Twin studies suggest that expressive vocabulary at ~24 months is modestly heritable. However, the genes influencing this early linguistic phenotype are unknown. Here we conduct a genome-wide screen and follow-up study of expressive vocabulary in toddlers of European descent from up to four studies of the EArly Genetics and Lifecourse Epidemiology consortium, analysing an early (15-18 months, 'one-word stage', NTotal=8,889) and a later (24-30 months, 'two-word stage', NTotal=10,819) phase of language acquisition. For the early phase, one single-nucleotide polymorphism (rs7642482) at 3p12.3 near ROBO2, encoding a conserved axon-binding receptor, reaches the genome-wide significance level (P=1.3×10-8) in the combined sample. This association links language-related common genetic variation in the general population to a potential autism susceptibility locus and a linkage region for dyslexia, speech-sound disorder and reading. The contribution of common genetic influences is, although modest, supported by genome-wide complex trait analysis (meta-GCTA h15-18-months 2=0.13, meta-GCTA h24-30-months 2 =0.14) and in concordance with additional twin analysis (5,733 pairs of European descent, h24-months 2=0.20).,
Nature Communications
Generation R Study Group

St Pourcain, B., Cents, R., Whitehouse, A., Haworth, C. M., Davis, O. S., O'Reilly, P., … Smith, D. (2014). Common variation near ROBO2 is associated with expressive vocabulary in infancy. Nature Communications, 5. doi:10.1038/ncomms5831