Cell-Specific Deletion of PGC-1α from Medium Spiny Neurons Causes Transcriptional Alterations and Age-Related Motor Impairment

J Neurosci. 2018 Mar 28;38(13):3273-3286. doi: 10.1523/JNEUROSCI.0848-17.2018. Epub 2018 Feb 28.

Abstract

Multiple lines of evidence indicate that a reduction in the expression and function of the transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) is associated with neurodegeneration in diseases such as Huntington's disease (HD). Polymorphisms in the PGC-1α gene modify HD progression and PGC-1α expression is reduced in striatal medium spiny neurons (MSNs) of HD patients and mouse models. However, neither the MSN-specific function of PGC-1α nor the contribution of PGC-1α deficiency to motor dysfunction is known. We identified novel, PGC-1α-dependent transcripts involved in RNA processing, signal transduction, and neuronal morphology and confirmed reductions in these transcripts in male and female mice lacking PGC-1α specifically in MSNs, indicating a cell-autonomous effect in this population. MSN-specific PGC-1α deletion caused reductions in previously identified neuronal and metabolic PGC-1α-dependent genes without causing striatal vacuolizations. Interestingly, these mice exhibited a hypoactivity with age, similar to several HD animal models. However, these newly identified PGC-1α-dependent genes were upregulated with disease severity and age in knock-in HD mouse models independent of changes in PGC-1α transcript, contrary to what would be predicted from a loss-of-function etiological mechanism. These data indicate that PGC-1α is necessary for MSN transcriptional homeostasis and function with age and that, whereas PGC-1α loss in MSNs does not replicate an HD-like phenocopy, its downstream genes are altered in a repeat-length and age-dependent fashion. Understanding the additive effects of PGC-1α gene functional variation and mutant huntingtin on transcription in this cell type may provide insight into the selective vulnerability of MSNs in HD.SIGNIFICANCE STATEMENT Reductions in peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α)-mediated transcription have been implicated in the pathogenesis of Huntington's disease (HD). We show that, although PGC-1α-dependent transcription is necessary to maintain medium spiny neuron (MSN) function with age, its loss is insufficient to cause striatal atrophy in mice. We also highlight a set of genes that can serve as proxies for PGC-1α functional activity in the striatum for target engagement studies. Furthermore, we demonstrate that PGC-1α-dependent genes are upregulated in a dose- and age-dependent fashion in HD mouse models, contrary to what would be predicted from a loss-of-function etiological mechanism. However, given this role for PGC-1α in MSN transcriptional homeostasis, it is important to consider how genetic variation in PGC-1α could contribute to mutant-huntingtin-induced cell death and disease progression.

Keywords: Huntington's disease; cellular specificity; medium spiny neuron; pgc-1alpha; striatum; transcription.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Corpus Striatum / cytology
  • Corpus Striatum / growth & development
  • Corpus Striatum / metabolism*
  • Corpus Striatum / physiology
  • Female
  • Gene Deletion
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Motor Activity*
  • Neurons / metabolism*
  • Neurons / physiology
  • Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha / genetics
  • Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha / metabolism*
  • Transcriptome*

Substances

  • Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha
  • Ppargc1a protein, mouse