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Title: GENE EXPRESSION PROFILES OF TWO B-COMPLEX DISPARATE, GENETICALLY INBRED FAYOUMI CHICKEN LINES THAT DIFFER IN SUSCEPTIBILITY TO EIMERIA MAXIMA

Author
item Lillehoj, Hyun
item KIM, DUK KYUNG - VIS SCI ANRI, ARS
item KIM, CHUL HONG - VIS SCI ANRI, ARS
item LAMONT, SUSAN - ISU AMES,IA

Submitted to: Animal Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2008
Publication Date: 9/21/2008
Citation: Lillehoj, H.S., Kim, D., Kim, C., Lamont, S.J. 2008. Immune-related gene expression in two B-complex disparate, genetically inbred Fayoumi chicken lines that differ in susceptibility following Eimeria maxima infection. Animal Genetics. 87:433-443.

Interpretive Summary: Recently, explosion of animal genomics technology allowed complete genome sequencing of many agricultural animals including poultry and there are now more than 580,000 chicken EST sequences from a wide variety of tissues and developmental stages publicly available (http://www.tigr.org/tdb/tgi/). Therefore, application of high-throughput genomic analyses is allowing the identification of transcriptional regulations involved in the immune response and large-scale gene expression profiles of host responses to infection provide enormous information of the interactions between pathogens and the host immune system. The Fayoumi breed, which originated in Egypt, was imported to the United States in 1954 primarily because of its reported resistance to the avian leukosis. In this paper, we investigated two sublines of chickens which are derived from the original Fayoumi breed. Thw two lines, M5.1 and M15.2 congenic pair of lines share an identical genetic background and differ only in the microchromosome bearing the major histocompatibility complex (MHC) and show different disease susceptibility to Eimeria parasites, which is causing more than $ 3.2 million annual economic loss. The present study was conducted by ARS scientists in collaboration with Iowa State University scientists to compare gene expression profiles between these two chicken congenic lines, which show a difference in disease resistance to coccidiosis, using our avian intestinal intraepithelial lymphocyte microarray (AVIELA). The AVIELA is specific for mucosal transcriptional investigations including immune response and the results showed that the changes in transcriptional regulation are increased during coccidiosis progress, and the higher number of differentially expressed genes arises because the more susceptible line has great pathology, which induces the gene-expression changes. These findings will help poultry industry to devise a genetic selection strategy to improve genetic disease resistance to intestinal parasites of broiler birds.

Technical Abstract: This study was conducted to discriminate the gene expression profiles following Eimeria maxima infection between two B complex congenic lines (lines M5.1 and M15.2) of Fayoumi chickens which display differences in disease resistance and innate immunity against avian coccidiosis. A cDNA microarray, constructed from 10,162 elements including 9,668 EST of chicken intestinal intraepithelial lymphocytes (IEL), was used to compare the transcript levels in IELs of the M5.1 and M15.2 lines from uninfected and E. maxima infected birds. When compared to uninfected controls and using a cutoff of > 2.0-fold alteration (P < 0.05), M5.1 demonstrated altered expression of 1 (down-regulated), 12 (6 up, 6 down), and 18 (5 up, 13 down) mRNAs at 3, 4, and 5 days post-infection respectively. In the M15.2 line, altered expression was observed in 6 (3 up, 3 down), 29 (11 up, 18 down), and 32 (8 up, 24 down) transcripts at the 3 time points, compared with uninfected controls. Comparison of the expression levels between M5.1 and M15.2 chickens following E. maxima infection revealed alterations in 32 (10 up, 22 down), 98 (43 up, 55 down), and 92 (33 up, 59 down) mRNAs at the 3 time points. Functional analysis using Gene Ontology categorized the genes exhibiting the different expression pattern between two chicken lines into several GO terms including immunity and defense. In summary, transcriptional profiles showed that more gene expression changes occurred with E. maxima infection in the M15.2 than the M5.1 line. The most gene expression differences between the two chicken lines were exhibited at days 4 and 5 following E. maxima infection. The results of this study are a foundation of future studies to comprehend the innate immune system in the chicken gut and develop the strategy against avian coccidiosis.