Haplotypes and polymorphism in the CCR5 gene in sickle cell disease.

Sickle cell disease shows several clinical manifestations in distinct levels of severity. This heterogeneity is due to the haplotype variability associated with the HbS gene, levels of fetal hemoglobin and environmental conditions, which modify the disease expression. Science community believes that the presence of a polymorphism in the CCR5 gene, which is related to chronic inflammatory state, could confer a higher survival rate and a lower number of inflammatory events to these patients since the deletion in CCR5Δ32 would knock out the CCR5 gene. Therefore, this study aimed to identify the haplotypes in ßS and ßC genes, as well as to investigate the presence of the CCR5Δ32 deletion in patients with sickle cell disease. For this purpose, DNA was isolated with the QIAamp DNA Investigator Kit, and PCR was the method chosen to detect the mutant allele CCR5Δ32. The haplotypes in ßS and ßC genes were detected by RFLP with the restriction enzymes XmnI, HindIII, HincII, and HinfI analyzing six polymorphic sites on the ß cluster, succeeded by electrophoresis. The atypical haplotype was the most common (54.3%), followed by Benin (28.6%), Bantu (11.5%), Senegal (2.8%), and Cameroon (2.8%). No patients presented CCR5Δ32 deletion. The increase in the frequency of atypical haplotypes suggests that these patients passed by variation in the genetic pattern from ancestral haplotypes throughout the years.

Genomic ancestry evaluated by ancestry-informative markers in patients with sickle cell disease.

The ß(s) mutation is responsible for the most aggressive form of sickle cell disease, has a predominantly African origin, and arrived in Brazil through the slave trade. However, the Brazilian population is highly miscegenated, underscoring the importance of ancestry-informative markers (AIMs) for the identification of the genetic structure of a population. In this study, we have estimated the genetic contributions of various ethnicities in individuals with sickle cell disease in the microregion of Jequié, Bahia, in Brazil, by using AIMs, and compared the findings to those from a phenotypic characterization. Eight AIMs were analyzed: AT3 (rs3138521), DRD2 (rs1079598), APO (rs3138522), PV92, Sb19.3 (rs3138524), CKM (rs4884), LPL (rs285), and CCR5Δ32 (rs333). Samples were subjected to polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism. The amplified products were electrophoresed on agarose gels, and the data were statistically analyzed using Genepop, FSTAT 2.9, and Admix3. Phenotypic classification showed a high frequency of mulattos  (85%) in the Brazilian population; however, ancestry-informative markers indicated that 44, 42, and 11% of the population had European, African, and native American ancestries, respectively. The phenotypic classification is justified as a complementary method for the characterization of the genetic ancestry in patients with sickle cell disease, as it confirms the molecular findings regarding ancestry.