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Nat Neurosci. 2019 Mar;22(3):386-400. doi: 10.1038/s41593-019-0338-y. Epub 2019 Feb 11.

Reduced mitochondrial fusion and Huntingtin levels contribute to impaired dendritic maturation and behavioral deficits in Fmr1-mutant mice.

Author information

1
Waisman Center, University of Wisconsin-Madison, Madison, WI, USA.
2
Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, USA.
3
State Key Laboratory of Medical Neurobiology, School of Basic Medical Sciences and Institutes of Brain Science, and the Collaborative Innovation Center for Brain Science, Fudan University, Shanghai, China.
4
Neuroplasticity and Behavior Unit, National Institute on Aging, Baltimore, MD, USA.
5
Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, WI, USA.
6
Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI, USA.
7
Department of Biomedical Science, Charles E. Schmidt College of Medicine; and Brain Institute, Florida Atlantic University, Jupiter, FL, USA.
8
Waisman Center, University of Wisconsin-Madison, Madison, WI, USA. Xinyu.zhao@wisc.edu.
9
Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, USA. Xinyu.zhao@wisc.edu.

Abstract

Fragile X syndrome results from a loss of the RNA-binding protein fragile X mental retardation protein (FMRP). How FMRP regulates neuronal development and function remains unclear. Here we show that FMRP-deficient immature neurons exhibit impaired dendritic maturation, altered expression of mitochondrial genes, fragmented mitochondria, impaired mitochondrial function, and increased oxidative stress. Enhancing mitochondrial fusion partially rescued dendritic abnormalities in FMRP-deficient immature neurons. We show that FMRP deficiency leads to reduced Htt mRNA and protein levels and that HTT mediates FMRP regulation of mitochondrial fusion and dendritic maturation. Mice with hippocampal Htt knockdown and Fmr1-knockout mice showed similar behavioral deficits that could be rescued by treatment with a mitochondrial fusion compound. Our data unveil mitochondrial dysfunction as a contributor to the impaired dendritic maturation of FMRP-deficient neurons and suggest a role for interactions between FMRP and HTT in the pathogenesis of fragile X syndrome.

PMID:
30742117
DOI:
10.1038/s41593-019-0338-y

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