Endogenous viral genes are non-essential in the chicken

Abstract

DNA sequences homologous to the genomes of type C retroviruses are widespread among vertebrates. Ten genetic loci containing endogenous viral DNA sequences have been documented in the white Leghorn chicken alone. Six of these genetic loci are associated with the production of virus or of viral proteins in embryonic fibroblasts (refs 2--4, and S.M.A., L, B. Crittenden and E.G.B., in preparation) and one of the loci may be expressed in the erythroblasts of 5-day-old embryos. The abiquitous presence of endogenous viral genes among vertebrate species and the association of their expression with development of the haematopoietic system in the mouse have led to the proposal that these genes are involved in ontogeny. In addition, the genes may be implicated in oncogenesis as in the case of the AKR mouse in which a high incidence of spontaneous leukaemia is associated with the expression of endogenous murine laukaemia virus genomes. We report here the production of a fertile rooster which lacks avian leukosis virus-related endogenous viral genes and which seems to be completely normal and healthy. Thus, endogenous viral genes are apparently not essential for the normal development of the chicken. An endogenous virus-free state has also been reported for three species of jungle fowl and for the B-type viral genes of the mouse.

Novel endogenous retroviral sequences in the chicken genome closely related to HPRS-103 (subgroup J) avian leukosis virus.

“…ALVE2, expressing the prototype endogenous RAV-0 virus) can produce a complete genome (Hughes et al, 1981). The ALVE family of ERVs has been shown to be not essential for birds, as it was possible to breed a chicken line (line 0) free from these elements (Astrin et al, 1979). It was shown subsequently that the line 0 chicken genome contained several other independent Author for correspondence : K. Venugopal.…”

Comparative analysis of avian leukosis virus-related endogenous viral genes in experimental strains of the domestic chicken

“…After transfer, the membranes were washed with 2 x SSPE (Maniatis et al, 1982) (Lamont et al, 1992). Birds free of ev genes have already been described in a White Leghorn background (Astrin et al, 1979;Gavora et al, 1989 (Iraqi et al, 1991). This possibility was supported by the discovery of a slightly larger number of BamHI than SacI fragments within each line.…”

Open reading frame L1 of Marek's disease herpesvirus is not essential for in vitro and in vivo virus replication and establishment of latency.

“…MDV strain CVI988 was propagated in secondary chicken embryo fibroblasts (CEF) following established procedures. Primary CEF were prepared from chicken embryos free of endogenous avian leukosis virus (line ev0) (Astrin et al, 1979).…”