Genetic characterisation of 22q11.2 variations and prevalence in patients with congenital heart disease.

Abstract

The 22q11.2 deletion syndrome is considered the most frequent chromosomal microdeletion syndrome in humans and the second leading chromosomal cause of congenital heart disease (CHD). We aimed to identify the prevalence and the detailed genetic characterisation of 22q11.2 region in children with CHD including simple defects and to explore the genotype-phenotype relationship between deletion/amplification type and clinical data. Patients with CHD for surgery were screened by multiplex ligation-dependent probe amplification and capillary electrophoresis methods. Universal Probe Library technology was applied for validation. In 354 patients with CHD, 40 (11.3%) carried different levels of deletions/amplifications at the 22q11.2 region with various phenotypes. The affected genes at this region include <i>CDC45</i> (15 patients), <i>TBX1</i> (8), <i>USP18</i> (8), <i>RTDR1</i> (7), <i>SNAP29</i> (6), <i>TOP3B</i> (6), <i>ZNF74</i> (4) and other genes with less frequency. Among those, two patients carried 3 Mb typically deleted region from <i>CLTCL1</i> to <i>LZTR1</i> (low copy repeats A-D) or 1.5 Mb deletions from <i>CLTCL1</i> to <i>MED15</i> (low copy repeats A-C). Clinical facial manifestations were found in 12 patients. This study revealed an unexpected high prevalence of chromosome 22q11.2 variations in patients with CHD even in simple defects. The genotype-phenotype relationship analysis suggests that genetic detection of 22q11.2 may become necessary in all patients with CHD and that detection of unique deletions or amplifications may provide useful insight into personalised management in patients with CHD.