Characterization of the role of microRNAs in spatiotemporal patterning of the vertebrate spinal cord

• Applicant: Estelle Renaux, Ph.D.
• Subject Area: Developmental Neurobiology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 573237392

How the immense diversity of neuronal cell types is specified and reproducibly generated during embryonic development remains a fundamental question of developmental biology. In the developing spinal cord, spatially defined cardinal classes of neurons are partitioned into molecularly and functionally distinct subtypes by a shared temporal patterning program. Early-born neurons express Onecut-family TFs, intermediate neurons Pou2f2 and Zfhx2-4, and late-born neurons Nfia/b/x and Neurod2/6. How this temporal patterning program is regulated is largely unclear. MicroRNAs are an important class of small non-coding RNAs that bind mRNAs in sequence-specific manner and thereby inhibit their translation and promote their degradation. My preliminary data show that deletion of Dgcr8, which disrupts microRNA biogenesis, results in the complete loss of late temporal identity neurons, while causing a concomitant increase in early and intermediate identity neurons. microRNAs thus appear to play a critical role in temporal patterning of the developing spinal cord. To test this hypothesis, I first aim to comprehensively characterize the transcriptional changes in neuron and progenitor cell populations throughout the spinal cord in the Dgcr8 mutants by single cell RNA sequencing. Candidate microRNAs that may underlie such transcriptional changes, including miR-9 and let-7, which I have already identified as potential candidates involved in temporal patterning, will then be further analyzed using in ovo electroporation and a stem cell-based in vitro differentiation model. My preliminary analysis moreover suggests that miR-9 controls temporal patterning in a level-dependent manner – a hypothesis I aim to test by assessing the phenotypic consequences of targeted deletion of miR-9 from an increasing number of its host genes. Collectively, the anticipated results of this study will provide detailed insights into the role of microRNAs in neuronal subtype specification in the developing spinal cord. Such detailed understanding may pave the way for the rational design of differentiation and reprogramming protocols aimed at generating specific neuronal subtypes for disease modeling and regenerative medicine applications.

• DFG Programme: WBP Position