An exploration of alternative therapeutic targets for aortic disease in Marfan syndrome.

Marfan syndrome is a rare connective tissue disorder that causes aortic dissection-related sudden death. Current conventional treatments, beta-blockers, and type 1 angiotensin II receptor blockers are prescribed to slow down aortic aneurysm progression and delay (prophylactic) aortic surgery. However, neither of these treatments ceases aortic growth completely. This review focuses on potential alternative therapeutic leads in the field, ranging from widely used medication with beneficial effects on the aorta to experimental inhibitors with the potential to stop aortic growth in Marfan syndrome. Clinical trials are warranted to uncover their full potential.

The Frequency of CYP2C19 Loss-of-Function Variants in Patients with Non-Cardioembolic Ischemic Stroke or Transient Ischemic Attack in the Dutch Population.

INTRODUCTION: The CYP2C19 enzyme converts clopidogrel into an active metabolite. Carriers of CYP2C19 loss-of-function (LOF) variants with a history of ischemic stroke or transient ischemic attack (TIA) using clopidogrel may have a higher risk of recurrent stroke. To study the implications of genetic CYP2C19 heterogeneity in treatment of cerebral ischemia, knowledge about the prevalence of CYP2C19 LOF variants within the population is important. We investigated the frequency of CYP2C19 LOF variants in patients with non-cardioembolic ischemic stroke or TIA in the Dutch population. METHODS: We performed a single-center observational study with a cross-sectional design in a Dutch thrombectomy-capable stroke center. We included all patients presenting with non-cardioembolic ischemic stroke or TIA. We determined the frequency of CYP2C19 LOF variants in the full cohort. Additionally, we compared the frequency of CYP2C19 LOF variants in two subgroups: patients with first-ever non-cardioembolic ischemic stroke or TIA versus patients with recurrent ischemic stroke or TIA using clopidogrel because of a history of ischemic stroke or TIA. RESULTS: We enrolled 410 patients between January 1, 2021, and July 1, 2021. 109 (26.6%) patients were carriers of CYP2C19 LOF variants. We found no difference in the frequency of CYP2C19 LOF variants between patients with first-ever ischemic stroke or TIA versus patients with recurrent ischemic stroke or TIA using clopidogrel (25.9 vs. 31.9%, respectively, p = 0.31). DISCUSSION AND CONCLUSION: About a quarter of patients with non-cardioembolic ischemic stroke or TIA in the Dutch population carry a CYP2C19 LOF variant. This is lower than estimates found in studies with Asian populations but similar to estimates found among Caucasian patients in other parts of the world.

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.

Molecular characterization and investigation of the role of genetic variation in phenotypic variability and response to treatment in a large pediatric Marfan syndrome cohort.

PURPOSE: In a large cohort of 373 pediatric patients with Marfan syndrome (MFS) with a severe cardiovascular phenotype, we explored the proportion of patients with MFS with a pathogenic FBN1 variant and analyzed whether the type/location of FBN1 variants was associated with specific clinical characteristics and response to treatment. Patients were recruited on the basis of the following criteria: aortic root z-score > 3, age 6 months to 25 years, no prior or planned surgery, and aortic root diameter < 5 cm. METHODS: Targeted resequencing and deletion/duplication testing of FBN1 and related genes were performed. RESULTS: We identified (likely) pathogenic FBN1 variants in 91% of patients. Ectopia lentis was more frequent in patients with dominant-negative (DN) variants (61%) than in those with haploinsufficient variants (27%). For DN FBN1 variants, the prevalence of ectopia lentis was highest in the N-terminal region (84%) and lowest in the C-terminal region (17%). The association with a more severe cardiovascular phenotype was not restricted to DN variants in the neonatal FBN1 region (exon 25-33) but was also seen in the variants in exons 26 to 49. No difference in the therapeutic response was detected between genotypes. CONCLUSION: Important novel genotype-phenotype associations involving both cardiovascular and extra-cardiovascular manifestations were identified, and existing ones were confirmed. These findings have implications for prognostic counseling of families with MFS.

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.

Clinically relevant variants in a large cohort of Indian patients with Marfan syndrome and related disorders identified by next-generation sequencing.

Marfan syndrome and related disorders are a group of heritable connective tissue disorders and share many clinical features that involve cardiovascular, skeletal, craniofacial, ocular, and cutaneous abnormalities. The majority of affected individuals have aortopathies associated with early mortality and morbidity. Implementation of targeted gene panel next-generation sequencing in these individuals is a powerful tool to obtain a genetic diagnosis. Here, we report on clinical and genetic spectrum of 53 families from India with a total of 83 patients who had a clinical diagnosis suggestive of Marfan syndrome or related disorders. We obtained a molecular diagnosis in 45/53 (85%) index patients, in which 36/53 (68%) had rare variants in FBN1 (Marfan syndrome; 63 patients in total), seven (13.3%) in TGFBR1/TGFBR2 (Loeys-Dietz syndrome; nine patients in total) and two patients (3.7%) in SKI (Shprintzen-Goldberg syndrome). 21 of 41 rare variants (51.2%) were novel. We did not detect a disease-associated variant in 8 (15%) index patients, and none of them met the Ghent Marfan diagnostic criteria. We found the homozygous FBN1 variant p.(Arg954His) in a boy with typical features of Marfan syndrome. Our study is the first reporting on the spectrum of variants in FBN1, TGFBR1, TGFBR2, and SKI in Indian individuals.