title: Alternatively used promoters and distinct elements direct tissue-specific expression of nephrin.
abstract: Nephrin, an essential component of the glomerular ultrafilter, the slit diaphragm, has also been found to be expressed in the central nervous system and pancreas. This study examined the regulation of the nephrin gene by analyzing the expression of different length nephrin promoter-lacZ reporter constructs in transgenic mice. An upstream segment between -4 kb and -4 bp was shown to be sufficient for driving expression in all three tissues. Surprisingly, a 5.7-kb construct lacking the transcription initiation site and the immediate upstream region of the gene could drive expression in the central nervous system. This led to the identification of a novel, alternatively used exon 1B located 1871 bp upstream of the ATG codon of the previously known first exon, now termed exon 1A. The existence and functionality of exon 1B was verified in nephrin knockout mice in which exon 1A is deleted. Deletion of exon 1B and its immediate surrounding sequence, introduced in the 4-kb promoter-lacZ reporter construct, abolished the expression of the transgene in pancreas and spinal cord but not in kidney and brain in transgenic mice. Analysis of five promoter-reporter gene constructs showed that regulatory elements driving expression encoded by exon 1A in kidney and brain are localized in the region between -4 kb and 2.1 kb.
authors.affiliation: Division of Matrix Biology, Department of Medical Biochemistry, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Olga
authors.initials: O
authors.lastname: Beltcheva
authors.forename: Sirpa
authors.initials: S
authors.lastname: Kontusaari
authors.forename: Sergueï
authors.initials: S
authors.lastname: Fetissov
authors.forename: Heli
authors.initials: H
authors.lastname: Putaala
authors.forename: Pekka
authors.initials: P
authors.lastname: Kilpeläinen
authors.forename: Tomas
authors.initials: T
authors.lastname: Hökfelt
authors.forename: Karl
authors.initials: K
authors.lastname: Tryggvason
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism; D001483:Base Sequence / Q000235:genetics; D002490:Central Nervous System / Q000378:metabolism; D004622:Embryo, Mammalian / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000235:genetics; D005091:Exons; D005786:Gene Expression Regulation; D018507:Gene Expression Regulation, Developmental; D008565:Membrane Proteins; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics / Q000502:physiology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D017385:Sequence Homology; D014018:Tissue Distribution
chemical_list: D008565:Membrane Proteins; D020033:Protein Isoforms; D011506:Proteins; C113267:nephrin