There are many inherited disorders associated with thoracic aortic aneurysms and dissections (TAADs), like Marfan syndrome and Loeys-Dietz syndrome (LDS). The 4 patients in this study all had TAADs and were initially diagnosed with suspected Marfan syndrome. We collected peripheral blood samples from the patients and their family members and then attempted to identify the causal mutation using different methods including PCR, Sanger sequencing, and next generation sequencing. We identified 3 novel heterozygous mutations including 2 splicing mutations of FBN1 and 1 missense mutation of TGFBR2 in our patients. Although these mutation sites have been reported in the Human Gene Mutation Database, the nucleotide changes are different. All novel mutations found in this study were confirmed to be absent in 50 unrelated normal individuals of the same ethnic background. The RT-PCR results of 2 splicing mutations verified that the mutations can lead to the skipping of exons. The RT-qPCR results indicated that FBN1 mRNA levels were nearly 50 percent lower in the patients than in normal controls, indicating that there is almost no expression of truncated fibrillin-1 because of the nonsense-mediated mRNA decay (NMD) mechanism. To the best of our knowledge, we are the first to report these 3 novel mutations. However, the pathogenicity of these mutations still needs further confirmation. Our study has confirmed or corrected the clinical diagnosis, and enlarged the mutation spectrum of FBN1 and TGFBR2. The results should be helpful for prenatal diagnosis and genetic counseling.
Keywords: Exon skipping; Loeys-Dietz syndrome; Marfan syndrome; Missense mutation; Mosaicism; RT-PCR; RT-qPCR; Splicing mutation.