Horizontal and vertical transfer of mouse endogenous retroviral DNA sequences in schistosomes

The in situ polymerase chain reaction (PCR) results revealed chat mouse typ e A and type C retroviral sequences were transmitted horizontally from the host to schistosomes. The signals to these retroviral sequences were observ ed in the nuclei of the mesenchymal and reproductive cells of 8-week Schist osoma japonicum. These signals were also detected in thr nuclei of the mese nchymal and reproductive cells and in the cytoplasm of the tegumental tuber cles of 24-week S. mansoni. Furthermore, mouse type A retroviral sequence w as detected in the DNA extracted from the cercariae of both species. Howeve r, mouse type C retroviral sequence and mouse type 2 Alu sequence (B2) sere difficult to detect in the cercarial DNA of either species. These findings may indicate that some host sequences are propagated in the schistosome pr ogeny, that is to say, not only horizontal but also vertical transfer of th e host gene may occur in schistosomes.