Multiple expressed MHC class II loci in salmonids; details of one non-classical region in Atlantic salmon (Salmo salar)

<p>Abstract</p> <p>Background</p> <p>In teleosts, the Major Histocompatibility Complex (MHC) class I and class II molecules reside on different linkage groups as opposed to tetrapods and shark, where the class I and class II genes reside in one genomic region. Several teleost MHC class I regions have been sequenced and show varying number of class I genes. Salmonids have one major expressed MHC class I locus (UBA) in addition to varying numbers of non-classical genes. Two other more distant lineages are also identifyed denoted L and ZE. For class II, only one major expressed class II alpha (DAA) and beta (DAB) gene has been identified in salmonids so far.</p> <p>Results</p> <p>We sequenced a genomic region of 211 kb encompassing divergent MHC class II alpha (<it>Sasa-DBA</it>) and beta (<it>Sasa-DBB</it>) genes in addition to NRGN, TIPRL, TBCEL and TECTA. The region was not linked to the classical class II genes and had some synteny to genomic regions from other teleosts. Two additional divergent and expressed class II sequences denoted DCA and DDA were also identified in both salmon and trout. Expression patterns and lack of polymorphism make these genes non-classical class II analogues. <it>Sasa-DBB</it>, <it>Sasa-DCA </it>and <it>Sasa-DDA </it>had highest expression levels in liver, hindgut and spleen respectively, suggestive of distinctive functions in these tissues. Phylogenetic studies revealed more yet undescribed divergent expressed MHC class II molecules also in other teleosts.</p> <p>Conclusion</p> <p>We have characterised one genomic region containing expressed non-classical MHC class II genes in addition to four other genes not involved in immune function. Salmonids contain at least two expressed MHC class II beta genes and four expressed MHC class II alpha genes with properties suggestive of new functions for MHC class II in vertebrates. Collectively, our data suggest that the class II is worthy of more elaborate studies also in other teleost species.</p

Effekt av botanisk sammensetning i surfôr på omsetning av fettløselige vitaminer i vom og overføring til melk

Det var en tilsynelatende netto økning av α-tokoferol i vomma mens omtrent halvparten av β-karoten ble brutt ned. Surfôr fra Kortvarig økologisk eng som inneholdt rødkløver ga melk med lavere innhold av fettløselige vitaminer enn de andre surfôrslagen

Comprehensive analysis of MHC class I genes from the U-, S-, and Z-lineages in Atlantic salmon

<p>Abstract</p> <p>Background</p> <p>We have previously sequenced more than 500 kb of the duplicated MHC class I regions in Atlantic salmon. In the IA region we identified the loci for the MHC class I gene <it>Sasa-UBA </it>in addition to a soluble MHC class I molecule, <it>Sasa-ULA</it>. A pseudolocus for <it>Sasa-UCA </it>was identified in the nonclassical IB region. Both regions contained genes for antigen presentation, as wells as orthologues to other genes residing in the human MHC region.</p> <p>Results</p> <p>The genomic localisation of two MHC class I lineages (Z and S) has been resolved. 7 BACs were sequenced using a combination of standard Sanger and 454 sequencing. The new sequence data extended the IA region with 150 kb identifying the location of one Z-lineage locus, <it>ZAA</it>. The IB region was extended with 350 kb including three new Z-lineage loci, <it>ZBA</it>, <it>ZCA </it>and <it>ZDA </it>in addition to a <it>UGA </it>locus. An allelic version of the IB region contained a functional <it>UDA </it>locus in addition to the <it>UCA </it>pseudolocus. Additionally a BAC harbouring two MHC class I genes (UHA) was placed on linkage group 14, while a BAC containing the S-lineage locus <it>SAA </it>(previously known as <it>UAA</it>) was placed on LG10. Gene expression studies showed limited expression range for all class I genes with exception of <it>UBA </it>being dominantly expressed in gut, spleen and gills, and <it>ZAA </it>with high expression in blood.</p> <p>Conclusion</p> <p>Here we describe the genomic organization of MHC class I loci from the U-, Z-, and S-lineages in Atlantic salmon. Nine of the described class I genes are located in the extension of the duplicated IA and IB regions, while three class I genes are found on two separate linkage groups. The gene organization of the two regions indicates that the IB region is evolving at a different pace than the IA region. Expression profiling, polymorphic content, peptide binding properties and phylogenetic relationship show that Atlantic salmon has only one MHC class Ia gene (<it>UBA</it>), in addition to a multitude of nonclassical MHC class I genes from the U-, S- and Z-lineages.</p

Genomic Organization of Duplicated Major Histocompatibility Complex Class I Regions in Atlantic Salmon (Salmo Salar)

Background: We have previously identified associations between major histocompatibility complex(MHC) class I and resistance towards bacterial and viral pathogens in Atlantic salmon. To evaluate if onlyMHC or also closely linked genes contributed to the observed resistance we ventured into sequencing ofthe duplicated MHC class I regions of Atlantic salmon.Results: Nine BACs covering more than 500 kb of the two duplicated MHC class I regions of Atlanticsalmon were sequenced and the gene organizations characterized. Both regions contained the proteasomecomponents PSMB8, PSMB9, PSMB9-like and PSMB10 in addition to the transporter for antigen processingTAP2, as well as genes for KIFC1, ZBTB22, DAXX, TAPBP, BRD2, COL11A2, RXRB and SLC39A7. TheIA region contained the recently reported MHC class I Sasa-ULA locus residing approximately 50 kbupstream of the major Sasa-UBA locus. The duplicated class IB region contained an MHC class I locusresembling the rainbow trout UCA locus, but although transcribed it was a pseudogene. No other MHCclass I-like genes were detected in the two duplicated regions. Two allelic BACs spanning the UBA locushad 99.2% identity over 125 kb, while the IA region showed 82.5% identity over 136 kb to the IB region.The Atlantic salmon IB region had an insert of 220 kb in comparison to the IA region containing threechitin synthase genes.Conclusion: We have characterized the gene organization of more than 500 kb of the two duplicatedMHC class I regions in Atlantic salmon. Although Atlantic salmon and rainbow trout are closely related,the gene organization of their IB region has undergone extensive gene rearrangements. The Atlanticsalmon has only one class I UCA pseudogene in the IB region while trout contains the four MHC UCA, UDA,UEA and UFA class I loci. The large differences in gene content and most likely function of the salmon andtrout class IB region clearly argues that sequencing of salmon will not necessarily provide informationrelevant for trout and vice versa

Physical mapping of MHC class I and class II in Atlantic salmon

In contrast to the mammalian major histocompatibility complex (MHC), where the MHC class I and class II loci reside in close vicinity to one another, the bony fishes have unlinked MHC class I and class II. Previous studies in Atlantic salmon have shown specific class I and class II genotypes of MHC that contribute to disease resistance. To learn more about MHC genomics in Atlantic salmon, bacterial artificial chromosome (BAC) clones positive for class I and class II probes were isolated. BAC contig maps of the Atlantic salmon MHC class I and class II regions were constructed and one selected BAC clone from each region was sequenced. BAC clone sequencing reveals an Atlantic salmon classical class Ia genomic region of ~150 kb encompassing the class I UBA locus, the proteosome subunits LMP7, MECL1, LMP2, the transport associated protein TAP2, and the non-immune genes BRD2 (RING3), COLL11A2 and ZNF297. Additionally, the class II like genomic region of ~210 kb encompassed potential class II pseudogenes DAA and DAB, as well as the putative non-immune genes TIP41 and a von Willebrand factor. Unfortunately, the upstream class Ia and the classical class II regions are not represented in the Atlantic salmon BAC library used in this study. The data presented here correlates with the MHC class I arrangements found so far in other bony fish. The described organization may have implications for the underlying genetics governing viral and bacterial disease resistance in Atlantic salmon

Cows’ diet and milk composition

The effect of cows' diets on milk composition is discussed, focusing on those components of particular interest for human health. First dietary sources of fatty acids and their digestion and metabolism are reviewed. Then feeding factors affecting milk fat content and fatty acid composition are discussed, with emphasis on those factors related to forage and fat supplements. The effects of diet on protein content and composition and milk content of minerals and vitamins are reviewed. Feeding strategies for improving the nutritional quality of milk are summarized