Cbx5-KO Mouse

CBX5, also known as HP1α, is an epigenetic regulatory protein. It is involved in maintaining chromatin state, as it can recognize histone 3 lysine trimethylation at residue K9 (H3K9me3), a transcriptionally suppressive epigenetic mark, and is associated with the formation of inaccessible heterochromatin and suppression of gene expression [6].

In myeloid leukemia, the RNA binding proteins RBMX and RBMXL1 control leukemia cell survival by regulating chromatin state through their downstream target CBX5. Loss of RBMX/L1 leads to significant chromatin changes, and forced CBX5 expression can rescue the effects of RBMX/L1 depletion on cell growth and apoptosis [1].

In lung cancer, loss of CBX5 drives EGFR inhibitor resistance. CBX5 loss increases the expression of E2F1, which in turn upregulates the anti-apoptotic gene BIRC5, attenuating apoptosis induction following EGFRi treatment [2].

In periodontitis, Porphyromonas gingivalis OMVs contain msRNA sRNA45033 that targets CBX5, and CBX5 regulates apoptosis through the methylation of p53 DNA [3].

In lung fibrosis, CBX5, along with histone methyltransferase G9a, is essential for fibroblast activation by epigenetically repressing the peroxisome proliferator-activated receptor gamma coactivator 1 alpha gene (PPARGC1A). Inhibition of the CBX5/G9a pathway reduces collagen accumulation in the lungs following bleomycin injury [4]. Targeting CBX5 promotes fibroblast metabolic reprogramming and inhibits lung fibrosis, as loss of mesenchymal CBX5 attenuates fibrosis development, accompanied by changes in the expression of pathogenic fibroblast and metabolic genes [5].

In glioma, the lncRNA LINC02381 can interact with CEBPβ to transcriptionally enhance CBX5, promoting cell proliferation and hindering apoptosis [7].

In summary, CBX5 plays crucial roles in multiple biological processes and disease conditions. Through gene knockout or conditional knockout mouse models and other functional studies, its functions in maintaining chromatin state, cell growth, apoptosis, and disease-related pathways have been revealed. These findings highlight its potential as a therapeutic target in myeloid malignancies, lung cancer, periodontitis, and lung fibrosis.