEN THE HISTONE ACETYLTRANSFERASE KAT6B AND THE PLURIPOTENCY TRANSCRIPTION FACTORS OCT4 AND NANOG IN EMBRYONIC STEM CELLS

VAZQUEZ ECHEGARAY C; ALVAREZ Y; SCHULTZ M.; LEVI V; OSES C; WAISMAN A; COSENTINO, MARÍA SOLEDAD; FRANCIA M; SOLARI C; MIRIUKA S; PETRONE MV; SEVLEVER G; GUBERMAN A; VAZQUEZ ECHEGARAY C; ALVAREZ Y; SCHULTZ M.; LEVI V; OSES C; WAISMAN A; FRANCIA M; MIRIUKA S; COSENTINO, MARÍA SOLEDAD; SOLARI C; PETRONE MV; SEVLEVER G; GUBERMAN A

Taller; IV Taller de Biología Celular y del Desarrollo; 2018

The transition between transcriptionalprograms associated with Stem Cell (SC) differentiation is related to changesin chromatin structure. Kat6b is a transcriptional coactivator with histoneacetyltransferase activity important for the establishment and self-renewal ofadult neural SC. Moreover, mutations in only one allele lead to intellectualdisability in humans. It was reported that Kat6b gene possess a ?super-enhancer?,a regulatory element highly occupied by Embryonic SC (ESC) key transcriptionfactors (TFs). However, the relevance of this chromatin modifier in ESC remainsto be established.The aim of this work was to study therole of Kat6b in the maintenance of ESC?s properties. We found that Kat6b isexpressed in mouse ESC (mESC) and is repressed along differentiation. Moreover,ChIP-seq analysis and shRNA experiments suggest that Kat6b expression isregulated by pluripotency TFs Nanog and Oct4. To study Kat6b relevance, we generateda knock-out (KO) mESC line by CRISPR/Cas9. Kat6b-/- cell colonies were flattenand less refringent than wild type (WT), however they did not displaysignificant differences regarding the expression of early differentiation andpluripotency markers. Moreover, KO cells remained pluripotent both in vitro and in vivo. Although Oct4 and Nanog levels were similar between thetwo cell lines, fluorescence correlation spectroscopy (FCS) experiments showeddifferent protein dynamics of these TFs and of heterochromatin protein 1 (HP1),suggesting an altered chromatin structure in KO cells. Remarkably, along a neuralprogenitor differentiation protocol, Kat6b-/- mESC gave rise to a higher numberof cells at the end of the protocol respect to WT. Additionally, KO cells presentedlower expression of the neural progenitor marker Sox1, and higher levels of themesoderm marker Brachyury, suggesting a reduced efficiency to neuraldifferentiation. Ourresults suggest that Kat6b is relevant in the maintenance of normal TFsdynamics and chromatin organization, and in neural differentiation of mESC. Comprehensionof ESC epigenetic regulation is critical to unravel the mechanisms involved in cellfate choices and to make possible promising stem cells? applications.