Extensive genetic screening of Iranian Factor FVII-deficient individuals unraveled several novel mutations and postulated founder effects in some cases

Abstract

BackgroundAs the most frequent congenital rare bleeding disorder that transmits in an autosomal recessive manner, factor VII (FVII) deficiency is a serious bleeding complication in populations with high rate of in-marriages. While diagnosis mainly relies on clinical and laboratory phenotypes, plasma FVII antigen and activity levels do not often correlate with symptoms’ severity. ObjectivesGenetic profiling of the affected individuals potentially improves our biological understanding of this complicated rare disorder. MethodsConventional polymerase chain reaction-Sanger sequencing and whole-exome sequencing were applied for genetic profiling of F7 gene in 66 symptomatic FVII-deficient individuals from 62 independent pedigrees. Thirty-nine asymptomatic relatives of the patients were also studied. ResultsThirty different F7 pathogenic variations were identified in the studied cases of which 11 have not been reported before. The novel mutations include 5 missenses (c.715G>A, c.794T>C, c.1090C>G, c.1222C>A, c.1265T>C), 3 splicing (c.316+1G>T, c.682-2A>G, c.572-16C>G), 2 nonsenses (c.790delC, c.1248G>A), and 1 frameshift (c.1346delA). A founder effect is proposed for c.790delC that was detected in 8 independent pedigrees who were all from similar geographical regions and ethnic backgrounds. Homozygous c.790delC reduces plasma FVII activity to <1% and causes spontaneous intracranial hemorrhage in early infancy. ConclusionFrom the 66 studied symptomatic FVII-deficient individuals, 58 were homozygous carriers of the identified variations. Identification of homozygotes clarifies the potential role of nucleotide variations in reducing FVII activity and their contributions to a certain phenotype. Some of those variations, such as c.1A>G, c.509G>A, c.634C>T, and c.1285G>A have only been previously reported as heterozygous.