Mist1 Expression Is Required for Paneth Cell Maturation

Abstract

BackgroundPaneth cells are professional secretory cells found within the small intestinal crypt epithelium. Although their role as part of the innate immune complex providing antimicrobial secretory products is well-known, the mechanisms that control secretory capacity are not well-understood. MIST1 is a scaling factor that is thought to control secretory capacity of exocrine cells.MethodsMist1+/+ and Mist1–/– mice were used to evaluate the function of MIST1 in small intestinal Paneth cells. We used histologic and immunofluorescence staining to evaluate small intestinal tissue for proliferation and lineage allocation. Total RNA was isolated to evaluate gene expression. Enteroid culture was used to evaluate the impact of the absence of MIST1 expression on intestinal stem cell function.ResultsAbsence of MIST1 resulted in increased numbers of Paneth cells exhibiting an intermediate cell phenotype but otherwise did not alter overall epithelial cell lineage allocation. Muc2 and lysozyme staining confirmed the presence of intermediate cells at the crypt base of Mist1–/– mice. These changes were not associated with changes in mRNA expression of transcription factors associated with lineage allocation, and they were not abrogated by inhibition of Notch signaling. However, the absence of MIST1 expression was associated with alterations in Paneth cell morphology including decreased granule size and distended rough endoplasmic reticulum. Absence of MIST1 was associated with increased budding of enteroid cultures; however, there was no evidence of increased intestinal stem cell numbers in vivo.ConclusionsMIST1 plays an important role in organization of the Paneth cell secretory apparatus and managing endoplasmic reticulum stress. This role occurs downstream of Paneth cell lineage allocation.

Plasticity of Paneth cells and their ability to regulate intestinal stem cells

“…Another growth factor named helix-loop-helix transcription factor (MIST1) is a scaling factor; this factor can control the fate of exocrine cells (such as pancreatic acinar cells, zymogenic cells of the stomach) to affect secretory capacity [105]. In the small intestine, the absence of MIST1 increased the numbers of PCs, which exhibit an LYZ/ MUC2+ intermediate cell phenotype and morphologically show immature features, including decreased granule size and distended rough endoplasmic reticulum [105,106] (Fig. 3).…”

Paneth cell α-defensin misfolding correlates with dysbiosis and ileitis in Crohn’s disease model mice

“…We showed that genes regulated downstream of XBP1 are modulated as disease progresses in SAMP1/YitFc mice. For example, levels of two ER stress makers, GRP78 and calreticulin, increase, and levels of MIST1, which inhibits ER stress (42), decrease, suggesting that pathophysiology in SAMP1/YitFc mice shares certain pathways with CD patients. In addition, environmental risk factors of CD such as high-fat diet (23) and zinc deficiency (62) induce ER stress in Paneth cells (63,64).…”

“…In SAMP1/YitFc mice at 20 wk, the expression of both GRP78 and calreticulin was remarkably increased in abnormal Paneth cells, in contrast to low expression in ICR mice (Fig S5A and B). Furthermore, we analyzed expression of transcription factor, MIST1, which is known to suppress ER stress and is specifically expressed in Paneth cells of the intestinal epithelium (42). By immunofluorescent staining, MIST1 was strongly expressed in the nucleus of Paneth cells in 20-wk ICR mice.…”

DeMISTifying Paneth Cell Maturation

“…Their secretory function depends on induction and maintenance of subcellular secretory architecture via unknown mechanisms. In this issue of Cellular and Molecular Gastroenterology and Hepatology , Dekaney et al 1 show that the basic helix-loop-helix Class A basic helix-loop-helix protien 15 (BHLHA15)/Muscle, Intestine, and Stomach expression 1 (MIST1) (BHLHA15) helps govern secretory function in Paneth cells.…”

“…In this issue of Cellular and Molecular Gastroenterology and Hepatology , Dekaney et al 1 make important steps toward increasing our understanding of Paneth and intermediate cells. Similar to pancreatic acinar and gastric chief cells, Paneth cells have long lifespans and elaborate exocrine secretory machinery.…”