Alternative splicing variants and DNA methylation status of BDNF in inbred chicken lines.

Brain-derived neurotrophic factor (BDNF) has multiple alternative splicing variants and plays diverse biological functions in mammals, including neuronal survival, cholesterol metabolism, cell differentiation and tumor development. However, genomic structures of chicken BDNF (cBDNF) variants and its potential functions are still undefined. Here, we characterized two novel alternative splicing variants of cBDNF, cBDNF1 and cBDNF2, via combining comparative genomics methods and molecular techniques in inbred chicken line 6(3) and line 7(2), which have been developed to be resistant and susceptible, respectively, to Marek's disease tumor since 1939. Both cBDNFs consist of a bipartite transcript, with different 5' exons, exon I (298 bp) in cBDNF1 and exon II (286 bp) in cBDNF2, each of which is spliced to the common 3' exon IV. Exon I and IV are highly conserved between chicken and mammals, whereas exon II is unique for chicken. The amino acid sequence of cBDNF1 contains 8 additional amino acids in the N terminal compared to cBDNF2. cBDNF1 and cBDNF2 were only expressed in the hypothalamus among eight tissues, and cBDNF2 showed lower expression than that of cBDNF1 in both lines. The expression level of cBDNF1 was significantly higher in line 7(2) than in line 6(3) (P<0.01). Notably, the DNA methylation levels on the cis-regulatory region of cBDNF1 was negatively correlated with its expression level, which suggests that the mRNA expression level of cBDNF1 may be related to the DNA methylation status in the chickens. We also discussed a potential role of variant cBDNF1 in MD tumor resistance and susceptibility.

Development of an endogenous virus-free line of chickens susceptible to all subgroups of avian leukosis virus.

Primary chicken embryo fibroblasts (CEF) from special specific pathogen-free chicken lines are used for detection of contamination of adult or embryonic tissues, meconium, or tissue culture fluids with avian leukosis viruses (ALV). The suitability and efficiency of such tests depend on the susceptibility of CEF to the various subgroups of exogenous as well as endogenous ALV. The ideal CEF for such tests should be not only susceptible to all retroviruses, but also free of endogenous viruses so that such tests are immune to any interference that may occur between the endogenous and the tested (exogenous) viruses. CEF and/or chickens free of endogenous viruses are also desirable for gene transfer studies using retroviral vectors, such as RNA interference (RNAi) experiments and transgenic work. The absence of ev genes in CEF or chickens can empower clean detection of successful RNAi construct delivery or gene transfer. CEF free of ev genes are also essential reagents routinely used in growing and detecting unknown retroviruses in varied viral assays. This report documents the development of a new line of chickens, 0.TVB*S1, that is free of endogenous viruses and susceptible to all subgroups of ALV identified in chickens.

At least one YMHCI molecule in the chicken is alloimmunogenic and dynamically expressed on spleen cells during development.

Transcriptionally active, MHC class I (MHCI) loci are located in two separate polymorphic genomic regions in the chicken called B and Y. The YMHCI gene sequences encode molecules with uncommon substitutions in the antigen-binding region indicating that YMHCI molecules are likely unique and may bind a specialized form of antigen distinct from that of other antigen-binding MHCI molecules. To learn whether YMHCI gene expression results in the production of alloantigens at the cell surface, we immunized 15I(5) x 7(2) : chickens using syngeneic RP9 cells expressing transduced YF1w*7.1, a potentially alloimmunogenic YMHCI allele from the Y7 haplotype present in line C. The resulting antisera show that YF1w*7.1 MHCI molecules are immunogenic and expressed on the surfaces of cells in blood and spleen of line C chickens. Virtually all CD3+, CD4+, and CD8+ cells circulating in line C blood are positive, as are BU1+ cells. The YF1w*7.1 MHCI allele is dynamically expressed at levels comparable to but transcriptionally independent of classical BMHCI on erythrocytes, lymphocytes, granulocytes, monocytes, and thrombocytes within the spleen pre- and post-hatching. The antisera react with cells from two among four haplotypes segregating in closed populations of lines N and P. YMHCI shares features associated with both classical and non-classical MHCI. It is becoming increasingly likely that YMHCI has a fundamental role in avian immunity and thereby needs to be included in the growing spectrum of functionally active, diverse MHCI molecules no longer adequately described by the classical/non-classical dichotomy.

Response of white leghorn chickens of various B haplotypes to infection at hatch with subgroup J avian leukosis virus.

White leghorn chickens from seven 15.B congenic lines (genetically similar except for genes linked to the major histocompatibility complex [MHC] B haplotype) and two Line 0.B semicongenic lines were infected at hatch with strain ADOL Hc-1 of subgroup J avian leukosis virus (ALV-J). At 5, 8, 16, and 36 wk of age, chickens were tested for viremia, serum-neutralizing antibody, and cloacal shedding. Chickens were also monitored for development of neoplasia. In the 15.B congenic lines (B*2, B*5, B*12, B*13, B*15, B*19, and B*21) there were no significant differences in the incidence of viremia between B haplotypes. In fact, infection at hatch in all of the 15.B congenic lines induced tolerance to ALV-J because 100% of these chickens were viremic and transient circulating serum-neutralizing antibody was detected in only a few chickens throughout the 36 wk experiment. However, at 16 wk of age more B*15 chickens had antibody and fewer B*15 chickens shed virus than did the 16-wk-old B*2, B*5, or B*13 chickens. Moreover, compared with B*15 chickens, a higher percentage of B*13 chickens consistently shed virus from 8 wk postinfection to termination at 36 wk postinfection. The B haplotype had a transient effect on viral clearance in Line 0.B semicongenics, as more B*13 than B*21 chickens remained viremic through 5 wk of age. Very few (0%-18%) of the Line 0.B semicongenic chickens shed virus. By 36 wk of age, all Line 0 B*13 and B*21 chickens produced serum-neutralizing antibodies and cleared the virus. These results show that following ALV-J infection at hatch the immune response is influenced transiently by the B haplotype and strongly by the line of chicken. Although this study was not designed to study the effect of endogenous virus on ALV-J infection, the data suggest that endogenous virus expression reduced immunity to ALV-J in Line 15I5, compared with Line 0, a line known to lack endogenous virus genes.

2004 Nomenclature for the chicken major histocompatibility (B and Y) complex.

The first standard nomenclature for the chicken (Gallus gallus) major histocompatibility (B) complex published in 1982 describing chicken major histocompatibility complex (MHC) variability is being revised to include subsequent findings. Considerable progress has been made in identifying the genes that define this polymorphic region. Allelic sequences for MHC genes are accumulating at an increasing rate without a standard system of nomenclature in place. The recommendations presented here were derived in workshops held during International Society of Animal Genetics and Avian Immunology Research Group meetings. A nomenclature for B and Y (Rfp-Y) loci and alleles has been developed that can be applied to existing and newly defined haplotypes including recombinants. A list of the current standard B haplotypes is provided with reference stock, allele designations, and GenBank numbers for corresponding MHC class I and class IIbeta sequences. An updated list of proposed names for B recombinant haplotypes is included, as well as a list of over 17 Y haplotypes designated to date.

Response of white leghorn chickens of various genetic lines to infection with avian leukosis virus subgroup J.

In Experiment 1, chickens from various white leghorn experimental lines were inoculated with strain ADOL-Hcl of subgroup J avian leukosis virus (ALV-J) either as embryos or at 1 day of age. At various ages, chickens were tested for ALV-J induced viremia, antibody, and packed cell volume (PCV). Also, at 4 and 10 wk of age, bursal tissues were examined for avian leukosis virus (ALV)-induced preneoplastic lesions with the methyl green-pyronine (MGP) stain. In Experiment 2, chickens harboring or lacking endogenous virus 21 (EV21) were inoculated with strain ADOL-Hcl of ALV-J at hatch. All embryo-inoculated chickens in Experiment 1 tested positive for ALV-J and lacked antibody throughout the experimental period of 30 wk and were considered viremic tolerant, regardless of line of chickens. By 10 wk of age, the incidence of ALV-J viremia in chickens inoculated with virus at hatch varied from 0 (line 0 chickens) to 97% (line 1515); no influence of ALV-J infection was noted on PCV. Results from microscopic examination of MGP-stained bursal tissues indicate that ALV-J can induce typical ALV-induced transformation in bursal follicles of white leghorn chickens. Lymphoid leukosis and hemangiomas were the most common ALV-J-induced tumors noted in chickens in Experiment 1. At termination of Experiment 2 (31 wk of age), 54% of chickens harboring EV21 were viremic tolerant compared with 5% of chickens lacking EV21 after inoculation with ALV-J at hatch. The data indicate that genetic differences among lines of white leghorn chickens, including the presence or absence of EV21, can influence response of chickens to infection with ALV-J.