Comprensión lectora, habilidades lingüísticas y decodificación en escolares con TEL

El propósito del presente trabajo es indagar sobre la comprensión lectora y su relación con la decodificación y con algunas habilidades lingüísticas (léxico, conciencia fonológica y discurso narrativo) en escolares con TEL. Para ello, se trabajó con 104 niños de 1° básico con un promedio de edad de 6 años 8 meses, que se distribuyeron en dos grupos: uno conformado por 51 escolares con TEL y el otro constituido por 53 niños con desarrollo típico de lenguaje (DT). Las habilidades que se evaluaron fueron léxico, conciencia fonológica, narración (comprensión y producción), decodificación y comprensión lectora. Los resultados mostraron que en los niños con TEL la comprensión lectora se correlacionó significativamente con el léxico y la decodificación. En el grupo con DT, además de advertir las mismas asociaciones, también se observó una relación entre conciencia fonológica y comprensión lectora. Los resultados confirman que la decodificación es una habilidad central para la comprensión lectora. Además, el nivel léxico aparece como la única habilidad lingüística que se asocia a la lectura comprensiva en el aprendizaje lector inicial de los niños con TEL

Candidate gene variant effects on language disorders in Robinson Crusoe Island

Robinson Crusoe Island is a geographically and socially isolated settlement located over 600km west of the Port of Valparíso, Chile. An unusually high incidence (30%) of the Chilean equivalent of developmental language disorder (TEL) has been reported in Islander children, with 90% of these affected children found to be direct descendants of a pair of original founder-brothers, therefore strongly suggesting a shared genetic basis. Here we utilise whole-genome sequencing to investigate potential underlying variants in a panel of thirty-four genes known to play a role in language disorders, in seven TEL affected and ten unaffected islanders. We use this targeted approach to look for rare, shared variants that may underlie the diagnosis of TEL in a Mendelian genetic model. We go on to test whether the overall burden of rare variants is enriched in individuals affected by TEL or with Islanders related to the founder-brother lineage. In the absence of explanatory rare variants, we further investigate these candidate genes within a complex model of inheritance, where inheriting a small number of moderate impact common variants may increase susceptibility of developing TEL. We examine if any variants segregate with affection status or with founder-brother-related status, and therefore may increase risk of developing a language disorder. Finally, we perform a pooled, gene-based tests to evaluate relationships between combined variation across candidate genes and TEL affection status. Here we report a comprehensive examination of genes directly implicated in language-related mechanisms to identify ‘low hanging fruit’ of causative monogenic Mendelian variants, and complex association model of increased susceptibility in developmental language disorder found on Robinson Crusoe Island

Family aggregation of language impairment in an isolated Chilean population from the Robinson Crusoe Island

Background: It has been reported that the inhabitants of the Chilean Robinson Crusoe Island have an increased frequency of Specific Language Impairment (SLI) or Developmental Language Disorder (DLD). Aims: In this paper, we aim to explore the familial aggregation of DLD in this community. Methods & procedures: We assessed the frequency of DLD amongst colonial children between the ages of 3 years and 8 years, 11 months (50 individuals from 45 nuclear families). Familial aggregation rates of language-disorder were calculated by assessing all available first-degree relatives (n= 107, 77 parents, 25 siblings, 5 half-siblings) of the probands. Outcomes & results: We found that 71% of the child population performed significantly below expected in measures of phonological production or expressive and receptive morphology. The majority of these children presented with severe expressive and/or receptive language difficulties. A quarter of language disordered probands primarily had phonological difficulties. Family members of affected probands, experienced a higher risk of language-disorder than those of typically-developing probands. This increased risk was apparent regardless of nonverbal IQ. Conclusions & implications: Our study substantiates the existence of a familial form of speech and language disorder on the Robinson Crusoe Island. Furthermore, we find that the familiality is stable regardless of non-verbal IQ, supporting the recent movement to reduce the importance of nonverbal IQ criterion in DLD diagnoses

La importancia de las dificultades fonológicas en el desempeño de la conciencia fonológica en niños con trastorno específico del lenguaje

Los objetivos de este trabajo fueron: a) establecer si los problemas fonológicos implican desempeños descendidos en la conciencia fonológica, y b) estudiar la posible relación entre las dificultades fonológicas y la conciencia fonológica. Para ello se trabajó con 25 niños con TEL expresivo y un grupo control constituido por 59 menores con desarrollo típico de lenguaje. Sus edades fluctúan entre 5,0 y 5,11 años. Todos pertenecían al nivel socioeconómico mediobajo y eran alumnos de escuelas públicas de Santiago de Chile. Los resultados indicaron que las dificultades fonológicas por sí solas no influyen en el desempeño de la conciencia fonológica. Sin embargo, cuando este problema fonológico coexiste con un déficit morfosintáctico los rendimientos en estas habilidades metalingüísticas aparecen descendidos. Además, se estableció que no existe relación entre el trastorno fonológico y la conciencia fonológica

The genetic population structure of Robinson Crusoe Island, Chile

Studies examining genetic conditions common in Latin America are highly underrepresented in the scientific literature. Understanding of the population structure is limited, particularly Chile, in part due to the lack of available population specific data. An important first-step in elucidating disease mechanisms in Latin America countries is to understand the genetic structure of isolated populations. Robinson Crusoe Island (RCI) is a small land mass off the coast of Chile. The current population of over 900 inhabitants are primarily descended from a small number of founders who colonized the island in the late 1800s. Extensive genealogical records can trace the ancestry of almost the entire population. We perform a comprehensive genetic analysis to investigate the ancestry of the island population, examining ancestral mitochondrial and Y chromosome haplogroups, as well as autosomal admixture. Mitochondrial and Y chromosome haplogroups indicated a substantial European genetic contribution to the current RCI population. Analysis of the mitochondrial haplogroups found in the present-day population revealed that 79.1% of islanders carried European haplogroups, compared to 60.0% of the mainland Chilean controls from Santiago. Both groups showed a substantially lower contribution of indigenous haplogroups than expected. Analysis of the Y chromosome haplogroups also showed predominantly European haplogroups detected in 92.3% of male islanders and 86.7% of mainland Chilean controls. Using the near-complete genealogical data collected from the RCI population, we successfully inferred the ancestral haplogroups of 16/23 founder individuals, revealing genetic ancestry from Northern and Southern Europe. As mitochondrial and Y investigations only provide information for direct maternal and paternal lineages, we expanded this to investigate genetic admixture using the autosomes. Admixture analysis identified substantial indigenous genetic admixture in the RCI population (46.9%), higher than that found in the Santiago mainland Chilean controls (43.4%), but lower than a more representative Chilean population (Chile_GRU) (49.1%). Our study revealed the Robinson Crusoe Island population show a substantial genetic contribution for indigenous Chileans, similar to the level reported in mainland Chileans. However, direct maternal and paternal haplogroup analysis revealed strong European genetic contributions consistent with the history of the Island

The effects of reading and language intervention on literacy skills in children in a remote community: A randomized controlled trial

This study explored the effects of a 27-week reading and language intervention, for low-income children living in a remote Chilean community, using a randomized controlled trial. At the end of the intervention, children in the intervention group showed improvements compared to the waiting group on pre-literacy, reading, language, and reading comprehension measures (effect sizes d >.25). The gains in pre-literacy skills, word reading and word knowledge were maintained at 9-month delayed follow-up, though the improvements in language and reading comprehension were not. Intervention programs designed to support literacy and language skills in remote communities can be delivered successfully by trained assistants. Our findings suggest that language and literacy programs can be useful for improving attainment in children living in disadvantaged and isolated communities

Genome-wide analysis of genetic susceptibility to language impairment in an isolated Chilean population

Specific language impairment (SLI) is an unexpected deficit in the acquisition of language skills and affects between 5 and 8% of pre-school children. Despite its prevalence and high heritability, our understanding of the aetiology of this disorder is only emerging. In this paper, we apply genome-wide techniques to investigate an isolated Chilean population who exhibit an increased frequency of SLI. Loss of heterozygosity (LOH) mapping and parametric and non-parametric linkage analyses indicate that complex genetic factors are likely to underlie susceptibility to SLI in this population. Across all analyses performed, the most consistently implicated locus was on chromosome 7q. This locus achieved highly significant linkage under all three non-parametric models (max NPL=6.73, P=4.0 × 10−11). In addition, it yielded a HLOD of 1.24 in the recessive parametric linkage analyses and contained a segment that was homozygous in two affected individuals. Further, investigation of this region identified a two-SNP haplotype that occurs at an increased frequency in language-impaired individuals (P=0.008). We hypothesise that the linkage regions identified here, in particular that on chromosome 7, may contain variants that underlie the high prevalence of SLI observed in this isolated population and may be of relevance to other populations affected by language impairments

Correction: Exome Sequencing in an Admixed Isolated Population IndicatesNFXL1 Variants Confer a Risk for Specific Language Impairment

Children affected by Specific Language Impairment (SLI) fail to acquire age appropriate language skills despite adequate intelligence and opportunity. SLI is highly heritable, but the understanding of underlying genetic mechanisms has proved challenging. In this study, we use molecular genetic techniques to investigate an admixed isolated founder population from the Robinson Crusoe Island (Chile), who are affected by a high incidence of SLI, increasing the power to discover contributory genetic factors. We utilize exome sequencing in selected individuals from this population to identify eight coding variants that are of putative significance. We then apply association analyses across the wider population to highlight a single rare coding variant (rs144169475, Minor Allele Frequency of 4.1% in admixed South American populations) in the NFXL1 gene that confers a nonsynonymous change (N150K) and is significantly associated with language impairment in the Robinson Crusoe population (p = 2.04 × 10–4, 8 variants tested). Subsequent sequencing of NFXL1 in 117 UK SLI cases identified four individuals with heterozygous variants predicted to be of functional consequence. We conclude that coding variants within NFXL1 confer an increased risk of SLI within a complex genetic model