Two novel ANK1 loss-of-function mutations in Chinese families with hereditary spherocytosis

Hereditary spherocytosis (HS) is the most common inherited haemolytic anaemia disorder. ANK1 mutations account for most HS cases, but pathogenicity analysis and functional research have not been widely performed for these mutations. In this study, in order to confirm diagnosis, gene mutation was screened in two unrelated Chinese families with HS by a next-generation sequencing (NGS) panel and then confirmed by Sanger sequencing. Two novel heterozygous mutations (c.C841T, p.R281X and c.T290G, p.L97R) of the ANK1 gene were identified in the two families respectively. Then, the pathogenicity of the two new mutations and two previously reported ANK1 mutations (c.C648G, p.Y216X and c.G424T, p.E142X) were studied by in vitro experiments. The four mutations increased the osmotic fragility of cells, reduced the stabilities of ANK1 proteins and prevented the protein from localizing to the plasma membrane and interacting with SPTB and SLC4A1. We classified these four mutations into disease-causing mutations for HS. Thus, conducting the same mutation test and providing genetic counselling for the two families were meaningful and significant. Moreover, the identification of two novel mutations enriches the ANK1 mutation database, especially in China.