Factor 8 gene mutation spectrum of 270 patients with hemophilia a: Identification of 36 novel mutations

Abstract

Objective: Hemophilia A (HA) is the most severe X-linked inherited bleeding disorder caused by hemizygous mutations in the factor 8 (F8) gene. The aim of this study is to determine the mutation spectrum of the F8 gene in a large HA cohort from Turkey, and then to establish a phenotype-genotype correlation. Materials and Methods: All HA cases (270 patients) analyzed molecularly in the Ege University Pediatric Genetics Molecular Laboratory between March 2017 and March 2018 were included in this study. To identify intron 22 inversion (Inv22), intron 1 inversion (Inv1), small deletion/insertions, and point mutations, molecular analyses of F8 were performed using a sequential application of molecular techniques. Results: The mutation detection success rate was 95.2%. Positive Inv22 was found in 106 patients (39.3%), Inv1 was found in 4 patients (1.5%), and 106 different disease-causing sequence variants were identified in 137 patients (50.6%). In 10 patients (3.7%), amplification failures involving one or more exonic regions, considered to be large intragenic deletions, were identified. Of 106 different F8 mutations, 36 were novel. The relationship between F8 genotype and inhibitor development was considered significant. Conclusion: A high mutation detection rate was achieved via the broad molecular techniques applied in this study, including 36 novel mutations. With regard to mutation types, mutation distribution and their impact on clinical severity and inhibitor development were found to be similar to those previously reported in other hemophilia population studies.

Amaç: Hemofili A (HA), faktör 8 (F8) genindeki hemizigot mutasyonların neden olduğu X’e bağlı kalıtsal kanama bozukluğudur. Bu çalışmanın amacı, Türkiye’den büyük bir HA kohortunda F8 geninin mutasyon spektrumunu belirlemek ve fenotip-genotip korelasyonu oluşturmaktır. Gereç ve Yöntemler: Mart 2017-Mart 2018 tarihleri arasında Ege Üniversitesi Pediatrik Genetik Moleküler Laboratuvarı’nda moleküler olarak analiz edilen tüm HA hastaları (270 hasta) çalışmaya dahil edildi. “İntron 22 inversiyonu” (Inv22), “intron 1 inversiyonu” (Inv1), “küçük delesyon/duplikasyonlar” ve “nokta mutasyonları” tanımlamak için F8’in moleküler analizleri, uygun bir algoritma kullanılarak gerçekleştirildi. Bulgular: Mutasyon saptama başarı oranı %95,2’ydi. Yüz altı hastada (%39,3) Inv22 pozitif, 4 hastada (%1,5) Inv1, 137 hastada (%50,6) Yüz altı farklı hastalık yapıcı sekans varyantı saptandı. On hastada (%3,7), büyük intragenik delesyonlar olduğu öngörülen bir veya daha failures involving one or more exonic regions, considered to be large intragenic deletions, were identified. Of 106 different F8 mutations, 36 were novel. The relationship between F8 genotype and inhibitor development was considered significant. Conclusion: A high mutation detection rate was achieved via the broad molecular techniques applied in this study, including 36 novel mutations. With regard to mutation types, mutation distribution and their impact on clinical severity and inhibitor development were found to be similar to those previously reported in other hemophilia population studies.