Multivariate genome-wide covariance analyses of literacy, language and working memory skills reveal distinct etiologies

Chin Yang Shapland,Brad Verhulst,Ellen Verhoef,Beate St Pourcain,Simon E Fisher,Philip S Dale,George Davey Smith

doi:10.1038/s41539-021-00101-y

Abstract

Several abilities outside literacy proper are associated with reading and spelling, both phenotypically and genetically, though our knowledge of multivariate genomic covariance structures is incomplete. Here, we introduce structural models describing genetic and residual influences between traits to study multivariate links across measures of literacy, phonological awareness, oral language, and phonological working memory (PWM) in unrelated UK youth (8–13 years, N = 6453). We find that all phenotypes share a large proportion of underlying genetic variation, although especially oral language and PWM reveal substantial differences in their genetic variance composition with substantial trait-specific genetic influences. Multivariate genetic and residual trait covariance showed concordant patterns, except for marked differences between oral language and literacy/phonological awareness, where strong genetic links contrasted near-zero residual overlap. These findings suggest differences in etiological mechanisms, acting beyond a pleiotropic set of genetic variants, and implicate variation in trait modifiability even among phenotypes that have high genetic correlations.

Highlights

Within most Indo-European languages, including English, an alphabetic writing system maps sequences of symbols to the sounds and meaning of words[1]
Close and reciprocal interrelationships manifest between phonological decoding, letter knowledge, and phonological awareness, the ability to dissect and transform words according to their phonological structure[3]
By modeling multivariate genetic variance within a populationrepresentative sample of unrelated youth using genome-wide markers, we demonstrated that literacy, phonological awareness, language and phonological working memory (PWM) abilities share a large proportion of their underlying genetic variation, and revealed substantial differences in their genetic variance composition

Summary

Introduction

Within most Indo-European languages, including English, an alphabetic writing system maps sequences of symbols to the sounds and meaning of words[1]. Symbols or graphemes (letters or groups of letters) represent individual sounds (phonemes). This correspondence of spoken language to printed words, known as the alphabetic principle, is, in turn, the basis of phonological decoding skills, which enable the interpretation of texts through phonetic transformation[2]. As links emerge and can be used in real-time to identify printed words, children apply this knowledge to develop reading and spelling skills[1]. Developed reading comprehension skills include the ability to identify and integrate word meanings along with contextual and world knowledge to construct the meanings of sentences and larger discourse structures[4]. Once mastered, reading has a profound impact on the acquisition of knowledge, including print exposure[5], and, on final educational attainment[6]

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