Mutation Analysis Of The NF1 Gene In Chinese Patients With Neurofibromatosis Type 1.

Background: Neurofibromatosis type 1(NF1)is an autosomal dominant genetic disorder with an incidence about 1/3500.The mutation rate is high,about 50% of which are spontaneous mutation,and the adult penetrance rate is about 100%.Common clinical manifestations include café-au-lait macules,axillary freckling,neurofibromas,and Lisch nodules.Neurofibromin 1 gene(NF1)has been well documented for causing NF1,approximately 350 kb in length,contains 57 constitutive exons and 3 variable splicing exons,which encodes a neurofibromin containing 2818 amino acids.Diagnosis is generally relies on clinical manifestations rather than routine genetic analysis.However,for suspected patients who do not meet the clinical diagnostic criteria of the National Institutes of Health and patients with genetic counseling,prenatal diagnosis,etc.,it is necessary to perform NFI gene mutation detection.At present,the main purpose of research is to find mutation hotspots and discover genotype-phenotype relationships.Objective: Determination of NF1 gene mutation in a Chinese NF1 family and 5 sporadic patients in Chinese Han population,aiming to detect mutation sites,hoping to find novel mutations to further enrich NF1 gene mutation spectrum in the Chinese population;explore the genotype-phenotype relationships to predict the development of the patient's condition and explain the characteristics of the diversification of complications;lay the foundation for the need of patients' genetic counseling and prenatal diagnosis.Methods: After the patient's informed consent,5ml peripheral blood was obtained from all the family members.Genomic DNA was extracted from their peripheral blood.Primers were designed to amplify the entire coding sequence of NF1.NF1 gene was amplified by polymerase chain reaction(PCR).After purification,the PCR products were sequenced by sanger sequencing.Results: In this study,only one patient did not detect a suspected pathogenic mutation site,while the other five patients successfully detected the suspected pathogenic site,four of them are novel mutations: c.4028C>A,p.Thr1343 Asn,c.5635 delG,c.7041-7062+4del,c.2714-2715 delAC.Two previously reported mutations were detected: c.1845+1G>A and c.2446C>A,P.Arg816 fs.The point mutation c.4028C>A and the splice mutation c.1845 1G>A were from the family 1 in this study.Conclusions: The detection rate of mutation in this study was 85.7%,and 6 mutations were detected.Of which four novel mutations enriched the mutation spectrum of NF1 gene in Chinese population,which laid the foundation for NF1 related research.The above mutations affect the normal function of neurofibromin due to direct mutation to stop codons,premature generation of stop codons or deletion of large fragment bases,and splice errors,ultimately leading to disease occurrence.In addition,although no mutations related to JXG were found in the previous literature,but we venture to guess that the mutation c.4028C>A may be the cause of JXG.For patients with clinically unsatisfactory clinical criteria,and patients with genetic counseling and prenatal diagnosis needs,NF1 gene mutation analysis can be considered to confirm the diagnosis and follow-up observation according to the development of the disease condition.