Systematic Approach Revealed SERPING1 Splicing-Affecting Variants to be Highly Represented in the Czech National HAE Cohort

Abstract

Hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE) is a rare and life-threatening condition characterized by recurrent localized edema. We conducted a systematic screening of SERPING1 defects in a cohort of 207 Czech patients from 85 families with C1-INH-HAE. Our workflow involved a combined strategy of sequencing extended to UTR and deep intronic regions, advanced in silico prediction tools, and mRNA-based functional assays. This approach allowed us to detect a causal variant in all families except one and to identify a total of 56 different variants, including 5 novel variants that are likely to be causal. We further investigated the functional impact of two splicing variants, namely c.550 + 3A > C and c.686-7C > G using minigene assays and RT-PCR mRNA analysis. Notably, our cohort showed a considerably higher proportion of detected splicing variants compared to other central European populations and the LOVD database. Moreover, our findings revealed a significant association between HAE type 1 missense variants and a delayed HAE onset when compared to null variants. We also observed a significant correlation between the presence of the SERPING1 variant c.-21 T > C in the trans position to causal variants and the frequency of attacks per year, disease onset, as well as Clinical severity score. Overall, our study provides new insights into the genetic landscape of C1-INH-HAE in the Czech population, including the identification of novel variants and a better understanding of genotype–phenotype correlations. Our findings also highlight the importance of comprehensive screening strategies and functional analyses in improving the C1-INH-HAE diagnosis and management.

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

“…The prevalence of C1–INH-HAE in the Slovak Republic according to this study is currently 1:41 280 and the incidence 1:1 360 000 (total population: 5 449 270 according to the 2021 population census). The prevalence is higher in comparison to data from other European countries: Sweden – 1:66 000, 50 Italy – 1:65 000, 51 Denmark – 1:70 900, 20 Greece −1:90 000, 52 Spain – 1:91 700, 53 the Czech Republic – 1:52 307, 6 and higher than average calculated prevalence 1:50 000. 2 …”

“…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.…”

“…Our cohort has higher percentage of inframe variants (11,5%) comparing to other studies. 5 , 6 , 7 Interpretation is challenging due to limitations of in-silico prediction tools and evaluation of impact on protein structure. All our novel inframe variants are rated as likely pathogenic according to ACMG criteria considering family history and segregation analysis.…”

“…Causative or probably causative variants were detected in 206 out of 207 (56 unique pathogenic or likely pathogenic sequence variants were found). 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 …”

Functional Characterization of Two Novel Intron 4 SERPING1 Gene Splice Site Pathogenic Variants in Families with Hereditary Angioedema

“…The SERPING1 gene is composed of eight exons and seven introns. Normally, this gene undergoes alternative splicing; however, the physiological role of alternative transcripts is unclear to this day [11,12]. All types of pathogenic variants are described for the gene: missense-32.2%, minor deletions and insertions-36.2%, deletions and duplications-8.3%, splicing affected variants-10.6%, nonsense-9.1% and promoter-3.7%?…”