OBJECTIVE: To identify the pathogenic variants from a patient with suspected congenital contractural arachnodactyly, and to explore the possible molecular genetic pathogenesis, so as to provide evidence for clinical diagnosis. METHODS: Whole exome sequencing was performed for the patient. The splicing site variation of candidate pathogenic genes was verified by Sanger sequencing, and the new transcript sequence was determined by RT-PCR and TA-cloning sequencing. RESULTS: The patient carried a heterozygous c.533-1G>C variant of FBN2 gene, which was not reported. The sequencing of mRNA showed that the variant leaded to the disappearance of the canonical splice acceptor site of FBN2 gene and the activation of a cryptic splice acceptor site at c.533-71, resulting in the insertion of 70 bp sequence in the new transcript. It was speculated that the polypeptide encoded by the new transcript changed from valine (Val) to serine (Ser) at amino acid 179, and prematurely terminated after 26 aminoacids. According to the guidelines of American College of Medical Genetics and Genomics, the variant of FBN2 gene c. 533-1G>C was determined as pathogenic (PVS1+PM2+PP3 ). CONCLUSION A novel splicing variant of FBN2 gene (c.533-1G>C) was identified, which can lead to congenital contractural arachnodactyly.
Arachnodactyly/genetics* ; Contracture/genetics* ; Fibrillin-2/genetics* ; Humans ; Mutation ; RNA Splice Sites ; Whole Exome Sequencing

OBJECTIVE: To detect pathological variant in a Chinese pedigree affected with congenital contractural arachnodactyly (CCA). METHODS: Next generation sequencing (NGS) was used to scan the whole exome of the proband. Potential variant of the FBN2 gene was also detected in all members of the pedigree and 100 healthy controls by Sanger sequencing. With the determination of the genotype, prenatal diagnosis was carried out by amniotic fluid sampling. RESULTS: A c.3528C>A (p.Asn1176Lys) variant was identified in the FBN2 gene of the proband, other patients from this pedigree, as well as the fetus. The same variant was not found among healthy members from this pedigree and the 100 healthy controls. CONCLUSION The c.3528C>A (p.Asn1176Lys) variant of the FBN2 gene probably underlies the pathogenesis of CCA in our case. The new variant has enriched pathological spectrum of the FBN2 gene.
Arachnodactyly ; complications ; genetics ; Contracture ; congenital ; etiology ; genetics ; Exome ; Female ; Fibrillin-2 ; genetics ; Humans ; Mutation ; Pedigree ; Pregnancy ; Prenatal Diagnosis

OBJECTIVE: To identify whether naringenin plays a protective role during thoracic aneurysm formation in Marfan syndrome. METHODS: To validate the effect of naringenin, Fbn1^C1039G/+ mice, the mouse model of Marfan syndrome, were fed with naringenin, and the disease progress was evaluated. The molecular mechanism of naringenin was further investigated via in vitro studies, such as bioluminescence resonance energy transfer (BRET), atomic force microscope and radioligand receptor binding assay. RESULTS: Six-week-old Fbn1^C1039G/+ mice were fed with naringenin for 20 weeks. Compared with the control group, naringenin significantly suppressed the aortic expansion [Fbn1^C1039G/+ vs. Fbn1^C1039G/++naringenin: (2.49±0.47) mm, n=18 vs. (1.87±0.19) mm, n=22, P < 0.05], the degradation of elastin, and the expression and activity of matrix metalloproteinase 2 (MMP2) and MMP9 in the ascending aorta of Fbn1^C1039G/+ mice. Besides, treatment with naringenin for 6 weeks also attenuated the disease progress among the 20-week-old Fbn1^C1039G/+ mice with established thoracic aortic aneurysms [Fbn1^C1039G/+ vs. Fbn1^C1039G/++naringenin: (2.24±0.23) mm, n=8 vs. (1.90±0.17) mm, n=8, P < 0.05]. To understand the underlying molecular mechanisms, we examined the effects of naringenin on angiotensin Ⅱ type 1 receptor (AT1) signaling and transforming growth factor-β (TGF-β) signaling respectively, which were the dominant signaling pathways contributing to aortopathy in Marfan syndrome as previously reported. The results showed that naringenin decreased angiotensin Ⅱ (Ang Ⅱ)-induced phosphorylation of protein kinase C (PKC) and extracellular regulating kinase 1/2 (ERK1/2) in HEK293A cell overexpressing AT1 receptor. Moreover, naringenin inhibited Ang Ⅱ-induced calcium mobilization and uclear factor of activated T-cells (NFAT) signaling. The internalization of AT1 receptor and its binding to β-arrestin-2 with Ang Ⅱ induction were also suppressed by naringenin. As evidenced by atomic force microscope and radioligand receptor binding assay, naringenin inhibited Ang Ⅱ binding to AT1 receptor. In terms of TGF-β signaling, we found that feeding the mice with naringenin decreased the phosphorylation of Smad2 and ERK1/2 as well as the expression of TGF-β downstream genes. Besides, the serum level of TGF-β was also decreased by naringenin in the Fbn1^C1039G/+ mice. Furthermore, we detected the effect of naringenin on platelet, a rich source of TGF-β, both in vivo and in vitro. And we found that naringenin markedly decreased the TGF-β level by inhibiting the activation of platelet. CONCLUSION Our study showed that naringenin has a protective effect on thoracic aortic aneurysm formation in Marfan syndrome by suppressing both AT1 and TGF-β signaling.
Angiotensin II/metabolism* ; Animals ; Aortic Aneurysm, Thoracic/prevention & control* ; Calcium/metabolism* ; Disease Models, Animal ; Elastin/metabolism* ; Fibrillin-1/metabolism* ; Flavanones ; Marfan Syndrome/metabolism* ; Matrix Metalloproteinase 2 ; Matrix Metalloproteinase 9 ; Mice ; Mice, Inbred C57BL ; Protein Kinase C/metabolism* ; Receptor, Angiotensin, Type 1/metabolism* ; Transforming Growth Factor beta/metabolism* ; Transforming Growth Factors/metabolism* ; beta-Arrestins/metabolism*