A molecular genetic investigation of hypoplastic left heart syndrome

• Main Author: Renforth, Glenn Lee
• Format: Dissertation
• Language: English
• Published: University of Southampton 2005

HLHS is a severe congenital heart defect. Significant associations have been made between HLHS and terminal deletions of chromosome llq (Jacobsen's Syndrome: JBS), suggesting that haploinsufficiency of a gene within this region causes HLHS. The aim of this thesis was to identify the genetic basis of the cardiac component of JBS and potentially isolated cases of HLHS, through the characterisation of patients with HLHS and 11q deletions. A molecular analysis of 3 patients with JBS was undertaken using loss of heterozygosity analysis and fluorescent chromosome in situ hybridisation to define the minimal region associated with HLHS and other congenital heart defects. A 6.6 Mb minimal region of deletion associated with HLHS was defined and genes mapping to this region were assessed as candidates for HLHS. The tight junction protein JAM3 was chosen as a good candidate and investigated further. JAM3 protein was detected in the foetal aorta and aortic/mitral valves, structures principally disrupted in HLHS. Furthermore, JAM3 colocalised with Elastin within the aortic valve, a significant finding considering the role of ELN in supravascular aortic stenosis. Twenty-five patients with HLHS were screened for mutations in JAM3. This did not conclusively identify any causative mutations, but a total of 4 sequence variants were identified. Using a separate approach, candidate genes causing HLHS were identified based on mouse gene knockouts that had a HLHS like phenotype. HANDl and SMAD6 were selected as good candidates and were assessed for mutations in twenty-five patients with HLHS. No sequence variants were identified in either gene.