Characterization of Endogenous Retroviruses in Sheep

Abstract

Endogenous retrovirus (ERV) sequences have been found in all mammals. In vitro and in vivo experiments revealed ERV activation and cross-species infection in several species. Sheep (Ovis aries) are used for various biotechnological purposes; however, they have not yet been comprehensively screened for ERV sequences. Therefore, the aim of the study was to classify the ERV sequences in the ovine genome (OERV) by analyzing the retroviral pro-pol sequences. Three OERV ␤ families and nine OERV ␥ families were revealed. Novel open reading frames (ORF) in the amplified proviral fragment were found in one OERV ␤ family and two OERV ␥ families. Hybrid OERV produced by putative recombination events were not detected. Quantitative analysis of the OERV sequences in the ovine genome revealed no relevant variations in the endogenous retroviral loads of different breeds. Expression analysis of different tissues from fetal and pregnant sheep detected mRNA from both gammaretrovirus families, showing ORF fragments. Thus, the release of retroviruses from sheep cells cannot be excluded.

Identification and classification of feline endogenous retroviruses in the cat genome using degenerate PCR and in silico data analysis

“…Additionally, we tried to compare the family number of ERV c elements in cats with those of other species which have reported genome-level analysis results on ERV elements. However, the lack of whole genome sequence information during the previous studies (Klymiuk et al, 2002(Klymiuk et al, , 2003Löwer et al, 1996;Patience et al, 2001;Xiao et al, 2008a) and differences in analysis methods (Garcia-Etxebarria & Jugo, 2010) prevented us from further evaluating species differences in ERV c diversity.…”

“…Amplification was performed in 25 ml reactions containing 40 pmol of each primer, 200 mM dNTPs, PCR buffer [10 mM Tris (pH 8.3), 50 mM KCl, 1.5 mM MgCl 2 ], 100 ng of genomic DNA, and 2 U of Taq polymerase (SuperTherm; Roche). Six pairs of degenerate primers (Herniou et al, 1998;Klymiuk et al, 2002Klymiuk et al, , 2003Tristem et al, 1996) included two forward primers, PRO (59-GTK TTI KTI GAY ACI GGI KC-39) and MLV-PRO (59-YTI KTI GAY ACI GGI GCT SA-39), and three reverse primers, CT (59-AGI AGG TCR TCI ACR TAS TG-39), JO (59-ATI AGI AKR TCR TCI ACR TA-39), and EM (59-ATI AGI AKR TCR TCC ATR TA-39). PCR products were gel purified using the QIAquick Gel Extraction kit (Qiagen) and ligated into the pGEM-T Easy vector (Promega).…”

“…ERVs were also detected based on their homology to synthetic primer binding site probes (Kröger & Horak, 1987) as well as DNA hybridization and sequencing (Dunwiddie et al, 1986;Lueders & Kuff, 1980;Ono et al, 1985). Recently, sufficient data for phylogenetic analyses were successfully obtained by using PCR to directly amplify ERV sequences from the host genomic DNA of pigs (Klymiuk et al, 2002;Patience et al, 2001), sheep (Klymiuk et al, 2003), cattle (Garcia-Etxebarria & Jugo, 2010;Xiao et al, 2008b), dog (Jo et al, 2012) and other vertebrates (Herniou et al, 1998) Several endogenous retroviruses have been detected in the genome of domestic cats (Felis catus); these viruses include endogenous feline leukaemia virus (enFeLV) (Soe et al, 1983), RD-114, a C-type retrovirus (McAllister et al, 1972), MAC-1 primate retrovirus-related virus (Bonner & Todaro, 1979), ECE1 (Beyer et al, 1987), FcEV (van der Kuyl et al, 1999), FERVmlu1 and FERVmlu2 (Yuhki et al, 2008), and ERV-DC (Anai et al, 2012). However, detailed analysis regarding their structural variations, genome-level diversity and their relationships has not been addressed.…”

Oncogenic transformation by the jaagsiekte sheep retrovirus envelope protein

“…In addition, serum harvested from the C57BL/6 mice exposed to the AAV6 vector encoding JSRV Env is able to block transduction by a JSRV retroviral vector (Wootton et al, 2005), indicating that a host humoral immune response was indeed mounted against JSRV Env. In contrast, normal sheep are immunotolerant of JSRV and are susceptible to JSRV oncogenesis because of the presence and expression of several closely related endogenous retroviruses in their genomes (Hecht et al, 1996;Palmarini et al, 2000b;Sanna et al, 2002;Klymiuk et al, 2003;Spencer et al, 2003). Indeed, no humoral or cellular immune response has been detected against JSRV, either in the naturally occurring or experimentally induced sheep (Sharp and Herring, 1983;Palmarini et al, 1996;Ortin et al, 1998;Summers et al, 2002).…”

Avian sarcoma and leukosis virus gag gene in the Anser anser domesticus genome

“…In addition to genome data releases, more effective in silicon approaches were used to search the ERVs in the host genome, including Gallus gallus (Barr et al, 2005), Bos taurus (Garcia-Etxebarria and Jugo, 2010), and Meleagris gallopavo and Poephila guttata (Bolisetty et al, 2012). ERVs have been detected in major animals, including human (Martin et al, 1997), cattle (Zhang et al, 2008), chicken (Tereba et al, 1979), sheep (Klymiuk et al, 2003), and pig (Klymiuk et al, 2002), among others (Syomin and Ilyin, 2006). Although ERVs are important in evolution and disease studies, few studies have examined ERVs in the domestic goose.…”