Maternal obesity disrupts histone modifications mediated by Ezh2 and Ampk interactions and induces cell fate defects during embryonic cortical neurogenesis. [RNA-seq]

In this study, we have used a rat model of maternal obesity induced by high fat diet (HFD) prior to and during gestation to investigate the cellular and molecular repercussions of maternal obesity on embryonic cortical neurogenesis. Maternal obesity is noted to substantially disrupt neurogenesis, leading not only to imbalances in cell proliferation vs neuronal differentiation ratios but also prompting a shift towards astrogliogenesis. Differentially expressed genes (DEGs) revealed disruptions in key developmental signaling pathways and reduced Akt phosphorylation particularly notable at the E14.5. These changes were associated with epigenetic alterations, mainly the differential expression and phosphorylation of Ezh2 and subsequent changes in global histone modifications. ChIP-seq revealed reduced H3K27me3 at genes upregulated due to maternal obesity which could have resulted from reduced expression and increased phosphorylation of Ezh2 at Thr311. Interestingly Ezh2 also showed increased O-GlcNAcylation in HFD embryos along with increased association with Ampk-Thr172 in accordance with previous studies showing that Ezh2-Thr311p is catalyzed by Ampk. These results led to propose an epigenetic gene regulatory mechanism mediated by Ampk and Ezh2 interactions resulting in reduced H3K27me3 and de-repression of key developmental genes which could have led to cell fate defects observed in the developing embryo brain cortex due to maternal obesity. Overall design: Healthy female and male Wistar Rats were fed on the normal chow and the 'High Fat Diet (HFD) group fed on the commercially available high fat diet produced by Research Diets Inc. (60% calories by fat, 20% calories by protein, and 20% calories by carbohydrate; Product No.: D14292). Normal Weight and obese female rats were crossed with healthy males and were sacrificed on embryonic days, E14.5, E16.4 and E18.5. Pups' brains were removed and dissected out for further processing.