Abstract
The colonial protochordate, Botryllus schlosseri, undergoes a natural transplantation reaction which is controlled by a single, highly polymorphic locus called the Fu/HC. We are using map-based cloning to identify Fu/HC gene(s), and have currently delineated their location to an approximately 1-cM region of the B. schlosseri genome. The Fu/HC physical map currently consists of 85 sequence-tagged sites mapped on a minimum tiling path of 800 kb which consists of five contigs, with four gaps remaining to be crossed, and is estimated to be 75% completed. Approximately half this region has been sequenced throughout the locus, allowing the first analysis of a metazoan histocompatibility locus outside of vertebrates. This has resulted in the identification of 18 predicted genes, a number of which have been found to be expressed. Several of these genes are well conserved among the chordates; however, none of the predicted or expressed genes are linked within the genome of any organism in the databases. In addition, the Fu/HC is one of the most polymorphic loci ever described, and physical mapping has revealed that the locus is quite dynamic, and includes features such as hotspots of recombination.
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Acknowledgements
We are indebted to Ron Davis, Audrey Southwick and Molly Miranda at the Stanford Genome and Technology Center for their generosity in the sequencing of large-insert clones. Fosmid sequencing is also being done at the University of Oklahoma Genome Center, under the auspices of the NIH-funded Genome Sequencing Network. We also thank David Ransom for tips and protocols on AFLP cloning. Kathi Ishizuka, Karla Palmeri and Vicki Tacaks have been responsible for B. schlosseri mariculture and breeding, and K. Palmeri has assisted in library screening. This work was supported by the NIH (RO1AI41588) to I.L.W. A.W.D. was an NIH postdoctoral scholar. Accession numbers for genomic sequence are: AC135107, AC139528, AC138022, AC140855, AC140856, AC139257, AC138953, AC139529 AC142501, AC136512, AC140854.
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De Tomaso, A.W., Weissman, I.L. Initial characterization of a protochordate histocompatibility locus. Immunogenetics 55, 480–490 (2003). https://doi.org/10.1007/s00251-003-0612-7
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DOI: https://doi.org/10.1007/s00251-003-0612-7