FBN1, TGFBR1, and the Marfan-craniosynostosis/mental retardation disorders revisited

High-Throughput Genomics Identify Novel FBN1/2 Variants in Severe Neonatal Marfan Syndrome and Congenital Heart Defects

Fibrillin-1 and fibrillin-2, encoded by FBN1 and FBN2, respectively, play significant roles in elastic fiber assembly, with pathogenic variants causing a diverse group of connective tissue disorders such as Marfan syndrome (MFS) and congenital contractural arachnodactyly (CCD). Different genomic variations may lead to heterogeneous phenotypic features and functional consequences. Recent high-throughput sequencing modalities have allowed detection of novel variants that may guide the care for patients and inform the genetic counseling for their families. We performed clinical phenotyping for two newborn infants with complex congenital heart defects. For genetic investigations, we employed next-generation sequencing strategies including whole-genome Single-Nucleotide Polymorphism (SNP) microarray for infant A with valvular insufficiency, aortic sinus dilatation, hydronephrosis, and dysmorphic features, and Trio whole-exome sequencing (WES) for infant B with dextro-transposition of the great arteries (D-TGA) and both parents. Infant A is a term male with neonatal marfanoid features, left-sided hydronephrosis, and complex congenital heart defects including tricuspid regurgitation, aortic sinus dilatation, patent foramen ovale, patent ductus arteriosus, mitral regurgitation, tricuspid regurgitation, aortic regurgitation, and pulmonary sinus dilatation. He developed severe persistent pulmonary hypertension and worsening acute hypercapnic hypoxemic respiratory failure, and subsequently expired on day of life (DOL) 10 after compassionate extubation. Cytogenomic whole-genome SNP microarray analysis revealed a deletion within the FBN1 gene spanning exons 7-30, which overlapped with the exon deletion hotspot region associated with neonatal Marfan syndrome. Infant B is a term male prenatally diagnosed with isolated D-TGA. He required balloon atrial septostomy on DOL 0 and subsequent atrial switch operation, atrial septal defect repair, and patent ductus arteriosus ligation on DOL 5. Trio-WES revealed compound heterozygous c.518C>T and c.8230T>G variants in the FBN2 gene. Zygosity analysis confirmed each of the variants was inherited from one of the parents who were healthy heterozygous carriers. Since his cardiac repair at birth, he has been growing and developing well without any further hospitalization. Our study highlights novel FBN1/FBN2 variants and signifies the phenotype-genotype association in two infants affected with complex congenital heart defects with and without dysmorphic features. These findings speak to the importance of next-generation high-throughput genomics for novel variant detection and the phenotypic variability associated with FBN1/FBN2 variants, particularly in the neonatal period, which may significantly impact clinical care and family counseling.

Severity of Autism Spectrum Disorder Symptoms Associated with de novo Variants and Pregnancy-Induced Hypertension

Genetic factors, particularly, de novo variants (DNV), and an environment factor, exposure to pregnancy-induced hypertension (PIH), were reported to be associated with risk of autism spectrum disorder (ASD); however, how they jointly affect the severity of ASD symptom is unclear. We assessed the severity of core ASD symptoms affected by functional de novo variants or PIH. We selected phenotype data from Simon's Simplex Collection database, used genotypes from previous studies, and created linear regression models. We found that ASD patients carrying DNV with PIH exposure had increased adaptive and cognitive ability, decreased social problems, and enhanced repetitive behaviors; however, there was no difference in patients without DNV between those with or without PIH exposure. In addition, the DNV genes carried by patients exposed to PIH were enriched in ubiquitin-dependent proteolytic processes, highlighting how candidate genes in pathways and environments interact. The results indicate the joint contribution of DNV and PIH to ASD.

Candidate genes under selection in song sparrows co-vary with climate and body mass in support of Bergmann's Rule

Ecogeographic rules denote spatial patterns in phenotype and environment that may reflect local adaptation as well as a species' capacity to adapt to change. To identify genes underlying Bergmann's Rule, which posits that spatial correlations of body mass and temperature reflect natural selection and local adaptation in endotherms, we compare 79 genomes from nine song sparrow (Melospiza melodia) subspecies that vary ~300% in body mass (17 - 50 g). Comparing large- and smaller-bodied subspecies revealed 9 candidate genes in three genomic regions associated with body mass. Further comparisons to the five smallest subspecies endemic to California revealed eight SNPs within four of the candidate genes (GARNL3, RALGPS1, ANGPTL2, and COL15A1) associated with body mass and varying as predicted by Bergmann's Rule. Our results support the hypothesis that co-variation in environment, body mass and genotype reflect the influence of natural selection on local adaptation and a capacity for contemporary evolution in this diverse species.

Genetic diagnosis for adult patients at a genetic clinic

Clinical utility of genetic testing has rapidly increased in the past decade to identify the definitive diagnosis, etiology, and specific management. The majority of patients receiving testing are children. There are several barriers for genetic tests in adult patients; barriers may arise from either patients or clinicians. Our study aims to realize the detection rate and the benefits of genetic tests in adults. We conducted a prospective study of 10 adult patients who were referred to a genetic clinic. Exome sequencing (ES) was pursued in all cases, and chromosomal microarray (CMA) was performed for six cases. Our result is impressive; six cases (60%) received likely pathogenic and pathogenic variants. Four definitive diagnosis cases had known pathogenic variants in KCNJ2, TGFBR1, SCN1A, and FBN1, whereas another two cases revealed novel likely pathogenic and pathogenic variants in GNB1 and DNAH9. Our study demonstrates the success in genetic diagnosis in adult patients: four cases with definitive, two cases with possible, and one case with partial diagnosis. The advantage of diagnosis is beyond obtaining the diagnosis itself, but also relieving any doubt for the patient regarding any previous questionable diagnosis, guide for management, and recurrence risk in their children or family members. Therefore, this supports the value of genetic testing in adult patients.

Impaired wound healing following cranial vault reconstruction in a patient with an atypical phenotype of Marfan syndrome: A case report

Background:

Marfan syndrome (MFS) is an autosomal dominant disorder of the connective tissues caused by mutations in the FBN1 gene which can result in widespread systemic involvement. Loeys-Dietz syndrome (LDS) is a related autosomal dominant disorder of connective tissue with widespread systemic involvement which has phenotypic overlap with MFS. LDS is caused by heterozygous pathogenic variants in six different genes, the most common of which involve transforming growth factor beta-receptor 1 or 2. While LDS is commonly associated with craniofacial manifestations, MFS is not typically characterized by craniosynostosis.

Case Description:

We present a 7-month-old female patient with MFS and metopic craniosynostosis with an unusual clinical presentation who underwent cranial vault reconstruction with fronto-orbital advancement and anterior cranial vault remodeling. Her course was complicated by impaired wound healing after surgery, requiring return to the operating room.

Conclusion:

Phenotypic overlap between genetic disorders can confound clinical diagnosis as illustrated in this case. Genetic testing can be highly valuable in the diagnosis of clinically variable disorders. Patients with MFS who undergo cranial surgery may be at increased risk for wound healing complications.

Understanding Musculoskeletal Disorders Through Next-Generation Sequencing

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An insight into musculoskeletal disorders through advancements in next-generation sequencing (NGS) promises to maximize benefits and improve outcomes through improved genetic diagnosis.

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The primary use of whole exome sequencing (WES) for musculoskeletal disorders is to identify functionally relevant variants.

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The current evidence has shown the superiority of NGS over conventional genotyping for identifying novel and rare genetic variants in patients with musculoskeletal disorders, due to its high throughput and low cost.

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Genes identified in patients with scoliosis, osteoporosis, osteoarthritis, and osteogenesis imperfecta using NGS technologies are listed for further reference.

Mechanism of Disease: Recessive ADAMTSL4 Mutations and Craniosynostosis with Ectopia Lentis

Craniosynostosis, the premature fusion of the calvarial bones, has numerous etiologies. Among them, several involve mutations in genes related to the TGFb signaling pathway, a critical molecular mediator of human development. These TGFb pathway-associated craniosynostosis syndromes include Loeys–Dietz syndrome (LDS) and Shprintzen–Goldberg syndrome (SGS). LDS and SGS have many similarities common to fibrillinopathies, specifically Marfan syndrome (MFS), which is caused by mutations in FBN1. Historically discriminating features of MFS from LDS and SGS are (1) the presence of ectopia lentis (the subluxation/dislocation of the ocular lens) and (2) the absence of craniosynostosis. Curiously, several instances of a seemingly novel syndrome involving only craniosynostosis and ectopia lentis have recently been reported to be caused by recessive mutations in ADAMTSL4, a poorly characterized gene as of yet. Here, we report on two new cases of craniosynostosis with ectopia lentis, each harboring recessive mutations in ADAMTSL4. We also discuss a proposed mechanism for the relationship between ADAMTSL4, FBN1, and TGFb pathway-related syndromes.

The outcome of targeted NGS screening in patients with syndromic forms of sagittal and pansynostosis - IL11RA is an emerging core-gene for pansynostosis

Here, we have studied the prevalence and spectrum of genetic alterations in syndromic forms of sagittal and pansynostosis. Eighteen patients with sagittal synostosis (isolated or combined with other synostoses, except coronal) or pansynostosis were phenotypically assessed by retrospective analysis of medical records, three-dimensional computed tomography skull reconstructions, and registered photos. Patient DNAs were analyzed using a targeted next-generation sequencing (NGS) panel including 63 craniosynostosis (CS) related genes. Pathogenic and likely pathogenic variants were found in 72% of the cases, mainly affecting FGFR2, TWIST1, IL11RA, and SKI. Two patients that were negative at NGS screening - one with a supernumerary marker chromosome with duplication of 15q25.2q26.3 and one with a pathogenic PHEX variant - were identified using microarray and single gene analysis, respectively. The overall diagnostic rate in the cohort was thus 83%. We identified two novel likely pathogenic variants in FGFR2 (NM_022970.3: c.811_812delGGinsCC, p.Gly271Pro) and TWIST1 (NM_000474.3: c.476T  >  A, p.Leu159His), and a novel variant of unclear phenotypic significance in RUNX2 (NM_001024630.3: c.340G > A, p.Val114Ile) which could suggest a modulatory effect. Notably, we also identified three new patients with pansynostosis and a Crouzon-like phenotype with IL11RA mutation. Targeted NGS using a broad panel of CS-related genes is a simple and powerful tool for detecting pathogenic mutations in patients with syndromic forms of CS and multiple suture involvement, in particular pansynostosis. Our results provide additional evidence of an association between pansynostosis and IL11RA, an emerging core gene for autosomal recessive CS.

Connective Tissue Disorders and Cardiovascular Complications: The Indomitable Role of Transforming Growth Factor-β Signaling

Marfan Syndrome (MFS) and Loeys-Dietz Syndrome (LDS) represent heritable connective tissue disorders that segregate with a similar pattern of cardiovascular defects (thoracic aortic aneurysm, mitral valve prolapse/regurgitation, and aortic dilatation with regurgitation). This pattern of cardiovascular defects appears to be expressed along a spectrum of severity in many heritable connective tissue disorders and raises suspicion of a relationship between the normal development of connective tissues and the cardiovascular system. With overwhelming evidence of the involvement of aberrant Transforming Growth Factor-beta (TGF-β) signaling in MFS and LDS, this signaling pathway may represent the common link in the relationship between connective tissue disorders and their associated cardiovascular complications. To further explore this hypothetical link, this chapter will review the TGF-β signaling pathway, the heritable connective tissue syndromes related to aberrant TGF-β signaling, and will discuss the pathogenic contribution of TGF-β to these syndromes with a primary focus on the cardiovascular system.

Fibrillin-1 gene mutations in a Chinese cohort with congenital ectopia lentis: spectrum and genotype-phenotype analysis

AIMS

To identify the mutation spectrum and genotype-phenotype correlations of fibrillin-1 (FBN1) mutations in a Chinese cohort with congenital ectopia lentis (EL).

METHODS

Patients clinically suspected of congenital zonulopathy were screened using panel-based next-generation sequencing followed by multiplex ligation-dependent probe amplification. All the probands were subjected to thorough ocular examinations. Molecular and clinical data were integrated in pursuit of genotype-phenotype correlation.

RESULTS

A total of 131 probands of FBN1 mutations from unrelated families were recruited. Around 65% of the probands were children younger than 9 years old. Overall, 110 distinct FBN1 mutations were identified, including 39 novel ones. The most at-risk regions were exons 13, 2, 6, 15, 24 and 33 in descending order of mutation frequency. The most prevalent mutation was c.184C>T (seven, 5.34%) in the coding sequence and c.5788+5G>A (three, 2.29%) in introns. Missense mutations were the most frequent type (103, 78.63%); half of which were distributed in the N-terminal regions (53, 51.46%). The majority of missense mutations were detected in one of the calcium-binding epidermal growth factor-like domains (62, 60.19%), and 39 (62.90%) of them were substitutions of conserved cysteine residues. Microspherophakia (MSP) was found in 15 patients (11.45%). Mutations in the middle region (exons 22-42), especially exon 26, had higher risks of combined MSP (OR, 5.51 (95% CI 1.364 to 22.274), p=0.017).

CONCLUSIONS

This study extended the knowledge of the FBN1 mutation spectrum and provided novel insights into its clinical correlation regarding EL and MSP in the Chinese population.

Assembly assay identifies a critical region of human fibrillin-1 required for 10-12 nm diameter microfibril biogenesis

The human FBN1 gene encodes fibrillin-1 (FBN1); the main component of the 10–12 nm diameter extracellular matrix microfibrils. Marfan syndrome (MFS) is a common inherited connective tissue disorder, caused by FBN1 mutations. It features a wide spectrum of disease severity, from mild cases to the lethal neonatal form (nMFS), that is yet to be explained at the molecular level. Mutations associated with nMFS generally affect a region of FBN1 between domains TB3-cbEGF18—the "neonatal region". To gain insight into the process of fibril assembly and increase our understanding of the mechanisms determining disease severity in MFS, we compared the secretion and assembly properties of FBN1 variants containing nMFS-associated substitutions with variants associated with milder, classical MFS (cMFS). In the majority of cases, both nMFS- and cMFS-associated neonatal region variants were secreted at levels comparable to wild type. Microfibril incorporation by the nMFS variants was greatly reduced or absent compared to the cMFS forms, however, suggesting that nMFS substitutions disrupt a previously undefined site of microfibril assembly. Additional analysis of a domain deletion variant caused by exon skipping also indicates that register in the neonatal region is likely to be critical for assembly. These data demonstrate for the first time new requirements for microfibril biogenesis and identify at least two distinct molecular mechanisms associated with disease substitutions in the TB3-cbEGF18 region; incorporation of mutant FBN1 into microfibrils changing their integral properties (cMFS) or the blocking of wild type FBN1 assembly by mutant molecules that prevents late-stage lateral assembly (nMFS).

Intraoperative absent bilateral medial recti in syndromic craniosynostosis

Patients with syndromic craniosynostosis are usually associated with the complexity of the malformation complex. We describe here detailed oculo-motility disorder and a remarkable finding of hypoplastic bilateral media recti on imaging and its intraoperative absence in patients with phenotypic features resembling Shprintzen-Goldberg syndrome (SGS). SGS is a rare congenital disorder with craniosynostosis affecting multiple systems including mentation and having a considerable overlap of its phenotypic features with Marfan syndrome. Large A-pattern exotropia found in these patients may be related to the craniofacial features and their bearing on extraocular muscle development and function. In this paper, we aimed to sensitise ophthalmologists and strabismologists concerning the necessity to recognise syndromic associations of patients with craniosynostosis presenting with a large squint, be aware of the intraoperative surprises and consider the challenges in its management.

Multiple Self-Healing Squamous Epithelioma (MSSE): A Digenic Trait Associated with Loss of Function Mutations in TGFBR1 and Variants at a Second Linked Locus on the Long Arm of Chromosome 9

MSSE (Ferguson-Smith disease) is a rare familial condition in which multiple skin tumors resembling squamous carcinomas invade locally and then regress spontaneously after several months, leaving disfiguring scars. We review evidence from haplotype studies in MSSE families with common ancestry that the condition is caused by loss of function mutations in TGFBR1 interacting with permissive variants at a second linked locus on the long arm of chromosome 9. The spectrum of TGFBR1 mutations in MSSE and the allelic disorder Loeys Dietz syndrome (characterized by developmental anomalies and thoracic aortic aneurysms) differ. Reports of patients with both MSSE and Loeys Dietz syndrome are consistent with variants at a second locus determining whether self-healing epitheliomas occur in patients with the loss of function mutations found in most MSSE patients or the missense mutations in the intracellular kinase domain of TGFBR1 that characterize Loeys Dietz syndrome.

Therapeutic Potential of Heme Oxygenase-1 in Aneurysmal Diseases

Abdominal aortic aneurysm (AAA) and intracranial aneurysm (IA) are serious arterial diseases in the aorta and brain, respectively. AAA and IA are associated with old age in males and females, respectively, and if rupture occurs, they carry high morbidity and mortality. Aneurysmal subarachnoid hemorrhage (SAH) due to IA rupture has a high rate of complication and fatality. Despite these severe clinical outcomes, preventing or treating these devastating diseases remains an unmet medical need. Inflammation and oxidative stress are shared pathologies of these vascular diseases. Therefore, therapeutic strategies have focused on reducing inflammation and reactive oxygen species levels. Interestingly, in response to cellular stress, the inducible heme oxygenase-1 (HO-1) is highly upregulated and protects against tissue injury. HO-1 degrades the prooxidant heme and generates molecules with antioxidative and anti-inflammatory properties, resulting in decreased oxidative stress and inflammation. Therefore, increasing HO-1 activity is an attractive option for therapy. Several HO-1 inducers have been identified and tested in animal models for preventing or alleviating AAA, IA, and SAH. However, clinical trials have shown conflicting results. Further research and the development of highly selective HO-1 regulators may be needed to prevent the initiation and progression of AAA, IA, or SAH.

The pattern and progression of hearing loss in Marfan Syndrome: A study of children and young adults

OBJECTIVE

(s): To describe the prevalence, type, severity, and progression of hearing loss (HL) in children and young adults with Marfan Syndrome (MFS), and to evaluate the influence of comorbidities on HL.

STUDY DESIGN

Retrospective database analysis.

RESULTS

Of 70 patients with MFS, 52.8% (N = 37) had HL. Within the HL group, 75.7% (N = 28) had bilateral HL, while 24.3% (N = 9) had unilateral HL. 21.4% (N = 15) had moderate or more severe HL. The overall prevalence of CHL was 40.5% (N = 15), SNHL 13.5% (N = 5), and mixed HL 37.8% (N = 14). The mean initial age of HL was 8.4 years (range 0.8-24.0). HL was more prevalent in patients with MFS who also experienced chronic otitis media (ES 1.00, 95% CI, 0.32-1.68) and skull anomalies (ES 0.75, 95% CI, 0.07-1.44) as well as for patients with hypertension (ES 2.17, 95% CI, -1.29-5.64).

CONCLUSIONS

Children and young adults with Marfan syndrome have a high likelihood of hearing loss, with high rates of CHL, chronic otitis media, and Eustachian tube dysfunction. SNHL is also prevalent in this syndrome; hypertension increased the likelihood of SNHL. Early audiologic screening is needed to ascertain type of HL and to efficiently direct patient care in this population.

Resilience priming: Translational models for understanding resiliency and adaptation to early life adversity

Despite the increasing attention to early life adversity and its long-term consequences on health, behavior, and the etiology of neurodevelopmental disorders, our understanding of the adaptations and interventions that promote resiliency and rescue against such insults are underexplored. Specifically, investigations of the perinatal period often focus on negative events/outcomes. In contrast, positive experiences (i.e. enrichment/parental care//healthy nutrition) favorably influence development of the nervous and endocrine systems. Moreover, some stressors result in adaptations and demonstrations of later-life resiliency. This review explores the underlying mechanisms of neuroplasticity that follow some of these early life experiences and translates them into ideas for interventions in pediatric settings. The emerging role of the gut microbiome in mediating stress susceptibility is also discussed. Since many negative outcomes of early experiences are known, it is time to identify mechanisms and mediators that promote resiliency against them. These range from enrichment, quality parental care, dietary interventions and those that target the gut microbiota.

Intragenic multi-exon deletion in the FBN1 gene in a child with mildly dilated aortic sinus: a retrotransposal event

Marfan syndrome is an autosomal dominant disorder affecting mainly the skeletal, ocular and cardiovascular systems. Most cases are caused by mutations in the fibrillin-1 gene (FBN1), although there are some reports on deletions involving FBN1 and other additional genes. We report a male patient who was first evaluated at 4 years of age. Echocardiogram showed a mildly dilated aortic sinus. He also had a history of muscular ventral septal defect which was closed spontaneously and trivial mitral regurgitation. Other phenotypic features include frontal bossing, anteverted ears, joint hyperlaxity, learning disability, skin striae, and height and weight in the >97th centile but no other diagnostic findings of MFS and does not fulfill the revised Ghent criteria. Chromosomal microarray analysis showed a deletion of approximately 36.8 kb at 15q21.1, which starts in intron 6 and ends in intron 9 and includes three FBN1 exons. Sequence analysis of the breakpoint region confirmed the deletion and revealed a concomitant insertion of a retrotransposon within the intron 6/intron 9 region. The intragenic deletion of exons 7-9 was likely the result of a retrotransposition event by a MAST2-SVA element mediated by repetitive sequences.

Are Patients With Loeys-Dietz Syndrome Misdiagnosed With Beals Syndrome?

Beals syndrome, also known as congenital contractural arachnodactyly (Online Mendelian Inheritance in Man: 121050), is an autosomal dominant disorder caused by a mutation in FBN2 that is typically characterized by congenital contractures and arachnodactyly. It shares a number of phenotypic features with Loeys-Dietz syndrome (Online Mendelian Inheritance in Man: 609192). Loeys-Dietz syndrome, initially described in 2005, is associated with mutations for the transforming growth factor β receptor and is characterized by findings of cerebral, thoracic, and abdominal arterial aneurysms. This report describes a 17-year-old male patient with a typical neonatal diagnosis of Beals syndrome. At age 15 years, an echocardiogram conducted in response to an aortic dissection in his father showed moderate aortic root dilation, prompting comprehensive testing for aortopathies, revealing a mutation in TGFBR1, thereby changing the diagnosis to Loeys-Dietz syndrome. Previously published reports have not implicated any mutation of the transforming growth factor β receptor genes in cases of Beals syndrome. This case underscores that due to significant phenotypic overlap, there is utility in a full panel of testing, including genes for hereditary connective tissue disorders with vascular involvement, as well as FBN2. Likewise, young patients who have tested negative for FBN2 should be tested for hereditary connective tissue disorders with vascular involvement.

Marfan syndrome: Report of a complex phenotype due to a 15q21.1 contiguos gene deletion encompassing FBN1, and literature review

Marfan syndrome (MFS) is an autosomal dominant connective tissue disorder that primarily involves skeletal, ocular, and cardiovascular systems with large inter- and intra-familial variability in terms of age of onset, severity, and aortic disease. The causal gene, FBN1, encodes for fibrillin 1, a multi-domain glycoprotein essential for many biological functions, including deposition and formation of elastic fibers. Reports describing chromosomal alterations involving FBN1 are rare, but in the last years their number has increased after copy number state analyses, such as multiplex ligation-dependent probe amplification and microarray-based comparative genomic hybridization, were adopted as routine diagnostic tools. Herein we report a patient with MFS and an atypical facial appearance and neuropsychiatric involvement likely not attributable to MFS due to a 15q21.1 deletion that involves part of FBN1 and 13 additional contiguous genes listed in OMIM. We compare his phenotype with those of the few patients described in the literature who share similar 15q11.2 deletions. This report expands the phenotype of patients with 15q11.2 deletion involving FBN1 and its contiguous genes, and suggests a possible role for these other genes in the pathogenesis of the observed unusual clinical signs that are not explained by FBN1 haploinsufficiency. © 2016 Wiley Periodicals, Inc.

The best-laid plans go oft awry: synaptogenic growth factor signaling in neuropsychiatric disease

Growth factors play important roles in synapse formation. Mouse models of neuropsychiatric diseases suggest that defects in synaptogenic growth factors, their receptors, and signaling pathways can lead to disordered neural development and various behavioral phenotypes, including anxiety, memory problems, and social deficits. Genetic association studies in humans have found evidence for similar relationships between growth factor signaling pathways and neuropsychiatric phenotypes. Accumulating data suggest that dysfunction in neuronal circuitry, caused by defects in growth factor-mediated synapse formation, contributes to the susceptibility to multiple neuropsychiatric diseases, including epilepsy, autism, and disorders of thought and mood (e.g., schizophrenia and bipolar disorder, respectively). In this review, we will focus on how specific synaptogenic growth factors and their downstream signaling pathways might be involved in the development of neuropsychiatric diseases.

Noninvasive diagnosis and management of spontaneous intracranial hypotension in patients with marfan syndrome: Case Report and Review of the Literature

Background:

Spontaneous intracranial hypotension is an uncommon clinical entity. Heritable connective tissue disorders (HCTD), such as Marfan syndrome, are frequently implicated as an underlying cause, due to dural structural weaknesses that predispose patients to spontaneous cerebrospinal fluid (CSF) leak. Due to the high prevalence of multi-system disease in HCTD, diagnosis and treatment are often complicated.

Case Description:

We present a 58-year-old female with Marfan syndrome on anticoagulation for a mechanical aortic valve replacement who came to medical attention with severe, acute-onset headache following a straining episode. Noninvasive magnetic resonance (MR) myelography confirmed thoracic CSF extravasations and multiple lumbar diverticula. The patient was treated conservatively and her symptoms resolved.

Conclusion:

We discuss the common presentation, diagnostic tools, and treatment options for spontaneous CSF leaks in patients with Marfan syndrome or related HCTD with an emphasis on noninvasive modalities and a review of the major radiographic criteria used to diagnose dural abnormalities, such as dural ectasia.

Cloning of TgfβR1 and TgfβR2 and Likely Exclusion as Loci of Origin in a Rabbit Craniosynostotic Model

Objective

To determine whether TgfβR1 or TgfβR2 cause the craniosynostotic phenotype in a rabbit model of nonsyndromic craniosynostosis.

Design

Full-length TgfβR1 and TgfβR2 cDNAs were sequenced and real-time reverse-transcription polymerase chain reaction (RT-PCR) was performed to measure TgfβR1 and TgfβR2 transcripts in suturai tissue from wild type (WT) and craniosynostotic (CS) rabbits. Single nucleotide polymorphisms (SNP) were identified within TgfβR1 and TgfβR2 and were assayed for segregation with disease phenotype in 22 craniosynostotic animals.

Results

No structural mutations in TgfβR1 and TgfβR2 were identified in the craniosynostotic rabbits. Real-time RT-PCR quantification of TgfβR1 and TgfβR2 mRNA showed no significant difference in TgfβR1 expression between CS and WT animals, while TgfβR2 showed 50% elevation in the CS animals compared to WT ( P < .05). SNP analysis within the TgfβR1 and TgfβR2 genes suggested that neither locus is linked to the craniosynostotic phenotype because no allelic combination showed any specific correlation with disease phenotype for either TgfβR1 or TgfβR2.

Conclusions

Our data indicate that the craniosynostotic phenotype in this rabbit model does not arise from any structural mutation in TgfβR1 or TgfβR2, and SNP analysis also likely excludes these genes more broadly as the site of causative mutation.

Connective tissue disorders and cardiovascular complications: the indomitable role of transforming growth factor-beta signaling

Marfan Syndrome (MFS) and Loeys-Dietz Syndrome (LDS) represent heritable connective tissue disorders that cosegregate with a similar pattern of cardiovascular defects (thoracic aortic aneurysm, mitral valve prolapse/regurgitation, and aortic root dilatation with regurgitation). This pattern of cardiovascular defects appears to be expressed along a spectrum of severity in many heritable connective tissue disorders and raises suspicion of a relationship between the normal development of connective tissues and the cardiovascular system. Given the evidence of increased transforming growth factor-beta (TGF-β) signaling in MFS and LDS, this signaling pathway may represent the common link in this relationship. To further explore this hypothetical link, this chapter will review the TGF-β signaling pathway, heritable connective tissue syndromes related to TGF-β receptor (TGFBR) mutations, and discuss the pathogenic contribution of TGF-β to these syndromes with a primary focus on the cardiovascular system.

De novo exon 1 missense mutations of SKI and Shprintzen-Goldberg syndrome: two new cases and a clinical review

Shprintzen-Goldberg syndrome (OMIM #182212) is a connective tissue disorder characterized by craniosynostosis, distinctive craniofacial features, skeletal abnormalities, marfanoid body habitus, aortic dilatation, and intellectual disability. Mutations in exon 1 of SKI have recently been identified as being responsible for approximately 90% of reported individuals diagnosed clinically with Shprintzen-Goldberg syndrome. SKI is a known regulator of TGFβ signaling. Therefore, like Marfan syndrome and Loeys-Dietz syndrome, Shprintzen-Goldberg syndrome is likely caused by deregulated TGFβ signals, explaining the considerable phenotypic overlap between these three disorders. We describe two additional patients with exon 1 SKI mutations and review the clinical features and literature of Shprintzen-Goldberg syndrome.

Elastic fibres in health and disease

Elastic fibres are insoluble components of the extracellular matrix of dynamic connective tissues such as skin, arteries, lungs and ligaments. They are laid down during development, and comprise a cross-linked elastin core within a template of fibrillin-based microfibrils. Their function is to endow tissues with the property of elastic recoil, and they also regulate the bioavailability of transforming growth factor β. Severe heritable elastic fibre diseases are caused by mutations in elastic fibre components; for example, mutations in elastin cause supravalvular aortic stenosis and autosomal dominant cutis laxa, mutations in fibrillin-1 cause Marfan syndrome and Weill–Marchesani syndrome, and mutations in fibulins-4 and -5 cause autosomal recessive cutis laxa. Acquired elastic fibre defects include dermal elastosis, whereas inflammatory damage to fibres contributes to pathologies such as pulmonary emphysema and vascular disease. This review outlines the latest understanding of the composition and assembly of elastic fibres, and describes elastic fibre diseases and current therapeutic approaches.

Systematic molecular and cytogenetic screening of 100 patients with marfanoid syndromes and intellectual disability

The association of marfanoid habitus (MH) and intellectual disability (ID) has been reported in the literature, with overlapping presentations and genetic heterogeneity. A hundred patients (71 males and 29 females) with a MH and ID were recruited. Custom-designed 244K array-CGH (Agilent®; Agilent Technologies Inc., Santa Clara, CA) and MED12, ZDHHC9, UPF3B, FBN1, TGFBR1 and TGFBR2 sequencing analyses were performed. Eighty patients could be classified as isolated MH and ID: 12 chromosomal imbalances, 1 FBN1 mutation and 1 possibly pathogenic MED12 mutation were found (17%). Twenty patients could be classified as ID with other extra-skeletal features of the Marfan syndrome (MFS) spectrum: 4 pathogenic FBN1 mutations and 4 chromosomal imbalances were found (2 patients with both FBN1 mutation and chromosomal rearrangement) (29%). These results suggest either that there are more loci with genes yet to be discovered or that MH can also be a relatively non-specific feature of patients with ID. The search for aortic complications is mandatory even if MH is associated with ID since FBN1 mutations or rearrangements were found in some patients. The excess of males is in favour of the involvement of other X-linked genes. Although it was impossible to make a diagnosis in 80% of patients, these results will improve genetic counselling in families.

Marfan syndrome with a complex chromosomal rearrangement including deletion of the FBN1 gene

Background

The majority of Marfan syndrome (MFS) cases is caused by mutations in the fibrillin-1 gene (FBN1), mapped to chromosome 15q21.1. Only few reports on deletions including the whole FBN1 gene, detected by molecular cytogenetic techniques, were found in literature.

Results

We report here on a female patient with clinical symptoms of the MFS spectrum plus craniostenosis, hypothyroidism and intellectual deficiency who presents a 1.9 Mb deletion, including the FBN1 gene and a complex rearrangement with eight breakpoints involving chromosomes 6, 12 and 15.

Discussion

This is the first report of MFS with a complex chromosome rearrangement involving a deletion of FBN1 and contiguous genes. In addition to the typical clinical findings of the Marfan syndrome due to FBN1 gene haploinsufficiency, the patient presents features which may be due to the other gene deletions and possibly to the complex chromosome rearrangement.

Skeletogenic phenotype of human Marfan embryonic stem cells faithfully phenocopied by patient-specific induced-pluripotent stem cells

Marfan syndrome (MFS) is a heritable connective tissue disorder caused by mutations in the gene coding for FIBRILLIN-1 (FBN1), an extracellular matrix protein. MFS is inherited as an autosomal dominant trait and displays major manifestations in the ocular, skeletal, and cardiovascular systems. Here we report molecular and phenotypic profiles of skeletogenesis in tissues differentiated from human embryonic stem cells and induced pluripotent stem cells that carry a heritable mutation in FBN1. We demonstrate that, as a biological consequence of the activation of TGF-β signaling, osteogenic differentiation of embryonic stem cells with a FBN1 mutation is inhibited; osteogenesis is rescued by inhibition of TGF-β signaling. In contrast, chondrogenesis is not perturbated and occurs in a TGF-β cell-autonomous fashion. Importantly, skeletal phenotypes observed in human embryonic stem cells carrying the monogenic FBN1 mutation (MFS cells) are faithfully phenocopied by cells differentiated from induced pluripotent-stem cells derived independently from MFS patient fibroblasts. Results indicate a unique phenotype uncovered by examination of mutant pluripotent stem cells and further demonstrate the faithful alignment of phenotypes in differentiated cells obtained from both human embryonic stem cells and induced pluripotent-stem cells, providing complementary and powerful tools to gain further insights into human molecular pathogenesis, especially of MFS.

Endovascular repair of an internal mammary artery aneurysm in a patient with Loeys-Dietz syndrome

Loeys-Dietz syndrome is a condition that predisposes the development of central and peripheral arterial aneurysms and dissections. The standard approach for treatment of these lesions has been open repair. We present the case of a 34-year-old woman with a previous history of multiple open aortic repairs who presented with a right large internal mammary artery aneurysm. The patient was successfully treated with endovascular coil embolization. This case report demonstrates the feasibility of using endovascular interventions to treat unusual aneurysms in patients with Loeys-Dietz syndrome.

Characterization of large genomic deletions in the FBN1 gene using multiplex ligation-dependent probe amplification

BACKGROUND

Connective tissue diseases characterized by aortic aneurysm, such as Marfan syndrome, Loeys-Dietz syndrome and Ehlers Danlos syndrome type IV are heterogeneous and despite overlapping phenotypes, the natural history, clinical manifestations and interventional course for each diagnosis can be quite unique. The majority of mutations involved in the etiology of these disorders are missense and nonsense mutations. However, large deletions and duplications undetected by sequencing may be implicated in their pathogenesis, and may explain the apparent lack of genotype-phenotype correlation in a subset of patients. The objective of this study was to search for large pathogenic deletions and/or duplications in the FBN1, TGFβR1, and TGFβR2 genes using multiplex-ligation dependent probe amplification (MLPA) in patients with aortopathy, in whom no mutations in the FBN1, TGFβR1, and TGFβR2 genes were identified by sequencing.

METHODS

The study included 14 patients from 11 unrelated families with aortic aneurysm. Of those, six patients (including 3 first-degree relatives), fulfilled the revised Ghent criteria for Marfan syndrome, and eight had predominantly aortic aneurysm/dilatation with variable skeletal and craniofacial involvement. MLPA for FBN1, TGFβR1, and TGFβR2 was carried out in all patients. A 385 K chromosome 15 specific array was used in two patients with a deletion of the entire FBN1 in order to define its size and boundaries.

RESULTS

We identified two novel large deletions in the FBN1 gene in four patients of two unrelated families who met clinical diagnostic criteria for Marfan syndrome. One patient was found to have a FBN1 deletion encompassing exons 1-5. The other three patients had a 542 Kb deletion spanning the whole FBN1 gene and five additional genes (SLC24A5, MYEF2, CTXN2, SLC12A1, DUT) in the chromosome 15.

CONCLUSIONS

Our findings expand the number of large FBN1 deletions, and emphasize the importance of screening for large genomic deletions in connective tissue disorders featuring aortopathies, especially for those with classic Marfan phenotype.

Molecular analysis of coronal perisutural tissues in a craniosynostotic rabbit model using polymerase chain reaction suppression subtractive hybridization

BACKGROUND

In the United States, the incidence of craniosynostosis (premature fusion of the sutures of the cranial vault) is one in 2000 to 3000 live births. The condition can cause increased intracranial pressure, severely altered head shape, and mental retardation. The authors have previously described a colony of rabbits with heritable coronal suture synostosis. This model has been instrumental in describing the postsurgical craniofacial growth associated with craniosynostosis. The molecular analysis of this model has been limited by the lack of molecular tools for use in rabbits. To understand the pathogenesis of craniosynostosis, the authors compared gene expression in perisutural tissues between wild-type and craniosynostotic rabbits using polymerase chain reaction suppression subtractive hybridization.

METHODS

Suppression subtractive hybridization polymerase chain reaction was performed on RNA derived from pooled samples of calvariae from 10-day-old wild-type (n = 3) and craniosynostotic (n = 3) rabbits to obtain cDNA clones enriched in either wild-type tissues (underexpressed in craniosynostotic tissue) or craniosynostotic tissues (overexpressed in craniosynostotic compared with wild-type).

RESULTS

Differential expression was identified for approximately 140 recovered cDNA clones up-regulated in craniosynostotic tissues and 130 recovered clones for wild-type tissues. Of these, four genes were confirmed by quantitative reverse-transcriptase polymerase chain reaction as being overexpressed in craniosynostotic sutural tissue: β-globin (HBB), osteopontin (SPP1), osteonectin (SPARC), and cathepsin K (CTSK). Two genes were confirmed to be underexpressed in the craniosynostotic samples: collagen 3, alpha 1 (COL3A1) and ring finger protein 12 (RNF12).

CONCLUSION

The differential expression of these gene products in our naturally occurring craniosynostotic model appears to be the result of differences in the normal bone formation/resorption pathway.

Association of Intracranial Aneurysm and Loeys-Dietz Syndrome: Case Illustration, Management, and Literature Review

BACKGROUND AND IMPORTANCE:

Loeys-Dietz syndrome (LDS) is a newly described connective tissue disease associated with aortic aneurysms. A strong association between LDS and intracranial aneurysms has not yet been documented in the literature. We present the first detailed report of an intracranial aneurysm finding in an LDS patient.

CLINICAL PRESENTATION:

The patient is a 20-year-old female recently diagnosed with LDS and found to harbor 2 incidental intracranial aneurysms on a screening magnetic resonance angiography: a 3-mm right carotid ophthalmic aneurysm and an 8-mm partially fusiform paraclinoid carotid artery aneurysm. A standard left pterional craniotomy was performed. Intraoperative adenosine was used instead of temporary clipping because her vessels were extremely friable. After reconstruction, an intraoperative indocyanine green angiogram was obtained, confirming complete aneurysmal obliteration and internal carotid artery patency.

CONCLUSION:

This is the first detailed report of a clear association between intracranial aneurysms and LDS. An association between LDS and intracranial aneurysms, if substantiated in a larger study, has implications for aneurysm screening in this population. Such an association may shed light on mechanisms of aneurysm formation, growth, and rupture.

Multiple self-healing squamous epithelioma is caused by a disease-specific spectrum of mutations in TGFBR1

Multiple self-healing squamous epithelioma (MSSE), also known as Ferguson-Smith disease (FSD), is an autosomal-dominant skin cancer condition characterized by multiple squamous-carcinoma-like locally invasive skin tumors that grow rapidly for a few weeks before spontaneously regressing, leaving scars. High-throughput genomic sequencing of a conservative estimate (24.2 Mb) of the disease locus on chromosome 9 using exon array capture identified independent mutations in TGFBR1 in three unrelated families. Subsequent dideoxy sequencing of TGFBR1 identified 11 distinct monoallelic mutations in 18 affected families, firmly establishing TGFBR1 as the causative gene. The nature of the sequence variants, which include mutations in the extracellular ligand-binding domain and a series of truncating mutations in the kinase domain, indicates a clear genotype-phenotype correlation between loss-of-function TGFBR1 mutations and MSSE. This distinguishes MSSE from the Marfan syndrome-related disorders in which missense mutations in TGFBR1 lead to developmental defects with vascular involvement but no reported predisposition to cancer.

The clinical spectrum of complete FBN1 allele deletions

The most common mutations found in FBN1 are missense mutations (56%), mainly substituting or creating a cysteine in a cbEGF domain. Other mutations are frameshift, splice and nonsense mutations. There are only a few reports of patients with marfanoid features and a molecularly proven complete deletion of a FBN1 allele. We describe the clinical features of 10 patients with a complete FBN1 gene deletion. Seven patients fulfilled the Ghent criteria for Marfan syndrome (MFS). The other three patients were examined at a young age and did not (yet) present the full clinical picture of MFS yet. Ectopia lentis was present in at least two patients. Aortic root dilatation was present in 6 of the 10 patients. In three patients, the aortic root diameter was on the 95th percentile and in one patient, the diameter of the aortic root was normal, the cross-section, however, had a cloverleaf appearance. Two patients underwent aortic root surgery at a relatively young age (27 and 34 years). Mitral valve prolapse was present in 4 of the 10 patients, and billowing of the mitral valve in 1. All patients had facial and skeletal features of MFS. Two patients with a large deletion extending beyond the FBN1 gene had an extended phenotype. We conclude that complete loss of one FBN1 allele does not predict a mild phenotype, and these findings support the hypothesis that true haploinsufficiency can lead to the classical phenotype of Marfan syndrome.

Progressive aortic root and pulmonary artery aneurysms in a neonate with Loeys-Dietz syndrome type 1B

Loeys-Dietz Syndrome (LDS) is an autosomal dominant aortic aneurysm syndrome with multisystem involvement, caused by heterozygous mutations of transforming growth factor beta receptor type 1 (TGFBR1) or type 2 (TGFBR2) genes. We report on a neonate with the disorder caused by a known TGFBR2 mutation, who developed neonatal-onset progressive dilation of the aortic valve and aneurysms of the aortic root and main pulmonary artery (PA) associated with a large left-to-right shunt via a ventricular septal defect (VSD) and an atrial septal defect. He also had skeletal features (flexion contractures of the fingers, talipes equinovarus, a cleft palate, and joint laxity), mild facial dysmorphisms, and developmental delay. The dilation and aneurysms progressed after PA banding at age 12 days; and the patient received an intracardiac repair of the defects and PA plasty at age 42 days, followed by no further progression of the dilation and the aneurysms. Neonates with generalized hypotonia, a cleft palate, inguinal herniae, musculoskeletal features such as camptodactyly and talipes equinovarus, and a cardiac murmur should be suspected to have LDS, and extensive cardiovascular evaluation and testing of TGFBR1 and TGFBR2 are recommended. LDS patients with cardiac defects that lead to a large left-to-right shunt and congestive heart failure such as VSD should be considered for intracardiac repair even in early infancy.

Marfan syndrome. Part 1: pathophysiology and diagnosis

Marfan syndrome is a connective-tissue disease inherited in an autosomal dominant manner and caused mainly by mutations in the gene FBN1. This gene encodes fibrillin-1, a glycoprotein that is the main constituent of the microfibrils of the extracellular matrix. Most mutations are unique and affect a single amino acid of the protein. Reduced or abnormal fibrillin-1 leads to tissue weakness, increased transforming growth factor beta signaling, loss of cell-matrix interactions, and, finally, to the different phenotypic manifestations of Marfan syndrome. Since the description of FBN1 as the gene affected in patients with this disorder, great advances have been made in the understanding of its pathogenesis. The development of several mouse models has also been crucial to our increased understanding of this disease, which is likely to change the treatment and the prognosis of patients in the coming years. Among the many different clinical manifestations of Marfan syndrome, cardiovascular involvement deserves special consideration, owing to its impact on prognosis. However, the diagnosis of patients with Marfan syndrome should be made according to Ghent criteria and requires a comprehensive clinical assessment of multiple organ systems. Genetic testing can be useful in the diagnosis of selected cases.

Genetic analysis of young adult patients with aortic disease not fulfilling the diagnostic criteria for Marfan syndrome

BACKGROUND

Although the existence of the young patients with aortic disease not fulfilling the diagnostic criteria for Marfan syndrome (MFS) has been known, the etiology of their disease has not yet been elucidated. The purpose of the present study was to elucidate the genetic and clinical features of the young patients with aortic disease not having MFS.

METHODS AND RESULTS

Eighty young adult patients with aortic disease were examined. They were divided into a definite MFS (n=51) and a non-definite MFS group (n=29) according to the Ghent nosology. Clinical and genetic characteristics were compared between the 2 groups. Among 29 non-definite MFS probands, 1 (3%) FBN1, 2 (7%) TGFBR1, and 3 (10%) TGFBR2 mutations were found, and 4 ACTA2 mutations were found in the 23 probands examined without FBN1, TGFBR1, or TGFBR2 mutations. In total, more than 10 out of 29 (34%) probands in the non-definite MFS group were associated with genetic mutations. Skeletal involvement was less frequent in the non-definite than in the definite MFS group (7% vs 82%, P<0.01).

CONCLUSIONS

In the probands with aortic diseases in young who cannot be diagnosed with MFS, mutations other than FBN1 mutations accounted for at least one-third of all causes of aortic disease.

A new sporadic case of early-onset Loeys-Dietz syndrome due to the recurrent mutation p.R528C in the TGFBR2 gene substantiates interindividual clinical variability

We report on a 2-year-old Polish girl with typical manifestations of Loeys-Dietz syndrome (LDS), a rare genetic condition belonging to the group of Marfan-related disorders. The characteristic LDS symptoms observed in the girl included craniofacial dysmorphism (craniosynostosis, cleft palate, hypertelorism), arachnodactyly, camptodactyly, scoliosis, joint laxity, talipes equinovarus, translucent and hyperelastic skin, and umbilical hernia. Mild dilatation of the ascending aorta and tortuous course of the left internal carotid artery were recognized during her second year of life. Molecular genetic testing revealed a heterozygous missense mutation (c.1582C>T, p.R528C) in the transforming growth factor beta receptor II gene (TGFBR2). This mutation has been previously associated with LDS in 5 unrelated cases, and was never reported in patients with other Marfan-related disorders. Comparison of the phenotypes of our patient and these 5 individuals with c.1582C>T showed that only the hallmark triad of the syndrome - consisting of hypertelorism, aortic root dilatation/aneurysm, and cleft palate or bifid uvula - was present in all 6 cases. Interestingly, none of the 5 individuals who underwent psychological evaluation showed developmental delay. The pattern of all other LDS features showed interindividual variability. Our data support the recently reported observation that symptoms of LDS can develop at a very young age, making early diagnosis and management essential for these patients. This is the first report on a Polish infant with typical LDS symptoms caused by a TGFBR2 mutation.

A review on the vascular features of the hyperimmunoglobulin E syndrome

Autosomal recessive, autosomal dominant and the sporadic forms of hyperimmunoglobulin E syndrome (HIES) are multi-system disorders. Although HIES patients may present with cold abscesses, the vascular features of HIES are not well recognized. The objective of this review is to characterize the nature and spectrum of vascular abnormalities in HIES patients. Vascular abnormalities in HIES patients were reviewed with Medline and Google Scholar-based searches. In brief, the searches combined terms related to HIES with the terms related to vasculature. Furthermore, reference lists from the original studies and review papers identified were screened. There were vascular abnormalities in 25 patients with HIES. These abnormalities were identified as aneurysms (coronary, aortic, carotid and cerebral), pseudoaneurysms, congenital patent ductus venosus, superior vena cava syndrome, vasculitides, vascular ectasia, thrombosis and others. They may be congenital or acquired, in the veins and arteries, affecting both sexes. These abnormalities can be seen in all subtypes of HIES. They could be also fatal in children and adults. Limited pathological investigations revealed the presence of vasculitis. Three of the patients were found to have overlap diseases. In this review, the spectrum of vascular abnormalities in HIES are documented and discussed in detail for the first time. They highlight a previously under-recognized and potentially devastating complication of these disorders. These vascular abnormalities constitute one of the major clinical characteristics in HIES. The presence of hypereosinophilia, vasculitis and defective angiogenesis in HIES may contribute to the formation of vascular abnormalities in HIES.

Loeys-Dietz syndrome type I and type II: clinical findings and novel mutations in two Italian patients

Background

Loeys-Dietz syndrome (LDS) is a rare autosomal dominant disorder showing the involvement of cutaneous, cardiovascular, craniofacial, and skeletal systems. In particular, LDS patients show arterial tortuosity with widespread vascular aneurysm and dissection, and have a high risk of aortic dissection or rupture at an early age and at aortic diameters that ordinarily are not predictive of these events. Recently, LDS has been subdivided in LDS type I (LDSI) and type II (LDSII) on the basis of the presence or the absence of cranio-facial involvement, respectively. Furthermore, LDSII patients display at least two of the major signs of vascular Ehlers-Danlos syndrome. LDS is caused by mutations in the transforming growth factor (TGF) beta-receptor I (TGFBR1) and II (TGFBR2) genes. The aim of this study was the clinical and molecular characterization of two LDS patients.

Methods

The exons and intronic flanking regions of TGFBR1 and TGFBR2 genes were amplified and sequence analysis was performed.

Results

Patient 1 was a boy showing dysmorphic signs, blue sclerae, high-arched palate, bifid uvula; skeletal system involvement, joint hypermobility, velvety and translucent skin, aortic root dilatation, tortuosity and elongation of the carotid arteries. These signs are consistent with an LDSI phenotype. The sequencing analysis disclosed the novel TGFBR1 p.Asp351Gly de novo mutation falling in the kinase domain of the receptor. Patient 2 was an adult woman showing ascending aorta aneurysm, with vascular complications following surgery intervention. Velvety and translucent skin, venous varicosities and wrist dislocation were present. These signs are consistent with an LDSII phenotype. In this patient and in her daughter, TGFBR2 genotyping disclosed in the kinase domain of the protein the novel p.Ile510Ser missense mutation.

Conclusion

We report two novel mutations in the TGFBR1 and TGFBR2 genes in two patients affected with LDS and showing marked phenotypic variability. Due to the difficulties in the clinical approach to a TGFBR-related disease, among patients with vascular involvement, with or without aortic root dilatation and LDS cardinal features, genotyping is mandatory to clarify the diagnosis, and to assess the management, prognosis, and counselling issues.

UMD-predictor, a new prediction tool for nucleotide substitution pathogenicity -- application to four genes: FBN1, FBN2, TGFBR1, and TGFBR2

Approximately half of gene lesions responsible for human inherited diseases are due to an amino acid substitution, showing that this mutational mechanism plays a large role in diseases. Distinguishing neutral sequence variations from those responsible for the phenotype is of major interest in human genetics. Because in vitro validation of mutations is not always possible in diagnostic settings, indirect arguments must be accumulated to define whether a missense variation is causative. To further differentiate neutral variants from pathogenic nucleotide substitutions, we developed a new tool, UMD-Predictor. This tool provides a combinatorial approach that associates the following data: localization within the protein, conservation, biochemical properties of the mutant and wild-type residues, and the potential impact of the variation on mRNA. To evaluate this new tool, we compared it to the SIFT, PolyPhen, and SNAP software, the BLOSUM62 and Yu's Biochemical Matrices. All tools were evaluated using variations from well-validated datasets extracted from four UMD-LSDB databases (UMD-FBN1, UMD-FBN2, UMD-TGFBR1, and UMD-TGFBR2) that contain all published mutations of the corresponding genes, that is, 1,945 mutations, among which 796 different substitutions corresponding to missense mutations. Our results show that the UMD-Predictor algorithm is the most efficient tool to predict pathogenic mutations in this context with a positive predictive value of 99.4%, a sensitivity of 95.4%, and a specificity of 92.2%. It can thus enhance the interpretation of variations in these genes, and could easily be applied to any other disease gene through the freely available UMD generic software (http://www.umd.be).