LMX1B is essential for the maintenance of differentiated podocytes in adult kidneys

Tillmann Burghardt, Jürgen Kastner, Hani Suleiman, Eric Rivera-Milla, Natalya Stepanova, Claudio Lottaz, Marion Kubitza, Carsten A. Böger, Sarah Schmidt, Mathias Gorski, Uwe De Vries, Helga Schmidt, Irmgard Hertting, Jeffrey Kopp, Anne Rascle, Markus Moser, Iris M. Heid, Richard Warth, Rainer Spang, Joachim WegenerClaudia T. Mierke, Christoph Englert, Ralph Witzgall

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

Mutations of the LMX1B gene cause nail - patella syndrome, a rare autosomal-dominant disorder affecting the development of the limbs, eyes, brain, and kidneys. The characterization of conventional Lmx1b knockout mice has shown that LMX1B regulates the development of podocyte foot processes and slit diaphragms, but studies using podocyte-specific Lmx1b knockout mice have yielded conflicting results regarding the importance of LMX1B for maintaining podocyte structures. In order to address this question, we generated inducible podocyte-specific Lmx1b knockout mice. One week of Lmx1b inactivation in adult mice resulted in proteinuria with only minimal foot process effacement. Notably, expression levels of slit diaphragm and basement membrane proteins remained stable at this time point, and basement membrane charge properties also did not change, suggesting that alternative mechanisms mediate the development ofproteinuria inthese mice. Cell biological and biophysical experiments with primary podocytes isolated after 1 week of Lmx1b inactivation indicated dysregulation of actin cytoskeleton organization, and time-resolved DNA microarray analysis identified the genes encoding actin cytoskeleton-associated proteins, including Abra and Arl4c, as putative LMX1B targets. Chromatin immunoprecipitation experiments in conditionally immortalized human podocytes and gel shift assays showed that LMX1B recognizes AT-rich binding sites (FLAT elements) in the promoter regions of ABRA and ARL4C, and knockdown experiments in zebrafish support a model in which LMX1B and ABRA act in a common pathway during pronephros development. Our report establishes the importance of LMX1 Binfully differentiated podocytes and argues that LMX1 Bisessential for the maintenance of an appropriately structured actin cytoskeleton in podocytes.

Original languageEnglish
Pages (from-to)1830-1848
Number of pages19
JournalJournal of the American Society of Nephrology
Volume24
Issue number11
DOIs
StatePublished - Nov 1 2013

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