ARS | Publication request: Identification and Regulation of Rainbow Trout Tapasin and Tapasin-Related Genes

Submitted to: Immunogenetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 11, 2005
Publication Date: January 27, 2006
Citation: Landis, E.D., Palti, Y., Dekoning, J., Drew, R., Phillips, R.B., Hansen, J.D. 2006. Identification and regulation of rainbow trout tapasin and tapasin-related genes. Immunogenetics 58(1):56-69.

Interpretive Summary: The U.S. salmonid aquaculture industry suffers severe economic loss to diseases. Every year, viral epidemics in farmed Atlantic salmon and rainbow trout have resulted in production losses of greater than 90% accounting for millions of dollars of lost revenue. The major histocompatibility complex (MHC) is known as the gateway to immune responses and is involved in both adaptive and innate immunity. Efforts to use molecular technologies in the genetic improvement of agricultural species have recently included the genetic mapping of rainbow trout. Detailed mapping of the MHC in rainbow trout and the development of genetic markers for the different major histocompatibility (MH) regions will provide useful tools for genetic improvement of disease resistance in rainbow trout. Tapasin (TAPBP) is a key member of the MHC class IA antigen loading complex, bridging the class IA molecule to the transporter associated with antigen presentation (TAP). This report gives details on the identification, sequencing and molecular characterization of two rainbow trout MH class I Tapasin genes (Onmy-TAPBP.1 and .2) and a similar but distinct Tapasin-related gene (Onmy-TAPBP-R) that had previously only been described in mammals.

Technical Abstract: Tapasin (TAPBP) is a key member of the MHC class IA antigen loading complex, bridging the class IA molecule to the transporter associated with antigen presentation (TAP). As part of an on-going study of MHC genomics in rainbow trout, we have identified two rainbow trout Tapasin genes (Onmy-TAPBP.1 and .2) and a similar but distinct Tapasin-related gene (Onmy-TAPBP-R) that had previously only been described in mammals. Physical and genetic mapping indicates that Onmy-TAPBP.1 is on chromosome 18 in the MHC class Ia region and that Onmy-TAPBP.2 resides on chromosome 14 in the MHC class Ib region. There are also at least two copies of TAPBP-R, Onmy-TAPBP-R.1 and Onmy-TAPBP-R.2, located on chromosomes 2 and 3, respectively. Due to the central role of Onmy-TAPBP expression during acute viral infection, we have characterized the transcriptional profile and regulatory regions for both Onmy-TAPBP and Onmy-TAPBP-R. Transcription of both genes increased during acute infection with infectious hematapoeitic necrosis virus (IHNV) in a fashion indicative of interferon-mediated regulation. Promoter-reporter assays in STE-137 cells demonstrate that the trout TAPBP and TAPBP-R promoters respond to interferon regulatory factors, Onmy-IRF1 and Onmy-IRF2. Overall, TAPBP is expressed at higher levels than TAPBP-R in naïve tissues and TAPBP transcription is more responsive to viral infection and IRF1 and 2 binding.