Olfactory functions scale with circuit restoration in a rapidly reversible Alzheimer's disease model

J Neurosci. 2013 Jul 24;33(30):12208-17. doi: 10.1523/JNEUROSCI.0291-13.2013.


Neural circuits maintain a precise organization that is vital for normal brain functions and behaviors, but become disrupted during neurological disease. Understanding the connection between wiring accuracy and function to measure disease progression or recovery has been difficult because of the complexity of behavioral circuits. The olfactory system maintains well-defined neural connections that regenerate throughout life. We previously established a reversible in vivo model of Alzheimer's disease by overexpressing a humanized mutated amyloid precursor protein (hAPP) in olfactory sensory neurons (OSNs). Using this model, we currently show that hAPP is present in the OSN axons of mutant mice, which exhibit strong caspase3 signal and reduced synaptic protein expression by 3 weeks of age. In the olfactory bulb, we show that glomerular structure is distorted and OSN axonal convergence is lost. In vivo functional imaging experiments further demonstrate disruption of the glomerular circuitry, and behavioral assays reveal that olfactory function is significantly impaired. Because OSNs regenerate, we also tested if the system could recover from hAPP-induced disruption. We found that after 1 or 3 weeks of shutting-off hAPP expression, the glomerular circuit was partially restored both anatomically and functionally, with behavioral deficits similarly reversed. Interestingly, the degree of functional recovery tracked directly with circuit restoration. Together, these data demonstrate that hAPP-induced circuit disruption and subsequent recovery can occur rapidly and that behavior can provide a measure of circuit organization. Thus, olfaction may serve as a useful biomarker to both follow disease progression and gauge potential recovery.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Agnosia / genetics
  • Agnosia / physiopathology*
  • Agnosia / therapy
  • Alzheimer Disease / genetics
  • Alzheimer Disease / physiopathology*
  • Alzheimer Disease / therapy
  • Amyloid beta-Protein Precursor / genetics*
  • Amyloid beta-Protein Precursor / metabolism
  • Animals
  • Axons / pathology
  • Axons / physiology
  • Caspase 3 / metabolism
  • Cell Count
  • Disease Models, Animal
  • Disease Progression
  • Feeding Behavior / physiology*
  • Female
  • Food
  • Genetic Therapy / methods
  • Humans
  • Lac Operon
  • Male
  • Mice
  • Mice, 129 Strain
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Nerve Degeneration / genetics
  • Nerve Degeneration / pathology
  • Nerve Degeneration / physiopathology
  • Odorants
  • Olfactory Bulb / pathology
  • Olfactory Bulb / physiology
  • Recovery of Function / physiology*
  • Smell / genetics
  • Smell / physiology*


  • Amyloid beta-Protein Precursor
  • Casp3 protein, mouse
  • Caspase 3