The Transcriptional Regulator MEIS2 Sets Up the Ground State for Palatal Osteogenesis in Mice

Haploinsufficiency of Meis homeobox 2 (), encoding a transcriptional regulator, is associated with human cleft palate, and inactivation leads to abnormal palate development in mice, implicating MEIS2 functions in palate development. However, its functional mechanisms remain unknown. Here we observed widespread MEIS2 expression in the developing palate in mice. -mediated inactivation in cranial neural crest cells led to a secondary palate cleft. Importantly, about half of the ; mice exhibited a submucous cleft, providing a model for studying palatal bone formation and patterning. Consistent with complete absence of palatal bones, the results from integrative analyses of MEIS2 by ChIP sequencing, RNA-Seq, and an assay for transposase-accessible chromatin sequencing identified key osteogenic genes regulated directly by MEIS2, indicating that it plays a fundamental role in palatal osteogenesis. motif analysis uncovered that the MEIS2-bound regions are highly enriched in binding motifs for several key osteogenic transcription factors, particularly short stature homeobox 2 (SHOX2). Comparative ChIP sequencing analyses revealed genome-wide co-occupancy of MEIS2 and SHOX2 in addition to their colocalization in the developing palate and physical interaction, suggesting that SHOX2 and MEIS2 functionally interact. However, although SHOX2 was required for proper palatal bone formation and was a direct downstream target of MEIS2, overexpression failed to rescue the palatal bone defects in a mutant background. These results, together with the fact that expression is associated with high osteogenic potential and required for chromatin accessibility of osteogenic genes, support a vital function of MEIS2 in setting up a ground state for palatal osteogenesis.