Case-control and family-based association studies between the neuregulin 1 (Arg38Gln) polymorphism and schizophrenia.

Genetic variations in the neuregulin 1 (NRG1), a critical gene in neuronal development, have been reported to be associated with schizophrenia in several reports. Association has been reported between a non-synonymous NRG1 polymorphism (Arg38Gln) and schizophrenia in a Chinese family-based association study; however, this finding is not yet confirmed by other research findings analyzed using independent sample. To replicate this finding and assess the association between age at onset of schizophrenia and the NRG1 Arg38Gln polymorphism, we investigated the prevalence of this polymorphism in a Chinese population (228 schizophrenic disorder patients and 269 controls). We were unable, however, to demonstrate a significant association between the NRG1 Arg38Gln polymorphism and schizophrenia (P = 0.869 for genotype and P = 0.597 for allelic frequencies) or age at onset (P = 0.940). Our family-based association study (15 schizophrenic bios and 221 schizophrenic trios) demonstrated 38Gln was transmitted in excess by the parent to the affected offspring (P = 0.052). However, this result contrasts with a previous finding in Chinese that 38Arg was transmitted in excess by the parent to the affected offspring. On the basis of the contrast between the findings of other study and our family-based study and the negative findings of our case-control association study, we conclude that NRG1 Arg38Gln polymorphism is not likely to play a major role in the pathogenesis of schizophrenia in Chinese populations.

Association study of a brain-derived neurotrophic-factor genetic polymorphism and mood disorders, age of onset and suicidal behavior.

Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin growth factor family, has been implicated in both mood disorders and suicidal behavior. This study has examined the association between the BDNF gene Val66Met polymorphism and mood disorders, age of onset and suicidal behavior in a Chinese sample population. The genotype and allele frequencies for the BDNF gene Val66Met polymorphism did not differ comparing depression groups (total, bipolar disorder or major depression) and control subjects. Furthermore, it was not demonstrated that this BDNF polymorphism was associated with age of onset or suicidal history in our mood disorder patients. Based on these results, it seems reasonable to suggest that this polymorphism is unlikely to play a major role in the genetic susceptibility to mood disorders. Given the fact that the positive association between BDNF gene Val66Met polymorphism and bipolar disorder has only been demonstrated for a Caucasian population but not for a Japanese analog or our Chinese sample, it appears likely that this association is ethnicity dependent.