Crabtree, G. R. | Search bioRxiv

bioRxiv2018

Nucleosome turnover is sufficient to establish varied histone methylation states

Transcription-dependent methylation of histone H3 at lysine 79 (H3K79) is evolutionarily conserved from yeast to mammals, critical for normal development and frequently deregulated by genetic recombination in Mixed Lineage Leukemia. Although this histone modification is associated with gene activity, little is known about the cellular mechanisms of H3K79 methylation regulation. Because no H3K79 demethylase has been discovered, the mechanism of its removal remains unclear. Utilizing chemical-induced-proximity to control histone methylation in vivo we show that the dynamics of methylation state (mono, di, tri-methylation) is genome-context specific. Further, Monte Carlo simulations coupling systems of kinetic reactions with histone turnover rates, suggest that nucleo-some turnover is sufficient to establish varied genome-wide methylation states without active demethylation.

molecular biology↗

bioRxiv2016

Lower brain pH as a shared endophenotype of psychotic disorders

Lower pH is a well-replicated finding in the postmortem brains of patients with schizophrenia and bipolar disorder. Interpretation of the data, however, is controversial as to whether this finding reflects a primary feature of the diseases or is a result of confounding factors such as medication, postmortem interval, and agonal state. To date, systematic investigation of brain pH has not been undertaken using animal models, which can be studied without confounds inherent in human studies. In the present study, we first confirmed that the brains of patients with schizophrenia and bipolar disorder exhibit lower pH values by conducting a meta-analysis of existing datasets. We then utilized neurodevelopmental mouse models of psychiatric disorders in order to test the hypothesis that lower brain pH exists in these brains compared to controls due to the underlying pathophysiology of the disorders. We measured pH, lactate levels, and related metabolite levels in brain homogenates from three mouse models of schizophrenia (Schnurri-2 KO, forebrain-specific calcineurin KO, and neurogranin KO mice) and one of bipolar disorder (Camk2a HKO mice), and one of autism spectrum disorders (Chd8 HKO mice). All mice were drug-naive with the same postmortem interval and agonal state at death. Upon postmortem examination, we observed significantly lower pH and higher lactate levels in the brains of model mice relative to controls. There was a significant negative correlation between pH and lactate levels. These results suggest that lower pH associated with increased lactate levels is a pathophysiology of such diseases rather than mere artifacts.

neuroscience↗