A genome-wide analysis of five reading- and language-based skills identifies shared biology contributing to these traits

A genome-wide investigation of five reading and language-based talents in tens of thousands of people, which was published in PNAS, has identified common biological factors that contribute to these characteristics.

The results of earlier, more limited genetic investigations were not able to be duplicated.

The multinational team, which was led by researchers from the Max Planck Institute for Psycholinguistics and the Donders Institute in Nijmegen, the Netherlands, discovered genetic connections with regions of the brain that are associated with language.

The ability to communicate verbally and in writing is one of the most essential aspects of being human.

“We have known for many years that individual differences in the relevant skills must be influenced by variations in our genomes,” says first author Else Eising from the Max Planck Institute for Psycholinguistics (MPI) in Nijmegen.

“This is the first time that datasets of tens of thousands of participants have been gathered together to really reliably investigate the many DNA variants that contribute.”

This is the first study to come out of the GenLang collaboration, which is an international network of top scholars interested in the genetics of speech and language. Simon Fisher, director of the MPI, and a number of his colleagues, from from a variety of nations throughout the world, established the collaboration.

The researchers were able to merge the data from 22 distinct cohorts that were gathered all across the world. Although the majority of participants spoke English, a few of them came from countries where other languages were used at home (Dutch, Spanish, German, Finnish, French and Hungarian).

The huge sample sizes, which can include as many as 34,000 individuals per trait, make it possible to evaluate the effects of several million common DNA variations, each of which has a very small effect size, using approaches that have previously been effectively applied to biological characteristics.

Reading and language skills

The researchers had previously evaluated the reading and language-related abilities of the individuals in each cohort using a wide variety of different tests. Reading aloud of words (horse) or pronounceable nonwords (chove) and spelling were three of the abilities that were engaged in this process.

To evaluate a person’s phoneme awareness, you can ask them to eliminate sounds from words (for example, “say stop without the s”) or to make spoonerisms (for example, “Paddington Bear—Baddington Pear”). Phoneme awareness is the capacity to differentiate and modify spoken sounds in words.

People are asked to repeat spoken nonwords of varied durations and complexity (loddernapish) in tests of nonword repetition. This is a task that assesses speech perception, verbal short-term memory, and articulation.

Because DNA was also available for all of the cohorts, the GenLang team was able to conduct what is known as a genome-wide association analysis (GWAS). The group investigated whether the DNA variations implicated with the five talents overlapped with each other as well as with other cognitive and brain imaging aspects using genetic correlation analysis.

“If we can uncover the biological bases of skills involved in speaking and reading, we may learn more about how language evolved in our species,” explains Eising.

“In addition, we can better understand why there are individual differences in these skills, even in societies where most people receive similar high quality education towards literacy and language.”

Reappraising the field

According to the findings of the GenLang study, the five reading- and language-related characteristics have a strong connection at the genetic level, which suggests that they have similar biological foundations. Although there was evidence of genetic overlaps with overall cognitive capacity (including verbal and nonverbal skills), associations with nonverbal IQ were modest. [Citation needed] [Citation needed]

The group was not successful in confirming past findings from far more limited research. According to Eising, “We have a strong suspicion that quite a few of the previously reported candidate gene connections with reading- and language-related qualities in studies with small samples are false-positive findings.”

The researchers discovered a genetic connection with individual variances in the neuroanatomy of a region of the brain that is associated with language; specifically, the left superior temporal sulcus. It is well established that this particular area of the brain, in conjunction with other regions, plays a significant role in the processing of both spoken and written language. There was also a genetic connection with some regions of the DNA that are responsible for regulatory functions in the developing brain of the fetus.

Nature intertwined with nurture

“This research shows the considerable value of team science approaches for understanding molecular genetic contributions to complex human traits like language,” concludes Fisher.

“The biology of reading- and language-related skills is highly complex. To develop these skills, exposure to language as well as education in reading are essential. Our work illustrates the intertwining of both nature and nurture in the development of language and literacy.”

“In the future, we hope to build on these efforts with genetically informative datasets covering a broader range of traits relevant for language, for instance including abilities related to grammatical processing.

“To more quickly and easily characterize reading and language skills in large groups of individuals, we will likely need development of tests that can be administered online, and this is a major focus of the GenLang consortium moving forward.”

Abstract

Genome-wide analyses of individual differences in quantitatively assessed reading- and language-related skills in up to 34,000 people

The ability to communicate verbally and in writing is one of the most essential aspects of being human. Heritability estimates for reading and language-related skills range from 30 to 80% based on twin studies, depending on the trait. Individual variations in reading and language-related skills are impacted by genetic variation. Investigations of the contributions of single-nucleotide polymorphisms (SNPs) have thus far been inadequate, despite the fact that the genetic architecture is complex, varied, and multifactorial.

We describe the results of a multicohort genome-wide association study (GWAS) that was conducted on samples ranging from 13,633 to 33,959 people aged 5 to 26 years old. The qualities that were studied were word reading, nonword reading, spelling, phoneme awareness, and nonword repetition.

At a gene that has not been related with either intellect or educational achievement, we found a genome-wide significant correlation with word reading (rs11208009, P = 1.098 * 10-8). The SNP heritability of all five reading and language-related characteristics was found to be high, accounting for 13–26% of the total trait variability.

A shared genetic factor was identified through genomic structural equation modeling as the primary contributor to the variation in word/nonword reading, spelling, and phoneme awareness. This factor only partially overlapped with the genetic variation that contributed to nonword repetition, intelligence, and educational attainment. The strength of the subsequent research was increased by the use of a multivariate GWAS of word/nonword reading, spelling, and phoneme awareness.

An examination of genetic correlations with neuroimaging characteristics revealed a connection with the surface area of the banks of the left superior temporal sulcus. This area of the brain is associated with the processing of both spoken and written language. Heritability was increased for genomic sites in the embryonic brain that regulate gene expression, as well as in chromosomal areas that lack Neanderthal variations.

These findings, taken as a whole, open up new lines of inquiry into the biological factors that contribute to distinctively human characteristics.