Identification and in silico characterization of a novel compound heterozygosity associated with hereditary aceruloplasminemia

Abstract

Background. Hereditary aceruloplasminemia is an adult-onset autosomal recessive disease characterized by increased iron overload in the liver, pancreas, retina, and central nervous system. So far, 45 families with cases of aceruloplasminemia have been reported world-wide and mainly missense and nonsense mutations in the ceruloplasmin gene were detected. Material and methods. Here, we report the identification, clinical characterization, and in silico analysis of a novel compound heterozygosity in the ceruloplasmin gene of a 31-year-old man with iron overload. Results. Increased serum ferritin levels, elevated iron saturation, as well as results of iron quantification in the liver and magnetic resonance imaging-based measurement of T2 relaxation times of the substantia nigra consistently suggested iron overload. By sequencing the ceruloplasmin gene, so far unknown nucleotide replacements G229C, and C2131A were detected in exons 2 and 12, respectively. In silico analyses showed that the resulting amino acid changes Asp58His and Gln692Lys are located at highly conserved positions. The Asp58His mutation is located on the surface of the protein, alters polarity, and may interfere with copper incorporation or ceruloplasmin trafficking. The Gln692Lys mutation is mapped to a β-strand of domain 4 and may lead to conformational change of the cupredoxin fold. Conclusions. As causative for aceruloplasminemia, a formerly unknown compound heterozygosity in the ceruloplasmin gene was identified. In silico characterization suggests an impact on ceruloplasmin conformation and function.