Objective: To detect potential mutation in a family affected with congenital dyserythropoietic anemia type II (CDA II).
Methods: Targeted sequence capture and next-generation sequencing (NGS) were used to analyze the exons and exon-intron boundaries of the SEC23B gene in a clinically suspected CDA II patient. Genotypes of the relatives were validated by Sanger sequencing. Potential impact of amino acid substitution on the structure and function of SEC23B protein was predicted with MutationTaster and PolyPhen-2. The protein structure was predicted with SWISS-MODEL software.
Results: The proband was found to harbor double heterozygous mutations of the SEC23B gene, c.1727T>C (p.F576S) and c.1831C>T (p.R611W), which resulted in amino acid substitutions p.F576S and p.R611W. Both mutations were confirmed by Sanger sequencing. The sister of the proband was found to have carried c.1727T>C (p.F576S), while her father and son have carried c.1831C>T (p.R611W) mutation. In addition, the proband was detected to have carried c.211C>T (p.R71X) of the HFE gene, which resulted in substitution of arginine by a stop codon. The impact of above mutations on the structure or function of protein was predicted to be harmful. Splenectomy and iron chelation therapy have achieved effective improvement of anemia and iron overload. Computer simulation suggested that the mutations have altered the 3D structure of the SEC23B protein.
Conclusion: The novel compound mutations of c.1727T>C and c.1831C>T of the SEC23B gene probably underlie the CDA II in the family, and there is a strong correlation between the genotype and phenotype.