Animal models of inherited neuropathies

PURPOSE OF REVIEW: Mutations in a number of genes have been associated with inherited neuropathies (Charcot-Marie-Tooth or CMT disease). This review highlights how animal models of demyelinating CMT have improved our understanding of disease mechanisms. Transgenic CMT models also allow therapies to be developed in a preclinical setting. RECENT FINDINGS: Rodent models for the most common subtypes of human CMT disease are now available, and two mouse mutants modeling the rare CMT4B subform have lately extended this repertoire. In a peripheral myelin protein 22 kDa (Pmp22) transgenic rat model of CMT1A, administration of a progesterone receptor antagonist reduced Pmp22 overexpression, axon loss and clinical impairments. Dietary ascorbic acid prevented dysmyelination and premature death in a Pmp22 transgenic mouse line. Neurotrophin-3 promoted small fiber remyelination in CMT1A xenografts and sensory functions in CMT1A patients. Gene expression profiling in rodent models of CMT may identify further therapeutical targets. While original classifications distinguish the demyelinating and axonal forms of CMT, recent findings emphasize that axon loss is a common feature, possibly caused by Schwann cell defects rather than demyelination per se. This supports our model that myelination and long-term axonal support are distinct functions of all myelinating glial cells. SUMMARY: Animal models have opened up new perspectives on the pathomechanisms and possible treatment strategies of inherited neuropathies.     

Mutation analysis of the small heat shock protein 27 gene in chinese patients with Charcot-Marie-Tooth disease

BACKGROUND: Charcot-Marie-Tooth (CMT) disease, the most common hereditary peripheral neuropathy, is highly clinically and genetically heterogeneous, and mutations in at least 18 genes have been identified. Recently, mutations in small heat shock protein 27 (Hsp27) were reported to cause CMT disease type 2F and distal hereditary motor neuropathy. OBJECTIVE: To investigate the frequency and phenotypic features of an Hsp27 mutation in Chinese patients with CMT disease. DESIGN: DNA samples from 114 unrelated patients with CMT disease were screened for mutations in Hsp27 by polymerase chain reaction and direct sequencing. A cosegregated study was performed using the MbiI restriction endonuclease, and 50 healthy control subjects were analyzed. Haplotype analysis was performed using 5 short tandem repeat markers to analyze whether the families with the same mutation probably had a common ancestor. RESULTS: One missense mutation, C379T, was detected in 4 autosomal dominant families with CMT disease type 2, and haplotype analysis indicated that the 4 families probably had a common founder. The frequency of the Hsp27 mutation is 0.9% (1/111) in Chinese patients with CMT disease in our study, and the phenotypes were characterized by later onset (age, 35-60 years) and mild sensory impairments. Electrophysiological findings showed moderately to severely slowed nerve conduction velocities in lower limb nerves but normal or mildly reduced velocities in upper limb nerves. CONCLUSIONS: To our knowledge, this is the first report of an Hsp27 mutation in the People's Republic of China. The C379T mutation in Hsp27 also causes CMT disease type 2, except for distal hereditary motor neuropathy, and the phenotypes are distinct from the family with CMT disease type 2F described previously. A mutation of Hsp27 may be uncommon in Chinese patients with CMT disease.     

Early abnormalities in sciatic nerve function and structure in a rat model of Charcot-Marie-Tooth type 1A disease

We investigated early peripheral nervous system impairment in PMP22-transgenic rats ("CMT rat"), an established animal model for Charcot-Marie-Tooth disease 1A, at postnatal day 30 (P30), when the clinical phenotype is not yet apparent. Hemizygous CMT1A rats and wildtype littermates were studied by means of behavioral examination, electrophysiology, molecular biology, and light microscopy analysis. Behavioral studies only showed, a mild, but significant, decrease in toe spread 1-5, suggesting a weakness of distal foot muscles in CMT1A rats compared with normal littermates. Nerve conduction studies disclosed a severe slowing in motor conduction velocity, a temporal dispersion and a dramatic decrease of amplitude of motor waves in P30 transgenic animals. Coherently with a demyelinating process, affected nerves showed a significant thinning of myelin. Interestingly, axonal diameter and area were unchanged, but expression of non-phosphorylated neurofilaments was increased in CMT1A rats compared with normal controls. Our results confirm the fidelity of this animal model to human disease. Similarly, in young CMT1A patients, the MCV is significantly reduced and the muscle weakness is confined to distal segments, whereas morphological and morphometrical signs of axonal atrophy are absent. However, the presence of a molecular and functional damage of the axons suggests that this may be the correct moment to start neuroprotective therapies.     

Antiprogesterone therapy uncouples axonal loss from demyelination in a transgenic rat model of CMT1A neuropathy

OBJECTIVE: Charcot-Marie-Tooth disease (CMT) is the most common inherited neuropathy, and a duplication of the Pmp22 gene causes the most frequent subform CMT1A. Using a transgenic rat model of CMT1A, we tested the hypothesis that long-term treatment with anti-progesterone (Onapristone) reduces Pmp22 overexpression and improves CMT disease phenotype of older animals, thereby extending a previous proof-of-concept observation in a more clinically relevant setting. METHODS: We applied placebo-controlled progesterone-antagonist therapy to CMT rats for 5 months and performed grip-strength analysis to assess the motor phenotype. Quantitative Pmp22 RT-PCR and complete histological analysis of peripheral nerves and skin biopsies were performed. RESULTS: Anti-progesterone therapy significantly increased muscle strength and muscle mass of CMT rats and reduced the performance difference to wildtype rats by about 50%. Physical improvements can be explained by the prevention of axon loss. Surprisingly, the effects of anti-progesterone were not reflected by improved myelin sheath thickness. Electrophysiology confirmed unaltered NCV, but less reduced CMAP recordings in the treatment group. Moreover, the reduction of Pmp22 mRNA, as quantified in cutaneous nerves, correlated with the clinical phenotype at later stages. INTERPRETATION: Progesterone-antagonist long-term therapy reduces [corrected] Pmp22 overexpression to a degree at which the axonal support function of Schwann cells is better maintained than myelination. This suggests that axonal loss in CMT1A is not caused by demyelination, but rather by a Schwann cell defect that has been partially uncoupled by anti-progesterone treatment. Pmp22 expression analysis in skin may provide a prognostic marker for disease severity and for monitoring future clinical trials.     

Sensorimotor and cognitive function of a NEFL(P22S) mutant model of Charcot-Marie-Tooth disease type 2E

Charcot-Marie-Tooth (CMT) disease is the most frequently encountered hereditary disease causing sensorimotor neuropathies and slowly progressive muscle weakness and atrophy. The P22S mutation of the NEFL gene encoding the light polypeptide neurofilament (NFL) is associated with CMT. To understand more clearly the pathogenesis of sensorimotor dysfunction in CMT, we generated transgenic mice with the NEFL(P22S) mutation under the tet-off tetracycline regulated system with involvement of the Thy1 neuron-specific promoter. NEFL(P22S) transgenic mice exhibited extended duration of the hindlimb clasping response and gait anomalies, as well as sensorimotor deficits in stationary beam and suspended bar tests. In addition, the NEFL(P22S) mice were deficient in the reversal phase of left-right discrimination learning in a water maze. This model mimics some aspects of human CMT pathology and provides an opportunity of ameliorating CMT symptoms with experimental therapies.     

剔除小鼠神经微管运动蛋白Kif1b基因导致类似Charcot-Marie-Tooth病动物模型

目的研究杂合子小鼠Kiflb基因剔除后导致的表现型,探讨其作为类似Charcot-Marie-Tooth （CMT）病动物模型的可行性。方法用Southern blotting和PCR检测同源重组和基因型,Western blotting测定杂合子KIF1B蛋白表达量,行为学实验观察其表现型。结果杂合子Kif1b基因剔除小鼠的KIF1B蛋白表达量减少了一半以上,行为学实验结果表明,杂合子基因剔除小鼠在运动和感觉方面均有异常。Rota-rod实验,Rod walking实验和Wire hanging实验中,野生型小鼠的停留时间均明显长于Kif1b基因剔除小鼠。同时,杂合子Kif1b基因剔除小鼠在热板实验和福尔马林实验中,表现出对温度觉和痛觉反应的迟钝,其反应时间与野生型小鼠相比明显延长,反应强度降低。结论杂合子Kif1b基因剔除小鼠的表现型与人类腓骨肌萎缩症相似,作为疾病模型具备可行性。     

Morphological And Electrophysiological Signs Of Dysmyelination In Transgenic Mice Expressing CMT1B (MPZ DELSer34) or DSS (MPZ Ser34Cys) Mutations

Charcot-Marie-Tooth 1B neuropathy (CMT1B), Déjèrine-Sottas syndrome (DSS) and Congenital Hypomyelination are each associated with mutations in MPZ , encoding P0 glycoprotein, the major structural protein of peripheral nerve myelin. To explore whether new abnormal functions of mutant MPZ can explain this phenotypic diversity, we expressed either of two MPZ mutations: DELSer34 (causing CMT1B) or Ser34Cys (causing DSS) in addition to the two normal endogeneous copies of Mpz in transgenic mice. We have shown previously that overexpression of wild type Mpz causes dose-dependent dysmyelination. However, multiple lines of mice containing the MPZ mutants showed not only hypomyelination, but also abnormalities in myelin sheaths and onion bulbs that were never observed in Mpz overexpressor mice. To create a mouse model of CMT1B with no Mpz overexpression, one line of DELSer34 that expresses mutant Mpz at levels similar to one wildtype Mpz allele was crossed with heterozygous Mpz knock-out mice, to obtain the genotype Mpz ^wt/−/ Mpz ^DELSer34. These mice manifest progressive peripheral neuropathy with hypomyelination, and onion bulbs that appear around 6 months of age. As a first step towards longitudinal studies of phenotype, we performed detailed neurophysiological analyses at 12 months of age. We found signs of demyelination, with statistically significant increases of both motor latency after proximal stimulation and F-wave latencies, and decreases in both motor and mixed afferent nerve conduction velocities of sciatic nerve. The motor response was polyphasic and there was a trend towards reduced CMAP amplitudes. Thus, the clinical onset and progression, pathological features and neurophysiological findings provide a reasonable model of CMT1B. Longitudinal studies to correlate the onset and progression of morphological and electrophysiological abnormalities in these mice are ongoing.     

Synergistic PXT3003 therapy uncouples neuromuscular function from dysmyelination in male Charcot–Marie–Tooth disease type 1A (CMT1A) rats

Charcot–Marie–Tooth disease 1 A (CMT1A) is caused by an intrachromosomal duplication of the gene encoding for PMP22 leading to peripheral nerve dysmyelination, axonal loss, and progressive muscle weakness. No therapy is available. PXT3003 is a low-dose combination of baclofen, naltrexone, and sorbitol which has been shown to improve disease symptoms in Pmp22 transgenic rats, a bona fide model of CMT1A disease. However, the superiority of PXT3003 over its single components or dual combinations have not been tested. Here, we show that in a dorsal root ganglion (DRG) co-culture system derived from transgenic rats, PXT3003 induced myelination when compared to its single and dual components. Applying a clinically relevant (“translational”) study design in adult male CMT1A rats for 3 months, PXT3003, but not its dual components, resulted in improved performance in behavioral motor and sensory endpoints when compared to placebo. Unexpectedly, we observed only a marginally increased number of myelinated axons in nerves from PXT3003-treated CMT1A rats. However, in electrophysiology, motor latencies correlated with increased grip strength indicating a possible effect of PXT3003 on neuromuscular junctions (NMJs) and muscle fiber pathology. Indeed, PXT3003-treated CMT1A rats displayed an increased perimeter of individual NMJs and a larger number of functional NMJs. Moreover, muscles of PXT3003 CMT1A rats displayed less neurogenic atrophy and a shift toward fast contracting muscle fibers. We suggest that ameliorated motor function in PXT3003-treated CMT1A rats result from restored NMJ function and muscle innervation, independent from myelination.     

Nerve conduction abnormalities in the trembler‐j mouse: A model for Charcot‐Marie‐Tooth disease type 1A?

The trembler-j mouse is a spontaneously occurring, demyelinating mutant secondary to a point mutation involving a leucine for proline substitution in the first transmembrane domain of the peripheral-myelin protein-22 (PMP-22) gene. It is considered to be a model for Charcot-Marie-Tooth disease type 1A (CMT1A), largely based upon pathologic observations. However, functional studies demonstrating homology with CMT1A patients have not been documented. Sciatic nerve conduction was performed on 30 and 72-day-old wildtype and trembler-j mice in a blinded fashion. The findings in the mutants in both age groups were consistent with profound demyelination. Trembler-j mice appear to have a greater degree of motor nerve conduction slowing relative to human studies involving patients with PMP-22 gene duplication. Functionally, the trembler-j is a good murine model for CMT1A associated with an identical point mutation but may represent a more severe disease phenotype than CMT1A secondary to PMP-22 gene duplication.     

A low expressor line of transgenic mice carrying a mutant human Cu,Zn superoxide dismutase (SOD1) gene develops pathological changes that most closely resemble those in human amyotrophic lateral sclerosis

About 15–20% of patients with familial amyotrophic lateral sclerosis (ALS) carry one of several missense mutations in the gene for Cu,Zn superoxide dismutase (SOD1). We have previously reported on an animal model of this disease produced by the transgenic expression of a mutant form of human SOD1 containing a Gly⁹³→Ala amino acid substitution. Several lines of transgenic mice were produced, characterized by a differing tempo and severity of disease that generally correlated with the number of mutant gene copies that these lines expressed. We reported that mice expressing high copy numbers (18–25) developed a disease with a relatively short course and with a pathology mainly characterized by severe vacuolar degeneration of motor neurons and their processes. Lewy-like bodies and swollen axons were also present. The exquisite localization to motor neurons was the feature that made the pathology in these overexpressors germane to the human disease. Severe vacuolar degeneration, however, was considered to be at variance with human ALS, in which similar changes have not been described. In the present study, we have made a temporal characterization of microscopic and immunohistochemical changes in a line of transgenic mice expressing lower copy numbers of the mutant gene. These mice, designated G5/G5, survive more than 400 days and present pathological changes which are virtually identical to those in the human disease. In fact, in these animals, anterior horn cell depletion, atrophy, astrocytosis, and the presence of numerous ubiquitinated Lewy-like bodies and axonal swellings are the main pathological features, while vacuolar pathology is minimal. This study underscores the importance of the level of expression of the mutant enzyme in the resulting clinical and pathological disease, and supports the value of this transgenic model as an excellent tool for investigating both pathogenesis of human ALS and possible therapeutic avenues. Received: 11 September 1996 / Revised, accepted: 18 October 1996     

Transgenic mice expressing mutant A53T human alpha-synuclein show neuronal dysfunction in the absence of aggregate formation

Alpha-synuclein was implicated in Parkinson's disease when missense mutations in the alpha-synuclein gene were found in autosomal dominant Parkinson's disease and alpha-synuclein was shown to be a major constituent of protein aggregates in sporadic Parkinson's disease and other synucleinopathies. We have generated transgenic mice expressing A53T mutant and wild-type human alpha-synuclein. The mutant transgenic protein was distributed abnormally to the axons, perikarya, and dendrites of neurons in many brain areas. In electron microscopic immunogold studies, no aggregation of alpha-synuclein was found in these mice. However, behavior analysis showed a progressive reduction of spontaneous vertical motor activity in both mutant lines correlating with the dosage of overexpression. In addition, deficits of grip strength, rotarod performance, and gait were observed in homozygous PrPmtB mice. Transgenic animals expressing mutant alpha-synuclein may be a valuable model to assess specific aspects of the pathogenesis of synucleinopathies.     

Rasagiline is neuroprotective in a transgenic model of multiple system atrophy

Rasagiline is a novel selective irreversible monoamine oxidase-B (MAO-B) inhibitor recently introduced for the symptomatic treatment of Parkinson disease. Like other propargylamines rasagiline has also shown neuroprotective effects independent of MAO-B-inhibition in various in vitro and in vivo models. The present study was performed to test the potential of rasagiline as a disease-modifying agent in multiple system atrophy (MSA) using a transgenic mouse model previously described by our group. (PLP)-alpha-synuclein transgenic mice featuring glial cytoplasmic inclusion pathology underwent 3-nitropropionic acid intoxication to model full-blown MSA-like neurodegeneration. Two doses of rasagiline were used (0.8 and 2.5 mg/kg) for a treatment period of 4 weeks. Rasagiline-treated animals were compared to placebo saline-treated mice by evaluation of motor behaviour and neuropathology. Motor behavioural tests including pole test, stride length test and general motor score evaluation showed improvements in motor deficits associated with 2.5 mg/kg rasagiline therapy. Immunohistochemistry and histology showed significant reduction of 3-NP-induced neuronal loss in striatum, substantia nigra pars compacta, cerebellar cortex, pontine nuclei and inferior olives of MSA mice receiving 2.5 mg/kg rasagiline. The results of the study indicate that rasagiline confers neuroprotection in a transgenic mouse model of MSA and may therefore be considered a promising disease-modifying candidate for human MSA.     

The developmental dynamics of behavioral growth processes in rodent egocentric and allocentric space

Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by marked impairments in motor function caused by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNc). Animal models of PD have traditionally been based on toxins, such as 6-hydroxydopamine (6-OHDA) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), that selectively lesion dopaminergic neurons. Motor impairments from 6-OHDA lesions of SNc neurons are well characterized in rats, but much less work has been done in mice. In this study, we compare the effectiveness of a series of drug-free behavioral tests in assessing sensorimotor impairments in the unilateral 6-OHDA mouse model, including six tests used for the first time in this PD mouse model (the automated treadmill "DigiGait" test, the challenging beam test, the adhesive removal test, the pole test, the adjusting steps test, and the test of spontaneous activity) and two tests used previously in 6-OHDA-lesioned mice (the limb-use asymmetry "cylinder" test and the manual gait test). We demonstrate that the limb-use asymmetry, challenging beam, pole, adjusting steps, and spontaneous activity tests are all highly robust assays for detecting sensorimotor impairments in the 6-OHDA mouse model. We also discuss the use of the behavioral tests for specific experimental objectives, such as simple screening for well-lesioned mice in studies of PD cellular pathophysiology or comprehensive behavioral analysis in preclinical therapeutic testing using a battery of sensorimotor tests.     

Modèles animaux dans la maladie de Charcot-Marie-Tooth et applications de la compréhension de la maladie chez l’homme

Charcot-Marie-Tooth neuropathies (CMT) are inherited neuromuscular disorders caused by length-dependent neurodegeneration of peripheral nerves. More than 900 mutations in 60 different genes are responsible for Charcot-Marie-Tooth neuropathy. Despite significant progress in therapeutic strategies, the disease remains incurable. The increasing number of genes linked to the disease, and their considerable clinical and genetic heterogeneity renders the development of these strategies particularly challenging. In this context, cellular and animals models provide powerful tools. Efficient motor and sensory tests have been developed to assess the behavioral phenotype in transgenic animal models (rodents and fly). When these models reproduce a phenotype comparable to CMT, they allow therapeutic approaches and the discovery of modifiers and biomarkers. The majority of these models concern the demyelinating form (type 1) of the disease. The axonal form (type 2) is less common. Both forms can further be divided into multiple subtypes reflecting the heterogeneity of the disease. In this review, we describe the most convincing transgenic rodent and fly models of CMT and how some of them led to clinical trials.     

Animal models and therapeutic prospects for Charcot–Marie–Tooth disease

Charcot–Marie–Tooth (CMT) neuropathies are inherited neuromuscular disorders caused by a length‐dependent neurodegeneration of peripheral nerves. More than 900 mutations in 60 different genes are causative of the neuropathy. Despite significant progress in therapeutic strategies, the disease remains incurable. The increasing number of genes linked to the disease, and their considerable clinical and genetic heterogeneity render the development of these strategies particularly challenging. In this context, cellular and animals models provide powerful tools. Efficient motor and sensory tests have been developed to assess the behavioral phenotype in transgenic animal models (rodent and fly). When these models reproduce a phenotype comparable to CMT, they allow therapeutic approaches and the discovery of modifiers and biomarkers. In this review, we describe the most convincing transgenic rodent and fly models of CMT and how they can lead to clinical trial. We also discuss the challenges that the research, the clinic, and the pharmaceutical industry will face in developing efficient and accessible treatment for CMT patients. Ann Neurol 2013;74:391–396     

Early Electrophysiological Changes In Transgenic Rat Model Of Charcot-Marie-Tooth

Recently, a reliable transgenic rat model of human Charcot-Marie-Tooth type 1 A has been developed. So far, neurophysiological studies have been performed only in advanced stages of rat disease. Moreover, axonal involvement, which is known to occur in human CMT1A, has never been observed in this rat model. Affected rats show overexpression of Peripheral Myelin Protein (PMP-22) and a peripheral hypomyelinating neuropathy. We perfomed an electrophysiological study in two heterozygous PMP-22 transgenic rats and in one normal control, matched for age (3 weeks) and weight (average: 60 g). Recordings were performed in vivo by stimulating the sciatic nerve at both sciatic notch and ankle sites and recording the Hoffman reflex and direct muscle responses (CMAP). The H-reflex related SNCV and MNCV were calculated by measuring the distance between the sciatic notch and the ankle sites and the respective latencies. The two transgenic rats showed different levels of PMP-22 overexpression, as judged by quantitative PCR. The rat with a lower PMP-22 gene level showed a 30% reduction of MNCV compared to the normal control, while SNCV was not reduced. The CMAP was sized approximately 45% of the normal rat while the ratio between H wave amplitude and CMAP was 30% of the normal, the H wave amplitude being more affected than the CMAP. The action potentials in the rat with a higher transgene level were not recordable. Our data demonstrate that slowing of MNCV is an early finding in the CMT1A rat model. The marked reduction of H wave amplitude in front of a normal SNCV suggests a possible early axonal damage of sensory fibers. The entity of electrophysiological compromission positively correlated with the number of copies for PMP-22 gene. All together these considerations prove the sensitivity of this method, however further studies are needed to confirm these results and to prove that this model may be suitable to investigate the effects of therapeutic approaches.     

Comparison between Clinical Disabilities and Electrophysiological Values in Charcot-Marie-Tooth 1A Patients with PMP22 Duplication

Background and Purpose

Charcot-Marie-Tooth disease (CMT) type 1A (CMT1A) is the demyelinating form of CMT that is significantly associated with PMP22 duplication. Some studies have found that the disease-related disabilities of these patients are correlated with their compound muscle action potentials (CMAPs), while others have suggested that they are related to the nerve conduction velocities. In the present study, we investigated the correlations between the disease-related disabilities and the electrophysiological values in a large cohort of Korean CMT1A patients.

Methods

We analyzed 167 CMT1A patients of Korean origin with PMP22 duplication using clinical and electrophysiological assessments, including the CMT neuropathy score and the functional disability scale.

Results

Clinical motor disabilities were significantly correlated with the CMAPs but not the motor nerve conduction velocities (MNCVs). Moreover, the observed sensory impairments matched the corresponding reductions in the sensory nerve action potentials (SNAPs) but not with slowing of the sensory nerve conduction velocities (SNCVs). In addition, CMAPs were strongly correlated with the disease duration but not with the age at onset. The terminal latency index did not differ between CMT1A patients and healthy controls.

Conclusions

In CMT1A patients, disease-related disabilities such as muscle wasting and sensory impairment were strongly correlated with CMAPs and SNAPs but not with the MNCVs or SNCVs. Therefore, we suggest that the clinical disabilities of CMT patients are determined by the extent of axonal dysfunction.     

α-Synuclein Transgenic Mice Reveal Compensatory Increases in Parkinson's Disease-Associated Proteins DJ-1 and Parkin and Have Enhanced α-Synuclein and PINK1 Levels After Rotenone Treatment

Parkinson's disease (PD) is a severe neurodegenerative disorder characterised by loss of dopaminergic neurons of the substantia nigra. The pathological hallmarks are cytoplasmic inclusions termed Lewy bodies consisting primarily of aggregated α-synuclein (αSN). Different lines of transgenic mice have been developed to model PD but have failed to recapitulate the hallmarks of this disease. Since treatment of rodents with the pesticide rotenone can reproduce nigrostriatal cell loss and other features of PD, we aimed to test chronic oral administration of rotenone to transgenic mice over-expressing human αSN with the A53T mutation. Initial assessment of this transgenic line for compensatory molecular changes indicated decreased brain β-synuclein expression and significantly increased levels of the PD-associated oxidative stress response protein, DJ-1, and the E3 ubiquitin ligase enzyme, Parkin. Rotenone treatment of 30 mg/kg for 25 doses over a 35-day period was tolerated in the transgenic mice and resulted in decreased spontaneous locomotor movement and increased cytoplasmic αSN expression. The mitochondrial Parkinson's-associated PTEN-induced kinase 1 protein levels were also increased in transgenic mouse brain after rotenone treatment; there was no change in brain dopamine levels or nigrostriatal cell loss. These hA53T αSN transgenic mice provide a useful model for presymptomatic Parkinson's features and are valuable for study of associated compensatory changes in early Parkinson's disease stages.