Enhancing a Wnt-Telomere Feedback Loop Restores Intestinal Stem Cell Function in Dyskeratosis Congenita

Patients with dyskeratosis congenita (DC) suffer from stem cell failure in numerous organs, including the skin, intestine, blood, lung, and liver, due to hypomorphic loss-of-function mutations in proteins that promote telomere elongation or capping. Few therapeutic options exist for this disorder, and while patients are treated with bone marrow transplantation to restore hematopoietic function, this does not address the multi-organ failure, and in some cases can exacerbate it. We generated isogenic DC patient and disease allele-corrected induced pluripotent stem (iPS) cell lines using clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated gene correction to model the stem cell failure characteristic of DC in multiple organ systems through the directed differentiation. We focused first on the intestinal epithelium, as GI manifestations of DC (enteropathy/enterocolitis ) are often the first and most severe symptoms in pediatric patients. We demonstrate that DC tissue has suboptimal Wnt pathway activity causing intestinal stem cell failure and that enhanced expression of the telomere-capping protein TRF2, a Wnt target gene, can alleviate DC phenotypes. Treatment with the clinically relevant Wnt agonists LiCl or CHIR99021 restored TRF2 expression and reversed gastrointestinal DC phenotypes, including organoid formation in vitro, and maturation of intestinal tissue and xenografted organoids in vivo. These findings establish the existence of a feed-forward loop between telomerase/telomere capping and the canonical Wnt pathway which is broken in DC, but can be restored by promoting capping and/or Wnt pathway agonists. Moving forward, we have begun to extend these investigations into the lung and liver, where fibrosis and organ failure are major clinical concerns in DC. Thus, the isogenic DC iPS cell model provides a framework for therapeutic discovery and identifies Wnt modulation as a potential strategy for treatment of DC patients.