Neonatal-Onset Chronic Diarrhea Caused by Homozygous Nonsense WNT2B Mutations

摘要

Homozygous nonsense mutations inWNT2Bwere identified in three individuals from two unrelated families with severe, neonatal-onset osmotic diarrhea after whole-exome sequencing was performed on trios from the two families. Intestinal biopsy samples from affected individuals were used for histology and immunofluorescence and to generate enteroidsex?vivo. Histopathologic evaluation demonstrated chronic inflammatory changes in the stomach, duodenum, and colon. Immunofluorescence demonstrated diminished staining for OLFM4, a marker for intestinal stem cells (ISCs). The enteroids generated from WNT2B-deficient intestinal epithelium could not be expanded and did not survive passage. Addition of CHIR-99021 (a GSK3A and GSK3B inhibitor and activator of canonical WNT/β-CATENIN signaling) could not rescue WNT2B-deficient enteroids. Addition of supplemental recombinant murine WNT2B was able to perpetuate small enteroids for multiple passages but failed to expand their number. Enteroids showed a 10-fold increase in the expression ofLEF1mRNA and a 100-fold reduction inTLR4expression, compared with controls by quantitative RT-PCR, indicating alterations in canonical WNT and microbial pattern-recognition signaling. In summary, individuals with homozygous nonsense mutations inWNT2Bdemonstrate severe intestinal dysregulation associated with decreased ISC number and function, likely?explaining their diarrheal phenotype. WNT2B deficiency should be considered for individuals with neonatal-onset diarrhea.