Analysis of genetic variants in a pedigree affected with hereditary multiple osteochondroma / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic basis for a pedigree affected with hereditary multiple osteochondroma (HMO).@*METHODS@#Peripheral blood samples were collected from the proband and members of his pedigree with informed consent. Following extraction of genomic DNA, all coding exons and flanking intronic sequences (-10 bp) of the EXT1 and EXT2 genes were subjected to targeted capture and next generation sequencing (NGS). Suspected variant was verified by Sanger sequencing.@*RESULTS@#A heterozygous nonsense variant (c.1911C>A) was found in exon 10 of the EXT1 gene in the proband and his affected father but not in a healthy sister and normal controls. The variant was classified as a pathogenic based on the guidelines of the American College of Medical Genetics and Genomics (PVS1+PM2+PP1). Bioinformatic analysis predicted that the c.1911C>A variant may be disease-causing via nonsense-mediated mRNA decay and anomalous splicing.@*CONCLUSION@#The c.1911C>A variant probably underlay the disease in this pedigree. Discovery of this variant enriched the variant spectrum of HMO.

Analysis of a multiple osteochondroma case caused by novel splice mutation (c.1164+1G to A) of EXT1 gene / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To detect potential mutation of EXT1 gene in a pedigree affected with multiple osteochondroma and explore its pathogenic mechanism.</p><p><b>METHODS</b>The coding regions and their flanking sequences of the EXT1/EXT2 genes were subjected to PCR amplification and Sanger sequencing. Suspected mutations were verified by excluding possible single nucleotide polymorphisms and bioinformatics analysis. Transcripts of the EXT1 gene in the proband were analyzed by TA clone-sequencing, with its abundance compared with that of healthy controls.</p><p><b>RESULTS</b>DNA sequencing has identified in the proband a novel heterozygous point mutation (c.1164+1G to A) at the 5'splice sites of intron 3 of the EXT1 gene. The same mutation was not found in the healthy controls. Bioinformatics analysis indicated that the mutation is highly conserved and can lead to skipping of exon 3 or aberrant splicing. TA clone-sequencing indicated that the numbers of transcripts with skipping of exon 3 has significantly increased in the proband (< 0.05) compared with the controls.</p><p><b>CONCLUSION</b>The c.1164+1G to A mutation has resulted in skipping of exon 3 in a proportion of EXT1 gene transcripts. As the result, the number of transcripts with tumor suppressing function is relatively reduced and has ultimately led to the tumors.</p>