Alternative splicing enables expression of functionally diverse protein isoforms. The structural and functional complexity of zinc-finger transcription factor ZBP-89 suggests that it may be among the class of alternatively spliced genes. We identified a human ZBP-89 splice isoform (ZBP-89δN), which lacks amino terminal residues 1-127 of the full-length protein (ZBP-89 FL). ZBP-89δN mRNA was co-expressed with its ZBP-89 FL cognate in gastrointestinal cell lines and tissues. Similarly, ZBP-89δN protein was expressed. To define its function in vivo, we generated ZBP-89δN knock-in mice by targeting exon 4 that encodes the amino terminus. Homozygous ZBP-89δN mice, expressing only ZBP-89δN protein, experienced growth delay, reduced viability and increased susceptibility to dextran sodium sulfate colitis. We conclude that ZBP-89δN antagonizes ZBP-89 FL function and that over-expression of the truncated isoform disrupts gastrointestinal homeostasis.
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