Complete Sequence of the 22q11.2 Allele in 1,053 Subjects with 22q11.2 Deletion Syndrome Reveals Modifiers of Conotruncal Heart Defects

Am J Hum Genet. 2020 Jan 2;106(1):26-40. doi: 10.1016/j.ajhg.2019.11.010. Epub 2019 Dec 20.

Abstract

The 22q11.2 deletion syndrome (22q11.2DS) results from non-allelic homologous recombination between low-copy repeats termed LCR22. About 60%-70% of individuals with the typical 3 megabase (Mb) deletion from LCR22A-D have congenital heart disease, mostly of the conotruncal type (CTD), whereas others have normal cardiac anatomy. In this study, we tested whether variants in the hemizygous LCR22A-D region are associated with risk for CTDs on the basis of the sequence of the 22q11.2 region from 1,053 22q11.2DS individuals. We found a significant association (FDR p < 0.05) of the CTD subset with 62 common variants in a single linkage disequilibrium (LD) block in a 350 kb interval harboring CRKL. A total of 45 of the 62 variants were associated with increased risk for CTDs (odds ratio [OR) ranges: 1.64-4.75). Associations of four variants were replicated in a meta-analysis of three genome-wide association studies of CTDs in affected individuals without 22q11.2DS. One of the replicated variants, rs178252, is located in an open chromatin region and resides in the double-elite enhancer, GH22J020947, that is predicted to regulate CRKL (CRK-like proto-oncogene, cytoplasmic adaptor) expression. Approximately 23% of patients with nested LCR22C-D deletions have CTDs, and inactivation of Crkl in mice causes CTDs, thus implicating this gene as a modifier. Rs178252 and rs6004160 are expression quantitative trait loci (eQTLs) of CRKL. Furthermore, set-based tests identified an enhancer that is predicted to target CRKL and is significantly associated with CTD risk (GH22J020946, sequence kernal association test (SKAT) p = 7.21 × 10-5) in the 22q11.2DS cohort. These findings suggest that variance in CTD penetrance in the 22q11.2DS population can be explained in part by variants affecting CRKL expression.

Keywords: CRKL; DiGeorge syndrome; TBX1; chromosome 22q11.2 deletion syndrome; complex trait; congenital heart disease; conotruncal heart defects; copy number variation; genetic association; genetic modifier; haploinsufficiency.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Case-Control Studies
  • Chromosome Deletion*
  • Chromosomes, Human, Pair 22 / genetics*
  • Cohort Studies
  • Female
  • Genome-Wide Association Study
  • Heart Defects, Congenital / genetics*
  • Heart Defects, Congenital / pathology
  • Humans
  • Linkage Disequilibrium
  • Male
  • Phenotype
  • Polymorphism, Single Nucleotide*
  • Proto-Oncogene Mas
  • Segmental Duplications, Genomic

Supplementary concepts

  • Conotruncal cardiac defects