Mutagenesis of the epithelial polarity gene, discs large 1, perturbs nephrogenesis in the developing mouse kidney.
BACKGROUND
During development of the permanent mammalian kidney (metanephros) several key epithelial events occur such as ureteric branching morphogenesis and nephrogenesis. One of the first stages of nephrogenesis involves the conversion of mesenchymal cells to epithelial cells, and thus the metanephros provides an excellent model to study epithelial polarization. The aim of this study was to investigate the role of the epithelial polarity gene, discs large 1 (dlg1), during development of the mouse kidney.


METHODS
We utilized mice with a gene trap vector insertion within dlg1 (dlg(gt)) resulting in a truncated Dlg1 protein, lacking the SH3, protein 4.1 and guanylate kinase-like (GUK) domains, fused to a LacZ reporter. These mice were used to analyze the expression of Dlg1 during kidney development, the subcellular localization of Dlg1 in epithelial cells, and the ability of Dlg1 to bind to calmodulin-associated serine/threonine kinase (CASK). Metanephric organ culture was used to study branching morphogenesis and nephrogenesis in wild-type and dlg(gt) mutant mice.


RESULTS
Dlg1 was expressed in ureteric and mesenchyme-derived epithelial cells during kidney development. Truncation of Dlg1 altered the normal basolateral localization of Dlg1 restricting it to the adherens junction. Due to the loss of the SH3 domain the binding capacity of Dlg1 to CASK was reduced. Nephrogenesis was altered in dlg(gt)/dlg(gt) metanephroi with a 30% decrease in nephron number.


CONCLUSIONS
Our results indicate that the loss of the SH3, protein 4.1 and/or GUK domains of Dlg1 disrupt epithelial polarity and perturb nephrogenesis either as a secondary consequence to a defect in ureteric branching morphogenesis and/or delay in mesenchyme-to- epithelial transition.
Naim
Eman
E
Department of Anatomy and Cell Biology, Monash University, Clayton, Victoria, Australia.
Bernstein
Alan
A
Bertram
John F
JF
Caruana
Georgina
G
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D016764:Cell Polarity / Q000502:physiology*; D000074288:Discs Large Homolog 1 Protein; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D051528:Guanylate Kinases; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008817:Mice, Mutant Strains; D016296:Mutagenesis; D009399:Nephrons / Q000002:abnormalities* / Q000166:cytology / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D009924:Organ Culture Techniques; D011247:Pregnancy; D017434:Protein Structure, Tertiary; D000074407:SAP90-PSD95 Associated Proteins; D014513:Ureter / Q000002:abnormalities* / Q000166:cytology / Q000502:physiology
D000074288:Discs Large Homolog 1 Protein; C000614189:Dlg1 protein, mouse; D009419:Nerve Tissue Proteins; D000074407:SAP90-PSD95 Associated Proteins; C106868:CASK kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D051528:Guanylate Kinases