Mucin Muc2 Deficiency and Weaning Influences the Expression of the Innate Defense Genes Reg3β, Reg3γ and Angiogenin-4

Abstract

Background Mucin Muc2 is the structural component of the intestinal mucus layer. Absence of Muc2 leads to loss of this layer allowing direct bacterial-epithelial interactions. We hypothesized that absence of the mucus layer leads to increased expression of innate defense peptides. Specifically, we aimed to study the consequence of Muc2 deficiency (Muc2 −/− ) on the expression of regenerating islet-derived protein 3 beta (Reg3β), regenerating islet-derived protein 3 gamma (Reg3γ), and angiogenin-4 (Ang4) in the intestine shortly before and after weaning. Methods Intestinal tissues of Muc2 −/− and wild-type (WT) mice were collected at postnatal day 14 (P14, i.e. pre-weaning) and P28 (i.e. post-weaning). Reg3β, Reg3γ, and Ang4 expression was studied by quantitative real-time PCR, Western-blot, in situ hybridization, and immunohistochemistry. Results Reg3β and Reg3γ were expressed by diverging epithelial cell types; namely enterocytes, Paneth cells, and goblet cells. Additionally, Ang4 expression was confined to Paneth cells and goblet cells. Expression of Reg3β , Reg3γ , and Ang4 differed between WT and Muc2 −/− mice before and after weaning. Interestingly, absence of Muc2 strongly increased Reg3β and Reg3γ expression in the small intestine and colon. Finally, morphological signs of colitis were only observed in the distal colon of Muc2 −/− mice at P28, where and when expression levels of Reg3β , Reg3γ , and Ang4 were the lowest. Conclusions Expression of Reg3 proteins and Ang4 by goblet cells point to an important role for goblet cells in innate defense. Absence of Muc2 results in up-regulation of Reg3β and Reg3γ expression, suggesting altered bacterial-epithelial signaling and an innate defense response in Muc2 −/− mice. The inverse correlation between colitis development and Reg3β , Reg3γ , and Ang4 expression levels might point toward a role for these innate defense peptides in regulating intestinal inflammation.

Bile Acid Administration Elicits an Intestinal Antimicrobial Program and Reduces the Bacterial Burden in Two Mouse Models of Enteric Infection

“…While intestinal ␣-defensins are exclusively produced by Paneth cells, the C-type lectins Reg3b and Reg3g are made by several cell types, including Paneth cells, goblet cells, and enterocytes (19,30,52). In keeping with that, immunofluorescence microscopy showed enhanced positive staining for Reg3b and Reg3g in the villi, outside the Paneth cell niche on the crypts.…”

Intestinal Metrnl released into the gut lumen acts as a local regulator for gut antimicrobial peptides

“…As shown in Figure 5B, contrary to the lack of change in Villin expression in Metrnl -/-mice, the expression of most antimicrobial peptides, such as regenerating islet-derived 3 gamma (Reg3g) [24][25][26] and lactotransferrin [27] , was significantly decreased. Others, such as serum amyloid A-3 (SAA3) [28] and regenerating islet-derived 3 beta (Reg3b) [25,29] , showed a trend towards a decrease. This suggests that Metrnl plays a role in regulating the expression of antimicrobial peptides.…”

Bacterial Sensor Nod2 Prevents Inflammation of the Small Intestine by Restricting the Expansion of the Commensal Bacteroides vulgatus

“…Mucus secreted by goblet cells forms a physical barrier that separates intestinal bacteria from the epithelium. Goblet cells in IBD patients have decreased Muc2 expression, and mice deficient in this dominant intestinal mucin display increased expression of antimicrobial genes including Reg3β (Burger-van Paassen et al, 2012; Sheng et al, 2012). Consistent with these observations, we observed decreased Muc2 expression in the small intestine of Nod2 −/− mice compared to WT mice (Figure 2A).…”