Spinocerebellar ataxia type 1 (SCA1) is one of several neurological disorders caused by a CAG repeat expansion. In SCA1, this expansion produces an abnormally long polyglutamine tract in the protein ataxin-1. Mutant polyglutamine proteins accumulate in neurons, inducing neurodegeneration, but the mechanism underlying this accumulation has been unclear. We have discovered that the 14-3-3 protein, a multifunctional regulatory molecule, mediates the neurotoxicity of ataxin-1 by binding to and stabilizing ataxin-1, thereby slowing its normal degradation. The association of ataxin-1 with 14-3-3 is regulated by Akt phosphorylation, and in a Drosophila model of SCA1, both 14-3-3 and Akt modulate neurodegeneration. Our finding that phosphatidylinositol 3-kinase/Akt signaling and 14-3-3 cooperate to modulate the neurotoxicity of ataxin-1 provides insight into SCA1 pathogenesis and identifies potential targets for therapeutic intervention.

Members of the ubiquitous 14-3-3 family of proteins are abundantly expressed in metazoan neurons. The Drosophila 14-3-3zeta gene leonardo is preferentially expressed in adult mushroom bodies, centers of insect learning and memory. Mutants exhibit defects in olfactory learning and memory and physiological neuroplasticity at the neuromuscular junction. Because strong mutations in this gene are lethal, we investigated the nature of the defects that precipitate the learning and memory deficit and the role of the two protein isoforms encoded by leonardo in these processes. We find that the behavioral deficit in the mutants is not caused by aberrant development, LEONARDO protein is acutely required for learning and memory, and both protein isoforms can function equivalently in embryonic development and behavioral neuroplasticity.

The functional specialization or redundancy of the ubiquitous 14-3-3 proteins constitutes a fundamental question in their biology and stems from their highly conserved structure and multiplicity of coexpressed isotypes. We address this question in vivo using mutations in the two Drosophila 14-3-3 genes, leonardo (14-3-3z) and D14-3-3e. We demonstrate that D14-3-3e is essential for embryonic hatching. Nevertheless, D14-3-3e null homozygotes survive because they upregulate transcripts encoding the LEOII isoform at the time of hatching, compensating D14-3-3e loss. This novel homeostatic response explains the reported functional redundancy of the Drosophila 14-3-3 isotypes and survival of D14-3-3e mutants. The response appears unidirectional, as D14-3-3e elevation upon LEO loss was not observed and elevation of leo transcripts was stage and tissue specific. In contrast, LEO levels are not changed in the wing disks, resulting in the aberrant wing veins characterizing D14-3-3e mutants. Nevertheless, conditional overexpression of LEOI, but not of LEOII, in the wing disk can partially rescue the venation deficits. Thus, excess of a particular LEO isoform can functionally compensate for D14-3-3e loss in a cellular-context-specific manner. These results demonstrate functional differences both among Drosophila 14-3-3 proteins and between the two LEO isoforms in vivo, which likely underlie differential dimer affinities toward 14-3-3 targets.

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As prenatal methamphetamine (MA) exposure results in long-term hippocampus-dependent cognitive deficits, the increased MA use in women of childbearing age is of great concern. As mice are most commonly used in genetic models, we started to study the potential effects of neonatal MA exposure in female and male mice on brain function 3 months later. As histamine (HA) might mediate some effects of MA in adulthood, we also tested whether in neonates HA might mediate the long-term effects of MA using HA H 3 receptor agonists and antagonists. Stimulation of HA H 3 receptors by H 3 agonists inhibits HA synthesis and release, whereas inhibition of H 3 receptors by H 3 receptor antagonists increases HA release. MA (5 mg/kg), the H 3 receptor antagonist thioperamide (5 mg/kg), and the H 3 receptor agonist immepip (5 mg/kg) alone or in the presence of MA (5 mg/kg) were administered once daily from postnatal days 11 to 20 and the mice were tested at 3 months of age. Here we show that in mice exposure to MA early in life causes sex-dependent impairments in object recognition, spatial learning, and memory in the water maze, and pre-pulse inhibition in adulthood. HA mediates these impairments. Increasing HA release mimicked, whereas inhibiting HA release blocked the long-term detrimental MA effects. This model could be used to determine the role of genetic and environmental factors in MA-dependent cognitive impairments and to develop therapeutic strategies to inhibit them. Neuropsychopharmacology (2007) 32, 665-672.

Diminished responses to stimuli defined as habituation can serve as a gating mechanism for repetitive environmental cues with little predictive value and importance. We demonstrate that wild-type animals diminish their responses to electric shock stimuli with properties characteristic of short-and long-term habituation. We used spatially restricted abrogation of neurotransmission to identify brain areas involved in this behavioral response. We find that the mushroom bodies and, in particular, the ␣/␤ lobes appear to guard against habituating prematurely to repetitive electric shock stimuli. In addition to protection from premature habituation, the mushroom bodies are essential for spontaneous recovery and dishabituation. These results reveal a novel modulatory role of the mushroom bodies on responses to repetitive stimuli in agreement with and complementary to their established roles in olfactory learning and memory.

Apolipoprotein E4 (apoE4) and female sex are risk factors for developing Alzheimer's disease. It is unclear whether apoE4 contributes to behavioral function at younger ages. Standard neuropsychological assessments [intelligence quotient (IQ), attention, and executive function] and a test developed in this laboratory (Memory Island test of spatial learning and memory) were used to determine whether E4 and sex affect neuropsychological performance in healthy primary school children (age 7-10). A medical history was also obtained from the mother to determine whether negative birth outcomes were associated with apoE4. Mothers of apoE4ϩ children were more likely to report that their newborn was placed in an intensive care unit. A sex difference in birth weight was noted among apoE4Ϫ (males Ͼ females), but not apoE4ϩ, offspring. Conversely, among apoE4ϩ, but not apoE4Ϫ children, there was a sex difference in the Wechsler Abbreviated Scale of Intelligence (WASI) vocabulary score favoring boys. ApoE4Ϫ girls had better visual recall than apoE4ϩ girls or apoE4Ϫ boys on the Family Pictures test. Finally, apoE4ϩ, unlike apoE4Ϫ, children did not show spatial memory retention during the Memory Island probe trial. Thus, apoE4 may affect neurobehavioral performance, particularly spatial memory, and antenatal health decades before any clinical expression of neurodegenerative processes. (Pediatr Res 67: 293-299, 2010)

To understand the molecular and neural mechanisms underlying alcohol addiction, many models ranging from vertebrates to invertebrates have been developed. In Drosophila melanogaster, behavioral paradigms from assaying acute responses to alcohol, to behaviors more closely modeling addiction, have emerged in recent years. However, both the CAFÉ assay, similar to a 2-bottle choice consumption assay, as well as conditioned odor preference, where ethanol is used as the reinforcer, are labor intensive and have low throughput. To address this limitation, we have established a novel ethanol consumption preference assay, called FRAPPÉ, which allows for fast, high throughput measurement of consumption in individual flies, using a fluorescence plate reader. We show that naïve flies do not prefer to consume ethanol, but various pre-exposures, such as ethanol vapor or voluntary ethanol consumption, induce ethanol preference. This ethanol-primed preference is long lasting and is not driven by calories contained in ethanol during the consumption choice. Our novel experience-dependent model of ethanol preference in Drosophila – a highly genetically tractable organism – therefore recapitulates salient features of human alcohol abuse and will facilitate the molecular understanding of the development of alcohol preference.