The function of PITHD1 (PITH domain containing 1, ENSG00000057757) is as follows. Promotes megakaryocyte differentiation by up-regulating RUNX1 expression (PubMed:25134913). Regulates RUNX1 expression by activating the proximal promoter of the RUNX1 gene and by enhancing the translation activity of an internal ribosome entry site (IRES) element in the RUNX1 gene (PubMed:25134913). .