Gene profile of PTIP deletion in adult murine cardiac tissue

Methylation of histone H3 lysine 4 (H3K4me) at actively expressed, cell type-specific genes is established during development by the Trithorax group of epigenetic regulators. In mammals, the Trithorax family includes KMT2A-D (MLL1-4), a family of SET domain proteins that function in large complexes to impart mono-, di-, and trimethylation at H3K4. Individual KMT2s and their co-factors are essential for embryonic development and the establishment of correct gene expression patterns, presumably by demarcating the active and accessible regions of the genome in a cell specific and heritable manner. Despite the importance of H3K4me marks in development, little is known about the importance of histone methylation in maintaining gene expression patterns in fully differentiated and non-dividing cell types. In this report, we utilized an inducible cardiac-specific Cre driver to delete the PTIP protein, a key component of a H3K4me complex, and ask whether this activity is still required to maintain the phenotype of terminally differentiated cardiomyocytes. Our results demonstrate that reducing the H3K4me3 marks is sufficient to alter gene expression patterns and significantly augment systolic heart function. These results clearly show that maintenance of H3K4me3 marks is necessary for the stability of the transcriptional program in differentiated cells. The array we performed allowed us to identify genes that are regulated by PTIP and histone methylation.

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Stein AB, Jones TA, Herron TJ, Patel SR, Day SM, Noujaim SF, Milstein ML, Klos M, Furspan PB, Jalife J, Dressler GR