CDX2 in congenital gut gastric-type heteroplasia and intestinal-type Meckel diverticula

Meckel’s Diverticulum in Children: A Monocentric Experience and Mini-Review of Literature

Vitelline duct anomalies (VDA, including Meckel’s diverticulum (MD)) result from failed embryologic obliteration. This study aimed for characteristics in symptomatic versus asymptomatic VDA, analyzing clinico-laboratory data from 73 children, aged 1 day to 17 years, treated at a tertiary Pediatric Surgery Institution from 2002–2017. A male preponderance was obtained (ratio 3.6:1). MD accounted for 85% of VDA. Incidence of symptomatic VDA decreased with older age. Leading symptoms were intestinal obstruction and hemorrhage. Mucosal heterotopia (present in 39% of symptomatic MD) was associated with anemia and lowered CRP-levels. On ROC-analysis, hemoglobin < 8.6 g/dL, CRP < 0.6 mg/dL and MD distance to ileocecal valve >40 cm were predictors of ectopic tissue in symptomatic MD. Our data confirmed known characteristics as male preponderance, declined incidence of symptomatic cases with age and predominance of gastric ectopia in symptomatic MD. Moreover, anemia and prolonged distance of MD to ileocecal valve were predictors of ectopic mucosa in symptomatic MD.

A Core Response to the CDX2 Homeoprotein During Development and in Pathologies

Whether a gene involved in distinct tissue or cell functions exerts a core of common molecular activities is a relevant topic in evolutionary, developmental, and pathological perspectives. Here, we addressed this question by focusing on the transcription factor and regulator of chromatin accessibility encoded by the Cdx2 homeobox gene that plays important functions during embryonic development and in adult diseases. By integrating RNAseq data in mouse embryogenesis, we unveiled a core set of common genes whose expression is responsive to the CDX2 homeoprotein during trophectoderm formation, posterior body elongation and intestinal specification. ChIPseq data analysis also identified a set of common chromosomal regions targeted by CDX2 at these three developmental steps. The transcriptional core set of genes was then validated with transgenic mouse models of loss or gain of function of Cdx2. Finally, based on human cancer data, we highlight the relevance of these results by displaying a significant number of human orthologous genes to the core set of mouse CDX2-responsive genes exhibiting an altered expression along with CDX2 in human malignancies.

Extending the functions of the homeotic transcription factor Cdx2 in the digestive system through nontranscriptional activities

The homeoprotein encoded by the intestinal-specific Cdx2 gene is a major regulator of gut development and homeostasis, also involved in colon cancer as well as in intestinal-type metaplasias when it is abnormally expressed outside the gut. At the molecular level, structure/function studies have demonstrated that the Cdx2 protein is a transcription factor containing a conserved homeotic DNA-binding domain made of three alpha helixes arranged in a helix-turn-helix motif, preceded by a transcriptional domain and followed by a regulatory domain. The protein interacts with several thousand sites on the chromatin and widely regulates intestinal functions in stem/progenitor cells as well as in mature differentiated cells. Yet, this transcription factor also acts trough original nontranscriptional mechanisms. Indeed, the identification of novel protein partners of Cdx2 and also of a splicing variant revealed unexpected functions in the control of signaling pathways like the Wnt and NF-κB pathways, in double-strand break DNA repair and in premessenger RNA splicing. These novel functions of Cdx2 must be considered to fully understand the complexity of the role of Cdx2 in the healthy intestine and in diseases.

Diverse presentations in pediatric Meckel's diverticulum: a review of 100 cases

BACKGROUND

Our objective was to analyze demographics and characteristics of Meckel's diverticulum with different manifestations in pediatric patients.

METHODS

This is a retrospective study in children with symptomatic Meckel's diverticulum who underwent resection between September 1998 and October 2010. The diagnosis was confirmed by surgery and pathology. Demographic characteristics, manifestations, Meckel's scan results, surgical and histological findings were analyzed.

RESULTS

One hundred symptomatic Meckel's diverticula were identified in 74 boys and 26 girls aged from one day to 18 years old over 13 years. Depending on whether or not obstruction occurred, the patients were classified into two categories. Each category was further subdivided into two diagnostic groups: 17 intussusception and 24 non-intussusception bowel obstruction in the obstructive category and 44 gastrointestinal bleeding and 15 diverticulitis and/or perforation in the non-obstructive category. The sex discrepancy was higher in the non-obstructive category than in the obstructive category (male-to-female, 4.36 vs. 1.73, p < 0.05). Forty-one of 44 patients with gastrointestinal bleeding underwent a Meckel's scan with a high positive rate (92.7%). The ectopic tissues were identified in 73 patients and included 61 gastric type, two pancreatic type and 10 mixed type. Ectopic tissues were more prevalent in non-obstructive category (p < 0.05) with ectopic gastric tissue even more pronounced (p < 0.01). Ectopic pancreatic tissue was significantly more prevalent in intussusception (p < 0.01). Laparoscopic surgery was performed more frequently in Meckel's diverticulum with non-obstructive symptoms (p < 0.001).

CONCLUSION

Diverse presentations in pediatric Meckel's diverticulum are affected by different ectopic tissue types and male sex. Laparoscopic surgery is widely used for children with non-obstructive symptoms.

Disturbed balance between SOX2 and CDX2 in human vitelline duct anomalies and intestinal duplications

Congenital gastric-type heteroplasia is common in intestinal duplications and anomalies, which originate from incomplete resorption of the omphalomesenteric duct during development. Two transcription factors determine the proximodistal specification of the gastrointestinal tract, SOX2, expressed exclusively in the proximal part of the primitive gut, and CDX2, expressed solely in the distal part. Aberrant expression of these factors may result in abnormal development and congenital abnormalities. Therefore, we analyzed the expression of SOX2 and CDX2 in a number of pediatric intestinal anomalies. We investigated the expression pattern of SOX2 and CDX2 in three congenital intestinal anomalies in which ectopic gastric tissue may be present, Meckel's diverticulum (N = 8), persistent ductus omphalomesentericus (N = 14), and intestinal duplications (N = 8). CDX2, but not SOX2, was detected in intestinal epithelial cells in tissue lacking gastric heteroplasia. In gastric-type heteroplasia, a reciprocal expression pattern existed between SOX2 and CDX2 in the gastric and intestinal tissues, respectively. Interestingly, patches of CDX2-positive cells were present within the gastric mucosa in a subset of Meckel's diverticula and intestinal duplications, suggesting that it is not the absence of CDX2, but rather the ectopic expression of SOX2 that leads to gastric tissue in the prospective intestinal tissue. This is in concordance with our previous mouse studies. Collectively, our data indicate that a fine balance between SOX2 and CDX2 expression in the gastrointestinal tract is essential for proper development and that ectopic expression of SOX2 may lead to malformations of the gut.