| Summary: | The major histocompatibility complex (MHC) is a genomic region comprised of a linked
cluster of genes and gene families that play an important role in both the adaptive and
innate immune responses. Genes within the MHC have also been associated with
susceptibility and/or resistance to certain diseases, such as haemochromatosis, insulindependent
diabetes, and psoriasis. As a result of these associations the MHC is one the
most extensively studied regions of the mammalian genome. The MHCs of a wide
variety of species, such as human (HLA), mouse (H-2), pig (SLA), and cow (BoLA),
have been characterized with respect to gene content, genomic organization of class I,
class II, and class III regions, and comparative organization. Comparative analyses have
been useful in delineating the evolutionary development of the MHC.
While the MHC of many mammalian species has been investigated, little research has
been performed on the equine (Equus caballus) MHC. The equine MHC is referred to
as the equine lymphocyte antigen (ELA) complex and is located on chromosome
ECA20q. The research that has been done on ELA focused on identifying gene copy
number and genetic polymorphisms in the classical class I and class II genes. To better
characterize the gene content and organization of ELA, we isolated 103 bacterial
artificial chromosome (BAC) clones from a horse BAC library containing well
conserved genes found within mammalian MHCs. These BAC clones were assembled
into two sequence-ready ordered contigs that span the ELA complex. The first contig
which has a minimum tiling path of nine BAC clones contains the ELA class II region
and spans 800 kb. The class I and III regions are contained within the second contig
which has a 14 BAC clone minimum tiling path and spans 1.6 Mb. This study will
report on the construction of the two BAC contigs which span the ELA complex, and
characterization of the gene content and organization of the ELA complex.
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