VEGFR-3 controls tip to stalk conversion at vessel fusion sites by reinforcing Notch signalling

Angiogenesis, the growth of new blood vessels, involves specification of endothelial cells to tip cells and stalk cells, which is controlled by Notch signalling, whereas vascular endothelial growth factor receptor (VEGFR)-2 and VEGFR-3 have been implicated in angiogenic sprouting. Surprisingly, we found that endothelial deletion of Vegfr3, but not VEGFR-3-blocking antibodies, postnatally led to excessive angiogenic sprouting and branching, and decreased the level of Notch signalling, indicating that VEGFR-3 possesses passive and active signalling modalities. Furthermore, macrophages expressing the VEGFR-3 and VEGFR-2 ligand VEGF-C localized to vessel branch points, and Vegfc heterozygous mice exhibited inefficient angiogenesis characterized by decreased vascular branching. FoxC2 is a known regulator of Notch ligand and target gene expression, and Foxc2(+/-);Vegfr3(+/-) compound heterozygosity recapitulated homozygous loss of Vegfr3. These results indicate that macrophage-derived VEGF-C activates VEGFR-3 in tip cells to reinforce Notch signalling, which contributes to the phenotypic conversion of endothelial cells at fusion points of vessel sprouts

Wide clinical spectrum in a family with hereditary lymphedema type I due to a novel missense mutation in VEGFR3.

Hereditary lymphedema type I (HL-I), also known as Milroy disease, is an autosomal dominant disorder characterized by typical phenotype of infantile onset lower-limb lymphedema accompanied by variable expression of recurrent episodes of cellulites, toenail changes, and papillomatosis. Mutations in the vascular endothelial growth factor receptor 3 (VEGFR3), also known as FLT4 gene, which encodes a lymphatic endothelial-specific tyrosine kinase receptor, have been identified as a genetic cause of HL-I. We report a large Muslim Arab family residing in northern Israel with 14 individuals presenting clinical features of HL-I. Genetic analysis revealed novel missense mutation E1106K in the tyrosine kinase domain II of VEGFR3 that cosegregates with the disorder in the family. Most affected individuals presented with bilateral congenital lower-limb lymphedema. Wide intrafamilial phenotypic variability included two asymptomatic individuals, a case of prenatal hydrothorax evolving to hydrops fetalis, and a late-onset complication, yet unreported, of chronic degenerative joint disease of the knees. This report broadens the known "classic" phenotype of HL-I

Hereditary lymphedema type I associated with VEGFR3 mutation: the first de novo case and atypical presentations.

Mutations in the vascular endothelial growth factor receptor 3 gene, VEGFR3/FLT4, have been identified in a subset of families with hereditary lymphedema type I or Milroy disease (MIM 153100). Individuals carrying a VEGFR3 mutation exhibit congenital edema of the lower limbs, usually bilaterally and below the knees, sometimes associated with cellulitis, prominent veins, papillomatosis, upturned toenails, and hydrocele. In this study, we report the first de novo VEGFR3 mutation in a patient with sporadic congenital lymphedema. We also describe three other families with a VEGFR3 mutation. In each family, one individual had an atypical clinical presentation of hereditary lymphedema type I, whereas the others had the classical VEGFR3 mutation-caused phenotype. The atypical presentations included pre-natal pleural effusion, spontaneous resorption of lymphedema and elephantiasis. Three of the four identified mutations were novel. These data show that de novo VEGFR3 mutations may be present in patients without family history of congenital lymphedema. This has implications for follow-up care, as such individuals have nearly a 50% risk for occurrence of lymphedema in their children. Our findings also indicate that although most patients with a VEGFR3 mutation have the well-defined phenotype for hereditary lymphedema type I, there are exceptions that should be considered in genetic counseling. Because VEGFR3 mutation can cause generalized lymphatic dysfunction and can thus result in hydrops fetalis, VEGFR3 screening should be added to the investigation of cases of hydrops fetalis of an unknown etiology

Mutations in the VEGFR3 signaling pathway explain 36% of familial lymphedema.

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Supplementary Material for: Mutations in the VEGFR3 Signaling Pathway Explain 36% of Familial Lymphedema

Lymphedema is caused by dysfunction of lymphatic vessels, leading to disabling swelling that occurs mostly on the extremities. Lymphedema can be either primary (congenital) or secondary (acquired). Familial primary lymphedema commonly segregates in an autosomal dominant or recessive manner. It can also occur in combination with other clinical features. Nine mutated genes have been identified in different isolated or syndromic forms of lymphedema. However, the prevalence of primary lymphedema that can be explained by these genetic alterations is unknown. In this study, we investigated 7 of these putative genes. We screened 78 index patients from families with inherited lymphedema for mutations in <i>FLT4, GJC2, FOXC2, SOX18, GATA2, CCBE1</i>, and <i>PTPN14</i>. Altogether, we discovered 28 mutations explaining 36% of the cases. Additionally, 149 patients with sporadic primary lymphedema were screened for <i>FLT4, FOXC2, SOX18,</i><i>CCBE1</i>, and <i>PTPN14</i>. Twelve mutations were found that explain 8% of the cases. Still unidentified is the genetic cause of primary lymphedema in 64% of patients with a family history and 92% of sporadic cases. Identification of those genes is important for understanding of etiopathogenesis, stratification of treatments and generation of disease models. Interestingly, most of the proteins that are encoded by the genes mutated in primary lymphedema seem to act in a single functional pathway involving VEGFR3 signaling. This underscores the important role this pathway plays in lymphatic development and function and suggests that the unknown genes also have a role

Mutations in KIF11 cause autosomal-dominant microcephaly variably associated with congenital lymphedema and chorioretinopathy

Item does not contain fulltextWe have identified KIF11 mutations in individuals with syndromic autosomal-dominant microcephaly associated with lymphedema and/or chorioretinopathy. Initial whole-exome sequencing revealed heterozygous KIF11 mutations in three individuals with a combination of microcephaly and lymphedema from a microcephaly-lymphedema-chorioretinal-dysplasia cohort. Subsequent Sanger sequencing of KIF11 in a further 15 unrelated microcephalic probands with lymphedema and/or chorioretinopathy identified additional heterozygous mutations in 12 of them. KIF11 encodes EG5, a homotetramer kinesin motor. The variety of mutations we have found (two nonsense, two splice site, four missense, and six indels causing frameshifts) are all predicted to have an impact on protein function. EG5 has previously been shown to play a role in spindle assembly and function, and these findings highlight the critical role of proteins necessary for spindle formation in CNS development. Moreover, identification of KIF11 mutations in patients with chorioretinopathy and lymphedema suggests that EG5 is involved in the development and maintenance of retinal and lymphatic structures

No evidence of locus heterogeneity in familial microcephaly with or without chorioretinopathy, lymphedema, or mental retardation syndrome.

BACKGROUND: Microcephaly with or without chorioretinopathy, lymphedema, or mental retardation syndrome (MCLMR) is a rare autosomal dominant disorder with variable expressivity. It is characterized by mild-to-severe microcephaly, often associated with intellectual disability, ocular defects and lymphedema. It can be sporadic or inherited. Eighty-seven patients have been described to carry a mutation in KIF11, which encodes a homotetrameric motor kinesin, EG5. METHODS: We tested 23 unreported MCLMR index patients for KIF11. We also reviewed the clinical phenotypes of all our patients as well as of those described in previously published studies. RESULTS: We identified 14 mutations, 12 of which are novel. We detected mutations in 12 affected individuals, from 6 out of 6 familial cases, and in 8 out of 17 sporadic patients. Phenotypic evaluation of patients (our 26 + 61 earlier published = 87) revealed microcephaly in 91%, eye anomalies in 72%, intellectual disability in 67% and lymphedema in 47% of the patients. Unaffected carriers were rare (4 out of 87: 5%). Family history is not a requisite for diagnosis; 31% (16 out of 52) were de novo cases. CONCLUSIONS: All inherited cases, and 50% of sporadic cases of MCLMR are due to germline KIF11 mutations. It is possible that mosaic KIF11 mutations cause the remainder of sporadic cases, which the methods employed here were not designed to detect. On the other hand, some of them might have another mimicking disorder and genetic defect, as microcephaly is highly heterogeneous. In aggregate, KIF11 mutations likely cause the majority, if not all, of MCLMR