We analyzed genetic linkage and association of measures of language, speech and reading phenotypes to candidate regions in a single set of families ascertained for SLI. Sib-pair and family-based analyses were carried out for candidate gene loci for Reading Disability (RD) on chromosomes 1p36, 3p12-q13, 6p22, and 15q21, and the speech-language candidate region on 7q31 in a sample of 322 participants ascertained for Specific Language Impairment (SLI). Replication or suggestive replication of linkage was obtained in all of these regions, but the evidence suggests that the genetic influences may not be identical for the three domains. In particular, linkage analysis replicated the influence of genes on chromosome 6p for all three domains, but association analysis indicated that only one of the candidate genes for reading disability, KIAA0319, had a strong effect on language phenotypes. The findings are consistent with a multiple gene model of the comorbidity between language impairments and reading disability and have implications for neurocognitive developmental models and maturational processes.
Right, there isn't a "language gene" (sorry FOXP2). Language is a complex phenotype dependent on a lot of genes which can be "broken" in a lot of different ways. Though since verbal fluency (or, verbal IQ) varies quite a bit, if not basal verbal competency, there are likely many genes which shape how well we can wield language. Cite:Journal of Neurodevelopmental Disorders, August 25, 2009, DOI: 10.1007/s11689-009-9031-x