Genomics of fetal haemoglobin: a targeted approach for reticulocyte transcriptome study.

Fetal haemoglobin (HbF) remains a major sickle cell disease modifier. The mechanism of HbF synthesis has been studied for several decades with the intention of increasing interventions for sickle cell disease (SCD), including drugs. However, the complex mechanism of HbF synthesis is influenced by multiple genetic factors interacting with environmental factors. In order to capture useful genetic information, especially with limited resources, one has to carefully design the study. This includes choosing the relevant participants, the correct phenotyping, the choice of samples, and the right genomic assays. This paper describes the approach undertaken as part of preparations for a reticulocyte transcriptome study intended to discover genes associated with HbF decline in newborns in Tanzania. Of the 152 newborns enrolled in the larger study, 40 babies were selected for the reticulocyte transcriptome study based on their HbF levels at birth and later stage of life. Of these, 30 individuals were included under the category of high HbF levels ranging from 72.6-90% and the remaining 10 under the category of low HbF levels ranging from 5.9 - 10.3%. The reticulocyte enrichment recovery purity ranged from 85% - 97%. The total RNA concentrations obtained were >250 ng total RNA, with the average purity of 1.9 (A 260/280) respectively. The total concentration obtained was sufficient for the transcriptome and other downstream assays. We have documented important steps and factors to consider in identifying the relevant participants and required laboratory sample processes prior to the final stage, which involves total reticulocyte RNA sequencing.