Unfolding the genetic pathways of dyslexia in Asian population: A review

Construct validity of international literacy measures: implications for dyslexia across cultures

Construct validity is essential to evaluate the generalizability of findings on literacy and dyslexia. Operational definitions of reading literacy determine the measurement method, yielding territory or country-wide literacy rates. This practice echoes the norm in diagnosis and prevalence estimates of dyslexia. International Large-Scale Assessments (ILSA) of literacy such as the Programme for International Student Assessment (PISA) compare countries' performances in relation to how well their students are reading. In this paper, we reexamine the validity claims and evidence using the examples of countries in Southeast Asia-Indonesia, Malaysia and Thailand, purported to have high proportions of poor readers. The challenge of characterizing reading performance and designing suitable measures for valid international comparisons is similar across phases of reading development and proficiency. The importance of the specificity of scripts and languages for reading abilities and impairments is highlighted. We suggest ways in which researchers can approach the assessment of reading proficiency from a cross-cultural and an interdisciplinary perspective. These can foster contextual caveats for generating and interpreting evidence.

Do Genes Associated with Dyslexia of Chinese Characters Evolve Neutrally?

Dyslexia, or reading disability, is found to have a genetic basis, and several related genes have been reported. We investigated whether natural selection has acted on single nucleotide polymorphisms (SNPs) that were reported to be associated with risk/non-risk for the reading disability of Chinese characters. We applied recently developed 2D SFS-based statistics to SNP data of East Asian populations to examine whether there is any sign of selective sweep. While neutrality was not rejected for most SNPs, significant signs of selection were detected for two linkage disequilibrium (LD) regions containing the reported SNPs of GNPTAB and DCDC2. Furthermore, we searched for a selection target site among the SNPs in these LD regions, because a causal site is not necessarily a reported SNP but could instead be a tightly linked site. In both LD regions, we found candidate target sites, which may have an effect on expression regulation and have been selected, although which genes these SNPs affect remains unknown. Because most people were not engaged in reading until recently, it is unlikely that there has been selective pressure on reading ability itself. Consistent with this, our results suggest a possibility of genetic hitchhiking, whereby alleles of the reported SNPs may have increased in frequency together with the selected target, which could have functions for other genes and traits apart from reading ability.

Familial study of attentional and behavioural problems in children with Dyslexia and their first-degree relatives in Indian setting

BACKGROUND

Dyslexia is one of the common problems seen in children worldwide. There is high co-morbidity of dyslexia with attentional and behaviour problems which could have familial pattern. This study aims to compare the attentional and behavioural problems in children with dyslexia and their first-degree relatives with controls.

METHODS

This is a cross-sectional comparative study with single interview method in an out-patient setting. Formally diagnosed (ICD-10) cases of 30 children with specific reading disorder and 30 healthy matched controls and their first-degree relatives were assessed using scales in a single setting after application of inclusion and exclusion criteria.

RESULTS

The children with dyslexia had significantly more problems in the domains of selective attention and behavioural problems as compared to controls and the siblings of the cases had significant problems in selective attention but not in behavioural problems. Also, no difference was seen in ADHD symptoms of parents in cases and controls.

CONCLUSION

The results from our study are keeping with most of the published literature. We expect that this study will help in laying a good foundation for further studies with stronger methodologies incorporating molecular genetics.