Regulation of chromatin and epigenetics by ubiquitin signaling. We have discovered multiple mechanisms by which the ubiquitin ligase Anaphase-Promoting Complex (APC) regulates chromatin environment in heterochromatin, which is crucial for the development of the mammalian brain. We are now applying state-of-the-art next-generation sequencing methods, including CUT&RUN, micro-C, ATAC-seq and RNA-seq, to understand their effect on gene regulation.
Identification and characterization of APC substrates in the brain. The ubiquitin ligase APC controls neuronal development by selectively degrading target proteins. To identify mechanistic substrates of APC-mediated ubiquitin signaling in the brain, we perform unbiased proteomics in mutant mice followed by functional validation through imaging and biochemistry. Through this approach, we have identified critical targets of APC activity in the brain and are actively exploring their roles in neurodevelopment.
Therapy for Inherited Disorders of Brain Development. We identified kinases that are substrates of APC-mediated ubiquitination in the brain. For some of these kinases, there are potent, specific and CNS penetrant small molecule inhibitors that block key cellular phenotypes in the brain of mutant mice, suggesting a possible route toward therapy for disorders of neurodevelopment caused by APC mutation.
Regulation of heterochromatin by phase separation. A major substrate of the APC in neurons, Ki-67 is a massive and highly disordered protein. During mitosis, Ki-67 organizes the chromosome periphery, whereas after mitotic exit Ki-67 contributes to the formation of heterochromatin, but how it accomplishes this feat is poorly defined. We have generated mouse models of Ki-67 deficiency in the brain and are currently exploring how Ki-67 loss impacts neuronal development through a combination of microscopy, genomics and behavior methods.
Role of the APC in inherited disorders of brain development. The multimeric APC enzyme is encoded by ~20 genes. We initially linked mutation of a core APC subunit to disorders of brain development when we described the recessive ANAPC7 neurodevelopmental syndrome (Ferguson-Bonni, OMIM 606949), in which loss of APC7 causes intellectual disability. Since then, additional APC subunits have been linked to atypical neurodevelopment in humans. We have ongoing collaborations with genetics consortia to identify new patients with mutations in APC subunits, which we will then explore through mouse genetics experiments.