166 - The role of Khdc3 in epigenetic inheritanceof obesity and metabolic disorders

Childhood obesity and metabolic disease is an ongoing public health epidemic. There is strong evidence that inherited factors contribute strongly to disease risk, but DNA-focused approaches have failed to explain much of this inheritance. Khdc3 is a predicted critical regulator of epigenetic inheritance. We hypothesize that Khdc3 is essential for integrating environmental signals, such as exposure to a high fat diet (HFD), into dynamic heritable changes in germ cell small RNAs, with important implications for the intergenerational inheritance of disease risk based on ancestral diet.

Objective:

To test how Khdc3 regulates murine sperm small RNAs in response to a HFD and the resultant disease risk in non-exposed descendants.

Design/Methods:

Khdc3-null (KO) and wild type (WT) male mice were fed either high fat diet (HFD) or control diet (CD) for 8 weeks. Weight gain was monitored, along with various metabolic tests. Males were then sacrificed to isolate sperm small RNA populations. In order to elucidate the inheritance of metabolic disease,WT mice descended from Khdc3 mutant ancestors were generated (Figure 1). “Wild type star (WT*)” mice develop from Khdc3-null grandfathers mated with WT grandmothers (F0). WT* male mice (F2) are differentiated from genetically identical WT mice derived from WT ancestors. The WT* mice will be compared to WT mice for weight gain and glucose regulation in response to a HFD, as well as comparing their sperm small RNA populations to both their KO ancestors and WT controls.

Results:

Mice on the HFD gained significantly more weight than their control diet counterparts, as expected. Interestingly, KO mice on a HFD gained significantly more weight than WT mice on the HFD (Figure 2a). KO mice on the control diet also have significantly higher levels of fasting serum glucose compared to WT mice (Figure 2b). Additionally, the sperm small RNA populations in all experimental conditions are significantly different from each other. We suspect these small RNA germ line changes underlie observed tissue-specific expression pattern changes in WT* mice. CYP17A1, a gene expressed in hepatocytes important for maintaining fasting blood glucose levels, is expressed at significantly higher levels in WT* mice, compared to WT, mimicking KO mice expression patterns (Figure 3).

Conclusion(s):

Khdc3-null (KO) mice have a baseline metabolic phenotype, predisposing to weight gain and glucose dysregulation. Along with observed small RNA sperm alterations, we believe future experiments will elucidate populations that can perpetuate these epigenetic and phenotypic changes, even those genetically wild type.
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