Genotyping of the human CTBP2 3’UTR SNP in the Maltese population

Abstract

Patients suffering from sickle cell disease or β-thalassaemia would benefit greatly from the reactivation of foetal haemoglobin (Hb F) synthesis in order to alleviate the symptoms in affected adults. To accomplish this, it is essential to gain the necessary knowledge on the genetic switch from foetal to adult haemoglobin also known as the γ to β globin gene switching. In recent years considerable progress has been made in this field; however the exact mechanism remains elusive. The combination of clinical research coupled with basic research should help in this regard. In a previous research project around 259 patients with borderline HbA2/HbF levels were identified and stored into the Malta BioBank. Extensive molecular studies conducted on these samples so far, have revealed a number of KLF1 and VEGF-A mutations, which are partially responsible for the borderline parameters observed. However, these data were still not sufficient to explain the heterogeneous distribution of HbF in different family members with KLF1 haploinsufficiency, with a range of 3.3 to 20% HbF and in the collection of patients with borderline HbA2/HbF. A polymorphism (rs3781408) was the centre of this project and depending on which CtBP2 transcript is quoted, can be either reported to be in the 3’UTR of the gene or else in an amino acid changing domain of the CtBP2 gene. During the course of Whole Genome Sequence analysis of family members with hereditary persistence of foetal haemoglobin, the CtBP2 polymorphism appeared to be tightly linked with a phenotype exhibiting an increase in HbF levels in vivo. This was genotyped by Sanger's DNA sequencing in a collection of patients exhibiting borderline HbA2/HbF, haemoglobin variants and in additional prospective patient DNA known to carry β-thalassaemia mutations.