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| Author(s): |
Gabriela Queila de Carvalho Siqueira
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Faculdade de Ciências Médicas |
| Defense date: | 2019-06-28 |
| Examining board members: |
Mônica Barbosa de Melo;
Cristiane de Souza Rocha;
Magnun Nueldo Nunes dos Santos;
Anderson Ferreira da Cunha;
Maria Stella Figueiredo
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| Advisor: | Mônica Barbosa de Melo |
| Abstract | |
Although sickle cell anemia (SCA) results from homozygosity of a single base change at position 7 of the â-globin gene, the clinical aspects of this disease are very heterogeneous. Many complications can occur, among them leg ulcers (LU), which have a high negative impact on patients¿ quality of life and are related to the severity of the disease. Nevertheless, the pathogenesis of this complication has not yet been elucidated. In order to identify novel variants associated with LU in SCA, we performed exome sequencing in a sample of Brazilian SCA patients with and without LU, followed by validation in another Brazilian population sample. Our discovery cohort consisted, initially, of 40 unrelated SCA patients selected based on extreme phenotypes: 20 patients without LU, over 40 years of age, and 20 with chronic LU, all of them treated at Hematology and Hemotherapy Center, University of Campinas, SP, Brazil. DNA was extracted from peripheral blood leukocytes and used for exome sequencing. After the bioinformatics analysis (which follows GATK pipeline), two approaches were applied for the selection of variants to be validated: literature analysis and lower p-values. Altogether, 12 variants were selected, one of them was a false positive. The 11 remaining variants were genotyped by direct sequencing and TaqMan probes in the validation cohort, which was comprised of 293 SCA patients (of these, 153 without LU) treated at the following centers from Northeast Brazil: Hematology and Hemotherapy Foundation of Bahia (HEMOBA) and Pernambuco (HEMOPE). After the genotyping of the validation cohort, Fisher¿s exact test revealed a statistically significant difference in a stop codon variant (rs12568784 G/T) in the FLG2 gene. This association was observed by comparing GT and GG genotypes between cases and controls (p=0.03). Literature provides evidence that justify this variant¿s involvement in LU in SCA, since it leads to loss of function of the fillagrin-2 protein, resulting in impairment of the skin barrier, predisposing the individual to inflammation and infection, a wound of difficult healing ¿ ulcers. Additionally, we suggest that the remaining variants and the genes in which they occur could be strong candidates for LU in SCA (AU) | |
| FAPESP's process: | 15/24029-3 - Analysis of susceptibility genes to leg ulcer in patients with sickle cell disease |
| Grantee: | Gabriela Queila de Carvalho Siqueira |
| Support Opportunities: | Scholarships in Brazil - Doctorate (Direct) |