Xin Jie Chen, PhD

Current Appointments

• Associate Professor of Biochemistry and Molecular Biology

Hospital Campus

• Downtown

Education & Fellowships

• PhD: University of Paris-Sud, 1987, Molecular and Cellular Genetics

Publications

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Research Abstract

Mitochondria are the powerhouses that generate energy by oxidative phosphorylation (OXPHOS) to support cellular activities. Mitochondria also receive and emit cellular signals to promote cell death. The biology of mitochondria is fascinating. Structurally, mitochondria are sub-compartmentalized into the outer and inner membranes, matrix and the inter-membrane space. Thus, dedicated molecular machineries are required for targeting the proteins to correct locations, and for maintaining them in the right conformations in order to fulfill their functions. Genetically, the operation of the OXPHOS apparatus requires a coordinated expression of genes from two physically separated genomes: the mitochondrial genome which encodes integral components of the OXPHOS pathway, and the nuclear genome that directly contributes to OXPHOS as well as looks after the mitochondrial genome for its replication, transcription, transmission and other mtDNA transactions. Effective nuclear-mitochondrial communication is therefore critical for maintaining mitochondrial activity. Functionally, mitochondria are intricate organelles that can switch from a life-supporting apparatus into a death-executing machinery, through the integration of intrinsic and extrinsic cellular signals.

In recent years, mitochondria have emerged as the “powerhouses of diseases”, as mitochondrial dysfunction is associated with a rapidly increasing number of aging-related neuromuscular degenerative diseases and metabolic disorders. Mitochondrial dysfunction is also believed to contribute to aging, but the underlying mechanism is not well understood.

The ongoing research in our laboratory is focused on the following two projects:

(1) We are interested in understanding how the mitochondrial system degenerates during aging and contributes to aging-related diseases. Our ultimate goal is to identify evolutionarily conserved cellular pathways that can potentially delay and possibly, reverse the degenerative process. We use yeast and cultured cell lines as model systems. Mouse models are being developed to address some of these questions.

(2) We investigate the mechanisms of mitochondrial DNA organization, recombination, replication and repair. Elucidating these fundamental processes could help better understanding the pathogenesis of a variety of human diseases resulting from mtDNA mutations/deletions.

Selected publications:

Nardozzi, J.D. *, Wang, X.* (* equal contribution), Mbantenkhu, M., Wilkens, S. and Chen, X.J. (2012) A properly configured ring structure is critical for the function of the mitochondrial DNA recombination protein, Mgm101. J Biol Chem, 2012 Sep 4. [Epub ahead of print]

Chen, X.J. (2011) The search for nonconventional mitochondrial determinants of aging. Mol Cell 42:271-273. (Preview)

Mbantenkhu, M.*, Wang, X.* (* equal contribution), Nardozzi, J.D., Wilkens, S., Hoffman, E., Patel, A., Costrove, M.S. and Chen, X.J. (2011) Mgm101 is a Rad52-related protein required for mitochondrial DNA recombination. J Biol Chem 286:42360-42370

Wang X, Zuo X, Kucejova B, Chen XJ. Reduced cytosolic protein synthesis suppresses mitochondrial degeneration (2008) Nat Cell Biol. 10:1090-7.

Wang X, Salinas K, Zuo X, Kucejova B, Chen XJ. (2008) Dominant membrane uncoupling by mutant adenine nucleotide translocase in mitochondrial diseases. Hum Mol Genet. 17:4036-44.

Chen XJ*, Wang X, Butow RA* (2007) Yeast aconitase binds and provides metabolically coupled protection to mitochondrial DNA. Proc Natl Acad Sci. 104:13738-43. (*co-corresponding authors)

Chen, X.J. and Butow, R.A. (2005) Organization and inheritance of mitochondrial nucleoids. Nature Review/Genetics 6:815-825.

Chen, X.J., Wang, X.W., Kaufman, B.A. and Butow, R.A. (2005) Aconitase couples metabolic regulation to mitochondrial DNA maintenance. Science 307:714-717.

Chen, X.J. (2004) Sal1p, a calcium-dependent carrier protein that suppresses an essential cellular function associated with the Aac2p isoform of ADP/ATP translocase in Saccharomyces cerevisiae. Genetics 167:607-617

Chen, X.J. (2002) Induction of an unregulated channel by mutant nucleotide translocase suggests an explanation for human ophthalmoplegia. Human Molecular Genetics 16: 1835-1843.

Zuo, X.M., Clark-Walker, G.D. and Chen, X.J (2002). The mitochondrial nucleoid protein, Mgm101p, of Saccharomyces cerevisiae is involved in the maintenance of r⁺ and ori/rep-devoid petite genomes but is not required for hypersuppressive r^- mtDNA. Genetics 160:1389-1400.