Mitochondrial Dysfunction in the Pathogenesis of Rett Syndrome: Implications for Mitochondria-Targeted Therapies.

First described over 50 years ago, Rett syndrome (RTT) is a neurodevelopmental disorder caused primarily by mutations of the X-linked gene. RTT affects predominantly females, and has a prevalence of roughly 1 in every 10,000 female births. Prior to the discovery that mutations of are the leading cause of RTT, there were suggestions that RTT could be a mitochondrial disease.

Differential expression of sirtuin family members in the developing, adult, and aged rat brain.

The sirtuins are NAD(+)-dependent protein deacetylases and/or ADP-ribosyltransferases that play roles in metabolic homeostasis, stress response and potentially aging. This enzyme family resides in different subcellular compartments, and acts on a number of different targets in the nucleus, cytoplasm and in the mitochondria. Despite their recognized ability to regulate metabolic processes, the roles played by specific sirtuins in the brain-the most energy demanding tissue in the body-remains less well investigated and understood.

Over-expression of the Sirt3 sirtuin Protects neuronally differentiated PC12 Cells from degeneration induced by oxidative stress and trophic withdrawal.

Sirt3 is a mitochondrial sirtuin whose deacetylase activity regulates facets of oxidative metabolic efficiency, anti-oxidative capacity, and intra-mitochondrial signaling. In this study, we tested whether the over-expression of a human Sirt3-myc transgene in differentiated PC12 cells, a model of sympathetic catecholaminergic neurons, would affect the sensitivity of these cells to oxidative stress or trophic withdrawal insults. Expression analysis revealed the Sirt3-myc product was expressed as a 45kDa pro-form, which localized primarily within the cytosol, and a 30kDa processed form that localized predominantly within mitochondria.

Vulnerability of glial cells to hydrogen peroxide in cultured hippocampal slices.

Massive production of free radicals (FR) has been associated with a variety of pathological conditions in the central nervous system (CNS). We have used the FR generating compound hydrogen peroxide (H2O2) in organotypic hippocampal slice cultures to model oxidative injury in the brain. Necrotic cell death was monitored for up to 48 h using propidium iodide (PI) and confocal microscopy.

Chronic exposure to sub-lethal beta-amyloid (Abeta) inhibits the import of nuclear-encoded proteins to mitochondria in differentiated PC12 cells.

Studies on amyloid beta (Abeta|), the peptide thought to play a crucial role in the pathogenesis of Alzheimer's disease, have implicated mitochondria in Abeta-mediated neurotoxicity. We used differentiated PC12 cells stably transfected with an inducible green fluorescent protein (GFP) fusion protein containing an N'-terminal mitochondrial targeting sequence (mtGFP), to examine the effects of sub-lethal Abeta on the import of nuclear-encoded proteins to mitochondria. Exposure to sub-lethal Abeta(25-35) (10 mumol/L) for 48 h inhibited mtGFP import to mitochondria; average rates decreased by 20 +/- 4%.