Abstract
Dyskeratosis congenita (DC) is a heterogeneous bone marrow failure disorder with known mutations in components of telomerase and telomere shelterin. Recent work in a mouse model with a dyskerin mutation has implicated an increased DNA damage response as part of the cellular pathology, while mouse models with Terc and Tert mutations displayed a normal response. To clarify how these contradictory results might apply to DC pathology in humans, we studied the cellular phenotype in primary cells from DC patients of several genetic subtypes, focussing on T lymphocytes to remain close to the haematopoietic system. We observed novel cell cycle abnormalities in conjunction with impaired growth and an increase in apoptosis. Using flow cytometry and confocal microscopy we examined induction of the DNA damage proteins γ-H2AX and 53BP1 and the cell cycle protein TP53 (p53). We found an increase in damage foci at telomeres in lymphocytes and an increase in the basal level of DNA damage in fibroblasts, but crucially no increased response to DNA damaging agents in either cell type. As the response to induced DNA damage was normal and levels of global DNA damage were inconsistent between cell types, DNA damage may contribute differently to the pathology in different tissues.
Highlights
Dyskeratosis congenita (DC) is an inherited disorder characterised by muco-cutaneous abnormalities consistent with a premature aging phenotype, bone marrow failure and a predisposition to cancer (Dokal 2001)
We found that the pattern remained similar for all phases but the reduction in γ-H2AX expression in DC samples was statistically significant in both the S and G2/M phases (p values of below 0.03 for all dosages), confirming a cell cycle dependent effect
We found no significant difference in the average number of 53BP1 foci per cell between controls and DC patients either with or ev without etoposide exposure (p > 0.1 in all cases) (Figure 6B), consistent with our flow cytometry data obtained with a single etoposide dose
Summary
Dyskeratosis congenita (DC) is an inherited disorder characterised by muco-cutaneous abnormalities consistent with a premature aging phenotype, bone marrow failure and a predisposition to cancer (Dokal 2001). As well as serving as a model of aging in humans it is a model disease for telomere dysfunction as it is the first disease that is thought to be caused by premature telomere shortening (Bessler, et al 2010, Calado and Young 2009). DC patients, as a group, have very short telomeres (Alter, et al 2007, Mitchell, et al 1999) and the clinical phenotype is consistent with premature loss of cells in tissues with high turnover such as the skin, gut and bone marrow.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
