|Brown, Wendy - WASHINGTON STATE UNIV|
Submitted to: Immunogenetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 8, 2005
Publication Date: December 5, 2005
Citation: Hoesing, L.M., Brown, W., Lewis, G.S., Knowles Jr, D.P. 2005. Identification and phylogenetic analysis of 15 MHC class II DRB1 B1 expressed alleles in a ewe-lamb flock. Immunogenetics. 57(11):855-863. Interpretive Summary: The Major Histocompatibility Complex (MHC) class II is a fundamental part of a host's immunogenetics. MHC class II is responsible for presenting exogenous and endogenous peptides to the immune system. Alleles or alternate gene copies of the Ovar-DRB1 loci are the most reported of the MHC class II loci in sheep. However, only a couple of Ovar-DRB1 alleles have been reported to be transcribed. We examined a ewe-lamb flock of 32 for transcribed Ovar-DRB1 alleles and discovered 4 new Ovar-DRB1 transcripts. These new Ovar-DRB1 transcripts were assigned new Ovar names based upon previously established Ovar nomenclature rules.
Technical Abstract: Ovar-DRB1 is part of the MHC class II of sheep and functions by presenting extracellular-derived peptides to the immune system. Although there are over 100 different Ovar-DRB1 DNA sequences reported in GenBank, only 2 Ovar-DRB1 mRNA sequences have been reported. Since there are examples of Ovar MHC II alleles that are not transcribed and/or translated, we evaluated Ovar-DRB1 mRNA encoding the peptide-binding site or the first domain ('1) of Ovar-DRB1 in a 32 ewe-lamb flock by using RT-PCR, cloning and sequencing. Sixteen new Ovar-DRB1 '1 cDNA sequences out of a total of 17 Ovar-DRB1 '1 cDNA sequences in an ewe-lamb flock of 32 sheep were identified. One Ovar-DRB1 '1 cDNA sequence was 100% identical to M93432, one of the two Ovar-DRB1 mRNA sequences reported in GenBank. Eleven of 16 Ovar-DRB1 '1 cDNA sequences were 100% identical to the corresponding previously reported Ovar-DRB1 genomic DNA sequences, indicating that these Ovar-DRB1 genomic DNA sequences are also transcribed. One of 5 of the remaining Ovar-DRB1 '1 cDNA sequences, DRB1*07012, had a synonymous substitution resulting in an identical deduced amino acid sequence to DRB1*0701. Four of the remaining 5 Ovar-DRB1 '1 cDNA sequences had nucleotide differences and subsequent deduced amino acid sequence differences when compared to known Ovar-DRB1 '1 genomic DNA sequences, and therefore, DRB1*0206, DRB1*0353, DRB1*0415, and DRB1*0142 represent new Ovar-DRB1 '1 expressed alleles. There is some discussion on whether specific Ovar-DRB1 alleles can be used as breed lineage markers.