microRNA-31 modulates skeletal patterning in the sea urchin embryos

Abstract

The microRNAs (miRNAs) are small non-coding RNAs that repress the translation and reduce the stability of target mRNAs in animal cells. microRNA-31 (miR-31) has been found to play a role in cancer, bone formation, and lymphatic development. However, limited studies have been conducted to understand function of miR-31 in embryogenesis. We examined the regulatory role of miR-31 in early development, using the sea urchin as a model. miR-31 is expressed in all stages of development and its knockdown (KD) disrupts the patterning and function of the primary mesenchyme cells (PMCs), which form the embryonic skeleton spicules. We identified miR-31 to repress directly Pmar1, Alx1, Snail and VegfR7 within the PMC gene regulatory network (GRN) using reporter constructs. Further, blocking the miR-31-mediated repression of Alx1 and/or VegfR7 genes in the developing embryo resulted in defects in PMC patterning and skeletogenesis. The majority of the mislocalized PMCs in miR-31 KD embryos did not express VegfR10, indicating that miR-31 regulated VegfRs within the PMCs. In addition, miR-31 indirectly suppresses Vegf3 expression in the ectoderm. These results indicate that miR-31 coordinately suppresses genes within the PMCs and in the ectoderm to impact PMC patterning and skeletogenesis. This study identifies the novel function and molecular mechanism of miR-31-mediated regulation in the developing embryo.