Acute intermittent porphyria (AIP) is an autosomal dominant genetic disease caused by a lack or decrease in hydroxymethylbilane synthase (HMBS) activity. It is characterized by acute nerve and visceral attacks caused by factors in the process of heme synthesis. The penetrance rate of this disease is low, and the heterogeneity is strong. Here, we reported two novel mutations from two unrelated Chinese AIP patients and confirmed the pathogenicity of these two mutations. We found the c.760-771+2delCTGAGGCACCTGGTinsGCTGCATCGCTGAA and c.88-1G>C mutations by second-generation sequencing and Sanger sequencing. The in vitro expression analysis showed that these mutations caused abnormal mRNA splicing and premature ... More
Acute intermittent porphyria (AIP) is an autosomal dominant genetic disease caused by a lack or decrease in hydroxymethylbilane synthase (HMBS) activity. It is characterized by acute nerve and visceral attacks caused by factors in the process of heme synthesis. The penetrance rate of this disease is low, and the heterogeneity is strong. Here, we reported two novel mutations from two unrelated Chinese AIP patients and confirmed the pathogenicity of these two mutations. We found the c.760-771+2delCTGAGGCACCTGGTinsGCTGCATCGCTGAA and c.88-1G>C mutations by second-generation sequencing and Sanger sequencing. The in vitro expression analysis showed that these mutations caused abnormal mRNA splicing and premature termination or partial missing of HMBS protein. Homologous modeling analysis showed that the HMBS mutants lacked the amino acids which are crucial for the enzyme activity or the protein stability. Consistently, enzyme activity analysis confirmed that the HMBS mutants' overexpression cells exhibited the reduced enzyme activity compared with the HMBS wildtype overexpression cells. Our study identified and confirmed two novel pathogenic mutations which will expand the molecular heterogeneity of AIP and provide further scientific basis for the clinical diagnosis of AIP.
