Telomere dysfunction represses HNF4α leading to impaired hepatocyte development and function

Telomere attrition is a risk factor for end-stage liver disease. Due to a lack of adequate models and intrinsic difficulties in studying telomerase in physiologically relevant cells, the molecular mechanisms responsible for liver disease in patients with telomere syndromes remain elusive. To circumvent that, we used genome editing to generate isogenic human embryonic stem cell lines (hESCs) harboring a clinically relevant mutation in telomerase (DKC1_A353V) and subjected them to an in vitro, stage-specific hepatocyte differentiation protocol, that resembles hepatocyte development in vivo. Our results show that while telomerase is highly expressed in hESCs, it is quickly silenced, due to TERT down-regulation, after endoderm differentiation, and completely absent in in vitro derived hepatocytes, similarly to what is observed in primary hepatocytes. While endoderm derivation is not impacted by telomere shortening, progressive telomere dysfunction impaired hepatic endoderm formation. Consequently, hepatocyte-derivation, as measured by expression of specific markers, as well by albumin expression and secretion, is severely compromised in telomerase mutant cells with short telomeres. Interestingly, this phenotype was not caused by cell death induction or senescence. Rather, telomere shortening induces down regulation of the human hepatocyte nuclear factor 4α (HNF4α), in a p53 dependent manner. Telomerase reactivation, as well as p53 silencing, rescued hepatocyte formation in telomerase mutants. Likewise, conditional expression of HNF4α even in cells that retained short telomeres, accrued DNA damage, and p53 stabilization, successfully restored hepatocyte formation from hESCS. Conclusions: Combined, our data shows that telomere dysfunction acts a major regulator of HNF4α during hepatocyte development and function, pointing to a potential novel target for the clinical management of liver disease in telomere-syndrome patients.