The association of rare copy number variants (CNVs) with complex disorders is almost exclusively evaluated using clinically ascertained cohorts. As a result, the contribution of these genetic variants to cognitive phenotypes in the general population remains unclear.
- To investigate the clinical features of genomic disorders in adult carriers without clinical pre-selection.
- To assess the genome-wide burden of rare CNVs on carriers’ educational attainment and intellectual disability prevalence in the general population.
Design, Setting, and Participants
The population biobank of Estonia (EGCUT) contains 52,000 participants, or 5% of the Estonian adults, enrolled in 2002-2010. General practitioners examined participants and filled out a questionnaire of health- and lifestyle-related questions, as well as reported diagnoses. As EGCUT is representative of the country's population, we investigated a random sample of 7877 individuals for CNV analysis and genotype-phenotype associations with education and disease traits.
Main Outcomes and Measures
Phenotypes of genomic disorders in the general population, prevalence of autosomal CNVs, and association of the latter variants with decreased educational attainment and increased prevalence of intellectual disability.
We identified 56 carriers of genomic disorders. Their phenotypes are reminiscent of those described for carriers of identical rearrangements ascertained in clinical cohorts. We also generated a genome-wide map of rare (frequency ≤0.05%) autosomal CNVs and identified 10.5% of the screened general population (n=831) as carriers of CNVs ≥250kb. Carriers of deletions ≥250kb or duplications ≥1Mb show, compared to the Estonian population, a greater prevalence of intellectual disability (P=0.0015, OR=3.16, (95%CI: 1.51-5.98); P=0.0083, OR=3.67, (95%CI: 1.29-8.54), respectively), reduced mean education attainment (a proxy for intelligence; P=1.06e-04; P=5.024e-05, respectively) and an increased fraction of individuals not graduating from secondary school (P=0.005, OR=1.48 (95%CI: 1.12-1.95); P=0.0016, OR=1.89 (95%CI: 1.27-2.8), respectively). The deletions show evidence of enrichment for genes with a role in neurogenesis, cognition, learning, memory and behavior. Evidence for an association between rare CNVs and decreased educational attainment was confirmed by analyses in adult cohorts of Italian (HYPERGENES) and European American (Minnesota Center for Twin and Family Research) individuals, as well as in the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort.
Conclusions and Relevance
Our results challenge the assumption that carriers of known syndromic CNVs identified in population cohorts are asymptomatic. They also indicate that individually rare but collectively common intermediate-size CNVs contribute to the variance in educational attainment. Refinements of these findings in additional population groups is warranted given the potential implications of this observation for genomics research, clinical care, and public health.