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Genetic modifiers of long-term survival in sickle cell anemia.

ABSTRACT: BACKGROUND:Sickle cell anemia (SCA) is a clinically heterogeneous, monogenic disorder. Medical care has less-than-optimal impact on clinical outcomes in SCA in Africa due to several factors, including patient accessibility, poor access to resources, and non-availability of specific effective interventions for SCA. METHODS:Against this background, we investigated 192 African participants who underwent whole exome sequencing. Participants included 105 SCA patients spanning variable clinical expression: a "long survivor" group (age over 40 years), a "stroke" group (at least one episode of overt stroke), and a "random" group (patients younger than 40 years without overt cerebrovascular disease). Fifty-eight ethnically matched homozygous hemoglobin A controls were also studied. Findings were validated in an independently recruited sample of 29 SCA patients. Statistical significance of the mutational burden of deleterious and loss-of-function variants per gene against a null model was estimated for each group, and gene-set association tests were conducted to test differences between groups. RESULTS:In the "long survivor" group, deleterious/loss-of-function variants were enriched in genes including CLCN6 (a voltage-dependent chloride channel for which rare deleterious variants have been associated with lower blood pressure) and OGHDL (important in arginine metabolism, which is a therapeutic target in SCA). In the "stroke" group, significant genes implicated were associated with increased activity of the blood coagulation cascade and increased complement activation, for example, SERPINC1, which encodes antithrombin. Oxidative stress and glutamate biosynthesis pathways were enriched in "long survivors" group. Published transcriptomic evidence provides functional support for the role of the identified pathways. CONCLUSIONS:This study provides new gene sets that contribute to variability in clinical expression of SCA. Identified genes and pathways suggest new avenues for other interventions.

SUBMITTER: Wonkam A

PROVIDER: S-EPMC7423184 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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Genetic modifiers of long-term survival in sickle cell anemia.

Wonkam Ambroise A Chimusa Emile R ER Mnika Khuthala K Pule Gift Dineo GD Ngo Bitoungui Valentina Josiane VJ Mulder Nicola N Shriner Daniel D Rotimi Charles N CN Adeyemo Adebowale A

Clinical and translational medicine 20200801 4

<h4>Background</h4>Sickle cell anemia (SCA) is a clinically heterogeneous, monogenic disorder. Medical care has less-than-optimal impact on clinical outcomes in SCA in Africa due to several factors, including patient accessibility, poor access to resources, and non-availability of specific effective interventions for SCA.<h4>Methods</h4>Against this background, we investigated 192 African participants who underwent whole exome sequencing. Participants included 105 SCA patients spanning variable ...[more]

PMID: 32898326

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Project description:Hematopoietic cell transplant for sickle cell disease is curative but is associated with life threatening complications most of which occur within the first 2 years after transplantation. In the current era with interest in gene therapy and gene editing we felt it timely to report on sickle cell disease transplant recipients who were alive for at least 2-year after transplantation, not previously reported. Our objectives were to (1) report the conditional survival rates of patients who were alive for 2 or more years after transplantation (2) identify risk factors for death beyond 2 years after transplantation and (3) compare all-cause mortality risks to those of an age-, sex- and race-matched general population in the United States. By limiting to 2-year survivors, we exclude deaths that occur as a direct consequence of the transplantation procedure. De-identified records of 1149 patients were reviewed from a publicly available data source and 950 patients were eligible (https://picsure.biodatacatalyst.nhlbi.nih.gov). All analyses were performed in this secure cloud environment using the available statistical software package(s). The validity of the public database was confirmed by reproducing results from an earlier publication. Conditional survival estimates were obtained using the Kaplan-Meier method for the sub-cohort that had survived a given length (x) of time after transplantation. Cox regression models were built to identify risk factors associated with mortality beyond 2 years after transplantation. The standardized relative mortality risk (SMR) or the ratio of observed to expected number of deaths, was used to quantify all-cause mortality risk after transplantation and compared to age, race and sex-matched general population. Person-years at risk were calculated from an anchor date (i.e., 2-, 5- and 7-years) after transplantation until date of death or last date known alive. The expected number of deaths was calculated using age, race and sex-specific US mortality rates. The median follow up was 5 years (range 2-20) and 300 (32%) patients were observed for more than 7 years. Among those who lived for at least 7 years after transplantation the 12-year probability of survival was 97% (95% CI, 92%-99%). Compared to an age-, race- and sex-matched US population, the risk for late death after transplantation was higher as late as 7 years after transplantation (hazard ratio (HR) 3.2; P= .020) but the risk receded over time. Risk factors for late death included age at transplant and donor type. For every 10-year increment in patient age, an older patient was 1.75 times more likely to die than a younger patient (P= .0004). Compared to HLA-matched siblings the use of other donors was associated with higher risk for late death (HR 3.49; P= .003). Graft failure (beyond 2-years after transplantation) was 7% (95% CI, 5%-9%) and graft failure was higher after transplantation of grafts from donors who were not HLA-matched siblings (HR 2.59, P< .0001). Long-term survival after transplantation is excellent and support this treatment as a cure for sickle cell disease. The expected risk for death recedes over time but the risk for late death is not negligible.

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Genetic modifiers of long-term survival in sickle cell anemia.

Publications

Genetic modifiers of long-term survival in sickle cell anemia.

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