Ybx1 Deficiency Causes ROS-Driven IBD-Like Intestinal Inflammation and Postnatal Lethality

Y box-binding protein 1 (YB-1; Ybx1/ybx1) is essential for zebrafish development. Maternal ybx1-/- mutants exhibited embryonic lethality, whereas zygotic mutants (Zybx1-/-) showed high postnatal mortality between 10 and 20 dpf, although a small fraction survived to adulthood. Western blot and immunohistochemical analysis revealed strong, transient expression of Ybx1 in intestinal enterocytes from 3 to 5 days post-fertilization (dpf), followed by rapid ubiquitin-mediated degradation at 6 dpf, coinciding with defective intestinal development and compromised gut homeostasis. RNA-seq analysis identified elevated reactive oxygen species (ROS) and upregulation of matrix metalloproteinases mmp9 and mmp13a in Zybx1-/- larvae. Antioxidant treatment with ascorbic acid rescued postnatal lethality and alleviated intestinal defects, whereas prooxidant exposure exacerbated them. Pharmacological inhibition of Mmp9 or Mmp13a similarly prevented lethality, highlighting a ROS-MMP axis driving tissue damage. By 30 dpf, surviving mutants exhibited progressive intestinal impairment and severe pathology. These findings demonstrate that Ybx1 deficiency triggers ROS-dependent intestinal inflammation, MMP-mediated gut damage, and postnatal lethality, establishing Ybx1-deficient zebrafish as a robust model for studying inflammatory bowel disease (IBD)-like intestinal disorders.