Molecualr Genetics Of Klippel-Trenaunay Syndrome And Long QT Syndrome

Cardiovascular diseases are the No.1 killer in the United States, other developedcountries and China. The molecular genetic research on cardiovascular disease will notonly lead to development of accurate genetic testing and novel therapies forcardiovascular diseases, but also provide insights into molecular mechanisms underlyingthe development and function of the heart and blood vessels. In this study, we havecloned a novel angiogenic factor, VG5Q, as a candidate gene for Klippel-TrenaunaySyndrome; we also identified a novel mutation L187P of KCNQ1 gene, in a fivegeneration family with autosomal dominant LQTS. Klippel-Trenaunay Syndrome (OMIM *149000) is a congenital vascular diseasecharacterized by malformations of capillary, venous, and lymphatic vessels, with bonyand soft tissue hypertrophy. It affects many parts of the body, and is associated withsignificant morbidity with a profound impact on a patient's life (e.g., pain, disability,disfigurement, and social stress). KTS is commonly sporadic, and its etiology isunknown. In this study, we used positional cloning to identify a novel gene, VG5Q, for KTS,and explore the physiological function of VG5Q in angiogenesis. A translocationt(5;11)(q13.3;p15.1) has previously been found to be associated with KTS. PCR analysiswith somatic cell hybrids containing only the derivative chromosome 5 or the derivativechromosome 11 defined the precise locations of two translocation breakpoints. It allowsus to identify KTS candidate gene, and a novel gene, named VG5Q (Vascular Gene on5q), close to the breakpoints on chromosome 5 has been identified. The 5q13.3translocation breakpoint is located in the promoter/regulatory region of VG5Q, and isonly 1274 bp upstream from the beginning of VG5Q cDNA. VG5Q promoter with thetranslocation junction fragment increased its expression by 3.0 fold in human umbilicalvein endothelial cells, suggests that the t (5; 11) translocation in the KTS patient is afunctional genetic defect that can lead to over-expression of VG5Q. We performed mutational analysis for VG5Q with 130 single KTS patients. Asingle non-conservative VG5Q mutation E133K was identified in five independent KTSpatients, and this mutation results in substitution of a negatively charged glutamineresidue for a positively charged lysine residue .Mutation E133K was not detected in 200normal subjects. With the chick chorioallantoic membrane (CAM) assay, we found that the purified,wild type VG5Q protein promoted strong angiogenesis as shown by the newly formed,radiated vessels on the CAM. Similar results were observed around the discs which werespotted with VEGF. Marked differences in angiogenesis were observed between wildtype and mutant VG5Q with the E133K substitution. Mutant VG5Q protein produced asignificantly more potent angiogenic factor than the wild type protein. 3复旦大学博士论文 先天性静脉畸形骨肥大综合征和长 QT 综合征的分子遗传学研究 Several lines of evidence strongly support the involvement of VG5Q in thepathogenesis of KTS: i) The KTS translocation breakpoint is located in the promoterregion of VG5Q, and the translocation increased expression of VG5Q by 3 fold inendothelial cells; ii) Mutation E133K of VG5Q was identified in five independentpatients, but not in 200 comparable controls; iii) VG5Q is highly expressed in bloodvessels; iv) VG5Q can cause angiogenesis (as potently as VEGF); v) Mutant VG5Qwith E133K causes greater angiogenesis than wild type VG5Q, establishing E133K as afunctional mutation that acts by a gain-of function mechanism; vi) No genes wereidentified at the chromosome 11p15.1 breakpoint (100 kb region). Together with thehistological finding of greatly increased numbers of capillary veins in affected tissuesfrom KTS patients, these results provide strong support for increased angiogenesis as themolecular pathogenic mechanism...