Mouse anti-Human MLL4 monoclonal antibody, clone 2G7

Kabuki syndrome (KS) is a congenital craniofacial disorder resulting from mutations in the KMT2D histone methylase (KS1) or the UTX histone demethylase (KS2). With small cohorts of KS2 patients, it is not clear whether differences exist in clinical manifestations relative to KS1. We mutated KMT2D in neural crest cells (NCCs) to study cellular and molecular functions in craniofacial development with respect to UTX. Similar to UTX, KMT2D NCC knockout mice demonstrate hypoplasia with reductions in frontonasal bone lengths. We have traced the onset of KMT2D and UTX mutant NCC frontal dysfunction to a stage of altered osteochondral progenitor differentiation. KMT2D NCC loss-of-function does exhibit unique phenotypes distinct from UTX mutation, including fully penetrant cleft palate, mandible hypoplasia and deficits in cranial base ossification. KMT2D mutant NCCs lead to defective secondary palatal shelf elevation with reduced expression of extracellular matrix components. KMT2D mutant chondrocytes in the cranial base fail to properly differentiate, leading to defective endochondral ossification. We conclude that KMT2D is required for appropriate cranial NCC differentiation and KMT2D-specific phenotypes may underlie differences between Kabuki syndrome subtypes.

The histone H3-lysine-4 methyltransferase mixed-lineage leukemia 3 (MLL3) and its closest homolog, MLL4 (aka KMT2D), belong to two homologous transcriptional coactivator complexes, named MLL3 and MLL4 complexes, respectively. MLL3 plays crucial roles in multiple metabolic processes. However, the physiological roles of MLL4 in metabolism and the relationship between MLL3 and MLL4 in metabolic gene regulation are unclear. To address these issues, we analyzed the phenotypes of newly generated MLL4 mutant mice, along with MLL3 mutant and MLL3;MLL4 compound mutant mice. We also performed comparative genome-wide transcriptome analyses in livers of MLL3, MLL4, and MLL3;MLL4 mutant mice. These analyses revealed that MLL3 and MLL4 complexes are key epigenetic regulators of common metabolic processes and the hepatic circadian clock. Subsequent mechanistic analyses uncovered that MLL3/4 complexes function as pivotal coactivators of the circadian transcription factors (TFs), retinoid-related orphan receptor (ROR)- and -, in the hepatic circadian clock. Consistent with disturbed hepatic clock gene expression in MLL4 mutant mice, we found that rhythmic fluctuation of hepatic and serum bile acid (BA) levels over the circadian cycle is abolished in MLL4 mutant mice. Our analyses also demonstrate that MLL4 primarily impinges on hepatic BA production among several regulatory pathways to control BA homeostasis. Together, our results provide strong in vivo support for important roles of both MLL3 and MLL4 in similar metabolic pathways. Conclusion: Both MLL3 and MLL4 complexes act as major epigenetic regulators of diverse metabolic processes (including circadian control of bile acid homeostasis) and as critical transcriptional coactivators of the circadian TFs, RORs. (Hepatology 2015;61:1012-1023)