Expression and phylogenetic analysis of human endogenous retrovirus HERV-W env family in brain tissues

A human endogenous retroviral family (HERV-W) has been related to multiple sclerosis associated retrovirus (MSRV) and schizophrenia associated retrovirus (SZRV) sequences. The HERV-W family was identified in the cerebrospinal fluids and brains of individuals with schizophrenia. Using cDNA libraries derived from human brains, we performed PCR amplification and identified new 16 HERV-W env elements (9 from human adult brain and 7 from human fetal brain). Those sequences showed a high degree of sequence similarity (89.2-99.6%) with HERV-W env (GenBank accession no. AF072506). Clones HB-1, HB-9 from adult brain and FB-2, FB-5 from fetal brain showed no frameshift and termination codons by deletion/insertion or point mutation. Synonymous and nonsynonymous calculation indicated that these sequences (HB-1, HB-9, FB-2, FB-5) could be associated with an active provirus in human brain tissues. In phylogenetic analysis, clones HB-1, HB-9, FB-2, FB-5 containing putative amino acid sequences showed sister relationship with the HERV-W and W-7-1 derived from human chromosome 7. Taken together, our data suggest that the related genes of the HERV-W env sequences are expressed in human brains and may contribute to an understanding of biological function connected to neuropsychiatric diseases.