Background Genetic association studies on populations of European origin have identified the DCDC2 gene as a susceptibility locus for developmental dyslexia.Here,we sought to investigate the association of DCDC2 polymorphisms with developmental dyslexia in children of Han Chinese origin.Methods We undertook a case-control genetic association study on 76 dyslexic children and 79 non-dyslexic matched controls.We isolated DNA from oral mucosal cell samples and genotyped two DCDC2 coding-sequence single nucleotide polymorphisms,rs2274305 and rs6456593,in each sample using SNaPshot single nucleotide extension.We compared the allele and genotype frequencies between the groups using the X2 test and analyzed the relationship between dyslexia and the polymorphism at both loci using unconditional logistic regression.We also predicted haplotypes and compared their frequencies between the two groups.Results The differences in the genotype distribution and the allelic genes of the two single nucleotide luci of the DCDC2 gene,rs2274305 and rs6456593,between the two dyslexic and non-dyslexic groups were statistically meaningless （P 〉0.05）.The differences in the haplotype distributions of the DCDC2 gene between the dyslexic and normal group were statistically meaningless （P 〉0.05）.Conclusion The DCDC2 gene may not be a susceptibility factor for developmental dyslexia among the Han Chinese.However,methodological issues may have prevented the detection of oositive associations.
The deficiency theories of dyslexia are quite contradictory and the cross-cultural studies in recent years mainly focused on whether the dyslexics among cultures shared the same cognitive profile or just based on the language.This study used Near-Infrared Spectroscopy (NIRS) imaging to measure the regional cerebral blood volume (BV) and the changes of cerebral activation in the left prefrontal cortex of 12 Chinese dyslexic children and their 12 age-matched normal controls during the Paced Vis-ual Serial Addition Test (PVSAT).Results showed that the scores of PVSAT of dyslexic children were significantly lower than those of the normal children (t=3.33,P<0.01).The activations of the left pre-frontal cortex in the normal group were significantly greater than those of dyslexic children (all P<0.01).Our results indicated that Chinese dyslexia had a general deficiency in working memory and this may be caused by the abnormal metabolic activity of brain blood volume in the left prefrontal cortex and the deficits in brain function might be the basis of neuropathology of Chinese dyslexia.Present study sup-ports the difference on brain activation of dyslexics from different languages may be caused by the same cognitive system related to reading.
