A Child

Genetic linkage of the Marfan syndrome, ectopia lentis, and congenital contractural arachnodactyly to the fibrillin genes on chromosomes 15 and 5

BACKGROUNDnThe large glycoprotein fibrillin is a structural component of elastin-containing microfibrils found in many tissues. The Marfan syndrome has been linked to the fibrillin gene on chromosome 15, but congenital contractural arachnodactyly, which shares some of the physical features of the syndrome, has been linked to the fibrillin gene on chromosome 5.nnnMETHODSnUsing specific markers for the fibrillin genes, we performed genetic linkage analysis in 28 families with the Marfan syndrome and 8 families with four phenotypically related disorders--congenital contractural arachnodactyly (3 families), ectopia lentis (2), mitral-valve prolapse syndrome (2), and annuloaortic ectasia (1).nnnRESULTSnGenetic linkage was established between the Marfan syndrome and only the fibrillin gene on chromosome 15, with a maximum lod score of 25.6 (odds for linkage, 10(25.6):1). Ectopia lentis was also linked to the fibrillin gene on chromosome 15, whereas congenital contractural arachnodactyly was linked to the fibrillin gene on chromosome 5. There was no linkage of mitral-valve prolapse to the fibrillin gene on chromosome 5; studies of chromosome 15 were not informative. Annuloaortic ectasia was not linked to either fibrillin gene.nnnCONCLUSIONSnThe Marfan syndrome appears to be caused by mutations in a single fibrillin gene on chromosome 15. Diagnosis of the Marfan syndrome by genetic linkage and analysis is now feasible in many families.

Analysis of the phenotypic abnormalities in lymphoedema-distichiasis syndrome in 74 patients with FOXC2 mutations or linkage to 16q24

Introduction: Lymphoedema-distichiasis syndrome (LD) (OMIM 153400) is a rare, primary lymphoedema of pubertal onset, associated with distichiasis. Causative mutations have now been described in FOXC2, a forkhead transcription factor gene. Numerous clinical associations have been reported with this condition, including congenital heart disease, ptosis, varicose veins, cleft palate, and spinal extradural cysts. Subjects: We report clinical findings in 74 affected subjects from 18 families and six isolated cases. All of them were shown to have mutations in FOXC2 with the exception of one family who had two affected subjects with lymphoedema and distichiasis and linkage consistent with the 16q24 locus. Results: The presence of lymphoedema was highly penetrant. Males had an earlier onset of lymphoedema and a significantly increased risk of complications. Lymphatic imaging confirmed the earlier suggestion that LD is associated with a normal or increased number of lymphatic vessels rather than the hypoplasia or aplasia seen in other forms of primary lymphoedema. Distichiasis was 94.2% penetrant, but not always symptomatic. Associated findings included ptosis (31%), congenital heart disease (6.8%), and cleft palate (4%). Other than distichiasis, the most commonly occurring anomaly was varicose veins of early onset (49%). This has not been previously reported and suggests a possible developmental role for FOXC2 in both venous and lymphatic systems. This is the first gene that has been implicated in the aetiology of varicose veins. Conclusion: Unlike previous publications, the thorough clinical characterisation of our patients permits more accurate prediction of various phenotypic abnormalities likely to manifest in subjects with FOXC2 mutations.

Analysis of lymphoedema-distichiasis families for FOXC2 mutations reveals small insertions and deletions throughout the gene

Abstract. Lymphoedema-distichiasis (LD) is a dominantly inherited form of primary lymphoedema with onset of lower limb swelling at puberty or later. There is variable penetrance of this disorder, but the most consistently inherited feature is distichiasis, viz. fine hairs arising inappropriately from the meibomian glands. We established linkage of this disorder to 16q24.3 and the gene has recently been identified as the forkhead transcription factorFOXC2. We report the mutational analysis of 14 families with LD. All but one of these pedigrees have small insertions or deletions in the gene, which seem likely to produce haploinsufficiency. The mutation sites are scattered throughout the gene. There is one family with a mis-sense mutation in the forkhead domain of the protein. This base alteration is not a common polymorphism, is co-inherited with the disease and produces a non-conservative amino acid change.

Rapid identification of mutations in GJC2 in primary lymphoedema using whole exome sequencing combined with linkage analysis with delineation of the phenotype

Background Primary lymphoedema describes a chronic, frequently progressive, failure of lymphatic drainage. This disorder is frequently genetic in origin, and a multigenerational family in which eight individuals developed postnatal lymphoedema of all four limbs was ascertained from the joint Lymphoedema/Genetic clinic at St Georges Hospital. Methods Linkage analysis was used to determine a locus, and exome sequencing was employed to look for causative variants. Results Linkage analysis revealed cosegregation of a 16.1 Mb haplotype on chromosome 1q42 that contained 173 known or predicted genes. Whole exome sequencing in a single affected individual was undertaken, and the search for the causative variant was focused to within the linkage interval. This approach revealed two novel non-synonymous single nucleotide substitutions within the chromosome 1 locus, in NVL and GJC2. NVL and GJC2 were sequenced in an additional cohort of individuals with a similar phenotype and non-synonymous variants were found in GJC2 in four additional families. Conclusion This report demonstrates the power of exome sequencing efficiently applied to a traditional positional cloning pipeline in disease gene discovery, and suggests that the phenotype produced by GJC2 mutations is predominantly one of 4 limb lymphoedema.

A Gene for Lymphedema-Distichiasis Maps to 16q24.3

Lymphedema-distichiasis (LD) is a dominantly inherited syndrome with onset of lymphedema at or just after puberty. Most affected individuals have distichiasis-fine hairs arising inappropriately from the eyelid meibomian glands-which is evident from birth. A study of three families with LD has shown linkage to chromosome 16q24.3, and subsequent analysis of the region for recombinant genes places the locus between D16S422 and D16S3074, a distance of approximately 16 cM. Possible candidate genes in this interval include the N-proteinase for type 3 collagen, PCOLN3; the metalloprotease PRSM1; and the cell matrix-adhesion regulator, CMAR.

Identification of eight novel VEGFR-3 mutations in families with primary congenital lymphoedema

Primary lymphoedema is oedema that occurs as a consequence of a failure of lymph drainage and arises from an intrinsic abnormality of the lymphatic system.1 Familial lymphoedema usually segregates as an autosomal dominant trait with reported variable expression and reduced penetrance.2,3 Primary lymphoedema can be classified according to age of onset, at birth as primary congenital lymphoedema (PCL) or Milroy disease (MIM 153100) or, more commonly, after puberty as Meige disease (MIM 153200).nnLymphoedema may occur as part of a well recognised syndrome, where the genetic defect may or may not be known, for example in Turner or Noonan syndrome (MIM 163950).4 Lymphoedema can also occur in association with other clinical features—for example, pubertal onset autosomal dominant lymphoedema with distichiasis (LD; MIM 153400), which has been linked to 16q24.3.5,6 The gene for LD has recently been identified as FOXC2 ( MFH-1 ) (MIM 602402), a member of the forkhead/winged-helix family of transcription factors, and mutations within this gene have been identified in families with LD.7–10nnWe have previously reported linkage to 5q35.3 in one large American family and four British families with PCL.3 This has also been shown independently by two other groups.11,12 Subsequent mutations were reported in the gene encoding the vascular endothelial growth factor receptor 3 ( VEGFR-3 , also known as FLT4 ; MIM 136352; GenBank X68203 and S66407), which resulted in defective VEGFR-3 tyrosine kinase activity and signalling, suggesting this was the cause of primary lymphoedema.12,,13 The VEGFR-3 gene is expressed in the lymphatic endothelium of adult tissues.14 Targeted disruption of Vegfr-3 in mice leads to embryonic death at day 9.5 owing to defective development of large blood vessels and cardiovascular failure.15 Moreover, cutaneous overexpression of its ligand, vascular endothelial growth factor C …

Novel TIGR/MYOC mutations in families with juvenile onset primary open angle glaucoma.

Mutations in the trabecular meshwork induced glucocorticoid response protein (TIGR) or myocilin (MYOC) has recently been shown to cause juvenile onset primary open angle glaucoma (JOAG). In this study, we identified two new mutations (Asp380Ala and Ser502Pro) in two British families and another (Pro370Leu) in a French-Canadian family. These mutations were not present in a total of 106 normal chromosomes. In another Turkish family with JOAG, we also detected a sequence variant that was proven to be an amino acid polymorphism (Arg76Lys). No other sequence changes were found in the entire coding region and splice junctions of the TIGR/MYOC gene in this family. However, it is still possible that mutations either in the TIGR promoter or in another neighbouring gene could cause glaucoma in this JOAG family. Our results confirm the role of the TIGR/MYOC gene in the aetiology of the JOAG phenotype.

Lymphoedema-distichiasis and FOXC2: unreported mutations, de novo mutation estimate, families without coding mutations

Lymphoedema-distichiasis (LD) is a syndromic form of primary lymphoedema, where mutations in the gene for the developmental transcription factor FOXC2 have been shown to be causative. The disorder has been considered very rare, but our group has now ascertained 34 families and 11 sporadic cases in the UK. Two families with LD have no mutation in the coding region of FOXC2, although both are consistent with linkage to the FOXC2 locus. A deletion has been ruled out as a possible cause of LD in these families, leaving promoter mutations as the most likely cause. Sixteen previously unpublished mutations are reported, plus an estimate of the frequency of new mutations in this disorder.

Aortic Disease Presentation and Outcome Associated with ACTA2 Mutations

Background—ACTA2 mutations are the major cause of familial thoracic aortic aneurysms and dissections. We sought to characterize these aortic diseases in a large case series of individuals with ACTA2 mutations. Methods and Results—Aortic disease, management, and outcome associated with the first aortic event (aortic dissection or aneurysm repair) were abstracted from the medical records of 277 individuals with 41 various ACTA2 mutations. Aortic events occurred in 48% of these individuals, with the vast majority presenting with thoracic aortic dissections (88%) associated with 25% mortality. Type A dissections were more common than type B dissections (54% versus 21%), but the median age of onset of type B dissections was significantly younger than type A dissections (27 years versus 36 years). Only 12% of aortic events were repair of ascending aortic aneurysms, which variably involved the aortic root, ascending aorta, and aortic arch. Overall, cumulative risk of an aortic event at age 85 years was 0.76 (95% confidence interval, 0.64–0.86). After adjustment for intrafamilial correlation, sex and race, mutations disrupting p.R179 and p.R258 were associated with significantly increased risk for aortic events, whereas p.R185Q and p.R118Q mutations showed significantly lower risk of aortic events compared with other mutations. Conclusions—ACTA2 mutations are associated with high risk of presentation with an acute aortic dissection. The lifetime risk for an aortic event is only 76%, suggesting that additional environmental or genetic factors play a role in expression of aortic disease in individuals with ACTA2 mutations.

Design and rationale of a prospective, collaborative meta-analysis of all randomized controlled trials of angiotensin receptor antagonists in Marfan syndrome, based on individual patient data: A report from the Marfan Treatment Trialists' Collaboration

Rationale A number of randomized trials are underway, which will address the effects of angiotensin receptor blockers (ARBs) on aortic root enlargement and a range of other end points in patients with Marfan syndrome. If individual participant data from these trials were to be combined, a meta-analysis of the resulting data, totaling approximately 2,300 patients, would allow estimation across a number of trials of the treatment effects both of ARB therapy and of β-blockade. Such an analysis would also allow estimation of treatment effects in particular subgroups of patients on a range of end points of interest and would allow a more powerful estimate of the effects of these treatments on a composite end point of several clinical outcomes than would be available from any individual trial. Design A prospective, collaborative meta-analysis based on individual patient data from all randomized trials in Marfan syndrome of (i) ARBs versus placebo (or open-label control) and (ii) ARBs versus β-blockers will be performed. A prospective study design, in which the principal hypotheses, trial eligibility criteria, analyses, and methods are specified in advance of the unblinding of the component trials, will help to limit bias owing to data-dependent emphasis on the results of particular trials. The use of individual patient data will allow for analysis of the effects of ARBs in particular patient subgroups and for time-to-event analysis for clinical outcomes. The meta-analysis protocol summarized in this report was written on behalf of the Marfan Treatment Trialists Collaboration and finalized in late 2012, without foreknowledge of the results of any component trial, and will be made available online (http://www.ctsu.ox.ac.uk/research/meta-trials).