An isoform of ZBP-89 predisposes the colon to colitis

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-89(DeltaN)), which lacks amino terminal residues 1-127 of the full-length protein (ZBP-89(FL)). ZBP-89(DeltaN) mRNA was co-expressed with its ZBP-89(FL) cognate in gastrointestinal cell lines and tissues. Similarly, ZBP-89(DeltaN) protein was expressed. To define its function in vivo, we generated ZBP-89(DeltaN) knock-in mice by targeting exon 4 that encodes the amino terminus. Homozygous ZBP-89(DeltaN) mice, expressing only ZBP-89(DeltaN) protein, experienced growth delay, reduced viability and increased susceptibility to dextran sodium sulfate colitis. We conclude that ZBP-89(DeltaN) antagonizes ZBP-89(FL) function and that over-expression of the truncated isoform disrupts gastrointestinal homeostasis.