RESUMO
OBJECTIVES: To identify factors that may be crucial for the initiation and progression of stone-induced injury in the developing mouse kidney by a prospective observational study using microarray analysis. Kidney stone diseases are common in premature infants, but the underlying molecular and cellular mechanisms are not fully defined. METHODS: Mice with adenine phosphoribosyltransferase deficiency develop 2,8-dihydroxyadenine (DHA) nephrolithiasis. The gene expression changes between Aprt(-/-) and Aprt(+/+) kidneys from newborn and adult mice were compared using Affymetrix gene chips. Targets of interest were further analyzed by quantitative real-time polymerase chain reaction and immunohistochemistry. RESULTS: We identified a set of genes that were differentially expressed in the developing kidney in response to DHA-induced injury. In 1-week-old Aprt(-/-) mice, the expression of Sprr2f and Clu was highly augmented and that of Egf was significantly decreased. We also observed that maturation-related gene expression changes were delayed in developing Aprt(-/-) kidneys, and immature Aprt(-/-) kidneys contained large numbers of intercalated cells that were blocked from terminal differentiation. CONCLUSIONS: This study presents a comprehensive picture of the transcriptional changes induced by DHA stone injury in the developing mouse kidney. Our findings help explain growth impairment in kidneys subject to injury during the early stages of development.
Assuntos
Adenina/análogos & derivados , Regulação da Expressão Gênica no Desenvolvimento , Rim/crescimento & desenvolvimento , Nefrolitíase/genética , Fatores Etários , Animais , Animais Recém-Nascidos , Camundongos , Análise em MicrossériesRESUMO
Laminins that possess three short arms contribute to basement membrane assembly by anchoring to cell surfaces, polymerizing, and binding to nidogen and collagen IV. Although laminins containing the alpha4 and alpha5 subunits are expressed in alpha2-deficient congenital muscular dystrophy, they may be ineffective substitutes because they bind weakly to cell surfaces and/or because they lack the third arm needed for polymerization. We asked whether linker proteins engineered to bind to deficient laminins that provide such missing activities would promote basement membrane assembly in a Schwann cell model. A chimeric fusion protein (alphaLNNd) that adds a short arm terminus to laminin through the nidogen binding locus was generated and compared with the dystrophy-ameliorating protein miniagrin (mAgrin) that binds to the laminin coiled-coil dystroglycan and sulfatides. alphaLNNd was found to mediate laminin binding to collagen IV, to bind to galactosyl sulfatide, and to selectively convert alpha-short arm deletion-mutant laminins LmDeltaalphaLN and LmDeltaalphaLN-L4b into polymerizing laminins. This protein enabled polymerization-deficient laminin but not an adhesion-deficient laminin lacking LG domains (LmDeltaLG) to assemble an extracellular matrix on Schwann cell surfaces. mAgrin, on the other hand, enabled LmDeltaLG to form an extracellular matrix on cell surfaces without increasing accumulation of non-polymerizing laminins. These gain-of-function studies reveal distinct polymerization and anchorage contributions to basement membrane assembly in which the three different LN domains mediate the former, and the LG domains provide primary anchorage with secondary contributions from the alphaLN domain. These findings may be relevant for an understanding of the pathogenesis and treatment of laminin deficiency states.
Assuntos
Membrana Basal/química , Laminina/química , Modelos Biológicos , Proteínas Recombinantes de Fusão/química , Agrina/química , Agrina/genética , Agrina/metabolismo , Sequência de Aminoácidos , Animais , Membrana Basal/metabolismo , Colágeno Tipo IV/química , Colágeno Tipo IV/genética , Colágeno Tipo IV/metabolismo , Distroglicanas/química , Distroglicanas/genética , Distroglicanas/metabolismo , Humanos , Laminina/genética , Laminina/metabolismo , Glicoproteínas de Membrana/química , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Camundongos , Distrofias Musculares/genética , Distrofias Musculares/metabolismo , Ligação Proteica , Subunidades Proteicas/química , Subunidades Proteicas/genética , Subunidades Proteicas/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Células de Schwann/metabolismo , Deleção de SequênciaRESUMO
Laminins contribute to basement membrane assembly through interactions of their N- and C-terminal globular domains. To further analyze this process, recombinant laminin-111 heterotrimers with deletions and point mutations were generated by recombinant expression and evaluated for their ability to self-assemble, interact with nidogen-1 and type IV collagen, and form extracellular matrices on cultured Schwann cells by immunofluorescence and electron microscopy. Wild-type laminin and laminin without LG domains polymerized in contrast to laminins with deleted alpha1-, beta1-, or gamma1-LN domains or with duplicated beta1- or alpha1-LN domains. Laminins with a full complement of LN and LG domains accumulated on cell surfaces substantially above those lacking either LN or LG domains and formed a lamina densa. Accumulation of type IV collagen onto the cell surface was found to require laminin with separate contributions arising from the presence of laminin LN domains, nidogen-1, and the nidogen-binding site in laminin. Collectively, the data support the hypothesis that basement membrane assembly depends on laminin self-assembly through formation of alpha-, beta-, and gamma-LN domain complexes and LG-mediated cell surface anchorage. Furthermore, type IV collagen recruitment into the laminin extracellular matrices appears to be mediated through a nidogen bridge with a lesser contribution arising from a direct interaction with laminin.
