DFG Research Training Group "TJ-Train" (GRK 2318)
Tight junctions and their proteins
Molecular features and actions in health and disease

Project B3

Prof. Dr. Dominik Müller

Klinik für Pädiatrie m.S. Nephrologie, Charité - Universitätsmedizin Berlin,
Campus Virchow-Klinikum

The magnesiome, an integrative view of magnesium regulation


Background
: Knowledge about renal physiology and pathophysiology of Mg2+ handling has been broadened by the identification of mutations in humans causing Mg2+-related disorders as well as by the generation of different mouse models of disordered Mg2+ handling.

Hypothesis: We hypothesize that maintaining Mg2+ homeostasis in the kidney is regulated by para- and transcellular mechanisms acting tightly concerted via a crosstalk between the TAL and the DCT thereby integrating paracellular (tight junction) and transcellular pathways.
Aims: The project aims to elucidate local, regional and global mechanisms of renal Mg2+ regulation, establishing a network of Mg2+ regulation. Different sources of mouse models with normal and disordered Mg2+ regulation will be used (RNA, protein) to identify differential regulation.

Methods: In this project, we will use our mouse models (deficient in Cldn16, Cldn10, Cldn10/16 and recently generated, Cnnm2) together with patient data to generate an integra-tive view on magnesium homeostasis, the ‚magnesiome‘. To reach this goal, we will pheno- and genotype the mentioned mouse models, which display hypo-, normo- or even hy-permagnesemia. Analysis will include RNAseq and ChiP analysis. Further, we aim to identify and characterize proteins interacting with claudin-16, claudin-10, claudin-10/-16 and Cnnm2 by protein affinity purification and SILAC (stable isotope labelling by amino acids in cell culture). Subsequently, patients of our large cohort with so far unexplained Mg2+ deficiency will be screened for mutations in the genes or transcripts of the identified proteins.

Thesis project: Upon completion of this project, the successful candidate will finally be able to conduct phenotyping and genotyping with special emphasis on renal homeostasis of mouse models. RNASeq and CHiP analysis will be performed as well as Proteomic studies. The data generated will then be analysed and assembled by means of bioinformatics tools in order to provide common pathways of Mg2+ homeostasis but also identify crucial variations in specific disorders.

Suggested reading: See Project-related publications, especially Refs. 4, 5, 7, and 11

PhD doctoral student

  • Murat Seker

Project-related publications

Note to TJ-Train students: If a paper is not accessible, please mail to  

  1. Corral-Rodríguez MA, Stuiver M, Abascal-Palacios G, Diercks T, Oyenarte I, Ereño-Orbea J, Ibáñez De Opakua A, Blanco FJ, Encinar JA, Spiwok V, Terashima H, Accardi A, Müller D, Martinez-Cruz LA (2014) Nucleotide binding triggers a conformational change of the CBS module of the magnesium transporter CNNM2 from a twisted towards a flat structure. Biochem. J. 464: 23-34

  2. Kooij G, Kopplin K, Blasig R, Stuiver M, Koning N, Goverse G, van der Pol SM, van Het Hof B, Gollasch M, Drexhage JA, Reijerkerk A, Meij IC, Mebius R, Willnow TE, Müller D, Blasig IE, de Vries HE (2014) Disturbed function of the blood-cerebrospinal fluid barrier aggravates neuro-inflammation. Acta Neuropathol. 128: 267-277

  3. de Baaij JH, Stuiver M, Meij IC, Lainez S, Kopplin K, Venselaar H, Müller D, Bindels RJ, Hoenderop JG (2012) Membrane topology and intracellular processing of cyclin M2 (CNNM2). J. Biol. Chem. 287: 13644-13655

  4. Breiderhoff T, Himmerkus N, Stuiver M, Mutig K, Will C, Meij IC, Bachmann S, Bleich M, Willnow TE, Müller D (2012) Deletion of claudin-10 (Cldn10) in the thick ascending limb impairs paracellular sodium permeability and leads to hypermagnesemia and nephrocalcinosis. Proc. Natl. Acad. Sci. USA 109: 14241-14246

  5. Stuiver M, Lainez S, Will C, Terryn S, Günzel D, Debaix H, Sommer K, Kopplin K, Thumfart J, Kampik NB, Querfeld U, Willnow TE, Němec V, Wagner CA, Hoenderop JG, Devuyst O, Knoers NV, Bindels RJ, Meij IC, Müller D (2011) CNNM2, encoding a basolateral protein required for renal Mg2+ handling, is mutated in dominant hypomagnesemia. Am. J. Hum. Genet. 88: 333-343

  6. Milatz S, Krug SM, Rosenthal R, Günzel D, Müller D, Schulzke JD, Amasheh S, Fromm M (2010) Claudin-3 acts as a sealing component of the tight junction for ions of either charge and uncharged solutes. Biochim. Biophys. Acta 1798: 2048-2057

  7. Will C, Breiderhoff T, Thumfart J, Stuiver M, Kopplin K, Sommer K, Günzel D, Querfeld U, Meij IC, Shan Q, Bleich M, Willnow TE, Müller D (2010) Targeted deletion of murine Cldn16 identifies extra- and intrarenal compensatory mechanisms of Ca2+ and Mg2+ wasting. Am. J. Physiol. Renal Physiol. 298: F1152-F1161

  8. Günzel D, Stuiver M, Kausalya PJ, Haisch L, Hunziker W, Krug S, Meij IC, Fromm M, Müller D (2009) Identification and characterization of six novel claudin-10 splice variants. J. Cell Sci. 122: 1507-1517

  9. Thumfart J, Jung S, Amasheh S, Krämer S, Peters H, Sommer K, Biber J, Murer H, Meij IC, Querfeld U, Wagner CA, Müller D (2008) Magnesium stimulates renal phosphate reabsorption. Am. J. Physiol. Renal Physiol. 295: F1126-F1133

  10. Müller D, Kausalya PJ, Claverie-Martin F, Meij IC, Eggert P, Garcia-Nieto V, Hunziker W (2003) A novel mutation in claudin-16 associated with childhood hypercalciuria abolishes binding to ZO-1 and leads to lysosomal mistargeting. Am. J. Hum. Genet. 73: 1293-1301

  11. Jeroen H. F. de Baaij, Joost G. J. Hoenderop, René J. M. Bindels (2014) Magnesium in man: Implications for health and disease. Physiol. Rev. 95: 1-46