The potential of gene therapy to rescue telomeric and extratelomeric defects in X-linked dyskeratosis congenita.

Dyskeratosis congenita (DC) is a rare inherited disorder characterized by bone marrow failure, pulmonary fibrosis, and cancer predisposition. X-linked DC (X-DC) is caused by mutations in the DKC1 gene, which encodes dyskerin, a multifunctional protein that is essential for telomere maintenance and multiple RNA-associated processes. Here, we first generated human X-DC HSPC models by introducing DKC1 frameshift mutations or the hypomorphic c.196 A>G mutation, into cord blood CD34+ cells from healthy male donors. These X-DC-like HSPCs recapitulated key hematopoietic features of the disease, including impaired proliferation, defective telomere maintenance and altered rRNA maturation. To correct these defects, lentiviral vectors were constructed carrying DKC1 under the PGK promoter or a weaker promoter driven by TERC regulatory sequences. While PGK-driven expression of dyskerin only restored the proliferation of X-DC-like HSPCs, pTERC-mediated expression of dyskerin also corrected the telomere maintenance and rRNA maturation defects characteristic of X-DC cells, without altering the functional properties of healthy HSPCs. These findings indicate that TERC promoter-driven dyskerin expression can functionally rescue key telomeric and extratelomeric defects in HSPCs carrying frameshift or hypomorphic DKC1 mutations, supporting further preclinical development of this strategy and providing a rationale for its evaluation as a therapeutic approach for X-linked dyskeratosis congenita.