Deletion of miRNA processing enzyme Dicer in POMC-expressing cells leads to neurodegeneration and development of obesity

The activity of the endoribonuclease Dicer is crucial to produce the mature form of most microRNAs (miRNAs). Recent studies indicate that lack of miRNAs in different neuronal types results in a range of anatomical and behavioural phenotypes. In the present study we aimed to investigate the developmental and metabolic consequences of miRNA ablation in hypothalamic POMC neurons studying mice with a conditional deletion of Dicer in this population of neurons (POMCDicerKO). These mice exhibited a progressive obese phenotype characterized by hyperphagia, increased adiposity, hyperleptinemia, defective glucose metabolism and alterations in the pituitary-adrenal axis. The development of the obese phenotype was paralleled by a POMC neuron degenerative process that was complete by 6 weeks of age. Furthermore, immunohistochemistry and gene expression studies in control C57Bl/6 adult mice showed that Dicer was expressed in relevant hypothalamic areas and neurons implicated in energy balance, and that its expression was regulated by nutrient availability. Collectively, our results highlight a crucial role for miRNAs in POMC neuron survival and the consequent development of neurodegenerative obesity. Total RNA was extracted from hypothalamic microdissections of 2-week old control and POMCDicerKO mice using the RNeasy micro spin columns (Qiagen, Venlo, The Netherlands). Ten micrograms of total RNA were converted into cRNA, biotinylated, fragmented, and hybridized to GeneChip Mouse Genome 430 2.0 (Affymetrix, Santa Clara, CA). Six microarrays were hybridized with three independent samples from control and POMCDicerKO mice.