GENOMIC CHARACTERIZATION OF NOVEL IMMUNOGLOBULIN-LIKE TRANSCRIPTS (NILTS) IN TELEOSTS
Dustin Wcisel, North Carolina State University
Dustin J. Wcisel1, Sean C. McConnell2, Jill L.O. de Jong2, Gary W. Litman3, and Jeffrey A. Yoder1,4
1. Functional Genomics Program, North Carolina State University, Raleigh, NC USA
2. Department of Pediatrics, The University of Chicago, Chicago, IL USA
3. Department of Pediatrics, University of South Florida Morsani College of Medicine, St. Petersburg, FL USA
4. Department of Molecular Biomedical Sciences, North Carolina State University, Raleigh, NC USA
The immunoglobulin (Ig) superfamily (IgSF) includes membrane bound and secreted proteins which possess one or more Ig domains that share core conserved residues and structural features with immunoglobulins (e.g. antibodies). Numerous IgSF members play significant roles in immune function and hundreds of IgSF members have been identified within genomes of various teleost fish species. For example, novel Ig-like transcripts (NILTs) that encode membrane bound proteins possessing one or two Ig domains have been identified in carp, salmon, and trout. Here, we investigate the NILT gene family in light of recent genome sequencing projects. We characterize NILT sequences in the zebrafish genome which encode a highly expanded and diverse cluster of NILTs compared to other teleost species. At least two gene content haplotypes are observed at a single locus on chromosome 1 within standard lab lines of zebrafish. Although numerous NILTs encode either activating or inhibitory signaling motifs, their cellular function remains undefined. Differential patterns of tissue expression and alternative mRNA splicing further expands the repertoire of NILTs. Utilizing spotted gar to bridge the gap between teleost and humans, we propose that NILTs may represent an alternative evolutionary pathway taken by the precursors of mammalian CD300/CMRF-35 and polymeric immunoglobulin receptor (pIgR) genes.