Mitochondrial protein Mrpl4 is required for zebrafish intestinal development

Mitochondrial ribosomal proteins are involved in many cellular processes and not only protein synthesis from mitochondrial DNA. We previously showed that zebrafish mitochondrial ribosomal protein L4 (Mrpl4) is highly expressed in larval intestine. However, the physiological significance of this expression pattern remains unclear. Here, we observed significant defects in intestinal growth and maturation in mrpl4 knockout fish; this was accompanied by disruption of intestinal epithelial integrity leading to inflammatory responses, demonstrating that Mrpl4 plays an essential role in regulating zebrafish intestinal development. Moreover, we found that Notch signaling was downregulated in these mutants, and reactivation of Notch signaling can partially rescue their intestinal defects, suggesting involvement of Notch signaling in the effects of Mrpl4 on intestinal development.