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ARS Home » Southeast Area » Stoneville, Mississippi » Warmwater Aquaculture Research Unit » Research » Publications at this Location » Publication #174389
Title: GENOMIC ORGANIZATION OF THE CHANNEL CATFISH CD45 FUNCTIONAL GENE AND CD45 PSEUDOGENES

Author
item KOUNTIKOV, E - UNIV. OF MISS. MED. CTR.
item WILSON, M - UNIV. OF MISS. MED. CTR.
item Quiniou, Sylvie
item MILLER, N - UNIV. OF MISS. MED. CTR.
item CLEM, L - UNIV. OF MISS. MED. CTR.
item BENGTEN, E - UNIV. OF MISS. MED. CTR.

Submitted to: Immunogenetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2005
Publication Date: 5/3/2005
Citation: Kountikov, E., Wilson, M., Quiniou, S.M., Miller, N.W., Clem, L.W., Bengten, E. 2005. Genomic organization of the channel catfish cd45 functional gene and cd45 pseudogenes. Immunogenetics.

Interpretive Summary: In mammals, CD45 plays an important role in T and B lymphocyte cell receptor and cytokine signaling, however very little is known about its role in fish. In this study, the CD45 gene was characterized in channel catfish by DNA sequencing. The catfish genome contains one functional CD45 gene, which can be differentially expressed depending of the cell type and the level of activation of the cell. This information provides basic information toward a better understanding of the catfish immune system and its role in response to pathogens.

Technical Abstract: CD45 is a transmembrane protein tyrosine phosphatase, which in mammals plays an important role in T and B cell receptor and cytokine signaling. Recently a catfish cDNA was shown to contain all characteristic CD45 features: an alternatively spliced amino-terminus, a cysteine-rich region, three fibronectin domains, a transmembrane region and two phosphotyrosine phosphatase domains. However analyses of CD45 cDNAs from various catfish lymphoid cell lines demonstrated that catfish CD45 is unique in that it contains a large number of alternatively spliced exons. Sequence analyses of cDNAs derived from the catfish clonal B cell line 3B11 indicated that this cell line expresses up to thirteen alternatively spliced exons. Furthermore sequence similarity among the alternatively spliced exons suggested duplication events. To establish the exact number and organization of alternatively spliced exons, a Bacterial Artificial Chromosome (BAC) library was screened and the catfish functional CD45 gene plus six CD45 pseudogenes were sequenced. The catfish functional CD45 gene spans 32 kb and contains 49 exons. In comparison, the human and pufferfish CD45 genes consist of 34 and 30 exons, respectively. This difference in the otherwise structurally conserved catfish gene is due to the presence of 18 alternatively spliced exons that were likely derived through several duplication events. In addition, duplication events were also likely involved in generating the six pseudogenes, truncated at the 3' end. A similarly truncated CD45 pseudogene is also present in the pufferfish genome, suggesting this specific CD45 gene duplication occurred before catfish and pufferfish diverged (~400 million years ago).