Cost-effective Whole Exome Sequencing discovers pathogenic variant causing Neurofibromatosis type 1 in a family from...

Neurofibromatosis type 1 (NF1) is a multisystemic hereditary disorder associated with an increased risk of benign and malignant tumor formation predominantly on the skin, bone, and peripheral nervous system. It has been reported that out of all the NF1 cases, more than 95% cases develop the disease due to heterozygous loss-of-function variants in Neurofibromin (NF1) gene. However, identification of NF1 causative variants by presently recommended method of gene-targeted Sanger sequencing is challenging and cost-intensive due to the large size of the NF1gene with 60 exons spanning about 350 kb. Further, conducting the genetic studies is difficult in low resource regions and among families with the limited financial capabilities, restricting them from availing diagnostic as well as proper disease management measures. Here, we studied a three-generation family from Jammu and Kashmir state in India, with multiple affected family members showing clinical indications of NF1. We combinedly used two applications, Whole Exome Sequencing (WES) and Sanger sequencing, for this study and discovered a nonsense variant NM_000267.3:c.2041C>T (NP_000258.1:p.Arg681Ter*) in exon 18 of NF1 gene in a cost effective manner. In silico analyses further substantiated the pathogenicity of this novel variant. The study also emphasized on the role of Next Generation Sequencing (NGS) as a cost-effective method for the discovery of pathogenic variants in disorders with known phenotypes found in large sized candidate genes. The current study is the first study based on the genetic characterization of NF1 from Jammu and Kashmir-India, highlighting the importance of the described methodology adopted for the identification and understanding of the disease in low resource region. The early diagnosis of genetic disorders would open the door to appropriate genetic counseling, reducing the disease burden in the affected families and the general population at large.