T1783 Kif26a-Deficient Mice Develop Megacolon Associated with Dysfunction of Enteric Neuronal Cells in the Colon

Abstract

BACKGROUND AND AIMS: Kinesin superfamily proteins (KIFs) are motor proteins that transport organelles and macromolecules along microtubules. Recent reports have revealed that a total of 45 KIFs have been identified in the mouse and human genomes. Dysfunctions of KIFs underlie some human diseases. These findings have prompted us to elucidate the role of KIF26A in the gastrointestinal systems, physiological functions of which remained totally unknown. METHODS: RT-PCR and in situ hybridization (ISH) were performed for detecting expression levels of mRNA. Kif26a gene knockout mice were generated using C57BL/6 mice by deletion of consensus motif for kinesin in KIF26A molecule (exons 711). Hematoxylin-eosin (HE) staining and Masson's trichrome staining were performed for exploring histological findings. Small intestinal transit was assessed by 13C breath test and charcoal method. The Magnus method was performed for examining contraction ability of the excised colonic tissues. RESULTS: RT-PCR using total RNA extracted from tissues of the wild-type mice revealed that kif26a mRNA is highly expressed in the brain, skeletal muscle, and colon. In contrast, very low expressions were detected in the liver, stomach, jejunum, and ileum. ISH for elucidating distribution of kif26a in the wild-type colonic tissues revealed that kif26amRNA was exclusively expressed in neuronal cells both in the Meissner's plexus and the Auerbach's plexus. Kif26a-/mice were viable but half of them died before 8 weeks after birth. Intriguingly, kif26a-/mice developed megacolon by age 4-8 wk, whereas the morphology of the stomach and the small intestines were unchanged. HE staining and Masson's trichrome staining showed neither infiltration of inflammatory cells nor overaccumulation of connective tissues in the colon of kif26a-/mice. 13C breath test and charcoal method showed no differences in the small intestinal transit between the wild-type and the homozygous mutant mice. Finally, the Magnus method revealed that contraction ability of the colonic tissues of kif26a-/mice by administration of acetylcholine was markedly disrupted as compared to those of the wild-type mice. CONCLUSIONS: To our knowledge, this is the first study demonstrating Kif26a-deficient mice develop megacolon. Deficiency of KIF26A is likely to bring about dysfunction of the enteric neuronal cells in the colonic tissues, followed by weakened contractions of the colon. We propose KIF26A play a critical role in maintenance of proper contractions of the colon. The mutant mice can be used to elucidate a novel pathogenesis for human colonic motility disorders.