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The evolving genetic landscape of dyskeratosis congenita (DC) and DC-like (DCL) disorders

ABSTRACT: Dyskeratosis congenita (DC) is a complex inherited bone marrow failure syndrome which is principally a disorder of telomere maintenance. To date approximately 35% of cases remain uncharacterised at the genetic level. Whole exome sequencing on a large collection of uncharacterized DC and DC-like (DCL) families (n=167) has revealed several novel pathogenic variants within known susceptibility loci, POT1 and ZCCHC8, as well as the novel locus POLA1. Functional characterisation of identified POLA1 and POT1 pathogenic variants, uncovered their effect on protein-protein interactions that have critical implications for telomere maintenance. ZCCHC8 variants disrupt protein interactions that affect nuclear exosome targeting (NEXT) complex stoichiometry and its binding with the human silencing hub (HUSH) complex chromatin modifier MPP8. Global transcriptomic analysis revealed signatures of pervasive transcription that include several short (snRNA and snoRD) and long non-coding RNA (transposable elements; LINE-1) driving inflammation in ZCCHC8 patient blood cells. In summary, our studies inform the current genetic architecture of DC and DCL disorders, by revealing novel gene loci such as POLA1 and extend our current knowledge on disease mechanisms beyond the regulation of long non-coding RNA TERC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE244915 | GEO | 2024/07/10

REPOSITORIES: GEO

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Project description:Aging is the consequence of intra- and extracellular events that promote cellular senescence. Dyskeratosis congenita (DC) is an example of a premature aging disorder caused by underlying telomere/telomerase-related mutations. Cells from these patients offer an opportunity to study telomere-related aging and senescence. Our previous work has found that telomere shortening stimulates DNA damage responses (DDR) and increases reactive oxygen species (ROS), thereby promoting entry into senescence. This work also found that telomere elongation via TERT expression, the catalytic component of the telomere-elongating enzyme telomerase, or p53 shRNA could decrease ROS by disrupting this telomere-DDR-ROS pathway. To further characterize this pathway, we performed a CRISPR/Cas9 knockout screen to identify genes that extend lifespan in DC cells. Of the cellular clones isolated due to increased lifespan, 34% had a guide RNA (gRNA) targeting CEBPB while gRNAs targeting WSB1, MED28 and p73 were observed multiple times. CEBPB is a transcription factor associated with activation of proinflammatory response genes suggesting that inflammation may be present in DC cells. The inflammatory response was investigated using RNA-Seq to compare DC and control cells. Expression of inflammatory genes were found to be significantly elevated (p<0.0001) in addition to a key subset of these inflammation-related genes (IL1B, IL6, IL8, IL12A, CXCL1 (GROa), CXCL2 (GROb), and CXCL5) which are regulated by CEBPB. Exogenous TERT expression led to downregulation of RNA/protein CEBPB expression and the inflammatory response genes suggesting a telomere-length dependent mechanism to regulate CEBPB. Furthermore, unlike exogenous TERT and p53 shRNA, CEBPB shRNA did not significantly decrease ROS suggesting that CEBPB’s contribution in DC cells’ senescence is ROS-independent. Our findings demonstrate a key role for CEBPB in engaging senescence by mobilizing an inflammatory response within DC cells.

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The evolving genetic landscape of dyskeratosis congenita (DC) and DC-like (DCL) disorders

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