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Characteristics of MHC Class I Genes in House Sparrows Passer domesticus as Revealed by Long cDNA Transcripts and Amplicon Sequencing.

In English

Författare

Summary, in English

In birds the major histocompatibility complex (MHC) organization differs both among and within orders; chickens Gallus gallus of the order Galliformes have a simple arrangement, while many songbirds of the order Passeriformes have a more complex arrangement with larger numbers of MHC class I and II genes. Chicken MHC genes are found at two independent loci, classical MHC-B and non-classical MHC-Y, whereas non-classical MHC genes are yet to be verified in passerines. Here we characterize MHC class I transcripts (α1 to α3 domain) and perform amplicon sequencing using a next-generation sequencing technique on exon 3 from house sparrow Passer domesticus (a passerine) families. Then we use phylogenetic, selection, and segregation analyses to gain a better understanding of the MHC class I organization. Trees based on the α1 and α2 domain revealed a distinct cluster with short terminal branches for transcripts with a 6-bp deletion. Interestingly, this cluster was not seen in the tree based on the α3 domain. 21 exon 3 sequences were verified in a single individual and the average numbers within an individual were nine and five for sequences with and without a 6-bp deletion, respectively. All individuals had exon 3 sequences with and without a 6-bp deletion. The sequences with a 6-bp deletion have many characteristics in common with non-classical MHC, e.g., highly conserved amino acid positions were substituted compared with the other alleles, low nucleotide diversity and just a single site was subject to positive selection. However, these alleles also have characteristics that suggest they could be classical, e.g., complete linkage and absence of a distinct cluster in a tree based on the α3 domain. Thus, we cannot determine for certain whether or not the alleles with a 6-bp deletion are non-classical based on our present data. Further analyses on segregation patterns of these alleles in combination with dating the 6-bp deletion through MHC characterization across the genus Passer may solve this matter in the future.

Publiceringsår

2013

Språk

Engelska

Sidor

8-21

Publikation/Tidskrift/Serie

Journal of Molecular Evolution

Volym

77

Issue

1-2

Dokumenttyp

Artikel i tidskrift

Förlag

Springer

Ämne

  • Biological Sciences

Nyckelord

  • MHC class I
  • House sparrow
  • Amplicon 454-sequencing
  • cDNA
  • Linkage

Status

Published

Projekt

  • Avian MHC genes

Forskningsgrupp

  • Molecular Ecology and Evolution Lab

ISBN/ISSN/Övrigt

  • ISSN: 0022-2844