Variable clinical expression of a Belgian TGFB3 founder variant suggests the presence of a genetic modifier.

Background: TGFB3 variants cause Loeys-Dietz syndrome type 5, a syndromic form of thoracic aortic aneurysm and dissection. The exact disease phenotype is hard to delineate because of few identified cases and highly variable clinical representation. Methodology: We provide the results of a haplotype analysis and a medical record review of clinical features of 27 individuals from 5 different families, originating from the Campine region in Flanders, carrying the NM_003239.5(TGFB3):c.787G>C p.(Asp263His) likely pathogenic variant, dbSNP:rs796051886, ClinVar:203492. The Asp263 residue is essential for integrin binding to the Arg-Gly-Asp (RGD) motif of the TGFß3-cytokine. Results: The haplotype analysis revealed a shared haplotype of minimum 1.92 Mb and maximum 4.14 Mb, suggesting a common founder originating >400 years ago. Variable clinical features included connective tissue manifestations, non-aneurysmal cardiovascular problems such as hypertrophic cardiomyopathy, bicuspid aortic valve, mitral valve disease, and septal defects. Remarkably, only in 4 out of the 27 variant-harboring individuals, significant aortic involvement was observed. In one family, a 31-year-old male presented with type A dissection. In another family, the male proband (65 years) underwent a Bentall procedure because of bicuspid aortic valve insufficiency combined with sinus of Valsalva of 50 mm, while an 80-year-old male relative had an aortic diameter of 43 mm. In a third family, the father of the proband (75 years) presented with ascending aortic aneurysm (44 mm). Conclusion: The low penetrance (15%) of aortic aneurysm/dissection suggests that haploinsufficiency alone by the TGFB3 variant may not result in aneurysm development but that additional factors are required to provoke the aneurysm phenotype.

IPSC reprogramming of two patients with spondyloepiphyseal dysplasia congenita (SEDC).

Spondyloepiphyseal dysplasia congenita (SEDC) is a severe non-lethal type 2 collagenopathy caused by pathogenic variants in the COL2A1 gene, which encodes the alpha-1 chain of type II collagen. SEDC is clinically characterized by severe short stature, degenerative joint disease, hearing impairment, orofacial anomalies and ocular manifestations. To study and therapeutically target the underlying disease mechanisms, human iPSC-chondrocytes are considered highly suitable as they have been shown to exhibit several key features of skeletal dysplasias. Prior to creating iPSC-chondrocytes, peripheral blood mononuclear cells of two male SEDC patients, carrying the p.Gly1107Arg and p.Gly408Asp pathogenic variants, respectively, were successfully reprogrammed into iPSCs using the CytoTune™-iPS 2.0 Sendai Kit (Invitrogen).

Generation of an induced pluripotent stem cell (iPSC) line (BBANTWi009-A) from a Meester-Loeys syndrome patient carrying a BGN mutation.

Meester-Loeys syndrome (MRLS) is an X-linked syndromic form of thoracic aortic aneurysm and dissection. Here, we report an iPSC line (BBANTWi009-A) of a boy carrying a hemizygous BGN mutation (chrX:153502980-153530518del, GRCh38) causing MRLS. iPSCs were generated from dermal fibroblasts by reprogramming with the Cytotune®-iPS 2.0 Sendai Reprogramming Kit (Invitrogen). The generated iPSCs showed a normal karyotype, expressed pluripotency markers, were differentiated into the three germ layers and carried the original genotype.

A generated induced pluripotent stem cell (iPSC) line (CMGANTi005-A) of a Marfan syndrome patient with an FBN1 c.7754T > C (p.Ile2585Thr) variation.

Marfan syndrome (MFS) is a connective tissue disorder with pleiotropic manifestations in the ocular, skeletal and cardiovascular system; and is typically cause by pathogenic variants in the fibrillin-1 (FBN1) gene. We report a generated induced pluripotent cell (iPSC) line of a MFS patient with an FBN1 c.7754T > C (p.Ile2585Thr) variant. The cell line was generated from peripheral blood mononuclear cells (PBMCs) and after reprogramming the line showed a no relevant copy number alterations, expression of pluripotency markers and was able to differentiate into three germ layers while carrying the original genotype.

Generation of a human TGFB3-hIPSC line, BBANTWi010-A, from a Loeys-Dietz syndrome type V patient.

Loeys-Dietz syndrome (LDS) is an autosomal dominant connective tissue disorder presenting with a variety of cardiovascular, skeletal, craniofacial and cutaneous manifestations. Aortic rupture or dissection of a thoracic aortic aneurysm (TAA) is the most life-threatening complication. We generated a an iPSC line from peripheral mononuclear blood cells of a TAA-presenting Loeys-Dietz syndrome type V patient with a causal, heterozygous variant in the TGFB3 gene (MIM* 190230, NM_003239.4:c.787G > C, p.(Asp263His)). The iPSCs present with the typical iPSC morphology, express pluripotency markers, have a normal karyotype and possess tri-lineage differentiation capability.

Current progress in clinical, molecular, and genetic aspects of adult fibromuscular dysplasia.

Fibromuscular dysplasia (FMD) is a non-atherosclerotic vascular disease that may involve medium-sized muscular arteries throughout the body. The majority of FMD patients are women. Although a variety of genetic, mechanical, and hormonal factors play a role in the pathogenesis of FMD, overall, its cause remains poorly understood. It is probable that the pathogenesis of FMD is linked to a combination of genetic and environmental factors. Extensive studies have correlated the arterial lesions of FMD to histopathological findings of arterial fibrosis, cellular hyperplasia, and distortion of the abnormal architecture of the arterial wall. More recently, the vascular phenotype of lesions associated with FMD has been expanded to include arterial aneurysms, dissections, and tortuosity. However, in the absence of a string-of-beads or focal stenosis, these lesions do not suffice to establish the diagnosis. While FMD most commonly involves renal and cerebrovascular arteries, involvement of most arteries throughout the body has been reported. Increasing evidence highlights that FMD is a systemic arterial disease and that subclinical alterations can be found in non-affected arterial segments. Recent significant progress in FMD-related research has led to improve our understanding of the disease's clinical manifestations, natural history, epidemiology, and genetics. Ongoing work continues to focus on FMD genetics and proteomics, physiological effects of FMD on cardiovascular structure and function, and novel imaging modalities and blood-based biomarkers that can be used to identify subclinical FMD. It is also hoped that the next decade will bring the development of multi-centred and potentially international clinical trials to provide comparative effectiveness data to inform the optimal management of patients with FMD.

Novel LOX Variants in Five Families with Aortic/Arterial Aneurysm and Dissection with Variable Connective Tissue Findings.

Thoracic aortic aneurysm and dissection (TAAD) is a major cause of cardiovascular morbidity and mortality. Loss-of-function variants in LOX, encoding the extracellular matrix crosslinking enzyme lysyl oxidase, have been reported to cause familial TAAD. Using a next-generation TAAD gene panel, we identified five additional probands carrying LOX variants, including two missense variants affecting highly conserved amino acids in the LOX catalytic domain and three truncating variants. Connective tissue manifestations are apparent in a substantial fraction of the variant carriers. Some LOX variant carriers presented with TAAD early in life, while others had normal aortic diameters at an advanced age. Finally, we identified the first patient with spontaneous coronary artery dissection carrying a LOX variant. In conclusion, our data demonstrate that loss-of-function LOX variants cause a spectrum of aortic and arterial aneurysmal disease, often combined with connective tissue findings.

A human importin-ß-related disorder: Syndromic thoracic aortic aneurysm caused by bi-allelic loss-of-function variants in IPO8.

Importin 8, encoded by IPO8, is a ubiquitously expressed member of the importin-ß protein family that translocates cargo molecules such as proteins, RNAs, and ribonucleoprotein complexes into the nucleus in a RanGTP-dependent manner. Current knowledge of the cargoes of importin 8 is limited, but TGF-ß signaling components such as SMAD1-4 have been suggested to be among them. Here, we report that bi-allelic loss-of-function variants in IPO8 cause a syndromic form of thoracic aortic aneurysm (TAA) with clinical overlap with Loeys-Dietz and Shprintzen-Goldberg syndromes. Seven individuals from six unrelated families showed a consistent phenotype with early-onset TAA, motor developmental delay, connective tissue findings, and craniofacial dysmorphic features. A C57BL/6N Ipo8 knockout mouse model recapitulates TAA development from 8-12 weeks onward in both sexes but most prominently shows ascending aorta dilatation with a propensity for dissection in males. Compliance assays suggest augmented passive stiffness of the ascending aorta in male Ipo8-/- mice throughout life. Immunohistological investigation of mutant aortic walls reveals elastic fiber disorganization and fragmentation along with a signature of increased TGF-ß signaling, as evidenced by nuclear pSmad2 accumulation. RT-qPCR assays of the aortic wall in male Ipo8-/- mice demonstrate decreased Smad6/7 and increased Mmp2 and Ccn2 (Ctgf) expression, reinforcing a role for dysregulation of the TGF-ß signaling pathway in TAA development. Because importin 8 is the most downstream TGF-ß-related effector implicated in TAA pathogenesis so far, it offers opportunities for future mechanistic studies and represents a candidate drug target for TAA.

Aortic aneurysm/dissection and osteogenesis imperfecta: Four new families and review of the literature.

Osteogenesis imperfecta (OI) is the commonest form of heritable bone fragility. It is mainly characterized by fractures, hearing loss and dentinogenesis imperfecta. OI patients are at increased risk of cardiovascular disease of variable severity. Aortic aneurysm/dissection is one of the rarer but potentially serious cardiovascular complications of OI. So far, only six patients with aortic dissection and OI have been reported. As such, present OI diagnostic guidelines do not recommend systematic screening of patients for aortopathy. Here, we report on the clinical and molecular characteristics of three new OI patients and one additional patient with a first degree relative who presented with aortic dissection and/or aneurysm surgery. This observation further opens up the discussion on the need for and extent of cardiovascular screening in adult patients with OI.