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Mir-1 regulates Cdc42 to mediate mitosis in early development
Date
2023
Authors
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Publisher
University of Delaware
Abstract
MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression by binding to the 3’UTR of their target and silencing translation. In vertebrates, miR-1 is known to regulate cardiac development, skeletal muscle proliferation and differentiation, and blood vessel formation. In the sea urchin embryo, miR-1 may play a crucial role in early embryonic development since miR-1 overexpression (OE) significantly delayed developmental progression, leading to a high percentage of embryos arrested at the cleavage stage and embryonic lethality. Our results indicate that miR-1 OE leads to chromosomal segregation defects, misaligned mitotic spindles, and defective cytokinesis, potentially leading to embryonic arrest. The functional role of miR-1 in mitosis and cell division is unknown; however, we have bioinformatically identified potential binding sites for miR-1 within Cdc42 and LGN-Gαi-NuMA transcripts, which are involved in anchoring astral microtubules to the cell cortex to mediate the spindle orientation during cell division. Cdc42 also mediates the binding of microtubules to the kinetochores of chromosomes, as well as remodeling actin polymerization to facilitate proper cytokinesis. Prior studies showed that perturbation of either the Cdc42 or members of the LGN-Gαi-NuMA complex leads to cytokinesis failure and misaligned mitotic spindles, respectively. Based on their role in mitosis and the potential miR-1 binding sites within Cdc42 and LGN-Gαi-NuMA, we hypothesize that miR-1 suppresses these transcripts to mediate mitosis. Using site-directed mutagenesis and dual luciferase assay, we demonstrated that miR-1 directly suppresses Cdc42. To examine the specific impact of miR-1’s suppression of Cdc42, we tested the loss-of-function of Cdc42 and observed similar phenotypes as miR-1 OE, indicating that miR-1 regulates mitosis at least in part through its regulation of Cdc42. This work provides a deeper understanding of post-transcriptional regulation of an evolutionarily conserved miRNA and its novel role in embryogenesis. The understanding of how miRNAs regulate cell division contributes to our knowledge of early development, birth defects, and predisposition to cancer.
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Keywords
Embryonic lethality, Developmental progression, Cell division, MicroRNAs, Cytokinesis