Ileal lipid-binding protein (Illbp) gene maps to mouse chromosome 11

• Published in: Mammalian genome 1994-12, Vol.5 (12), p.805-806
• Main Authors: Birkenmeier, E H, Rowe, L B, Crossman, M W, Gordon, J I
• Format: Article
• Language: English
• Subjects: Animals; Carrier Proteins - genetics; Carrier Proteins - metabolism; Chromosome Mapping - methods; DNA, Complementary; Fatty Acid-Binding Protein 7; Fatty Acid-Binding Proteins; Female; Gene Frequency; Ileum - cytology; Ileum - metabolism; Lipoproteins - metabolism; Male; Mammalia; Mice; Mice, Inbred C57BL; Neoplasm Proteins; Nerve Tissue Proteins; Organic Anion Transporters, Sodium-Dependent; Symporters
• ISSN: 0938-8990; 1432-1777
• DOI: 10.1007/BF00292019

Mouse ileal lipid-binding protein (ILBP) is a member of a family of intracellular fatty acid, retinoid, and bile acid binding proteins. This 128-residue protein is expressed only in differentiated members of the enterocytic lineage located in ileal villi. ILBP binds conjugated and unconjugated bile salts and appears to function as the cytosolic receptor for bile acids that have undergone sodium-dependent active transport by the ileal bile acid transporter (IBAT). Illbp has been used as a model system for studying axial patterning in the developing mouse intestine. Illbp is activated in a distal-to-proximal wave during a critical period in gut morphogenesis (E18-P28) when the crypts of Lieberkuehn form and establish their final stem cell hierarchy. Promoter mapping studies conducted in transgenic mice have shown that sequences located between -145 and the start site of Illbp transcription are sufficient to recapitulate this distal-to-proximal wave of gene activation in the ileum and to correctly direct expression to ileal villus-associated enterocytes. These studies have also disclosed several suppressor functions located between nucleotides -913 and -146. They include a temporal suppressor that delays gene activation until the third to fourth postnatal week, spatial suppressors that prohibit expression in the proximal ileum and allow expression in the proximal colon, and a cell lineage suppressor that prohibits expression in members of the intestine's goblet cell lineage during the perinatal period. We mapped Illbp to begin identifying additional genetic factors that might influence its temporal and spatial patterns of expression. A mouse Illbp cDNA clone was amplified by PCR with an upstream primer (+3 to +22 of the coding region) and a downstream primer (+377 to +358 of the coding region) to generate a fragment that includes codons encompassing amino acids 1 through 126. This 375-bp fragment was random-nonamer super(32)P-labeled to make probes for Southern blot hybridization. Southern blots containing a survey of restriction enzyme digests of inbred strain DNAs showed very little polymorphism. However, standard inbred strains were distinguishable from CAST and SPRET with several enzymes. The Illbp probe hybridized to one major band of approximately 5.2 kb and to a very faint minor band of 1.3 kb in TaqI digests of C57BL/6J DNA. In contrast, the strongly hybridizing band in SPRET/Ei DNA was 2.9 kb and a very faint second band was 0.7 kb. Therefore, 94 pro