title: Sam68-like mammalian protein 2, identified by digital differential display as expressed by podocytes, is induced in proteinuria and involved in splice site selection of vascular endothelial growth factor.
abstract: Podocytes, the glomerular epithelial cells of the kidney, share important features with neuronal cells. In addition to phenotypical and functional similarities, a number of gene products have been found to be expressed exclusively or predominantly by both cell types. With the hypothesis of a common transcriptome shared by podocytes and neurons, digital differential display was used to identify novel podocyte-expressed gene products. Comparison of brain and kidney cDNA libraries with those of other organs identified Sam68-like mammalian protein 2 (SLM-2), a member of the STAR family of RNA processing proteins, as expressed by podocytes. SLM-2 expression was found to be restricted in the kidney to podocytes. In proteinuric diseases, SLM-2, a known regulator of neuronal mRNA splice site selection, was found significantly upregulated on mRNA and protein levels. Knockdown of SLM-2 by short interfering RNA in podocytes was performed to evaluate its biologic role. RNA splicing of vascular endothelial growth factor (VEGF), a key regulator of the filtration barrier and expressed as functionally distinct splice isoforms, was evaluated. VEGF(165) expression was found to be reduced by 25% after SLM-2 knockdown. In vivo, the glomerular expression of SLM-2 correlated with the mRNA levels of VEGF(165). This study demonstrates the power of digital differential display to predict cell type-specific gene expression by hypothesis-driven analysis of tissue cDNA libraries. SLM-2-dependent VEGF splicing indicates the importance of mRNA splice site selection for glomerular filtration barrier function.
authors.affiliation: Medizinische Poliklinik, Ludwig-Maximilians-University, Pettenkoferstrasse 8A, Munich, 80336, Germany. ccohen@med.uni-muenchen.de
authors.forename: Clemens D
authors.initials: CD
authors.lastname: Cohen
authors.forename: Peter P
authors.initials: PP
authors.lastname: Doran
authors.forename: Simone M
authors.initials: SM
authors.lastname: Blattner
authors.forename: Monika
authors.initials: M
authors.lastname: Merkle
authors.forename: Guo Q
authors.initials: GQ
authors.lastname: Wang
authors.forename: Holger
authors.initials: H
authors.lastname: Schmid
authors.forename: Peter W
authors.initials: PW
authors.lastname: Mathieson
authors.forename: Moin A
authors.initials: MA
authors.lastname: Saleem
authors.forename: Anna
authors.initials: A
authors.lastname: Henger
authors.forename: Maria P
authors.initials: MP
authors.lastname: Rastaldi
authors.forename: Matthias
authors.initials: M
authors.lastname: Kretzler
mesh_terms: D000818:Animals; D002460:Cell Line; D004847:Epithelial Cells / Q000502:physiology; D020869:Gene Expression Profiling; D015723:Gene Library; D006801:Humans; D007678:Kidney Glomerulus / Q000166:cytology / Q000502:physiology; D051379:Mice; D011507:Proteinuria / Q000378:metabolism*; D012326:RNA Splicing; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A / Q000502:physiology*
chemical_list: C486528:Khdrbs3 protein, mouse; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D042461:Vascular Endothelial Growth Factor A