FOXC2 and FLT4 Gene Variants in Lymphatic Filariasis Yasmeen Sheik, 1 Sameera Fatima Qureshi, 1 Basheeruddin Mohhammed, 2 and Pratibha Nallari 1 Abstract Lymphatic filariasis is the leading cause of secondary lymphedema wherein lymph transport is impaired due to lymphatic damage. FLT4 signaling and transcription factors such as FOXC2 play an important role in this type of lymphangiogenesis process induced by filarial parasites. The present study aims to assess the association of FLT4 and FOXC2 genes in lymphatic development/remodeling in lymphatic filariasis. A total of 118 lymphatic filariasis patients and 100 non-endemic and 50 endemic healthy subjects were enrolled for the present study. Allele-specific PCR and PCR-RFLP were adopted for the genotyping, and screening of FLT4 and FOXC2 genes was carried out by PCR-SSCP, followed by in-silico and statistical analysis. A novel variation (G357A SNP) was identified on FOXC2 gene screening that may have an effect on codon usage frequency during translational process. In FLT4, A3123G mutation was found in 3.39% of the case subjects but the functional role of this mutation, along with subject’s clinical presentations and patient’s age, emphasize its pathogenic role in lym- phedema development. Two of the subjects exhibit compound heterozygosity (A3123G FLT4 mutation and G357A SNP of FOXC2 gene). As these two genes share a common pathway, we hypothesise a synergistic interaction of these two SNPs in inhibiting the downstream signaling resulting in lymphedema progression. Introduction T he human lymphatic system is a complex network of nodes and vessels that maintain the fluid balance be- tween blood and tissues that is a critical component of the body’s immune system. The lymph carries both antigens and immune cells to the lymph nodes, a function important to the initiation of an immune response. Lymphedema, which is associated with high morbidity, is characterized by a chronic swelling of the tissues due to blockage or absence of lym- phatic vessel, resulting in an excess draining of protein rich interstitial fluid. In all forms of lymphedema, the persistent accumulation of stagnant, protein-rich fluid in the inter- stitium reduces oxygen availability to tissues leading to de- ficiency of normal immune defense. As a consequence, the affected area often shows increased tissue fibrosis and adi- pose degeneration, interference with wound healing, and susceptibility to infections. 1 Lymphatic filariasis is the leading cause of secondary lymphedema wherein lymph transport is impaired due to lymphatic damage. Among the 120 million people infected with the lymphatic dwelling nematodes, approximately 40 million have lymphedema and/or other pathologic manifes- tations, including hydroceles and episodic adenolymphangi- tis. 2,3 The lymphedema characterized in filariasis is due to insufficient lymphatic drainage. The presence of adult worms triggers inflammation that may progress to fibrosis and sub- sequent obstruction of lymphatic vessels. 1 Adult filarial parasite within the lymphatic vessels of the host triggers a cascade of events that leads to abnormalities in lymphatic integrity and function. 3,4 The dead and decalcifying adult worm elicit responses leading to lymphatic blockage and gross pathological lesions which, when coupled with pre- existing lymphatic dilation, may lead to damage of the lymphatic valves that may in turn induce lymphatic backflow and lymphedema. The aberrant lymph vessel development, innate immune responses that are triggered by the filarial antigen, ultimately result in the activation of vascular endo- thelial growth factors (VEGF), promoting lymph vessel hy- perplasia as a first step to lymphedema development. Further the proinflammatory responses (IL-1, TNF-a), resulting from chronic lymphatic obstructions, render the lymphatic endo- thelial cells (LEC) hyperpermeable, leading to lymphedema. 5 Filarial parasites are capable of inducing lymphangio- genesis in vitro, a process that is LEC specific and relates to the excretory-secretory components of the filarial parasites and/or the elevated levels of circulating lymphangiogenic factors. 6 FLT4 signaling and transcription factors such as FOXC2 play an important role in this type of lymphagio- genesis process. Recent studies have implicated the role of 1 Department of Genetics, Osmania University, Hyderabad, Telangana, India. 2 NFCP (National Filariasis Control program Centre), Siddipet, Medak, Telangana, India. LYMPHATIC RESEARCH AND BIOLOGY Volume 13, Number 2, 2015 ª Mary Ann Liebert, Inc. DOI: 10.1089/lrb.2014.0025 112