New insights on the clinical variability of FKBP10 mutations

To date 45 autosomal recessive disease-causing variants are reported in the FKBP10 gene. Those variant were found to be associated with Osteogenesis Imperfecta (OI) for which the hallmark phenotype is bone fractuers or Bruck Syndrome (BS) where bone fractures are accompanied with contractures. In addition, a specific homozygous FKBP10 mutation (p.Tyr293del) has been described in Yup'ik Inuit population to cause Kuskokwim syndrome (KS) in which contractures without fractures are observed. Here we present an extended Palestinian family with 10 affected individuals harboring a novel homozygous splice site mutation, c.391+4A > T in intron 2 of the FKBP10 gene, in which the three above mentioned syndromes segregate as a result of skipping of exon 2 and absence of the FKBP65 protein. At the biochemical level, Hydroxylysyl pyridinoline (HP)/lysyl pyridinoline (LP) values were inversely correlated with OI phenotypes, a trend we could confirm in our patients. Our findings illustrate that single familial FKBP10 mutations can result in a phenotypic spectrum, ranging from fractures without contractures, to fractures and contractures and even to only contractures. This broad intrafamilial clinical variability within one single family is a new finding in the field of bone fragility

Loss-of-Function Variants in EFEMP1 Cause a Recognizable Connective Tissue Disorder Characterized by Cutis Laxa and Multiple Herniations

Hereditary disorders of connective tissue (HDCT) compromise a heterogeneous group of diseases caused by pathogenic variants in genes encoding different components of the extracellular matrix and characterized by pleiotropic manifestations, mainly affecting the cutaneous, cardiovascular, and musculoskeletal systems. We report the case of a 9-year-old boy with a discernible connective tissue disorder characterized by cutis laxa (CL) and multiple herniations and caused by biallelic loss-of-function variants in EFEMP1. Hence, we identified EFEMP1 as a novel disease-causing gene in the CL spectrum, differentiating it from other HDCT.</jats:p

The establishment of the first reported zebrafish model for thoracic aortic dissection and rupture

About 0,16 percent of the Western population suffers from thoracic aortic aneurysms and dissections (TAAD). Weakening of the vessel wall of the thoracic aorta increases the risk for aortic dissection and rupture, which associates with a high mortality rate. Current treatment options in TAAD are limited to a pharmacological reduction of hemodynamic stress and surgical repair at a critical diameter. Despite the availability of different mouse models for TAAD, the underlying molecular mechanisms remain elusive. We therefore developed a zebrafish model for aortic dissection/rupture. For this purpose, we targeted 2 genes involved in angiogenesis, SMAD3 and SMAD6. In humans, loss of function (LOF) of SMAD3 results in TAAD, arterial tortuosity and early onset osteoarthritis. SMAD6 LOF mutations increase the risk for a bicuspid aortic valve and TAAD. In zebrafish, both SMAD3 and SMAD6 have 2 paralogues. Using CRISPR/Cas9 gene editing technology, we developed a quadruple knockout (KO): smad3a-/-;smad3b-/-;smad6a-/-;smad6b-/-. At 5 days post fertilization, quadruple KO embryos showed asymmetrical branching of the aortic arches. Survival of adult quadruple KO zebrafish was severely decreased and all quadruple mutants died before the age of one year. A stress-inducing protocol caused sudden death in 60% of the mutant zebrafish. Histochemical investigation of consecutive sections of the ventral aorta in quadruple mutants stained for elastin showed medial elastolysis, intramural hematomas, aortic dissections and ruptures, which was further supported by 3D reconstructions. These observations indicate that we successfully developed the first ever reported zebrafish model for aortic dissection/rupture. This model will be highly valuable to better understand the pathogenic processes underlying TAAD and to evaluate potential therapeutic compounds

The establishment of the first reported zebrafish model for thoracic aortic dissection and rupture

Per year, 3-4 persons per 100,000 suffer from thoracic aortic dissection (TAD), causing significant morbidity and mortality. Dissections occur often at sites where neural crest and mesodermal derived cell populations interact. In TAD, an interplay between hemodynamic stress, tissue remodeling due to impaired extracellular matrix assembly, aberrant growth factor signaling and cell-matrix mechanosensing weakens the vessel wall. Despite the availability of different mouse models for TAD, the cascade of underlying mechanisms remains largely elusive. Consequently, current treatment options are limited to a pharmacological reduction of hemodynamic stress and surgical repair at a critical diameter. We therefore developed a zebrafish model for aortic dissection/rupture targeting two genes involved in angiogenesis, SMAD3 and SMAD6. In humans, loss of function (LOF) of SMAD3 results in thoracic aortic aneurysm and dissection (TAAD), arterial tortuosity and early onset osteoarthritis. SMAD6 LOF mutations increase the risk for a bicuspid aortic valve and TAAD. In zebrafish, both SMAD3 and SMAD6 have 2 paralogues. Using CRISPR/Cas9 gene editing technology, we developed a quadruple knockout (KO): smad3a-/-;smad3b-/-;smad6a-/-;smad6b-/-. At 5 days post fertilization, quadruple KO embryos showed asymmetrical branching of the aortic arches. Survival of adult quadruple KO zebrafish was severely decreased and all but one quadruple mutants died before the age of one year. A stress-inducing protocol caused sudden death in 60% of the mutant zebrafish. Histology of consecutive sections of the ventral aorta in quadruple mutants stained for elastin showed medial elastolysis, intramural hematomas, aortic dissections and ruptures, which was further supported by 3D reconstructions. RNA sequencing revealed upregulation of melanogenesis as well as mitfa, an important transcription factor in neural crest, relevant for the pathogenesis. In conclusion, we successfully developed the first zebrafish model for aortic dissection/rupture. This model will be highly relevant to better understand the pathogenesis underlying TAD and to evaluate potential therapeutic compounds

The establishment of the first reported zebrafish model for thoracic aortic dissection and rupture

3-4 cases per 100,000 persons per year are estimated to suffer from thoracic aortic dissection (TAD). Weakening of the vessel wall of the thoracic aorta increases the risk for TAD and rupture, which associates with a high mortality rate. Current treatment options in thoracic aortic dissections (TAAD) are limited to a pharmacological reduction of hemodynamic stress and surgical repair at a critical diameter. Despite the availability of different mouse models for TAD, the underlying molecular mechanisms remain elusive. We therefore developed a zebrafish model for aortic dissection/rupture. For this purpose, we targeted 2 genes involved in angiogenesis, SMAD3 and SMAD6. In humans, loss of function (LOF) of SMAD3 results in thoracic aortic aneurysm and dissection (TAAD), arterial tortuosity and early onset osteoarthritis. SMAD6 LOF mutations increase the risk for a bicuspid aortic valve and TAAD. In zebrafish, both SMAD3 and SMAD6 have 2 paralogues. Using CRISPR/Cas9 gene editing technology, we developed a quadruple knockout (KO): smad3a-/-;smad3b-/-;smad6a-/-;smad6b-/-. At 5 days post fertilization, quadruple KO embryos showed asymmetrical branching of the aortic arches. Survival of adult quadruple KO zebrafish was severely decreased and all but one quadruple mutants died before the age of one year. A stress-inducing protocol caused sudden death in 60% of the mutant zebrafish. Histochemical investigation of consecutive sections of the ventral aorta in quadruple mutants stained for elastin showed medial elastolysis, intramural hematomas, aortic dissections and ruptures, which was further supported by 3D reconstructions. RNA sequencing revealed upregulation of melanogenesis as well as upregulation of transcription factor mitfa, which might be involved in the pathogenesis. These observations indicate that we successfully developed the first ever reported zebrafish model for aortic dissection/rupture. This model will be highly valuable to better understand the pathogenic processes underlying TAAD and to evaluate potential therapeutic compounds

The establishment of the first reported zebrafish model for thoracic aortic dissection and rupture

3-4 cases per 100,000 persons per year are estimated to suffer from thoracic aortic dissection (TAD). Weakening of the vessel wall of the thoracic aorta increases the risk for TAD and rupture, which associates with a high mortality rate. Current treatment options are limited to a pharmacological reduction of hemodynamic stress and surgical repair at a critical diameter. Despite the availability of different mouse models for TAD, the underlying molecular mechanisms remain elusive. We therefore developed a zebrafish model for aortic dissection/rupture. For this purpose, we targeted 2 genes involved in angiogenesis, SMAD3 and SMAD6. In humans, loss of function (LOF) of SMAD3 results in thoracic aortic aneurysm and dissection (TAAD), arterial tortuosity and early onset osteoarthritis. SMAD6 LOF mutations increase the risk for a bicuspid aortic valve and TAAD. In zebrafish, both SMAD3 and SMAD6 have 2 paralogues. Using CRISPR/Cas9 gene editing technology, we developed a quadruple knockout (KO): smad3a-/-;smad3b-/-;smad6a-/-;smad6b-/-. Survival of adult quadruple KO zebrafish was severely decreased. All but one quadruple mutant died before the age of one year. A stress-inducing protocol caused sudden death in 60% of the mutant zebrafish. Histochemical investigation of consecutive sections of the ventral aorta in quadruple mutants stained for elastin showed medial elastolysis, intramural hematomas, aortic dissections and ruptures, which was further supported by 3D reconstructions. RNA sequencing revealed upregulation of melanogenesis and transcription factor mitfa, which might be involved in the pathogenesis. These observations indicate that we successfully developed the first ever reported zebrafish model for aortic dissection/rupture

The establishment of the first reported zebrafish model for thoracic aortic dissection and rupture

With 3-4 cases per 100,000 person-years, thoracic aortic dissection (TAD) is a relatively rare but devastating disease that associates with a high mortality rate. Weakening of the vessel wall and progressive dilatation of the thoracic aorta may precede TAD, but often remains undetected. Treatment options are limited and consist of surgical repair at the critical diameter as there is currently no pharmacological intervention available. Despite the existence of different mouse models for TAD, the underlying disease mechanisms remain largely elusive. We developed a zebrafish model for aortic dissection/rupture targeting 2 genes involved in angiogenesis, SMAD3 and SMAD6. In humans, loss of function (LOF) of SMAD3 results in thoracic aortic aneurysm and dissection (TAAD), arterial tortuosity and early onset osteoarthritis. SMAD6 LOF mutations increase the risk for a bicuspid aortic valve and TAAD. In zebrafish, both SMAD3 and SMAD6 have 2 paralogues. Using CRISPR/Cas9 gene-editing technology, we developed a quadruple knockout (KO): smad3a-/-;smad3b-/-;smad6a-/-;smad6b-/-. Survival of adult quadruple KO zebrafish is severely decreased (<1 year). A stress-inducing protocol causes sudden death in 60% of the mutant zebrafish. Histochemical investigation of consecutive sections of the ventral aorta in quadruple mutants stained for elastin shows medial elastolysis, intramural hematomas, false lumens and aortic dissections and ruptures at sites with high hemodynamic stress, as supported by 3D-reconstructions. RNA-sequencing reveals upregulation of melanogenesis and the transcription factor mitfa, a previously unaddressed athway. Hence, we successfully developed the first-ever reported zebrafish model for TAD that reveals unexpected novel mechanistic insights in TAD, targetable for therapy