Genotype-degree of hemolysis correlation in hereditary spherocytosis

Abstract

Background: Hereditary spherocytosis (HS) is a common inherited hemolytic anemia, caused by mutations in five genes that encode erythrocyte membrane skeleton proteins. The red blood cell (RBC) lifespan could directly reflect the degree of hemolysis. In the present cohort of 23 patients with HS, we performed next-generation sequencing (NGS) and Levitt's carbon monoxide (CO) breath test to investigate the potential genotype-degree of hemolysis correlation.

Results: In the present cohort, we identified 8 ANK1,9 SPTB,5 SLC4A1 and 1 SPTA1 mutations in 23 patients with HS, and the median RBC lifespan was 14(8-48) days. The median RBC lifespan of patients with ANK1, SPTB and SLC4A1 mutations was 13 (8-23), 13 (8-48) and 14 (12-39) days, respectively, with no statistically significant difference (P = 0.618). The median RBC lifespan of patients with missense, splice and nonsense/insertion/deletion mutations was 16.5 (8-48), 14 (11-40) and 13 (8-20) days, respectively, with no significant difference (P = 0.514). Similarly, we found no significant difference in the RBC lifespan of patients with mutations located in the spectrin-binding domain and the nonspectrin-binding domain [14 (8-18) vs. 12.5 (8-48) days, P = 0.959]. In terms of the composition of mutated genes, 25% of patients with mild hemolysis carried ANK1 or SPTA1 mutations, while 75% of patients with mild hemolysis carried SPTB or SLC4A1 mutations. In contrast, 46.7% of patients with severe hemolysis had ANK1 or SPTA1 mutations and 53.3% of patients with severe hemolysis had SPTB or SLC4A1 mutations. However, there was no statistically significant difference in the distribution of mutated genes between the two groups (P = 0.400).

Conclusion: The present study is the first to investigate the potential association between genotype and degree of hemolysis in HS. The present findings indicated that there is no significant correlation between genotype and degree of hemolysis in HS.

Keywords: Degree of hemolysis; Hereditary spherocytosis; Levitt’s carbon monoxide breath test; Next-generation sequencing; Red blood cell lifespan.

Fig. 1

Comparison of RBC lifespan between different mutation genes, types and sites(a-e). Mutated gene distribution in different degree of hemolysis (f)

Fig. 2

The spectrum of mutations mapped along the protein structures of ankyrin, α/β-spectrin, band 3. Mutations were colored by hemolysis phenotype. The degree of hemolysis was classified as mild(RBC lifespan>14 days) or severe(RBC lifespan ≤ 14 days). Ankyrin [–12] consists of three domains: a membrane-binding domain, a spectrin-binding domain and a regulatory domain (a).α/β-spectrin [13] contains several spectrin-type repeats with specialized domains(b/c). Band 3 [14, 15] comprises an intracellular domain and a transmembrane domain (d)