Aberrant brain microRNA target and miRISC gene expression in the anx/anx anorexia mouse model

Abstract

The anorexia mouse model, anx/anx, carries a spontaneous mutation not yet identified and homozygous mutants are characterized by anorexia-cachexia, hyperactivity, and ataxia. In order to test if the microRNA function was altered in these mice, hypothalamus and cortex transcriptomes were evaluated and the data was analyzed taking into account the presence of microRNA target sites. Subsequent validation of the expression of a subset of miRISC coding genes and microRNA targets was performed by TaqMan real time PCR. In anx/anx hypothalamus we found that predicted microRNA targets were preferentially upregulated in a linearly dependent manner according to the number of microRNA target sites in each mRNA (p=10(-139)). Conversely, we observed that in anx/anx cortex mRNAs predicted to be targeted by microRNAs were preferentially downregulated (p<10(-74)), suggesting a de-regulation of genes targeted by microRNAs in two brain areas in anx/anx mice. A closer look to the mRNA transcriptome allowed us to identify upregulation of five miRISC genes, including Dgcr8 and Fmr1, and Ago2, which were later confirmed by real time PCR. The results suggest alteration of microRNA machinery expression in anx/anx mice and are consistent with its involvement in inflammatory/cancer-associated anorexia-cachexia. The data also support the previously reported link between microRNA machinery and ataxia. Further functional studies and the cloning of the anx gene should be pursued in order to elucidate the causality of microRNA machinery and microRNA target de-regulation, its relationship with the anx/anx phenotype and to propose this mouse as a model for microRNA research.