Secreted ADAMTS-like 2 promotes myoblast differentiation by potentiating WNT signaling.

Myogenesis is the process that generates multinucleated contractile myofibers from muscle stem cells during skeletal muscle development and regeneration. Myogenesis is governed by myogenic regulatory transcription factors, including MYOD1. Here, we identified the secreted matricellular protein ADAMTS-like 2 (ADAMTSL2) as part of a Wnt-dependent positive feedback loop, which augmented or sustained MYOD1 expression and thus promoted myoblast differentiation. ADAMTSL2 depletion resulted in severe retardation of myoblast differentiation in vitro and its ablation in myogenic precursor cells resulted in aberrant skeletal muscle architecture. Mechanistically, ADAMTSL2 potentiated WNT signaling by binding to WNT ligands and WNT receptors. We identified the WNT-binding ADAMTSL2 peptide, which was sufficient to promote myogenesis in vitro. Since ADAMTSL2 was previously described as a negative regulator of TGFß signaling in fibroblasts, ADAMTSL2 now emerges as a signaling hub that could integrate WNT, TGFß and potentially other signaling pathways within the dynamic microenvironment of differentiating myoblasts during skeletal muscle development and regeneration.

Advances in acromelic dysplasia caused by FBN1 mutation / 国际儿科学杂志

The mutation of FBN1 gene results in the abnormality of its encoded fibrillin-1 protein, which affects musculoskeletal growth and results in two opposing phenotypes of tall and short stature, with clinical manifestations of Marfan syndrome and acromelic dysplasia.Acromelic dysplasia caused by FBN1 mutation includes acromicric dysplasia(AD), geleophysic dysplasia(GD)and Weill-Marchesani syndrome(WMS). As some FBN1 mutations have been reported to cause both AD and GD.The dysregulation of TGF-β signal pathway is the underlying mechanism of acromelic dysplasia.Currently, there is no specific treatment, mainly symptomatic treatment, early identification, diagnosis and treatment will improve prognosis of patients.This article will review the pathogenesis, clinical phenotype, treatment and follow-up of acromelic dysplasia caused by FBN1 mutation.

FBN1 gene mutation in a Chinese pedigree of mild Geleophysic dysplasia type 2/Acromicric dysplasia and the exploration of growth-promoting therapy / 中华内分泌代谢杂志

Objective:To summarize the clinical and genetic features of 7 patients with a mild form of Geleophysic dysplasia type 2(GD2)/Acromicric dysplasia(AD) induced by fibrillin 1(FBN1) gene mutation from one Chinese family.Methods:A Chinese pedigree of mild GD2/AD treated at the Pediatric Endocrinology Department at the First Affiliated Hospital of Sun Yat-sen University between August 2017 and May 2022 was collected. Whole-exome genetic sequencing of the FBN1 gene were performed to establish the diagnosis. Additionally, a literature review was further conducted.Results:In this family, among 13 individuals spanning three generations, there were 7 affected cases, including 1 adult female, 1 adult male, and 5 children. All individuals exhibited postnatal growth failure, severe disproportionate short stature, and lacked typical facial features. Exome sequencing and Sanger sequencing confirmed the presence of a heterozygous missense mutation c. 5099A>G(p.Tyr1700Cys) in exon 42 of the FBNI gene in 6 affected individuals(Ⅱ-1, Ⅲ-1 to Ⅲ-5), which was identified as a pathogenic mutation. This mutation was previously reported in a Chinese classical achondroplasia(AD) family. Based on comprehensive genetic analysis, clinical features, and multisystem evaluation, 3 cases were diagnosed with mild type 2 growth hormone deficiency(GD2), and 4 cases were diagnosed with mild AD. Recombinant human growth hormone(rhGH; 1.1-1.4 IU·kg -1·week -1) was applied to all the 5 children, and additional gonadotropin releasing hormone analogue(GnRHa) was administered to the 2 girls in late puberty, resulting in certain growth-promoting effect. Conclusions:The c. 5099A>G(p.Tyr1700Cys) mutation not only leads to the classical type of achondroplasia(AD) as reported in the literature but also causes the non-classical GD2 or AD(mild GD2/AD). Further research is warranted to investigate the long-term therapeutic effects of rhGH treatment.

Geleophysic dysplasia caused by a mutation in FBN1: A case report.

BACKGROUND: Geleophysic dysplasia (GD) presents the characterized clinical manifestations of acromelic dysplasia, including extremely short stature, short limbs, small hands and feet, stubby fingers and toes, joint stiffness and others. It is clinically distinct from the other acromelic dysplasia in terms of symptoms such as cardiac valvular abnormalities, progressive hepatomegaly and tracheal stenosis. CASE SUMMARY: We report on a Chinese 9-year-old girl with GD with the c.5243G>T (p.C1748F) mutation in FBN1 (fibrillin 1, OMIM 134797). She was born in Guangxi Zhuang Autonomous Region of China. The patient presented with typical clinical features of GD and recurrent respiratory tract infections over 6 years. Laboratory studies and chest computed tomography (CT) scan indicated bronchopneumonia. Her echocardiography revealed mild mitral valve thickening with regurgitation. Laryngopharyngeal CT and electronic bronchoscopy revealed severe glottic stenosis. Echocardiography examination displayed mild mitral valve thickening and regurgitation. Ophthalmic examination did not reveal myopia or lens dislocation. Treated with ceftriaxone sodium and methylprednisolone sodium succinate for injection as well as methylprednisolone orally, patient's symptoms had improved. CONCLUSION: GD is a rare genetic condition that can cause life-threatening cardiovascular and respiratory problems. This study also found that the identified genotype of GD could be related to different clinical phenotypes.

A Review of Three Chinese Cases of Acromicric/Geleophysic Dysplasia with FBN1 Mutations.

OBJECTIVE: This study aims to explore the clinical features and molecular diagnosis of FBN1-related acromelic dysplasia in Chinese patients. METHODS: The clinical and genetic features of three FBN1-related acromicric dysplasia (AD)/geleophysic dysplasia (GD) Chinese patients from two families were reviewed, and comprehensive medical evaluations were performed. Targeted next-generation sequencing was used to detect genetic mutations associated with short statures, including FBN1. Sanger sequencing was used to determine the de novo mutation origin. RESULTS: Patient 1 presented with short stature, short and stubby hands and feet, mild facial dysmorphism, hepatomegaly, delayed bone age and beak-like femoral heads. Patient 2 and this patient's father merely presented with short stature, wide and short hands, and beak-like femoral heads. One novel mutation, c.5272G>T(p.D1758Y), and one known mutation, c.5183C>T(p.A1728V), were identified in these patients. CONCLUSION: The clinical features varied among these patients. The variant c.5272G>T(p.D1758Y) is a novel mutation.

Geleophysic and acromicric dysplasias: natural history, genotype-phenotype correlations, and management guidelines from 38 cases.

PURPOSE: Geleophysic dysplasia (GD) and acromicric dysplasia (AD) are characterized by short stature, short extremities, and progressive joint limitation. In GD, cardiorespiratory involvement can result in poor prognosis. Dominant variants in the FBN1 and LTBP3 genes are responsible for AD or GD, whereas recessive variants in the ADAMTSL2 gene are responsible for GD only. The aim of this study was to define the natural history of these disorders and to establish genotype-phenotype correlations. METHODS: This monocentric retrospective study was conducted between January 2008 and December 2018 in a pediatric tertiary care center and included patients with AD or GD with identified variants (FBN1, LTBP3, or ADAMTSL2). RESULTS: Twenty-two patients with GD (12 ADAMTSL2, 8 FBN1, 2 LTBP3) and 16 patients with AD (15 FBN1, 1 LTBP3) were included. Early death occurred in eight GD and one AD. Among GD patients, 68% presented with heart valve disease and 25% developed upper airway obstruction. No AD patient developed life-threatening cardiorespiratory issues. A greater proportion of patients with either a FBN1 cysteine variant or ADAMTSL2 variants had a poor outcome. CONCLUSION: GD and AD are progressive multisystemic disorders with life-threatening complications associated with specific genotype. A careful multidisciplinary follow-up is needed.

Separation in genetic pathogenesis of mutations in FBN1-TB5 region between autosomal dominant acromelic dysplasia and Marfan syndrome.

Mutations in the transforming growth factor ß-binding protein-like domain 5 (TB5) region of FBN1 can lead to autosomal acromelic dysplasia and Marfan syndrome, which are two diseases with apparently opposite phenotypes. We identified six patients with acromelic dysplasia carrying either the previously reported mutations c.5284G > A (p.Gly1762Ser) and c.5096A > G (p.Tyr1699Cys) or the novel mutation c.5260G > A (p.Gly1754Ser). A systematic review of patients with mutations in the FBN1-TB5 region showed that acromelic dysplasia is caused only by in-frame amino acid substitutions. In contrast, truncating mutations in the FBN1-TB5 have been reported only in Marfan syndrome. Acromelic dysplasia subtypes that share symptoms with Marfan syndrome are associated with FBN1-TB5 disulfide disruptions, which are also commonly found in Marfan syndrome. These results suggest that the type and location of mutations in the FBN1-TB5 region determine the clinical spectrum of fibrillinopathy.

Genotype-phenotype correlation and expansion of orodental anomalies in LTBP3-related disorders.

The latent transforming growth factor-beta-binding protein 3 (LTBP3), encoding extracellular matrix proteins, plays a role in skeletal formation. Mutations in LTBP3 have been associated with various types of skeletal dysplasia. We aimed to characterize clinical and molecular features of more patients with mutations in the gene, which may help suggest genotype-phenotype correlation. The first two East Asian patients with short stature, heart defects, and orodental anomalies having LTBP3 mutations were identified. Whole exome and Sanger sequencing revealed that the one with a novel heterozygous missense (c.2017G>T, p.Gly673Cys) mutation in LTBP3 had clinical features consistent with acromicric dysplasia (ACMICD). The variant was located in the highly conserved EGF-like calcium-binding domain adjacent to the single reported LTBP3 variant associated with ACMICD. This finding supports that LTBP3 is a disease gene for ACMICD. Another patient with a novel homozygous splice site acceptor (c.1721-2A>G) mutation in LTBP3 was affected with dental anomalies and short stature (DASS). Previously undescribed orodental features included multiple unerupted teeth, high-arched palate, and microstomia found in our patient with ACMICD, and extensive dental infection, condensing osteitis, and deviated alveolar bone formation in our patient with DASS. Our results and comprehensive reviews suggest a genotype-phenotype correlation: biallelic loss-of-function mutations cause DASS, monoallelic missense gain-of-function mutations in the EGF-like domain cause ACMICD, and monoallelic missense gain-of-function mutations with more drastic effects on the protein functions cause geleophysic dysplasia (GPHYSD3). In summary, we expand the phenotypic and genotypic spectra of LTBP3-related disorders, support that LTBP3 is a disease gene for ACMICD, and propose the genotype-phenotype correlation of LTBP3 mutations.

Limb- and tendon-specific Adamtsl2 deletion identifies a role for ADAMTSL2 in tendon growth in a mouse model for geleophysic dysplasia.

Geleophysic dysplasia is a rare, frequently lethal condition characterized by severe short stature with progressive joint contractures, cardiac, pulmonary, and skin anomalies. Geleophysic dysplasia results from dominant fibrillin-1 (FBN1) or recessive ADAMTSL2 mutations, suggesting a functional link between ADAMTSL2 and fibrillin microfibrils. Mice lacking ADAMTSL2 die at birth, which has precluded analysis of postnatal limb development and mechanisms underlying the skeletal anomalies of geleophysic dysplasia. Here, detailed expression analysis of Adamtsl2 using an intragenic lacZ reporter shows strong Adamtsl2 expression in limb tendons. Expression in developing and growing bones is present in regions that are destined to become articular cartilage but is absent in growth plate cartilage. Consistent with strong tendon expression, Adamtsl2 conditional deletion in limb mesenchyme using Prx1-Cre led to tendon anomalies, albeit with normal collagen fibrils, and distal limb shortening, providing a mouse model for geleophysic dysplasia. Unexpectedly, conditional Adamtsl2 deletion using Scx-Cre, a tendon-specific Cre-deleter strain, which does not delete in cartilage, also impaired skeletal growth. Recombinant ADAMTSL2 is shown here to colocalize with fibrillin microfibrils in vitro, and enhanced staining of fibrillin-1 microfibrils was observed in Prx1-Cre Adamtsl2 tendons. The findings show that ADAMTSL2 specifically regulates microfibril assembly in tendons and that proper microfibril composition in tendons is necessary for tendon growth. We speculate that reduced bone growth in geleophysic dysplasia may result from external tethering by short tendons rather than intrinsic growth plate anomalies. Taken together with previous work, we suggest that GD results from abnormal microfibril assembly in tissues, and that ADAMTSL2 may limit the assembly of fibrillin microfibrils.

Adamts10 inactivation in mice leads to persistence of ocular microfibrils subsequent to reduced fibrillin-2 cleavage.

Mutations in the secreted metalloproteinase ADAMTS10 cause recessive Weill-Marchesani syndrome (WMS), comprising ectopia lentis, short stature, brachydactyly, thick skin and cardiac valve anomalies. Dominant WMS caused by FBN1 mutations is clinically similar and affects fibrillin-1 microfibrils, which are a major component of the ocular zonule. ADAMTS10 was previously shown to enhance fibrillin-1 assembly in vitro. Here, Adamts10 null mice were analyzed to determine the impact of ADAMTS10 deficiency on fibrillin microfibrils in vivo. An intragenic lacZ reporter identified widespread Adamts10 expression in the eye, musculoskeletal tissues, vasculature, skin and lung. Adamts10-/- mice had reduced viability on the C57BL/6 background, and although surviving mice were slightly smaller and had stiff skin, they lacked brachydactyly and cardiovascular defects. Ectopia lentis was not observed in Adamts10-/- mice, similar to Fbn1-/- mice, most likely because the mouse zonule contains fibrillin-2 in addition to fibrillin-1. Unexpectedly, in contrast to wild-type eyes, Adamts10-/- zonule fibers were thicker and immunostained strongly with fibrillin-2 antibodies into adulthood, whereas fibrillin-1 staining was reduced. Furthermore, fibrillin-2 staining of hyaloid vasculature remnants persisted post-natally in Adamts10-/- eyes. ADAMTS10 was found to cleave fibrillin-2, providing an explanation for persistence of fibrillin-2 at these sites. Thus, analysis of Adamts10-/- mice led to identification of fibrillin-2 as a novel ADAMTS10 substrate and defined a proteolytic mechanism for clearance of ocular fibrillin-2 at the end of the juvenile period.

A report of three families with FBN1-related acromelic dysplasias and review of literature for genotype-phenotype correlation in geleophysic dysplasia.

Acromelic dysplasia is a heterogeneous group of rare skeletal dysplasias characterized by distal limb shortening. Weill-Marchesani syndrome (WMS), Geleophysic dysplasia (GD) and Acromicric dysplasia (AD) are clinically distinct entities within this group of disorders and are characterized by short stature, short hands, stiff joints, skin thickening, facial anomalies, normal intelligence and skeletal abnormalities. Mutations of the Fibrillin-1 (FBN1) gene have been reported to cause AD, GD and related phenotypes. We reported three families with acromelic short stature. FBN1 analysis showed that all affected individuals carry a heterozygous missense mutation c.5284G > A (p.Gly1762Ser) in exon 42 of the FBN1 gene. This mutation was previously reported to be associated with GD. We reviewed the literature and compared the clinical features of the patients with FBN1 mutations to those with A Distintegrin And Metalloproteinase with Thrombospondin repeats-like 2 gene (ADAMTSL2) mutations. We found that tip-toeing gait, long flat philtrum and thin upper upper lip were more consistently found in GD patients with ADAMTSL2 mutations than in those with FBN1 mutations. The results have shed some light on the phenotype-genotype correlation in this group of skeletal disorders. A large scale study involving multidisciplinary collaboration would be needed to consolidate our findings.

Cervical artery dissection expands the cardiovascular phenotype in FBN1-related Weill-Marchesani syndrome.

Weill-Marchesani syndrome (WMS) is a rare form of acromelic dysplasia that is characterized by distinctive skeletal, ocular, and cardiovascular abnormalities. Previously described cardiac manifestations of WMS include aortic and pulmonary valve stenosis, mitral valve prolapse, mitral stenosis, and QTc prolongation. Autosomal dominant forms of WMS result from heterozygous pathogenic variants in FBN1, a gene with a well characterized role in the pathogenesis of thoracic aortic aneurysm (TAA) in the context of Marfan syndrome. In contrast, only one patient has been reported with aortic disease in WMS. Although the risk of aortic dissection from preceding TAA remains the leading cause of morbidity for individuals with Marfan syndrome, rare reports of arterial dissection in the peripheral vasculature have been described. Peripheral artery dissection has not been previously reported in other FBN1-related diseases. We describe a three generation family with FBN1-related WMS whose cardiovascular manifestations include TAA and cervical artery dissection, thus expanding the cardiovascular phenotype of WMS. Further research is required to quantify these risks and establish appropriate recommendations for cardiovascular imaging, medical management, and prophylactic surgical intervention in individuals with FBN1--related acromelic dysplasia.

Rapidly progressive mitral valve stenosis in patients with acromelic dysplasia.

Acromelic dysplasias are a group of skeletal dysplasias characterised by short-limbed short stature with other distinctive phenotypic features including small hands and feet and stiff joints. Geleophysic dysplasia is an acromelic dysplasia that is associated with characteristic facial features, progressive cardiac valvular thickening, and tracheal stenosis. Owing to overlapping clinical features with other types of short-limbed skeletal dysplasias, it is important to make a precise diagnosis as they have different cardiac morbidity and mortality. We present the cases of three patients with geleophysic dysplasia and progressive mitral valve disease to emphasise the natural history of this disorder and provide guidance regarding cardiac health supervision in these individuals.

Mutations in LTBP3 cause acromicric dysplasia and geleophysic dysplasia.

BACKGROUND: Acromelic dysplasias are a group of disorders characterised by short stature, brachydactyly, limited joint extension and thickened skin and comprises acromicric dysplasia (AD), geleophysic dysplasia (GD), Myhre syndrome and Weill-Marchesani syndrome. Mutations in several genes have been identified for these disorders (including latent transforming growth factor ß (TGF-ß)-binding protein-2 (LTBP2), ADAMTS10, ADAMSTS17 and fibrillin-1 (FBN1) for Weill-Marchesani syndrome, ADAMTSL2 for recessive GD and FBN1 for AD and dominant GD), encoding proteins involved in the microfibrillar network. However, not all cases have mutations in these genes. METHODS: Individuals negative for mutations in known acromelic dysplasia genes underwent whole exome sequencing. RESULTS: A heterozygous missense mutation (exon 14: c.2087C>G: p.Ser696Cys) in latent transforming growth factor ß (TGF-ß)-binding protein-3 (LTBP3) was identified in a dominant AD family. Two distinct de novo heterozygous LTPB3 mutations were also identified in two unrelated GD individuals who had died in early childhood from respiratory failure-a donor splice site mutation (exon 12 c.1846+5G>A) and a stop-loss mutation (exon 28: c.3912A>T: p.1304*Cysext*12). CONCLUSIONS: The constellation of features in these AD and GD cases, including postnatal growth retardation of long bones and lung involvement, is reminiscent of the null ltbp3 mice phenotype. We conclude that LTBP3 is a novel component of the microfibrillar network involved in the acromelic dysplasia spectrum.