Overview of SERPING1 Variations Identified in Hungarian Patients With Hereditary Angioedema

Abstract

BackgroundHereditary angioedema (HAE) due to C1-inhibitor (C1-INH) deficiency (C1-INH-HAE) is a rare autosomal dominant disorder, characterized by recurrent, unpredictable edematous symptoms involving subcutaneous, and/or submucosal tissue. C1-INH-HAE may be caused by more than 700 different mutations in the gene encoding C1-INH (SERPING1) that may lead to decreased protein synthesis or to functional deficiency.MethodsConcentrations of C1-INH, C4, C1q, and anti-C1-INH antibodies, as well as functional C1-INH activity were determined in subjects suffering from edematous symptoms and admitted to the Hungarian Angioedema Center of Reference and Excellence. In those patients, who were diagnosed with C1-INH-HAE based on the complement measurements, SERPING1 was screened by bidirectional sequencing following PCR amplification and multiplex ligation-dependent probe amplification. For detecting large deletions, long-range PCRs covering the entire SERPING1 gene by targeting 2–7 kb long regions were applied.ResultsAltogether 197 individuals with C1-INH deficiency belonging to 68 families were identified. By applying Sanger sequencing or copy number determination of SERPING1 exons, 48 different mutations were detected in 66/68 families: 5 large and 15 small insertions/deletions/delins, 16 missense, 6 nonsense, and 6 intronic splice site mutations. Two novel variations (p.Tyr199Ser [c.596A>C] and the duplication of exon 7) were shown to cosegregate with deficient C1-inhibitor level and activity, while two other variations were detected in single patients (c.797_800delinsCTTGGAGCTCAAGAACTTGGAGCT and c.812dup). A series of long PCRs was applied in the remaining 2 families without an identified mutation and a new, 2606 bp long deletion including the last 91 bp of exon 6 (c.939_1029+2515del) was identified in all affected members of one pedigree. In the remaining one family, a deep intronic SERPING1 variation (c.1029+384A>G) was detected by a targeted next-generation sequencing panel as reported previously.ConclusionsSequencing and copy number determination of SERPING1 exons uncover most pathogenic variants in C1-INH-HAE patients, and further methods are worth to be applied in cases with unrevealed genetic background. Since knowledge of the genetic background may support the establishment of the correct and early diagnosis of C1-INH-HAE, identification of causative mutations and reporting data supporting the interpretation on the pathogenicity of these variants is of utmost importance.

Complex analysis of the national Hereditary angioedema cohort in Slovakia – Identification of 12 novel variants in SERPING1 gene

“…Variation type distribution in our cohort is different compared to neighbouring countries. 6 , 7 We found a higher proportion of frameshift and inframe variants. Proportion of missense variants and gross deletions is similar to distribution according to the LOVD database.…”

“…4 ) C1–INH-HAE-1 1 8 c.1371_1373del p.Ala459del Inframe deletion pathogenic not published ∗ 4 ( Fig. 4 ) C1–INH-HAE-1 1 8 c.1396C > T p.Arg466Cys Missense pathogenic 25.4 7 , 26 , 28 , 29 , 30 , 31 , 32 , 36 , 37 , 38 , 39 6 ( Fig. 4 ) C1–INH-HAE-2 3 8 c.1397G > A p.Arg466His Missense pathogenic 24.0 20 , 23 , 26 , 29 , 30 , 31 , 39 , 40 , 41 2 (father, son) C1–INH-HAE-2 1 8 c.1397G > T p.Arg466Leu Missense pathogenic 23.8 4 , 24 , 33 , 34 , 35 , 36 , 37 , 40 , 42 3 (father, 2 daughters) C1–INH-HAE-2 1 8 Exon 8 deletion Gross ...…”

“… 6 In the study of Hungarian HAE patients (neighbouring country of Slovakia), missense variants were found in 30.1%, large deletions or duplications in 20.6%, frameshift variants in 19.1%, nonsense variants in 17.6%, and splicing variants in 11.8% of the index cases. 7 …”

Application of a dried blood spot based proteomic and genetic assay for diagnosing hereditary angioedema

“…In each C1-INH-HAE patient, a potentially pathogenic SERPING1 mutation was identified previously as recently reported. 23 Genetic analyses from DBS samples were capable of verifying each mutation, both substitutions located in the exonic or intronic regions of SERP-ING1 and deletions/duplications ranging from one base up to the whole gene (Table 2, Supplementary Table S2). Additionally Pro904Arg) (Supplementary Table S2).…”

“…This CNV was detected due to the next-generation sequencing (NGS)-based CNV analysis as MLPA analysis resulted negative in the presence of decreased concentration of C1-INH. The location of the MLPA probe in the exon 6 was before the start of the deletion, leading to a falsenegative result 23. This stresses the importance of the combination of different genetic methods to identify the genetic cause of the disease and provide an accurate diagnosis to the patients.At last, the use of an extended NGS panel of genes and WGS also allowed us to identify 3 patients with novel rare variants in other genes (ADGRE2, XPNPEP2 and SOX18).…”