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Updated: Dec 5, 2025
Determining the Likelihood of Variant Pathogenicity Using Amino Acid-level Signal-to-Noise Analysis of Genetic Variation
Published on: January 16, 2019
Optimising the mutation screening strategy in Marfan syndrome and identifying genotypes with more severe aortic
Roland Stengl1,2,3, András Bors4, Bence Ágg5,6,7
1Heart and Vascular Center, Semmelweis University, Városmajor u. 68, Budapest, 1122, Hungary. rolandstengl01@gmail.com.
Background:
Marfan syndrome (MFS) is a systemic connective tissue disorder with life-threatening manifestations affecting the ascending aorta. MFS is caused by dominant negative (DN) and haploinsufficient (HI) mutations of the FBN1 gene. Our aim was to identify mutations of MFS patients with high detection rate and to investigate the use of a gene panel for patients with Marfanoid habitus. We also aimed to examine correlations between genotype and cardiovascular manifestations to predict "malignant" mutations.
Methods:
136 individuals were enrolled. In the first phase, next-generation sequencing (NGS) and Sanger sequencing were performed for 57 patients to screen the FBN1 gene, followed by multiplex ligation-dependent probe amplification (MLPA) in negative cases. For repeated negative results, NGS gene panel involving 9 genes was used. In the second phase, 79 patients were tested primarily with the same gene panel, negative samples were tested by MLPA.
Results:
84 pathogenic mutations were detected, out of which 78 affected FBN1, 6 non-FBN1 mutations (2 TGFB2, 1 TGFBR2, 2 TGFBR1, 1 SMAD3) are associated with Loeys-Dietz syndrome (LDS). LDS patients had lower systemic score and they were younger, but their aortic involvement did not differ. MLPA detected 4 multi-exon deletions of FBN1 gene, which could not be identified by our first-step screening method. Aortic involvement (aortic dissection and/or dilation) did not differ significantly among HI and DN mutations (p = 0.061). Combined group of HI and DN mutations eliminating a disulphide-bonding cysteine (DN Cys) had significantly higher aortic involvement rate than DN mutations not eliminating a disulphide-bonding cysteine (DN non-Cys) (p < 0.001). Patients with DN Cys required significantly more aortic surgeries than HI and DN non-Cys mutations (p = 0.042 and p = 0.015, respectively).
Conclusions:
Due to the relevant number of mutations affecting genes other than FBN1, preferred approach for testing individuals with Marfanoid habitus is using a gene panel rather than single-gene analysis, followed by MLPA for negative samples. DN Cys and HI mutations should be considered as risk factors for aortic involvement. Genetic testing for patients with Marfanoid features and a systemic score under 7 is recommended, as LDS patients may have lower scores, but they may have severe cardiovascular manifestations.
Insights
Genetic testing using a gene panel is recommended for Marfanoid habitus, identifying FBN1 and other gene mutations. Specific FBN1 mutations (DN Cys) are linked to higher aortic involvement risk.
Area of Science:
- Genetics
- Cardiovascular Medicine
- Medical Diagnostics
Background:
- Marfan syndrome (MFS) is a genetic connective tissue disorder primarily affecting the aorta.
- MFS arises from mutations in the FBN1 gene, leading to dominant negative (DN) or haploinsufficient (HI) effects.
- Identifying causative mutations is crucial for understanding disease progression and predicting cardiovascular risks.
Purpose of the Study:
- To identify mutations in Marfan syndrome (MFS) patients with a high detection rate.
- To evaluate the efficacy of a gene panel for diagnosing Marfanoid habitus.
- To correlate genotypes with cardiovascular manifestations for predicting severe outcomes.
Main Methods:
- Employed next-generation sequencing (NGS) and Sanger sequencing for FBN1 gene screening.
- Utilized multiplex ligation-dependent probe amplification (MLPA) for detecting deletions missed by sequencing.
- Implemented a 9-gene panel for patients with Marfanoid habitus, followed by MLPA for negative cases.
Main Results:
- Detected 84 pathogenic mutations, including 78 in FBN1 and 6 in other genes (TGFB2, TGFBR2, TGFBR1, SMAD3) associated with Loeys-Dietz syndrome (LDS).
- Identified 4 multi-exon FBN1 deletions via MLPA.
- Found that mutations eliminating a disulphide-bonding cysteine (DN Cys) significantly increased aortic involvement and surgical needs compared to other mutation types.
Conclusions:
- A gene panel approach is preferred over single-gene testing for Marfanoid habitus, detecting a broader range of mutations.
- Haploinsufficient (HI) and DN Cys mutations are significant risk factors for aortic disease.
- Genetic testing is recommended for individuals with Marfanoid features, even with lower systemic scores, due to potential severe cardiovascular manifestations in LDS.
