Peptide localization and gene structure of cryptdin 4, a differentially expressed mouse paneth cell alpha-defensin.
Paneth cells in crypts of the small intestine express antimicrobial peptides, including alpha-defensins, termed cryptdins in mice. Of the known Paneth cell alpha-defensins, the cryptdin 4 gene is unique, because it is inactive in the duodenum and expressed at maximal levels in the distal small bowel (D. Darmoul and A. J. Ouellette, Am. J. Physiol. 271:G68-G74, 1996). With a cryptdin 4-specific antibody, immunohistochemical staining of ileal Paneth cells was strong and specific for cytoplasmic granules, demonstrating that this microbicidal peptide is a secretory product of Paneth cells in the distal small intestine. Consistent with the pattern of cryptdin 4 mRNA distribution along the length of the gut, the cryptdin 4 peptide was not detected in duodenum. Structurally, the cryptdin 4 gene resembles other Paneth cell alpha-defensin genes. Its two exons, transcriptional start site, intron, splice sites, and 3' flanking sequences are characteristic of the highly conserved mouse alpha-defensin genes. However, in the region upstream of the transcriptional initiation site, the cryptdin 4 gene contains a repeated 130-bp element that is unique to this alpha-defensin gene. Every independent cryptdin 4 genomic clone examined carries the repeated element, which contains putative recognition sequences for TF-IID-EIIA, cMyc-RS-1, and IgHC.2/CuE1.1; the repeat proximal to the start of transcription replaces DNA at the corresponding position in other mouse alpha-defensin genes. We speculate that this unique duplicated element may have a cis-acting regulatory role in the positional specificity of cryptdin 4 gene expression.
Ouellette
A J
AJ
Department of Pathology, College of Medicine, University of California, Irvine, California 92697, USA. aouellet@uci.edu
Darmoul
D
D
Tran
D
D
Huttner
K M
KM
Yuan
J
J
Selsted
M E
ME
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D007150:Immunohistochemistry; D007421:Intestine, Small / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D019879:Paneth Cells / Q000378:metabolism*; D011498:Protein Precursors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D017422:Sequence Analysis, DNA
D011498:Protein Precursors; C059569:cryptdin