Department of Biological Sciences, Dar es Salaam University College of Education, Dar es Salaam, Tanzania.
Sickle Cell Program, Department of Hematology and Blood Transfusion, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania.
BMC Med Genet. 2020 Jun 5;21(1):125. doi: 10.1186/s12881-020-01059-1.
Sickle cell disease (SCD) is a blood disorder caused by a point mutation on the beta globin gene resulting in the synthesis of abnormal hemoglobin. Fetal hemoglobin (HbF) reduces disease severity, but the levels vary from one individual to another. Most research has focused on common genetic variants which differ across populations and hence do not fully account for HbF variation.
We investigated rare and common genetic variants that influence HbF levels in 14 SCD patients to elucidate variants and pathways in SCD patients with extreme HbF levels (≥7.7% for high HbF) and (≤2.5% for low HbF) in Tanzania. We performed targeted next generation sequencing (Illumina_Miseq) covering exonic and other significant fetal hemoglobin-associated loci, including BCL11A, MYB, HOXA9, HBB, HBG1, HBG2, CHD4, KLF1, MBD3, ZBTB7A and PGLYRP1.
Results revealed a range of genetic variants, including bi-allelic and multi-allelic SNPs, frameshift insertions and deletions, some of which have functional importance. Notably, there were significantly more deletions in individuals with high HbF levels (11% vs 0.9%). We identified frameshift deletions in individuals with high HbF levels and frameshift insertions in individuals with low HbF. CHD4 and MBD3 genes, interacting in the same sub-network, were identified to have a significant number of pathogenic or non-synonymous mutations in individuals with low HbF levels, suggesting an important role of epigenetic pathways in the regulation of HbF synthesis.
This study provides new insights in selecting essential variants and identifying potential biological pathways associated with extreme HbF levels in SCD interrogating multiple genomic variants associated with HbF in SCD.
镰状细胞病（SCD）是一种由β珠蛋白基因突变引起的血液疾病，导致异常血红蛋白的合成。胎儿血红蛋白（HbF）可降低疾病严重程度，但个体之间的水平存在差异。大多数研究都集中在常见的遗传变异体上，这些变异体在不同人群中存在差异，因此不能完全解释 HbF 的变异。
我们研究了影响 14 名 SCD 患者 HbF 水平的罕见和常见遗传变异体，以阐明坦桑尼亚 HbF 水平极高（≥7.7%为高 HbF）和极低（≤2.5%为低 HbF）的 SCD 患者中的变异体和途径。我们进行了靶向下一代测序（Illumina_Miseq），涵盖了外显子和其他重要的胎儿血红蛋白相关基因座，包括 BCL11A、MYB、HOXA9、HBB、HBG1、HBG2、CHD4、KLF1、MBD3、ZBTB7A 和 PGLYRP1。
结果揭示了一系列遗传变异体，包括双等位基因和多等位基因 SNPs、移码插入和缺失，其中一些具有功能重要性。值得注意的是，高 HbF 水平个体的缺失明显更多（11%比 0.9%）。我们在高 HbF 水平个体中发现了移码缺失，在低 HbF 水平个体中发现了移码插入。CHD4 和 MBD3 基因，在同一子网络中相互作用，被确定为低 HbF 水平个体中具有大量致病性或非同义突变的基因，这表明表观遗传途径在 HbF 合成的调节中具有重要作用。
本研究为 SCD 中与 HbF 相关的多个基因组变异体的选择提供了新的见解，确定了与 HbF 水平极端相关的关键变异体，并鉴定了潜在的生物学途径。
