HMGXB4 (also known as HMG2L1) is a non-histone DNA-binding protein containing a single HMG-box domain that functions as a negative regulator of Wnt/β-catenin signaling 1. In smooth muscle cells, HMGXB4 represses smooth muscle-specific gene expression by disrupting myocardin-serum response factor interactions, thereby inhibiting myocardin-induced activation of differentiation markers 2. The protein also regulates transcriptional activity of transposable elements and is itself subject to feedback regulation by transposase 3. In hematopoietic contexts, HMGXB4 loss-of-function has cell-type specific effects: copy number loss and transcriptional downregulation of HMGXB4 in primary myelofibrosis patients correlates with megakaryocyte hyperplasia, as HMGXB4 silencing promotes megakaryocyte differentiation while inhibiting erythroid development 4. Dental pulp fibroblast-derived exosomes contain regulatory axes involving miR-493-5p targeting HMGXB4, linking the protein to mesenchymal stem cell-associated molecular programs 5. Clinically, biallelic frameshift mutations in HMGXB4 cause intellectual disability, global developmental delay, and dysmorphic facial features, establishing a neurodevelopmental role 1. Genetic association studies suggest HMGXB4 variants may contribute to psychotic bipolar affective disorder, consistent with its role in Wnt signaling pathways targeted by psychiatric medications 6.