{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n The H3‐3A gene (commonly referred to as H3F3A) encodes the replication‐independent histone variant H3.3, which plays a central role in maintaining chromatin structure and dynamics. In normal cells, H3.3 is deposited at active genes, telomeres, centromeres, and pericentric heterochromatin—contributing to the regulation of transcription, chromatin accessibility, and genomic stability (see."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "3"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n A number of studies have revealed that somatic mutations in H3F3A, notably the lysine‐to‐methionine (K27M) and glycine‐to‐arginine/valine (G34R/V) substitutions, are frequent in pediatric and young adult gliomas. These mutations disrupt key post‐translational modifications—such as the trimethylation of lysine 27 (H3K27me3) or alteration of lysine 36 methylation patterns—thereby reprogramming the epigenetic landscape. As a consequence, these aberrations perturb the regulation of gene expression, contribute to distinct transcriptional profiles and cellular identities, and drive oncogenic pathways including the upregulation of potent oncogenes (for instance, MYCN) (see."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}, {"type": "fg_fs", "start_ref": "4", "end_ref": "10"}]}, {"type": "t", "text": " \n "}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n In addition to its role in transcriptional regulation, H3.3 functions in preserving chromosomal integrity. Its incorporation at telomeric and pericentromeric regions is critical for proper heterochromatin organization; loss or mutation of H3.3 can lead to telomere dysfunction and genomic instability, both of which are frequently observed in tumor cells (see."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "2"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n Cumulatively, these studies establish that H3-3A/H3F3A is not only a core component required for normal chromatin architecture and gene regulation, but that mutations in this gene act as key driving events in pediatric high-grade gliomas by impairing normal histone modification landscapes and reprogramming transcription. This dual role—with disruption of both epigenetic signaling and chromatin stability—underlines its importance as a molecular link between developmental chromatin regulation and oncogenic transformation.\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Jeremy Schwartzentruber, Andrey Korshunov, Xiao-Yang Liu, et al. 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"}, {"type": "b", "children": [{"type": "t", "text": "Hotspot mutations in H3F3A and IDH1 define distinct epigenetic and biological subgroups of glioblastoma."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Cancer Cell (2012)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1016/j.ccr.2012.08.024"}], "href": "https://doi.org/10.1016/j.ccr.2012.08.024"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "23079654"}], "href": "https://pubmed.ncbi.nlm.nih.gov/23079654"}]}, {"type": "r", "ref": 5, "children": [{"type": "t", "text": "Peter W Lewis, Manuel M Müller, Matthew S Koletsky, et al. 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