MicroRNAs Promote Granule Cell Expansion in the Cerebellum Through Gli2
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MicroRNAs (miRNAs) are important regulators of cerebellar function and homeostasis. Their deregulation results in cerebellar neuronal degeneration and spinocerebellar ataxia type 1 and contributes to medulloblastoma. Canonical miRNA processing involves Dicer, which cleaves precursor miRNAs into mature double-stranded RNA duplexes. In order to address the role of miRNAs in cerebellar granule cell precursor development, loxP-flanked exons of Dicer1 were conditionally inactivated using the granule cell precursor-specific Atoh1-Cre recombinase. A reduction of 87 % in Dicer1 transcript was achieved in this conditional Dicer knockdown model. Although knockdown resulted in normal survival, mice had disruptions to the cortical layering of the anterior cerebellum, which resulted from the premature differentiation of granule cell precursors in this region during neonatal development. This defect manifested as a thinner external granular layer with ectopic mature granule cells, and a depleted internal granular layer. We found that expression of the activator components of the Hedgehog-Patched pathway, the Gli family of transcription factors, was perturbed in conditional Dicer knockdown mice. We propose that loss of Gli2 mRNA mediated the anterior-restricted defect in conditional Dicer knockdown mice and, as proof of principle, were able to show that miR-106b positively regulated Gli2 mRNA expression. These findings confirm the importance of miRNAs as positive mediators of Hedgehog-Patched signalling during granule cell precursor development.
KeywordsCerebellum Dicer1 protein Mouse Gli2 protein Mirn106 microRNA Mouse Growth and development
The authors would like to thank Professor Witold Filipowicz for the kind gift of the Dicer 349 antibody, Professor Michael Waters for critical reading of the manuscript, and Mr. Hou Jiapeng for optimizing the Dicer immunofluorescence protocol. All imaging was performed in the Australian Cancer Research Foundation’s Imaging Facility at the Institute for Molecular Bioscience.
This research was financially supported by the National Health and Medical Research Council of Australia and The John Trivett Foundation. Lena Constantin is an Australian Postgraduate Award Scholar.
Conflict of Interest
The authors declare no conflict of interest.
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