Characterisation of two genetic loci involved in fetal haemoglobin production

: BCLIIA and HBSIL-MYB intergenic region

Abstract

The continuous production of fetal haemoglobin (HbF, a2Ya) into adulthood is an ameliorating factor in sickle cell disease and B-thalassemia. We have previously mapped two quantitative trait loci (QTLs) controlling HbF levels, one in intron 2 of BCL11A gene, and the other, an intergenic region on chromosome 6 between the genes HBS1L and MYB, known as HMIP. Histone modification and RNA polymerase II binding at these loci and at the globin genes themselves were analysed using microarray-based chromatin immunoprecipitation studies of primary human erythroid progenitor cells. In addition, we analysed binding of GATA-1 and KLF1, two major erythroid-specific transcription factors. Strong GATA-1 binding at the HMIP region coinciding with strong histone acetylation and RNA polymerase II activity was seen, indicative of the presence of regulatory elements in the intergenic region. Moreover, differential GATA-1 binding was observed between individuals with low HbF and raised HbF levels at a site within the HMIP region most strongly associated with HbF variance. BCL11A intron 2 also showed strong GATA-1 binding and histone H3 acetylation, and may therefore be responsible for the overall regulation of BCL11A. I have carried out extensive sequence analysis of individuals from the upper and lower extremes of BCLllA-associated HbF levels to fully characterize DNA variants. The nature of this sequence as a regulator of BCL11A expression remains to be determined and functional tests are on-going. The role of BCL11A, in conjunction with KLF1, as a transcriptional regulator of the a and P globin loci, as well as the QTLs themselves, was also investigated. These results show that BCL11A, often alongside GATA-1, is intimately involved in the transcriptional regulation of the globin genes and that KLF1 also regulates BCL11A. The importance of different protein isoforms of BCL11A is also explored.

Date of Award	1 Apr 2013
Original language	English
Awarding Institution	King's College London
Supervisor	Steven Best (Supervisor) & Swee Lay Thein (Supervisor)