Analysis of the coding regions of VEGFR3 and VEGFC in Milroy disease and other primary lymphoedemas

Congenital lower limb enlargement in a newborn

A full-term newborn presented with swelling of his right leg soon after birth. There was no alteration in Doppler. The grandmother and other relatives were said to have shown a similar history at birth. Milroy's disease was then diagnosed and compressive massage was advised.

Massively parallel sequencing and identification of genes for primary lymphoedema: a perfect fit

Primary lymphoedema is a clinically and genetically heterogeneous group of disorders characterized by disruption of the lymphatic system. To date, the majority of the causative genes in primary lymphoedema have been identified through linkage analysis in large families with multiple affected subjects. Studies aimed at isolating additional genes responsible for primary lymphoedema have been hampered by cohorts comprised primarily of sporadic cases and small affected kindreds. In the absence of genetic heterogeneity, recent development of massively parallel DNA sequencing technology, specifically exome sequencing, has provided novel paradigms for disease gene identification in such cohorts. In this review, we summarize the novel approaches to disease gene discovery with massively parallel sequencing also known as Next Generation Sequencing (NGS), and show how the selection of unrelated affected cases from clinically homogenous phenotypic subclassifications is proving to be a successful approach for disease gene discovery in primary lymphoedema.

Lymphatic capillary hypoplasia in the skin of fetuses with increased nuchal translucency and Turner's syndrome: comparison with trisomies and controls

Fetuses with Turner's syndrome or trisomies 21, 18 and 13 show excess of skin, which can be visualized by ultrasonography as increased nuchal translucency at 11-13(+6) weeks' gestation. The objective of this study was to gain insight in the development and distribution of blood vessels, lymphatic capillaries of the cutis and lymphatic collectors of the cutis and subcutis and to study developmental changes with increasing gestation. Immunofluorescence of cryosections with 10 specific antibodies was used to investigate the nuchal skin of three fetuses with Turner syndrome's and to differentiate lymphatics, lymph capillaries (FLT4, PTN 63, LYVE1, PROX1), blood vessels (KDR, CD 31, PDPN), blood clotting activity (von Willebrand factor), basement membranes and big vessels (Laminin, Collagen Type IV). The findings were compared with those in seven fetuses with trisomy 21 and two fetuses each with trisomies 18 or 13, respectively, as well as six normal controls. Immunoreactive receptors for vascular endothelial growth factors (FLT4) were decreased in lymphatic capillaries of the skin of Turner fetuses. Accordingly, LYVE1 was scarce and PROX1 staining was less intense in the dermis of Turner fetuses. Lymphatic collectors were, however, evenly stained. In normal fetuses and in those with trisomies, lymphatic capillaries were evenly distributed. We conclude that lymphatic capillary hypoplasia might be responsible for nuchal cystic hygroma in Turner syndrome. The biological basis for increased nuchal translucency in trisomies may however be different.

Lymphangiogenesis: Molecular mechanisms and future promise

The growth of lymphatic vessels (lymphangiogenesis) is actively involved in a number of pathological processes including tissue inflammation and tumor dissemination but is insufficient in patients suffering from lymphedema, a debilitating condition characterized by chronic tissue edema and impaired immunity. The recent explosion of knowledge on the molecular mechanisms governing lymphangiogenesis provides new possibilities to treat these diseases.

Lymphatic development

The lymphatic system is essential for fluid homeostasis, immune responses, and fat absorption, and is involved in many pathological processes, including tumor metastasis and lymphedema. Despite its importance, progress in understanding the origins and early development of this system has been hampered by lack of defining molecular markers and difficulties in observing lymphatic cells in vivo and performing genetic and experimental manipulation of the lymphatic system. Recent identification of new molecular markers, new genes with important functional roles in lymphatic development, and new experimental models for studying lymphangiogenesis has begun to yield important insights into the emergence and assembly of this important tissue. This review focuses on the mechanisms regulating development of the lymphatic vasculature during embryogenesis.