Genome-wide association study shows BCL11A associated with persistent fetal hemoglobin and amelioration of the phenotype of beta-thalassemia.

beta-Thalassemia and sickle cell disease both display a great deal of phenotypic heterogeneity, despite being generally thought of as simple Mendelian diseases. The reasons for this are not well understood, although the level of fetal hemoglobin (HbF) is one well characterized ameliorating factor in both of these conditions. To better understand the genetic basis of this heterogeneity, we carried out genome-wide scans with 362,129 common SNPs on 4,305 Sardinians to look for genetic linkage and association with HbF levels, as well as other red blood cell-related traits. Among major variants affecting HbF levels, SNP rs11886868 in the BCL11A gene was strongly associated with this trait (P < 10(-35)). The C allele frequency was significantly higher in Sardinian individuals with elevated HbF levels, detected by screening for beta-thalassemia, and patients with attenuated forms of beta-thalassemia vs. those with thalassemia major. We also show that the same BCL11A variant is strongly associated with HbF levels in a large cohort of sickle cell patients. These results indicate that BCL11A variants, by modulating HbF levels, act as an important ameliorating factor of the beta-thalassemia phenotype, and it is likely they could help ameliorate other hemoglobin disorders. We expect our findings will help to characterize the molecular mechanisms of fetal globin regulation and could eventually contribute to the development of new therapeutic approaches for beta-thalassemia and sickle cell anemia.

New analytical tools and epidemiological data for the identification of HbA2 borderline subjects in the screening for beta-thalassemia.

The increase of HbA(2) is the most important feature in the identification of beta-thalassemia carriers. However, some carriers are difficult to identify, because the level of HbA(2) is not in the typical range. Few data are available concerning the prevalence of such unusual phenotypes, and knowing their expected prevalence could be helpful in detecting systematic drifts in the analytical systems for HbA(2) quantification. In this study we report a retrospective investigation in two centres with high prevalence of beta-thalassemia. The prevalence of borderline subjects was found to be 2.2 and 3.0%, respectively. The genotypes of a subgroup of these subjects were then analyzed and in about 25% of cases a mutation in the globin genes was identified. We conclude that the occurrence of HbA(2) borderline phenotypes is not a rare event. In order to obtain more accurate HbA(2) measurements the development of an international reference measurement system for HbA(2), based on quantitative peptide mapping, has been recently started. We believe that the innovative approach of our method could also be used as a model to develop accurate quantitative methods for other red cell proteins relevant to the biodynamic properties and the surface electrochemistry of erythrocytes.

Glucose-6-phosphate dehydrogenase polymorphism and lymphoma risk.

AIMS AND BACKGROUND: Evidence linking the glucose-6-phosphate dehydrogenase (G6PD) polymorphism and risk of non-Hodgkin's lymphoma is conflicting. Risk of non-Hodgkin's lymphoma was increased in subjects expressing the G6PD deficient phenotype, whereas subjects under medication with statins, a lipid-lowering class of drugs partially mimicking G6PD deficiency, seemed to enjoy a protective effect. METHODS: We conducted a case-control study on lymphoma risk associated with the self-reported G6PD deficient phenotype in 122 lymphoma male cases and 116 male controls in Sardinia, Italy. The association with the GdMed+ genotype, the most frequent variant expressing a deficient enzyme activity, was also tested in 49 male lymphoma cases and 31 controls. The WHO classification was used to identify lymphoma subentities. RESULTS: Neither self-reported G6PD deficient phenotype nor the GdMed+ genotype showed an association with lymphoma risk or its subentities. CONCLUSIONS: Our results do not confirm an association either positive or negative between the G6PD polymorphism and lymphoma risk.

Molecular characterization of alpha-thalassemia in Pakistan.

Common alpha-thalassemia (thal) rearrangements were studied in a normal random population and in six ethnic groups of Pakistan. Analyses of 204 individuals from the normal population revealed the presence of only the -alpha(3.7) allele with an overall frequency of 8.3%. Ethnic differences were statistically significant for Pashtoon vs. Balochi (p < 0.0005) and Pashtoon vs. Sindhi (p < 0.002). Two hundred and eighty-five thalassemia patients were also studied to identify rare alpha-thal alleles. In this group, 24.6% of the patients had one or two alpha genes deleted. Two rare alleles in the Pakistani population, -alpha(4.2) (0.2%) and alphaalphaalpha(anti3.7) (0.9%), were identified in these patients. The -alpha(4.2) allele was found only in Sindhis, while alphaalphaalpha(anti3.7) was present in Punjabis, Sindhis and Balochis. Five patients with triplicated alpha genes were homozygous for either the beta+ or the beta(0) genotype.