Background: Lung function is a highly heritable trait. So far there is limited knowledge of the genetic factors that influence lung function. Vascular endothelial growth factor A (VEGF-A) is expressed in the lung at high levels and is known to play a role in angiogenesis and lung remodelling, both in utero and throughout life. A candidate gene study was carried out in order to investigate the role of variants within the VEGF-A gene in determining lung function in childhood and adult life.Methods: Using available longitudinal data previously collected for an unselected birth cohort (Manchester Asthma and Allergy Study-MAAS) the relationship between lung function and single-nucleotide polymorphisms (SNPs) in VEGF-A was assessed. Replication studies were performed in cross-sectional studies of adults from Manchester and children with asthma from Croatia, in whom FEV1/FVC ratio was measured using spirometry. The potential functional roles of two consistently associated SNPs were then further investigated. Finally, using the genome-wide data generated in the discovery cohort (MAAS) I assessed why associations between VEGF-A and lung function had not been reported in recent genome-wide association studies of lung function.Results: Two VEGF-A SNPs, rs10434 and rs3025028, were significantly associated with lung function at multiple ages in a discovery population (MAAS). Subjects with a GG genotype for either SNP had significantly diminished lung function compared to subjects with other genotypes. These findings were replicated in two additional populations (631 parents of children participating in MAAS and in 410 Croatian children with physician-diagnosed asthma aged 6-18 years). SNP rs10434 is located in the 3’UTR and based on its location I hypothesised that it may affect mRNA stability. No significant difference in the rate of VEGF-A mRNA degradation was found between GG and the AA homozygotes. SNP rs3025028 is an intronic SNP in a close proximity to the splice site involved in alternative splicing which generates two different isoforms of VEGF-A; I therefore tested the hypothesis that a change of base at this position could affect the splicing mechanism and cause a change in the ratio of the isoforms. Western blot analysis was used to demonstrate a difference in the ratio of the splice variants VEGF-A165b and total VEGF-A165 (relative to a reference sample) between genotype groups. The VEGF-A165b/panVEGF-A165 ratio was significantly higher at birth (cord plasma), in school-age children and in adults amongst CC compared to GG homozygotes at rs3025038 (p<0.03). Finally, the genome-wide data for the discovery cohort showed that the region containing VEGF-A was not well targeted by either genotyped or imputed SNPs in genome-wide arrays. Conclusion: Evidence was provided to demonstrate that variants within the VEGF-A gene are significantly associated with lung function in both children and adults. Furthermore, data was presented to support a functional role for one of the SNPs (rs3025028). I investigated why associations between VEGF-A and lung function had not previously been reported in recent GWAS and concluded that the region containing VEGF-A was poorly covered by all of the currently available arrays.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:574292 |
| Date | January 2013 |
| Creators | Hankinson, Jenny |
| Contributors | Custovic, Adnan; Curtin, John |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/the-role-of-vegf-in-lung-function(763b07ca-4ba3-481e-894b-46abccd29250).html |
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