Innovative Family-Based Genetically Informed Series of Analyses of Whole-Exome Data Supports Likely Inheritance for Grammar in Children with Specific Language Impairment

Individuals with specific language impairment (SLI) struggle with language acquisition despite average non-verbal intelligence and otherwise typical development. One SLI account focuses on grammar acquisition delay. The current study aimed to detect novel rare genetic variants associated with performance on a grammar assessment, the Test of Early Grammatical Impairment (TEGI), in English-speaking children. The TEGI was selected due to its sensitivity and specificity, consistently high heritability estimates, and its absence from all but one molecular genetic study. We performed whole exome sequencing (WES) in eight families with SLI (n = 74 total) and follow-up Sanger sequencing in additional unrelated probands (n = 146). We prioritized rare exonic variants shared by individuals with low TEGI performance (n = 34) from at least two families under two filtering workflows: (1) novel and (2) previously reported candidate genes. Candidate variants were observed on six new genes (PDHA2, PCDHB3, FURIN, NOL6, IQGAP3, and BAHCC1), and two genes previously reported for overall language ability (GLI3 and FLNB). We specifically suggest PCDHB3, a protocadherin gene, and NOL6 are critical for ribosome synthesis, as they are important targets of SLI investigation. The proposed SLI candidate genes associated with TEGI performance emphasize the utility of precise phenotyping and family-based genetic study.

Language phenotypes in children with autism spectrum disorder, expressive language disorder, and typical language development

The aim of this study was to compare language abilities in 4-6-year-old Georgian-speaking children with typical language development (TLD), expressive language disorder (ELD), and autism spectrum disorder (ASD). Language linguistic components, such as phonology, semantics, syntax, morphology, and pragmatics, were examined along with verbal behavior types like "mand," "tact," "echoic," and "intraverbal." Our sample comprised 148 children, with a gender distribution of 50 girls and 98 boys. Significant differences were observed in the application of various parts of speech across the three groups. Children with ELD were found to use pronouns more frequently compared to TLD and ASD groups. Conversely, children exhibiting typical language development displayed a greater usage of conjunctions and particles than the other groups. Notably, linguistic error patterns varied across groups: children with ELD predominantly committed errors in phonetics and morphosyntax, while children with ASD had more pragmatic errors and also struggled with morphosyntax. Moreover, the ASD group was found to use "mands" and "echoics" more frequently than both the TLD and ELD groups.

Language growth and genetics of specific language impairment

Behavioural studies of children with specific language impairment (SLI) have reported long-term growth outcomes across different dimensions of language. Genetic studies of children with SLI have identified candidate genes and putative associations of gene variants with SLI. The aims of this review are to summarize these two lines of investigation and to highlight the possible role of underlying growth timing mechanisms that influence the trajectory of language outcomes throughout childhood and into adolescence. Behavioural growth trajectories demonstrate that children with SLI have notable strengths in language acquisition, as well as limitations, across different dimensions of language. Language onset appears delayed, although the rate and pattern of change over time is similar to unaffected children. Growth rate decelerates early in adolescence for some dimensions of language. Genetic investigations reveal candidate genes that are known to influence neuronal development, and reveal possible gene interactions along a causal pathway. Epigenetic studies reveal other genetic influences implicated in the cognitive decline associated with ageing. This review highlights possible parallels between underlying genetic mechanisms and characteristics of linguistic growth trajectories. The conclusion is that new developmental perspectives are needed to inform language intervention in ways that align nurture with nature.