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Dysgenesis of enteroendocrine cells in Aristaless-Related Homeobox polyalanine expansion mutations.

Terry NA, Lee RA, Walp ER, Kaestner KH, Lee May C - J. Pediatr. Gastroenterol. Nutr. (2015)

Bottom Line: Immunohistochemistry and quantitative real-time polymerase chain reaction were the primary modalities used to characterize the enteroendocrine populations.Daily weights were determined for the growth curves, and Oil-Red-O staining on stool and tissue identified neutral fats.In human tissue, cholecystokinin, glucagon-like peptide 1, and somatostatin populations were reduced, whereas the chromogranin A population was unchanged.

View Article: PubMed Central - PubMed

Affiliation: *Department of Pediatrics, Division of Gastroenterology, Hepatology, and Nutrition, The Children's Hospital of Philadelphia †Department of Genetics and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine at the University of Pennsylvania ‡Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA.

ABSTRACT

Objectives: Severe congenital diarrhea occurs in approximately half of patients with Aristaless-Related Homeobox (ARX) mutations. The cause of this diarrhea is unknown. In a mouse model of intestinal Arx deficiency, the prevalence of a subset of enteroendocrine cells is altered, leading to diarrhea. Because polyalanine expansions within the ARX protein are the most common mutations found in ARX-related disorders, we sought to characterize the enteroendocrine population in human tissue of an ARX mutation and in a mouse model of the corresponding polyalanine expansion (Arx).

Methods: Immunohistochemistry and quantitative real-time polymerase chain reaction were the primary modalities used to characterize the enteroendocrine populations. Daily weights were determined for the growth curves, and Oil-Red-O staining on stool and tissue identified neutral fats.

Results: An expansion of 7 alanines in the first polyalanine tract of both human ARX and mouse Arx altered enteroendocrine differentiation. In human tissue, cholecystokinin, glucagon-like peptide 1, and somatostatin populations were reduced, whereas the chromogranin A population was unchanged. In the mouse model, cholecystokinin and glucagon-like peptide 1 populations were also lost, although the somatostatin-expressing population was increased. The ARX protein was present in human tissue, whereas the Arx protein was degraded in the mouse intestine.

Conclusions: ARX/Arx is required for the specification of a subset of enteroendocrine cells in both humans and mice. Owing to protein degradation, the Arx mouse recapitulates findings of the intestinal Arx model, but is not able to further the study of the differential effects of the ARX protein on its transcriptional targets in the intestine.

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Enteroendocrine hormone expression changes in adult mouse duodenum. Expression of mRNA was quantified by RT-PCR for chromogranin A (A), SST (B), preproglucagon (C), and CCK (D). The dark bars designate controls, whereas the open bars designate ArxGCG7. ∗∗∗Designated P value is <0.05. ARX = aristaless-related homeobox; CCK = cholecystokinin; mRNA = messenger RNA; RT-PCR = real-time polymerase chain reaction; SST = somatostatin.
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Figure 4: Enteroendocrine hormone expression changes in adult mouse duodenum. Expression of mRNA was quantified by RT-PCR for chromogranin A (A), SST (B), preproglucagon (C), and CCK (D). The dark bars designate controls, whereas the open bars designate ArxGCG7. ∗∗∗Designated P value is <0.05. ARX = aristaless-related homeobox; CCK = cholecystokinin; mRNA = messenger RNA; RT-PCR = real-time polymerase chain reaction; SST = somatostatin.

Mentions: These hormone changes were also present in the ileum, with increased SST and decreased GLP-1 at P0 and P14 by cell counts and qRT-PCR (supplemental Fig. 3). We also assayed mRNA expression in the duodenum of older animals (5–7 weeks) to find the same downregulation of preproglucagon and CCK and upregulation of SST mRNAs without a change in chromogranin A (Fig. 4).


Dysgenesis of enteroendocrine cells in Aristaless-Related Homeobox polyalanine expansion mutations.

Terry NA, Lee RA, Walp ER, Kaestner KH, Lee May C - J. Pediatr. Gastroenterol. Nutr. (2015)

Enteroendocrine hormone expression changes in adult mouse duodenum. Expression of mRNA was quantified by RT-PCR for chromogranin A (A), SST (B), preproglucagon (C), and CCK (D). The dark bars designate controls, whereas the open bars designate ArxGCG7. ∗∗∗Designated P value is <0.05. ARX = aristaless-related homeobox; CCK = cholecystokinin; mRNA = messenger RNA; RT-PCR = real-time polymerase chain reaction; SST = somatostatin.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4308495&req=5

Figure 4: Enteroendocrine hormone expression changes in adult mouse duodenum. Expression of mRNA was quantified by RT-PCR for chromogranin A (A), SST (B), preproglucagon (C), and CCK (D). The dark bars designate controls, whereas the open bars designate ArxGCG7. ∗∗∗Designated P value is <0.05. ARX = aristaless-related homeobox; CCK = cholecystokinin; mRNA = messenger RNA; RT-PCR = real-time polymerase chain reaction; SST = somatostatin.
Mentions: These hormone changes were also present in the ileum, with increased SST and decreased GLP-1 at P0 and P14 by cell counts and qRT-PCR (supplemental Fig. 3). We also assayed mRNA expression in the duodenum of older animals (5–7 weeks) to find the same downregulation of preproglucagon and CCK and upregulation of SST mRNAs without a change in chromogranin A (Fig. 4).

Bottom Line: Immunohistochemistry and quantitative real-time polymerase chain reaction were the primary modalities used to characterize the enteroendocrine populations.Daily weights were determined for the growth curves, and Oil-Red-O staining on stool and tissue identified neutral fats.In human tissue, cholecystokinin, glucagon-like peptide 1, and somatostatin populations were reduced, whereas the chromogranin A population was unchanged.

View Article: PubMed Central - PubMed

Affiliation: *Department of Pediatrics, Division of Gastroenterology, Hepatology, and Nutrition, The Children's Hospital of Philadelphia †Department of Genetics and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine at the University of Pennsylvania ‡Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA.

ABSTRACT

Objectives: Severe congenital diarrhea occurs in approximately half of patients with Aristaless-Related Homeobox (ARX) mutations. The cause of this diarrhea is unknown. In a mouse model of intestinal Arx deficiency, the prevalence of a subset of enteroendocrine cells is altered, leading to diarrhea. Because polyalanine expansions within the ARX protein are the most common mutations found in ARX-related disorders, we sought to characterize the enteroendocrine population in human tissue of an ARX mutation and in a mouse model of the corresponding polyalanine expansion (Arx).

Methods: Immunohistochemistry and quantitative real-time polymerase chain reaction were the primary modalities used to characterize the enteroendocrine populations. Daily weights were determined for the growth curves, and Oil-Red-O staining on stool and tissue identified neutral fats.

Results: An expansion of 7 alanines in the first polyalanine tract of both human ARX and mouse Arx altered enteroendocrine differentiation. In human tissue, cholecystokinin, glucagon-like peptide 1, and somatostatin populations were reduced, whereas the chromogranin A population was unchanged. In the mouse model, cholecystokinin and glucagon-like peptide 1 populations were also lost, although the somatostatin-expressing population was increased. The ARX protein was present in human tissue, whereas the Arx protein was degraded in the mouse intestine.

Conclusions: ARX/Arx is required for the specification of a subset of enteroendocrine cells in both humans and mice. Owing to protein degradation, the Arx mouse recapitulates findings of the intestinal Arx model, but is not able to further the study of the differential effects of the ARX protein on its transcriptional targets in the intestine.

Show MeSH
Related in: MedlinePlus