Recurrent F8 and F9 gene variants result from a founder effect in two large French haemophilia cohorts.

INTRODUCTION: Haemophilia A (HA) and haemophilia B (HB) are X-linked recessive diseases, caused by a large number of pathogenic variants in the F8 and F9 genes. With the exception of introns 22 and 1 inversions which are frequent in severe HA cases, about 2000 unique variants in F8 and 1000 in F9 have been described in databases and their recurrence remains limited. AIM AND METHODS: During routine analysis, we identified two recurrent missense variants, the F8 gene c.1244C>T, p.Ala415Val variant in 27 HA patients and the F9 gene c.835G>A, p.Ala279Thr variant in 34 HB patients, in two groups of haemophiliac patients from two different regions of France. We aimed to identify whether these variants result from a founder effect. We performed haplotype reconstruction after analysis of extragenic and intragenic polymorphic markers. The ESTIAGE programme was used to estimate the age of the variant. RESULTS: We identified a common ancestral haplotype HA1, in all the HA patients sharing the p.Ala415Val variant, and HB1 for 22 of 34 HB patients sharing the p.Ala279Thr variant. The estimated time of occurrence of the founder variant was between the 13th and 17th century (95% CI: 16 to 29 generations) for the F8 variant and between the 3rd and the 11th century for the F9 variant (95% CI: 44 to 72 generations). CONCLUSION: This study supports a founder effect for these two variants in the two largest reported cohorts of haemophilia patients with an identical variant. These pathogenic variants are among the three most early reported variants in haemophilia.

Single, short in-del, and copy number variations detection in monogenic dyslipidemia using a next-generation sequencing strategy.

Optimal molecular diagnosis of primary dyslipidemia is challenging to confirm the diagnosis, test and identify at risk relatives. The aim of this study was to test the application of a single targeted next-generation sequencing (NGS) panel for hypercholesterolemia, hypocholesterolemia, and hypertriglyceridemia molecular diagnosis. NGS workflow based on a custom AmpliSeq panel was designed for sequencing the most prevalent dyslipidemia-causing genes (ANGPTL3, APOA5, APOC2, APOB, GPIHBP1, LDLR, LMF1, LPL, PCSK9) on the Ion PGM Sequencer. One hundred and forty patients without molecular diagnosis were studied. In silico analyses were performed using the NextGENe software and homemade tools for detection of copy number variations (CNV). All mutations were confirmed using appropriate tools. Eighty seven variations and 4 CNV were identified, allowing a molecular diagnosis for 40/116 hypercholesterolemic patients, 5/13 hypocholesterolemic patients, and 2/11, hypertriglyceridemic patients respectively. This workflow allowed the detection of CNV contrary to our previous strategy. Some variations were found in previously unexplored regions providing an added value for genotype-phenotype correlation and familial screening. In conclusion, this new NGS process is an effective mutation detection method and allows better understanding of phenotype. Consequently this assay meets the medical need for individualized diagnosis of dyslipidemia.