Molecular characterization of two novel VEGFR3 mutations in Japanese families with Milroy's disease

A novel stop-gain pathogenic variant in FLT4 and a nonsynonymous pathogenic variant in PTPN11 associated with congenital heart defects

BACKGROUND

Congenital heart defects (CHDs) are the most common congenital malformations, including structural malformations in the heart and great vessels. CHD complications such as low birth weight, prematurity, pregnancy termination, mortality, and morbidity depend on the type of defect.

METHODS

In the present research, genetic analyses via whole-exome sequencing (WES) was performed on 3 unrelated pedigrees with CHDs. The candidate variants were confirmed, segregated by PCR-based Sanger sequencing, and evaluated by bioinformatics analysis.

RESULTS

A novel stop-gain c.C244T:p.R82X variant in the FLT4 gene, as well as a nonsynonymous c.C1403T:p.T468M variant in the PTPN11 gene, was reported by WES. FLT4 encodes a receptor tyrosine kinase involved in lymphatic development and is known as vascular endothelial growth factor 3.

CONCLUSIONS

We are the first to report a novel c.C244T variant in the FLT4 gene associated with CHDs. Using WES, we also identified a nonsynonymous variant affecting protein-tyrosine phosphatase, the non-receptor type 11 (PTPN11) gene. The clinical implementation of WES can determine gene variants in diseases with high genetic and phenotypic heterogeneity like CHDs.

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 FLT4, GJC2, FOXC2, SOX18, GATA2, CCBE1, and PTPN14. Altogether, we discovered 28 mutations explaining 36% of the cases. Additionally, 149 patients with sporadic primary lymphedema were screened for FLT4, FOXC2, SOX18, CCBE1, and PTPN14. 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.