Transcriptomic profiling of the human brain reveals that altered synaptic gene expression is associated with chronological aging.

Aging is a biologically universal event, and yet the key events that drive aging are still poorly understood. One approach to generate new hypotheses about aging is to use unbiased methods to look at change across lifespan. Here, we have examined gene expression in the human dorsolateral frontal cortex using RNA- Seq to populate a whole gene co-expression network analysis. We show that modules of co-expressed genes enriched for those encoding synaptic proteins are liable to change with age. We extensively validate these age-dependent changes in gene expression across several datasets including the publically available GTEx resource which demonstrated that gene expression associations with aging vary between brain regions. We also estimated the extent to which changes in cellular composition account for age associations and find that there are independent signals for cellularity and aging. Overall, these results demonstrate that there are robust age-related alterations in gene expression in the human brain and that genes encoding for neuronal synaptic function may be particularly sensitive to the aging process.

Genetic Variations and mRNA Expression of NRF2 in Parkinson's Disease.

Nuclear factor erythroid 2-like 2 (NRF2) encodes a transcription factor regulating mechanisms of cellular protection and is activated by oxidative stress. NRF2 has therefore been hypothesized to confer protection against Parkinson's disease and so far an NRF2 haplotype has been reported to decrease the risk of developing disease and delay disease onset. Also NRF2 adopts a nuclear localization in Parkinson's disease, which is indicative of increased NRF2 activity. We have investigated the association between NRF2 and Parkinson's disease in a Swedish case-control material and whether NRF2 expression levels correlate with NRF2 genetic variants, disease, or disease onset. Using pyrosequencing, we genotyped one intronic and three promoter variants in 504 patients and 509 control subjects from Stockholm. Further, we quantified NRF2 mRNA expression in EBV transfected human lymphocytes from patients and controls using quantitative real-time reverse transcription PCR. We found that one of the promoter variants, rs35652124, was associated with age of disease onset (Χ2 = 14.19, p value = 0.0067). NRF2 mRNA expression levels however did not correlate with the rs35652124 genotype, Parkinson's disease, or age of onset in our material. More detailed studies on NRF2 are needed in order to elucidate how this gene affects pathophysiology of Parkinson's disease.

Myeloperoxidase-immunoreactive cells are significantly increased in brain areas affected by neurodegeneration in Parkinson's and Alzheimer's disease.

Myeloperoxidase (MPO) is a key enzyme in inflammatory and degenerative processes, although conflicting reports have been presented concerning its expression in the brain. We studied the cellular localization of MPO and compared numbers of MPO cells in various brain regions between neurologically healthy individuals and patients with Parkinson's disease (PD) or Alzheimer's disease (AD; n = 10-25). We also investigated two rodent PD models. MPO immunoreactivity (ir) was detected in monocytes, perivascular macrophages and amoeboid microglia in the human brain parenchyma, whereas no co-localization with glial fibrillary acidic protein (GFAP) ir was observed. In the midbrain, caudate and putamen, we found a significant increase of MPO-immunoreactive cells in PD compared with control brains, whereas in the cerebellum, no difference was apparent. MPO ir was detected neither in neurons nor in occasional small beta-amyloid-immunoreactive plaques in PD or control cases. In the frontal cortex of AD patients, we found significantly more MPO-immunoreactive cells compared with control cases, together with intense MPO ir in extracellular plaques. In the hippocampus of several AD cases, MPO-like ir was observed in some pyramidal neurons. Neither rapid dopamine depletion in the rat PD model, nor slow degeneration of dopamine neurons in MitoPark mice induced the expression of MPO ir in any brain region. MPO mRNA was not detectable with radioactive in situ hybridization in any human or rodent brain area, although myeloid cells from bone marrow displayed clear MPO signals. Our results indicate significant increases of MPO-immunoreactive cells in brain regions affected by neurodegeneration in PD and AD, supporting investigations of MPO inhibitors in novel treatment strategies.

Histamine induces KCNQ channel-dependent gamma oscillations in rat hippocampus via activation of the H1 receptor.

Histamine is an aminergic neurotransmitter, which regulates wakefulness, arousal and attention in the central nervous system. Histamine receptors have been the target of efforts to develop pro-cognitive drugs to treat disorders such as Alzheimer's disease and schizophrenia. Cognitive functions including attention are closely associated with gamma oscillations, a rhythmical electrical activity pattern in the 30-80 Hz range, which depends on the synchronized activity of excitatory pyramidal cells and inhibitory fast-spiking interneurons. We set out to explore whether histamine has a role in promoting gamma oscillations in the hippocampus. Using in-situ hybridization we demonstrate that histamine receptor subtypes 1, 2 and 3 are expressed in stratum pyramidale of area CA3 in rats. We show that both pyramidal cells and fast-spiking interneurons depolarize and increase action potential firing in response to histamine in vitro. The activation of histamine receptors generates dose-dependent, transient gamma oscillations in area CA3 of the hippocampus - the locus of the gamma rhythm generator. We also demonstrate that this histamine effect is independent of muscarinic receptors. Using specific antagonists we provide evidence that histamine gamma rhythmogenesis specifically depends on the H1 receptor. Histamine also depolarized both pyramidal cells and fast-spiking interneurons and increased membrane resistance in pyramidal cells. The increased membrane resistance is potentially mediated by the inhibition of potassium channels because application of the KCNQ channel opener ICA110381 abolished the oscillations. Taken together our data demonstrate a novel and physiological mechanism for generating gamma oscillations in hippocampus and suggest a role for KCNQ channels in this cognition-relevant brain activity.

Altered Expression of Growth Associated Protein-43 and Rho Kinase in Human Patients with Parkinson's Disease.

Causative treatment strategies for Parkinson's disease (PD) will have to address multiple underlying pathomechanisms to attenuate neurodegeneration. Additionally, the intrinsic regenerative capacity of the central nervous system is also an important factor contributing to restoration. Extracellular cues can limit sprouting and regrowth of adult neurons, but even aged neurons have a low intrinsic regeneration capacity. Whether this capacity has been lost or if growth inhibitory cues are increased during PD progression has not been resolved yet. In this study, we assessed the regenerative potential in the nigrostriatal system in post-mortem brain sections of PD patients compared to age-matched and young controls. Investigation of the expression pattern of the regeneration-associated protein GAP-43 suggested a lower regenerative capacity in nigral dopaminergic neurons of PD patients. Furthermore, the increase in protein expression of the growth-inhibitory protein ROCK2 in astrocytes and a similar trend in microglia, suggests an important role for ROCK2 in glial PD pathology, which is initiated already in normal aging. Considering the role of astro- and microglia in PD pathogenesis as well as beneficial effects of ROCK inhibition on neuronal survival and regeneration in neurodegenerative disease models, our data strengthens the importance of the ROCK pathway as a therapeutic target in PD.

Strong association between glucocerebrosidase mutations and Parkinson's disease in Sweden.

Several genetic studies have demonstrated an association between mutations in glucocerebrosidase (GBA), originally implicated in Gaucher's disease, and an increased risk of Parkinson's disease (PD). We have investigated the possible involvement of genetic GBA variations in PD in the Swedish population. Three GBA variants, E326K, N370S, and L444P were screened in the largest Swedish Parkinson cohort reported to date; 1625 cases and 2025 control individuals. We found a significant association with high effect size of the rare variant L444P with PD (odds ratio 8.17; 95% confidence interval: 2.51-26.23; p-value = 0.0020) and a significant association of the common variant E326K (odds ratio 1.60; 95% confidence interval: 1.16-2.22; p-value = 0.026). The rare variant N370S showed a trend for association. Most L444P carriers (68%) were found to reside in northern Sweden, which is consistent with a higher prevalence of Gaucher's disease in this part of the country. Our findings support the role of GBA mutations as risk factors for PD and point to lysosomal dysfunction as a mechanism contributing to PD etiology.

ADAR2 affects mRNA coding sequence edits with only modest effects on gene expression or splicing in vivo.

Adenosine deaminases bind double stranded RNA and convert adenosine to inosine. Editing creates multiple isoforms of neurotransmitter receptors, such as with Gria2. Adar2 KO mice die of seizures shortly after birth, but if the Gria2 Q/R editing site is mutated to mimic the edited version then the animals are viable. We performed RNA-Seq on frontal cortices of Adar2(-/-) Gria2(R/R) mice and littermates. We found 56 editing sites with significantly diminished editing levels in Adar2 deficient animals with the majority in coding regions. Only two genes and 3 exons showed statistically significant differences in expression levels. This work illustrates that ADAR2 is important in site-specific changes of protein coding sequences but has relatively modest effects on gene expression and splicing in the adult mouse frontal cortex.

An organic electronic biomimetic neuron enables auto-regulated neuromodulation.

Current therapies for neurological disorders are based on traditional medication and electric stimulation. Here, we present an organic electronic biomimetic neuron, with the capacity to precisely intervene with the underlying malfunctioning signalling pathway using endogenous substances. The fundamental function of neurons, defined as chemical-to-electrical-to-chemical signal transduction, is achieved by connecting enzyme-based amperometric biosensors and organic electronic ion pumps. Selective biosensors transduce chemical signals into an electric current, which regulates electrophoretic delivery of chemical substances without necessitating liquid flow. Biosensors detected neurotransmitters in physiologically relevant ranges of 5-80 µM, showing linear response above 20 µm with approx. 0.1 nA/µM slope. When exceeding defined threshold concentrations, biosensor output signals, connected via custom hardware/software, activated local or distant neurotransmitter delivery from the organic electronic ion pump. Changes of 20 µM glutamate or acetylcholine triggered diffusive delivery of acetylcholine, which activated cells via receptor-mediated signalling. This was observed in real-time by single-cell ratiometric Ca(2+) imaging. The results demonstrate the potential of the organic electronic biomimetic neuron in therapies involving long-range neuronal signalling by mimicking the function of projection neurons. Alternatively, conversion of glutamate-induced descending neuromuscular signals into acetylcholine-mediated muscular activation signals may be obtained, applicable for bridging injured sites and active prosthetics.

No dopamine cell loss or changes in cytoskeleton function in transgenic mice expressing physiological levels of wild type or G2019S mutant LRRK2 and in human fibroblasts.

Mutations within the LRRK2 gene have been identified in Parkinson's disease (PD) patients and have been implicated in the dysfunction of several cellular pathways. Here, we explore how pathogenic mutations and the inhibition of LRRK2 kinase activity affect cytoskeleton dynamics in mouse and human cell systems. We generated and characterized a novel transgenic mouse model expressing physiological levels of human wild type and G2019S-mutant LRRK2. No neuronal loss or neurodegeneration was detected in midbrain dopamine neurons at the age of 12 months. Postnatal hippocampal neurons derived from transgenic mice showed no alterations in the seven parameters examined concerning neurite outgrowth sampled automatically on several hundred neurons using high content imaging. Treatment with the kinase inhibitor LRRK2-IN-1 resulted in no significant changes in the neurite outgrowth. In human fibroblasts we analyzed whether pathogenic LRRK2 mutations change cytoskeleton functions such as cell adhesion. To this end we compared the adhesion characteristics of human skin fibroblasts derived from six PD patients carrying one of three different pathogenic LRRK2 mutations and from four age-matched control individuals. The mutant LRRK2 variants as well as the inhibition of LRRK2 kinase activity did not reveal any significant cell adhesion differences in cultured fibroblasts. In summary, our results in both human and mouse cell systems suggest that neither the expression of wild type or mutant LRRK2, nor the inhibition of LRRK2 kinase activity affect neurite complexity and cellular adhesion.

Conditional expression of Parkinson's disease-related R1441C LRRK2 in midbrain dopaminergic neurons of mice causes nuclear abnormalities without neurodegeneration.

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene cause late-onset, autosomal dominant Parkinson's disease (PD). The clinical and neurochemical features of LRRK2-linked PD are similar to idiopathic disease although neuropathology is somewhat heterogeneous. Dominant mutations in LRRK2 precipitate neurodegeneration through a toxic gain-of-function mechanism which can be modeled in transgenic mice overexpressing human LRRK2 variants. A number of LRRK2 transgenic mouse models have been developed that display abnormalities in dopaminergic neurotransmission and alterations in tau metabolism yet without consistently inducing dopaminergic neurodegeneration. To directly explore the impact of mutant LRRK2 on the nigrostriatal dopaminergic pathway, we developed conditional transgenic mice that selectively express human R1441C LRRK2 in dopaminergic neurons from the endogenous murine ROSA26 promoter. The expression of R1441C LRRK2 does not induce the degeneration of substantia nigra dopaminergic neurons or striatal dopamine deficits in mice up to 2years of age, and fails to precipitate abnormal protein inclusions containing alpha-synuclein, tau, ubiquitin or autophagy markers (LC3 and p62). Furthermore, mice expressing R1441C LRRK2 exhibit normal motor activity and olfactory function with increasing age. Intriguingly, the expression of R1441C LRRK2 induces age-dependent abnormalities of the nuclear envelope in nigral dopaminergic neurons including reduced nuclear circularity and increased invaginations of the nuclear envelope. In addition, R1441C LRRK2 mice display increased neurite complexity of cultured midbrain dopaminergic neurons. Collectively, these novel R1441C LRRK2 conditional transgenic mice reveal altered dopaminergic neuronal morphology with advancing age, and provide a useful tool for exploring the pathogenic mechanisms underlying the R1441C LRRK2 mutation in PD.

Behavioral deficits and striatal DA signaling in LRRK2 p.G2019S transgenic rats: a multimodal investigation including PET neuroimaging.

BACKGROUND: A major risk-factor for developing Parkinson's disease (PD) is genetic variability in leucine-rich repeat kinase 2 (LRRK2), most notably the p.G2019S mutation. Examination of the effects of this mutation is necessary to determine the etiology of PD and to guide therapeutic development. OBJECTIVE: Assess the behavioral consequences of LRRK2 p.G2019S overexpression in transgenic rats as they age and test the functional integrity of the nigro-striatal dopamine system. Conduct positron emission tomography (PET) neuroimaging to compare transgenic rats with previous data from human LRRK2 mutation carriers. METHODS: Rats overexpressing human LRRK2 p.G2019S were generated by BAC transgenesis and compared to non-transgenic (NT) littermates. Motor skill tests were performed at 3, 6 and 12 months-of-age. PET, performed at 12 months, assessed the density of dopamine and vesicular monoamine transporters (DAT and VMAT2, respectively) and measured dopamine synthesis, storage and availability. Brain tissue was assayed for D2, DAT, dopamine and cAMP-regulated phosphoprotein (DARPP32) and tyrosine hydroxylase (TH) expression by Western blot, and TH by immunohistochemistry. RESULTS: Transgenic rats had no abnormalities in measures of striatal dopamine function at 12 months. A behavioral phenotype was present, with LRRK2 p.G2019S rats performing significantly worse on the rotarod than non-transgenic littermates (26% reduction in average running duration at 6 months), but with normal performance in other motor tests. CONCLUSIONS: Neuroimaging using dopaminergic PET did not recapitulate prior studies in human LRRK2 mutation carriers. Consistently, LRRK2 p.G2019S rats do not develop overt neurodegeneration; however, they do exhibit behavioral abnormalities.

Comparison of three hypothermic target temperatures for the treatment of hypoxic ischemia: mRNA level responses of eight genes in the piglet brain.

Hypothermia can reduce neurodevelopmental disabilities in asphyxiated newborn infants. However, the optimal cooling temperature for neuroprotection is not well defined. We studied the effects of transient piglet brain hypoxic ischemia (HI) on transcriptional activity of eight genes and if mRNA level alterations could be counteracted by whole body cooling to 35, 33.5 or 30 °C. BDNF mRNA was globally upregulated by the insult, and none of the cooling temperatures counteracted this change. In contrast, MANF mRNA was downregulated, and these changes were modestly counteracted in different brain regions by hypothermic treatment at 33.5 °C, while 30 °C aggravated the MANF mRNA loss. MAP2 mRNA was markedly downregulated in all brain regions except striatum, and cooling to 33.5 °C modestly counteract this downregulation in the cortex cerebri. There was a tendency for GFAP mRNA levels in core, but not mantle regions to be downregulated and for these changes to be modestly counteracted by cooling to 33.5 or 35 °C. Cooling to 30 °C caused global GFAP mRNA decrease. HSP70 mRNA tended to become upregulated by HI and to be more pronounced in cortex and CA1 of hippocampus during cooling to 33.5 °C. We conclude that HI causes alterations of mRNA levels of many genes in superficial and deep piglet brain areas. Some of these changes may be beneficial, others detrimental, and lowering body temperature partly counteracts some, but not all changes. There may be general differences between core and mantle regions, as well as between the different cooling temperatures for protection. Comparing the three studied temperatures, cooling to 33.5 °C, appears to provide the best cooling temperature compromise.

Modulation of the endoplasmic reticulum-mitochondria interface in Alzheimer's disease and related models.

It is well-established that subcompartments of endoplasmic reticulum (ER) are in physical contact with the mitochondria. These lipid raft-like regions of ER are referred to as mitochondria-associated ER membranes (MAMs), and they play an important role in, for example, lipid synthesis, calcium homeostasis, and apoptotic signaling. Perturbation of MAM function has previously been suggested in Alzheimer's disease (AD) as shown in fibroblasts from AD patients and a neuroblastoma cell line containing familial presenilin-2 AD mutation. The effect of AD pathogenesis on the ER-mitochondria interplay in the brain has so far remained unknown. Here, we studied ER-mitochondria contacts in human AD brain and related AD mouse and neuronal cell models. We found uniform distribution of MAM in neurons. Phosphofurin acidic cluster sorting protein-2 and σ1 receptor, two MAM-associated proteins, were shown to be essential for neuronal survival, because siRNA knockdown resulted in degeneration. Up-regulated MAM-associated proteins were found in the AD brain and amyloid precursor protein (APP)Swe/Lon mouse model, in which up-regulation was observed before the appearance of plaques. By studying an ER-mitochondria bridging complex, inositol-1,4,5-triphosphate receptor-voltage-dependent anion channel, we revealed that nanomolar concentrations of amyloid ß-peptide increased inositol-1,4,5-triphosphate receptor and voltage-dependent anion channel protein expression and elevated the number of ER-mitochondria contact points and mitochondrial calcium concentrations. Our data suggest an important role of ER-mitochondria contacts and cross-talk in AD pathology.

mRNA expression, splicing and editing in the embryonic and adult mouse cerebral cortex.

The complexity of the adult brain is a result of both developmental processes and experience-dependent circuit formation. One way to look at the differences between embryonic and adult brain is to examine gene expression. Previous studies have used microarrays to address this in a global manner. However, the transcriptome is more complex than gene expression levels alone, as alternative splicing and RNA editing generate a diverse set of mature transcripts. Here we report a high-resolution transcriptome data set of mouse cerebral cortex at embryonic and adult stages using RNA sequencing (RNA-Seq). We found many differences in gene expression, splicing and RNA editing between embryonic and adult cerebral cortex. Each data set was validated technically and biologically, and in each case we found our RNA-Seq observations to have predictive validity. We provide this data set and analysis as a resource for understanding gene expression in the embryonic and adult cerebral cortex.

Enhanced dendritogenesis and axogenesis in hippocampal neuroblasts of LRRK2 knockout mice.

Adult neurogenesis, the formation of new neurons in the mammalian forebrain, is one important mechanism maintaining lifelong neuronal plasticity. The generation and maturation of adult neural stem and progenitor cells is impaired in models of neurodegenerative diseases, in particular Parkinson's disease (PD). Monogenetic forms of PD were identified and associated with several genes including the leucine-rich-repeat kinase 2 (LRRK2). Some of the underlying mechanisms in neurodegenerative diseases are closely linked to neuronal plasticity, and induce changes in adult neurogenesis, neuritic maintenance, synaptic transmission, and neural connectivity. We investigated adult neurogenesis and neuritic development of newly formed neurons in the hippocampal dentate gyrus of LRRK2 knockout mice. Proliferation and survival of newly generated cells were unchanged. However, the expression profile of maturation markers in surviving newly generated cells was altered. While immature neuronal phenotypes were significantly increased, the mature neuronal phenotype of surviving cells remained unchanged. Importantly, the absolute number of immature doublecortin positive neuroblasts was significantly increased in the hippocampus of LRRK2 knockout mice. These neuroblasts presented extended dendritic length with a more complex arborization. Furthermore, LRRK2 deletion resulted in an increased volume of the axonal mossy fiber bundle projecting from dentate granule cells to CA3 pyramidal neurons. Our findings suggest that LRRK2 influences neurogenesis and particularly neuronal morphogenesis. As neurogenesis and the pre-/post- synaptic compartments are significantly altered in PD, our data advance LRRK2 as a potent candidate in addressing neuroregenerative processes.

Association of a protective paraoxonase 1 (PON1) polymorphism in Parkinson's disease.

Pesticide exposure has been suggested to increase the risk to develop Parkinson's disease (PD). The arylesterase paraoxonase 1 (PON1) is mainly expressed in the liver and hydrolyzes organophosphates such as pesticides. The polymorphism Leu54Met (rs854560) in PON1, impairing enzyme activity and leading to decreased PON1 expression levels, has been reported to be associated with Parkinson's disease (PD). PON1 is part of a cluster on chromosome 7q21.3 together with PON2 and PON3. We investigated the occurrence of four additional polymorphisms in PON1 and two in PON2 in a Swedish PD case-control material. We found a significant association (p=0.007) with a PON1 promoter polymorphism, rs854571. The minor allele was more common among controls than PD cases which suggest a protective effect. This is strengthened by the fact that rs854571 is in strong linkage disequilibrium with another PON1 promoter polymorphism, rs854572, reported to increase PON1 gene expression. Our findings support the hypothesis that PON1 is involved in the etiology of PD and that higher PON1 levels are reducing the risk for PD.

Genetic Screening of the Mitochondrial Rho GTPases MIRO1 and MIRO2 in Parkinson's Disease.

MIRO1 and MIRO2 (mitochondrial Ras homolog gene family, member T1 and T2) also referred to as RHOT1 and RHOT2, belong to the mitochondrial Rho GTPase family and are involved in axonal transport of mitochondria in neurons. Because mitochondrial dysfunction is strongly implicated in Parkinson's disease (PD), MIRO1 and MIRO2 can be considered as new candidate genes for PD. We analyzed two non-synonymous polymorphisms and one synonymous polymorphism in MIRO1 and two non-synonymous polymorphisms in MIRO2, in a Swedish Parkinson case-control material consisting of 241 patients and 307 neurologically healthy controls. None of the analyzed polymorphisms in MIRO1 and MIRO2 were significantly associated with PD. Although we did not find a significant association with PD in our Swedish case-control material, we cannot exclude these Rho GTPases as candidate genes for PD or other neurodegenerative disorders.

MAGI1 copy number variation in bipolar affective disorder and schizophrenia.

BACKGROUND: Bipolar affective disorder (BPAD) and schizophrenia (SZ) are devastating psychiatric disorders that each affect about 1% of the population worldwide. Identification of new drug targets is an important step toward better treatment of these poorly understood diseases. METHODS: Genome-wide copy number variation (CNV) was assessed and variants were ranked by co-occurrence with disease in 48 BPAD families. Additional support for involvement of the highest-ranking CNV from the family-based analysis in psychiatric disease was obtained through analysis of 4084 samples with BPAD, SZ, or schizoaffective disorder. Finally, a pooled analysis of in-house and published datasets was carried out including 10,925 cases with BPAD, SZ, or schizoaffective disorder and 16,747 controls. RESULTS: In the family-based analysis, an approximately 200 kilobase (kb) deletion in the first intron of the MAGI1 gene was identified that segregated with BPAD in a pedigree (six out of six affected individuals; parametric logarithm of the odds score = 1.14). In the pooled analysis, seven additional insertions or deletions over 100 kb were identified in MAGI1 in cases, while only two such CNV events were identified in the same gene in controls (p = .023; Fisher's exact test). Because earlier work had identified a CNV in the close relative MAGI2 in SZ, the study was extended to include MAGI2. In the pooled analysis of MAGI2, two large deletions were found in cases, and two duplications were detected in controls. CONCLUSIONS: Results presented herein provide further evidence for a role of MAGI1 and MAGI2 in BPAD and SZ etiology.

Neurodegenerative phenotypes in an A53T α-synuclein transgenic mouse model are independent of LRRK2.

Mutations in the genes encoding LRRK2 and α-synuclein cause autosomal dominant forms of familial Parkinson's disease (PD). Fibrillar forms of α-synuclein are a major component of Lewy bodies, the intracytoplasmic proteinaceous inclusions that are a pathological hallmark of idiopathic and certain familial forms of PD. LRRK2 mutations cause late-onset familial PD with a clinical, neurochemical and, for the most part, neuropathological phenotype that is indistinguishable from idiopathic PD. Importantly, α-synuclein-positive Lewy bodies are the most common pathology identified in the brains of PD subjects harboring LRRK2 mutations. These observations may suggest that LRRK2 functions in a common pathway with α-synuclein to regulate its aggregation. To explore the potential pathophysiological interaction between LRRK2 and α-synuclein in vivo, we modulated LRRK2 expression in a well-established human A53T α-synuclein transgenic mouse model with transgene expression driven by the hindbrain-selective prion protein promoter. Deletion of LRRK2 or overexpression of human G2019S-LRRK2 has minimal impact on the lethal neurodegenerative phenotype that develops in A53T α-synuclein transgenic mice, including premature lethality, pre-symptomatic behavioral deficits and human α-synuclein or glial neuropathology. We also find that endogenous or human LRRK2 and A53T α-synuclein do not interact together to influence the number of nigrostriatal dopaminergic neurons. Taken together, our data suggest that α-synuclein-related pathology, which occurs predominantly in the hindbrain of this A53T α-synuclein mouse model, occurs largely independently from LRRK2 expression. These observations fail to provide support for a pathophysiological interaction of LRRK2 and α-synuclein in vivo, at least within neurons of the mouse hindbrain.

Adh1 and Adh1/4 knockout mice as possible rodent models for presymptomatic Parkinson's disease.

Alcohol dehydrogenases (ADH) catalyze the reversible metabolism of many types of alcohols and aldehydes to prevent the possible toxic accumulation of these compounds. ADHs are of interest in Parkinson's disease (PD) since these compounds can be harmful to dopamine (DA) neurons. Genetic variants in ADH1C and ADH4 have been found to associate with PD and lack of Adh4 gene activity in a mouse model has recently been reported to induce changes in the DA system. Adh1 knockout (Adh1-/-) and Adh1/4 double knockout (Adh1/4-/-) mice were investigated for possible changes in DA system related activity, biochemical parameters and olfactory function compared to wild-type (WT) mice. Locomotor activity was tested at ∼7 (adult) and >15 months of age to mimic the late onset of PD. Adh1-/- and Adh1/4-/- mice displayed a significantly higher spontaneous locomotor activity than WT littermates. Both apomorphine and d-amphetamine increased total distance activity in Adh1-/- mice at both age intervals and in Adh1/4-/- mice at 7 months of age compared to WT mice. No significant changes were found regarding olfactory function, however biochemical data showed decreased 3,4-dihydroxyphenylacetic acid (DOPAC)/DA ratios in the olfactory bulb and decreased homovanillic acid (HVA)/DA ratios in the olfactory bulb, frontal cortex and striatum of Adh1/4-/- mice compared to WT mice. Our results suggest that lack of Adh1 alone or Adh1 and Adh4 together lead to changes in DA system related behavior, and that these knockout mice might be possible rodent models to study presymptomatic PD.