Segregation of EAV-HP Ancient Endogenous Retroviruses within the Chicken Population

Sacco, Melanie; Venugopal, K.

doi:10.1128/jvi.75.23.11935-11938.2001

Cited by 14 publications

(9 citation statements)

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“…The close genomic proximity (23 bp) of the different insertion sites, observed in Mapuche fowl and Dongxiang chicken, suggests a possible integration site preference for EAV-HP, as has been suggested for several retroviruses [22]. Active ongoing insertion and segregation of EAV-HP in chicken populations have been shown with a typical prevalence of 10 to 15 copies per genome [23], [24]. Such EAV-HP genome dynamism is thought to play a recombinant role in the emergence of exogenous avian retrovirus ALV-J due to a uniquely similar env sequence with the ALV-J prototype HPRS-103 [23].…”

Section: Discussionmentioning

confidence: 68%

Endogenous Retrovirus EAV-HP Linked to Blue Egg Phenotype in Mapuche Fowl

et al. 2013

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Oocyan or blue/green eggshell colour is an autosomal dominant trait found in native chickens (Mapuche fowl) of Chile and in some of their descendants in European and North American modern breeds. We report here the identification of an endogenous avian retroviral (EAV-HP) insertion in oocyan Mapuche fowl and European breeds. Sequencing data reveals 100% retroviral identity between the Mapuche and European insertions. Quantitative real-time PCR analysis of European oocyan chicken indicates over-expression of the SLCO1B3 gene (P<0.05) in the shell gland and oviduct. Predicted transcription factor binding sites in the long terminal repeats (LTR) indicate AhR/Ar, a modulator of oestrogen, as a possible promoter/enhancer leading to reproductive tissue-specific over-expression of the SLCO1B3 gene. Analysis of all jungle fowl species Gallus sp. supports the retroviral insertion to be a post-domestication event, while identical LTR sequences within domestic chickens are in agreement with a recent de novo mutation.

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Section: Discussionmentioning

confidence: 68%

Endogenous Retrovirus EAV-HP Linked to Blue Egg Phenotype in Mapuche Fowl

et al. 2013

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“…This small proportion (approximately 8%) is suggestive of a genotype with both genes recessive and provides the first indication that ALV-J tolerance might be due to two unlinked yet interacting gene products. This result contradicts the previous hypothesis that tolerance develops from the expression of EAV-HP env peptides that provide epitopes for MHC presentation that are shared with ALV-J during lymphocyte negative selection (30)(31)(32)37 From a comparison of the two animal experiments described here, the development of immunological tolerance and development of the myeloid leukosis tumors typically induced by ALV-J appear to be determined by distinct genetic elements. None of the immunologically tolerant line 15I layer birds developed tumors throughout the duration of the experiment despite the fact that this line was originally selected for its susceptibility to lymphoid leukosis induction by other ALV subgroups (3).…”

Section: Discussioncontrasting

confidence: 55%

“…In our previous attempts to characterize EAV-HP proviruses from various chicken lines, particularly from meat-type chicken lines in which ALV-J may have arisen, we were unable to identify viruses that had intact provirus structures (5Ј-LTR-gag-pol-env-LTR-3Ј). Subsequent studies to find out the distribution of three specific provirus deletion loci revealed that these elements were segregating within the chicken population (32). This suggested that moreintact genomes may have eluded detection due to the chance selection of embryos from the outbred meat-type chicken lines.…”

Section: Resultsmentioning

confidence: 99%

“…on April 30, 2019 by guest http://jvi.asm.org/ pol reverse transcriptase region probe (31), was also included for further analysis, as this line harbors the spliced subgenomic transcript provirus designated ev/J clone 4-1 (28,32). Expression of this locus has not been examined, and the presence of this provirus may complicate analysis of the expression of spliced subgenomic transcripts derived from intact proviruses.…”

Section: Vol 78 2004 Eav-hp and Alv-j Retrovirus Interactions 10527mentioning

confidence: 99%

“…Southern blot hybridizations with env or LTR sequences have demonstrated that EAV-HP proviruses exist in the Gallus genus at approximately 10 to 15 copies per genome (30,35). Studies on the distribution of three EAV-HP proviruses in several inbred layer-type chicken lines demonstrated that the loci were present only in some of the lines, suggesting that they are still segregating within the outbred layer-type chicken population from which these homozygous lines were derived (32). A single EAV-HP provirus termed ev/J clone 4-1, with a structure comprising a DNA copy of the subgenomic env transcript flanked by LTRs, from a white leghorn layer-type chicken line has been previously described (28).…”

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confidence: 99%

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Assessing the Roles of Endogenous Retrovirus EAV-HP in Avian Leukosis Virus Subgroup J Emergence and Tolerance

Sacco¹,

Howes²,

Smith³

et al. 2004

J Virol

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Avian leukosis virus (ALV) subgroup J is thought to have emerged through a recombination event between an unknown exogenous ALV and the endogenous retrovirus elements designated EAV-HP. All EAV-HP elements identified to date in the chicken genome show large deletions, including that of the entire pol gene. Here we report the identification of four segregating chicken EAV-HP proviruses with complete pol genes, one of which shows exceptionally high sequence identity and a close phylogenetic relationship with ALV-J with respect to the env gene. Embryonic expression of EAV-HP env has been suggested as a factor associated with immunological tolerance induction in a proportion of ALV-J-infected meat-type chickens. In support of this, env gene transcripts expressed from two of the four newly identified EAV-HP proviruses were demonstrated in chicken embryos. However, when ALV-J-infected outbred meat-type chickens were assessed, the presence of intact EAV-HP proviruses failed to directly correlate with ALV-J tolerance. This association was further examined using F 2 progeny of two inbred lines of layer chicken that differed in EAV-HP status and immunological responses to ALV-J. Immunological tolerance developed in a small proportion of F 2 progeny birds, reflecting the expected phenotypic ratio for inheritance of a double-recessive genotype; however, the status of tolerance did not show any direct correlation with the presence of the intact EAV-HP sequence. Nevertheless, identification of an intact chicken EAV-HP locus showing a uniquely close relationship to the ALV-J prototype clone HPRS-103 in the env region provides the strongest evidence of its contribution to the emergence of ALV-J by recombination.The EAV-HP endogenous retroviruses are members of the ancient endogenous avian retrovirus (EAV) family identified in various species of the genus Gallus. The significance of EAV-HP elements was first recognized following the discovery of elements within the chicken genome with a high degree (Ͼ97%) of sequence identity to the env gene of the avian leukosis virus subgroup J (ALV-J), a new avian pathogen that emerged in the late 1980s (4). ALV-J was identified in the United Kingdom in 1988 as the causative agent of myeloid leukosis, which rapidly became a worldwide health and welfare problem in meat-type chickens (1,21,23,24). The env genes of ALV subgroups A to E are closely related, sharing around 80 to 85% nucleotide sequence identity with each other; the ALV-J env is more distantly related, demonstrating only 40% identity to members of these other subgroups (4). The higher sequence similarity of the ALV-J env to that of EAV-HP suggested that ALV-J emerged as a result of a recombination event between EAV-HP transcripts and genomic RNA of an exogenous ALV (4, 35).EAV-HP elements have a typical provirus structure consisting of 5Ј-long terminal repeat (LTR)-gag-pol-env-LTR-3Ј, and full-length EAV-HP proviruses have been detected in the Sonnerat's or gray jungle fowl (SJF; Gallus sonneratii) (31). In spite of the detection o...

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Neoplastic Diseases

2013

Diseases of Poultry

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Segregation of EAV-HP Ancient Endogenous Retroviruses within the Chicken Population

Cited by 14 publications

References 14 publications

Endogenous Retrovirus EAV-HP Linked to Blue Egg Phenotype in Mapuche Fowl

Endogenous Retrovirus EAV-HP Linked to Blue Egg Phenotype in Mapuche Fowl

Assessing the Roles of Endogenous Retrovirus EAV-HP in Avian Leukosis Virus Subgroup J Emergence and Tolerance

Neoplastic Diseases

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