Microarray expression data from HDAC1 and HDAC2 conditional knock-out mouse embryonic stem cells

Histone deacetylase 1 and 2 (HDAC1/2) are the core catalytic components of co-repressor complexes which modulate gene expression. In most cell types, deletion of both Hdac1 and Hdac2 is required to generate a discernible phenotype, suggesting their activity is largely redundant. We have therefore generated an embryonic stem cell (ES) line in which Hdac1 and Hdac2 can be inactivated simultaneously using a Tamoxifen inducible CreER fusion. Loss of HDAC1/2 results in a 60% reduction in total HDAC activity and a loss of cell viability. Cell death is cell cycle dependent, since differentiated, non-proliferating cells, retain their viability. Furthermore, we observe increased mitotic defects, lagging chromosomes and micronuclei, suggesting HDAC1/2 maintain chromosomal stability. Consistent with a critical role in the regulation of gene expression, microarray analysis of Hdac1/2 deleted cells reveals 1,708 differentially expressed genes. Significantly for the maintenance of stem cell self-renewal, we detected a reduction in the expression of the pluripotent transcription factors, Oct4, Nanog and Rex1. HDAC1/2 activity is regulated through binding of inositol tetraphosphate molecule [Ins(1,4,5,6)P4] (IP4) sandwiched between the HDAC and its cognate co-repressor. This raises the important question of whether the IP4 actually regulates the activity of the complex in cells. By rescuing the viability of DKO cells, we demonstrate for the first time that mutations which abolish IP4 binding reduce the activity of HDAC1/2 in vivo. Our data indicate that HDAC1/2 have a generic, but essential role in cellular proliferation and regulate stem cell self-renewal by maintaining expression of key pluripotent transcription factors. Comparative gene expression profiles of wild type (Day 0) were compared to Hdac1lox/lox, Hdac2lox/lox; CreER ES cells on days 1, 2 and 3 following for OHT treatment using the Illumina mouseWG-6 v2 expression BeadChip platform. wild type (Day 0) were compared to Hdac1lox/lox, Hdac2lox/lox; CreER ES cells on days 1, 2 and 3 following for OHT treatment. Four time points were analyzed in triplicate.