Human endogenous retroviruses with transcriptional potential in the brain

Genetic studies of neuropsychiatric disorders have often produced conflicting results, which might partly result from the involvement of epigenetic modifications. We intended to explore the possible implication of DNA methylation and human endogenous retroviruses (HERVs) in neuropsychiatric disorders. In the present study, we identified two HERV loci that are expected to retain the transcriptional activity in the brain. One was located on chromosome 1q21-q22 and the other on 22q12. Interestingly, these regions were overlapped with or included in those of schizophrenia-susceptible loci, SCZD9 and SCZD4, respectively. Particularly, the HERV on 22q12 was located in the opposite direction 4 kb downstream of the Synapsin III gene. These HERV loci could afford clear targets for methylation and expression analyses in postmortem brains of patients with psychiatric disorders such as schizophrenia. In addition, we confirmed our previous finding that only a few of particular HERV-K loci were activated among a number of highly homologous loci in teratocarcinoma cell lines. These activated loci included ones common to all teratocarcinoma cell lines analyzed and depending on their male or female origin.