Study of genetic profiles and haematological phenotypes of δ-thalassemia in Guangdong population / 中华检验医学杂志

ABSTRACT

Objective:To investigate genetic variation profiles of δ-globin (HBD gene) and hematological phenotypes in Guangdong population.Methods:Retrospective case analysis was performed in this study. Blood samples of 11 616 couples who participated in free thalassemia screening in Guangzhou from July 2020 to December 2022 were collected which underwent blood routine tests and hemoglobin (Hb) capillary electrophoresis. According to the results, 154 samples were enrolled in this study: (1)group of 35 cases with HbA 2 <2.0% but no HbF band; (2)group of 64 cases with HbA 2 < 2.0% and HbF band; (3)group of 25 cases with HbA 2 <2.0% and suspected HbA 2 variants; (4) group of 25 cases with HbA 2 ≥2.0% and <3.5% and HbF band, as well as abnormal blood routine report [mean corpuscular volume (MCV) <82 fl and/or mean corpuscular hemoglobin (MCH) <27 pg]; (5)group of 5 cases with HbA 2 ≥2.0% and <3.0% accompanied with β thalassemia gene carriers Sanger sequencing was used to detect single nucleotide variants of δ-globin. Results:(1) A total of 22 genetic variations were detected, including 6 de novo variations, and the top 3 genetic variations were respectively c.-127T>C (57.02%, 65/114), c.-80T>C (9.65%, 11/114), c.349C>T (7.89%, 9/114). (2) In group of patients with HbA 2 <2.0% but no HbF band, 22 cases (62.85%, 22/35) had HBD gene variation, including 7 cases with MCV and MCH lower than reference values, 4 cases with α thalassemia; 13 cases had no HBD gene variation, including 12 cases with lower MCV and MCH. Among 19 cases with abnormal blood routine test results, levels of HbA 2 in patients (7 cases) with HBD gene variation were lower compared with those without HBD gene variation (12 cases) ( P<0.01%). (3)In group of patients with HbA 2<2.0% with HbF band, 59 cases (92.18%, 59/64) had HBD gene variations whose mutations all occurred in promoter region, and the HbF were all lower than 5.0%; 5 cases with HbF >5.0% had no HBD gene variation. (4) In group of patients with HbA 2 <2.0% and suspected HbA 2 variants, the detection rate was 100% (25/25) and δ-globin variants <1.0%. (5) In group of patients with HbA 2 ≥2.0% and <3.5% and HbF band accompanied with abnormal blood routine results, no HBD gene variation was found. (6) In group of 5 patients with HbA 2 ≥2.0% and <3.0% with β thalassemia gene carriers, HBD gene variation were found in all cases, and the level of HbA 2 was (2.62±0.17)% and HbF was (3.62±2.22)%. Conclusions:There are various genotypes of HBD gene variation, among which HBD: c.-127T>C is the most common in Guangdong population in China. Mutations in the promoter region may cause decrease in HbA 2 and increase in HbF which is mostly less than 5% but exceeds 5.0% when combined with β thalassemia. Our study enriched the gene mutation profiles of HBD gene in Guangdong population.