Biology subjects

Ameen, N. A.

Publications and source records attributed to Ameen, N. A..

3 recordsLinked to original sources

bioRxiv2025

CFTR High Expresser BEST4+ cells are pH-sensing neuropod cells: new implications for intestinal physiology and Cystic Fibrosis disease

Single-cell RNA sequencing (scRNA-seq) studies identified a novel subpopulation of epithelial cells along the rostrocaudal axis of human intestine specifically marked by bestrophin 4 (BEST4) that are enriched for genes regulating pH, GPCR acid-sensing receptors, satiety, cGMP signaling, HCO3- secretion, ion transport, neuropeptides, and paracrine hormones. Interestingly, BEST4+ cells in the proximal small intestine express CFTR but have not been linked to the previously described CFTR High Expresser Cell (CHE) subpopulation in rat and human intestine. ScRNA-seq studies in rat jejunum identified CHEs and a gene expression profile consistent with human small intestinal BEST4+ and neuropod cells. Protein immunolocalization confirmed that CHEs express CFTR, BEST4, neuropod proteins, high levels of intracellular uroguanylin (UGN), guanylyl cyclase-C (GC-C), and the proton channel otopetrin 2 (OTOP2), and display long basal processes connecting to neurons. OTOP2, GC-C, and CFTR traffic robustly into the apical domain of CHEs in response to acidic luminal conditions, indicating their roles in luminal pH regulation. In the {Delta}F508 cystic fibrosis (CF) rat jejunum, the loss of apical CFTR did not affect BEST4 protein expression in CHEs. However, there was an increased abundance of CHE cells in the {Delta}F508 rat jejunum compared to wild-type animals. Furthermore, {Delta}F508 rat CHEs expressed higher levels of GC-C at the apical domain compared to wild-type. These data implicate CHEs in intestinal CF disease pathogenesis. NEW & NOTEWORTHYThis is the first study to identify CFTR High Expresser cells in the rat small intestine as neuropod cells capable of sensing and responding to luminal pH. This study also provides the first characterization of CFTR and relevant mRNA and proteins in CHEs in CF rat models that provide insights into the significance of CHEs to CF intestinal disease.

physiology↗

bioRxiv2025

Fibroblast contractility drives network reorganization and epithelial proliferation in intestinal polyposis

Fibroblasts are critical regulators of epithelial homeostasis through mechanics and signaling. However, the regulatory principles governing fibroblast behaviors are largely unknown. Fibroblast dysregulation has emerged as a pathological contributor in epithelial diseases such as intestinal polyposis. Here, using an inducible Bmp-loss-of-function polyposis model, we define stepwise mechanisms unraveling how dysregulated signaling perturbs fibroblast behaviors, which in turn, disrupt their function to regulate epithelial homeostasis. Intriguingly, the first initiating event leading to epithelial polyps was architectural and impacted the fibroblasts, not the epithelium. Bmp signaling inhibition caused fibroblasts to become hypercontractile, leading to their reorganization from an elaborate network into collapsed clusters beneath crypts. Disrupted fibroblast mechanics and compartmentalization preceded epithelial hyperproliferation in polyps. Using in vitro models, we show that fibroblast hypercontractility not only disrupted fibroblast organization, but also enhanced the ability of fibroblasts to support epithelial growth, leading to epithelial dysregulation. Overall, our studies reveal stepwise regulatory mechanisms underlying fibroblast signaling, mechanics and organization critical for their function to regulate epithelial homeostasis.

cell biology↗

bioRxiv2024

A second wave of Notch signaling diversifies the intestinal secretory lineage

The small intestine is well known for the function of its nutrient-absorbing enterocytes; yet equally critical for the maintenance of homeostasis is a diverse set of secretory cells, all of which are presumed to differentiate from the same intestinal stem cell. Despite major roles in intestinal function and health, understanding how the full spectrum of secretory cell types arises remains a longstanding challenge, largely due to their comparative rarity. Here, we investigate the fate specification of a rare and distinct population of small intestinal epithelial cells found in rats and humans but not mice: CFTR High Expressers (CHEs). We use pseudotime trajectory analysis of single-cell RNA-seq data from rat intestinal jejunum to provide evidence that CHEs are specified along the secretory lineage and appear to employ a second wave of Notch-based signal transduction to distinguish these cells from other secretory cell types. We further validate the general order of transcription factors that direct these cells from unspecified progenitors within the crypt and experimentally demonstrate that Notch signaling is necessary to induce CHE fate both in vivo and in vitro. Our results suggest a model in which Notch is reactivated along the secretory lineage to specify the CHE population: a rare secretory cell type with putative functions in localized coordination of luminal pH and direct relevance to cystic fibrosis pathophysiology.

cell biology↗