A novel gain‐of‐function PIP4K2A mutation elevates the expression of β‐globin and aggravates the severity of α‐thalassemia

Abstract

SummaryHaemoglobin H (Hb H) disease (intermediate status of α‐thalassemia) shows marked phenotypic variability from asymptomatic to severe anaemia. Apart from the combined β‐thalassemia allele ameliorating clinical severity, reports of genetic modifier genes affecting the phenotype of Hb H disease are scarce which bring inconvenience to precise diagnosis and genetic counselling of the patients. Here, we present a novel mutation (c.948C>A, p.S316R) in the PIP4K2A gene in a female Hb H disease patient who displayed moderate anaemia and a relatively high Hb H level. Haematological analysis in her family members revealed that individuals carrying this mutation have upregulated β‐globin expression, leading to a more imbalanced β/α‐globin ratio and more Hb H inclusion bodies in peripheral red blood cells. According to functional experiments, the mutant PIP4K2A protein exhibits enhanced protein stability, increased kinase activity and a stronger regulatory effect on downstream proteins, suggesting a gain‐of‐function mutation. Moreover, introduction of the S316R mutation into HUDEP‐2 cells increased expression of β‐globin, further inhibiting erythroid differentiation and terminal enucleation. Thus, the S316R mutation is a novel genetic factor associated with β‐globin expression, and the PIP4K2A gene is a new potential modifier gene affecting the α‐thalassemia phenotype.