Defining functional classes of Barth syndrome mutation in humans

Lu, Y.-W. et al. (2016) Defining functional classes of Barth syndrome mutation in humans. Human Molecular Genetics, 25(9), pp. 1754-1770. (doi: 10.1093/hmg/ddw046) (PMID:26908608)

Abstract

The X-linked disease Barth syndrome (BTHS) is caused by mutations in TAZ; TAZ is the main determinant of the final acyl chain composition of the mitochondrial-specific phospholipid, cardiolipin. To date, a detailed characterization of endogenous TAZ has only been performed in yeast. Further, why a given BTHS-associated missense mutation impairs TAZ function has only been determined in a yeast model of this human disease. Presently, the detailed characterization of yeast tafazzin harboring individual BTHS mutations at evolutionarily conserved residues has identified seven distinct loss-of-function mechanisms caused by patient-associated missense alleles. However, whether the biochemical consequences associated with individual mutations also occur in the context of human TAZ in a validated mammalian model has not been demonstrated. Here, utilizing newly established monoclonal antibodies capable of detecting endogenous TAZ, we demonstrate that mammalian TAZ, like its yeast counterpart, is localized to the mitochondrion where it adopts an extremely protease-resistant fold, associates non-integrally with intermembrane space-facing membranes and assembles in a range of complexes. Even though multiple isoforms are expressed at the mRNA level, only a single polypeptide that co-migrates with the human isoform lacking exon 5 is expressed in human skin fibroblasts, HEK293 cells, and murine heart and liver mitochondria. Finally, using a new genome-edited mammalian BTHS cell culture model, we demonstrate that the loss-of-function mechanisms for two BTHS alleles that represent two of the seven functional classes of BTHS mutation as originally defined in yeast, are the same when modeled in human TAZ.

• Item Type: Articles
• Additional Information: This work was supported by the Barth Syndrome Foundation (to S.M.C.); the National Institutes of Health (R00HL089185 and R01HL108882 to S.M.C., R01GM061721 to C.M.K., NIH/ORIP 1S10RR023454-01 to J.M.M.); and a pre-doctoral fellowship from the American Heart Association (12PRE11910004 to Y.-W.L.).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Gottlieb, Professor Eyal and Galbraith, Dr Laura
• Authors: Lu, Y.-W., Galbraith, L., Herndon, J., Lu, Y.-L., Pras-Raves, M., Vervaart, M., Van Kampen, A., Luyf, A., Koehler, C. M., McCaffery, J.M., Gottlieb, E., Vaz, F. M., and Claypool, S. M.
• College/School: College of Medical Veterinary and Life Sciences > School of Cancer Sciences
• Journal Name: Human Molecular Genetics
• Publisher: Oxford University Press
• ISSN: 0964-6906
• ISSN (Online): 1460-2083
• Published Online: 16 February 2016
• Copyright Holders: Copyright © 2016 The Authors
• First Published: First published in Human Molecular Genetics 25(9): 1754-1770
• Publisher Policy: Reproduced in accordance with the publisher copyright policy