# The Zebrafish miR-183 Family Regulates Endoderm Convergence and Heart Development via S1Pr2 Signaling Pathway

## TL;DR

This study shows that the miR-183 family in zebrafish controls early heart development by regulating endoderm cell movement through the S1Pr2 signaling pathway.

## Contribution

The study identifies the miR-183 family as a novel regulator of endoderm convergence and heart development via the S1Pr2 pathway in zebrafish.

## Key findings

- Overexpression of miR-183 family members causes defects in endoderm convergence and downregulation of sox32 in zebrafish embryos.
- miR-183 family overexpression leads to cardia bifida and reduced expression of heart development-related genes like cmlc2 and gata4.
- miR-183 targets the s1pr2 gene, and its overexpression mimics the phenotype of s1pr2 loss, confirming S1Pr2 as a key signaling component.

## Abstract

MicroRNA (miRNA), as a key post-transcriptional regulatory factor, plays a crucial role in embryonic development. The coordination of endoderm cell convergence and cardiac precursor cell (CPC) migration is critical for cardiac tube fusion. Defects in endoderm can impair the normal migration of CPCs towards the midline, leading to cardia bifida. Although the role of the microRNA-183 family (miR-183, miR-96 and miR-182) in cardiovascular diseases has been reported, the mechanism by which they regulate early heart development remains unclear. In this study, we used zebrafish as a model to elucidate the roles of the microRNA-183 family in early heart development. miRNA mimics were injected into Tg (cmlc2: eGFP) and Tg (sox17: eGFP) transgenic embryos to overexpress the miR-183 family. The results showed that, at 36 hpf, single or co-injection of miR-183/96/182 mimics caused defects in endoderm convergence, with a hole in the endoderm, and a significant down-regulation of the endoderm marker gene sox32. Additionally, embryos with single or co-injection of miR-183/96/182 mimics exhibited cardia bifida and tail blisters, with significantly down-regulated expression levels of genes related to heart development, including cmlc2, vmhc, amhc, nppa, gata4, gata5, nkx2.5, bmp2b, and bmp4. The phenotype caused by overexpression of the miR-183 family is highly consistent with loss of the sphingosine 1-phosphate receptor S1Pr2. Bioinformatics analysis result found that miR-183 can bind to 3′-UTR of the s1pr2 to regulate its expression; overexpression of miR-183 led to a significant decrease in the expression of the s1pr2 gene. Dual luciferase assay results suggest that s1pr2 is a bona fide target of miR-183. In summary, the miR-183 family regulates endoderm convergence and cardiac precursor cell migration via the S1Pr2 signaling pathway. This study reveals that the miR-183 family is a key regulatory factor in endoderm convergence and cardiac precursor cell migration during the early zebrafish development, elucidating the molecular mechanisms underlying early cardiac precursor cell and endoderm cell movement.