Transforming growth factor-beta 2 causes an acute improvement in the motor performance of transgenic ALS mice

Knockdown of tgfb1a partially improves ALS phenotype in a transient zebrafish model

Amyotrophic lateral sclerosis (ALS) corresponds to a neurodegenerative disorder marked by the progressive degeneration of both upper and lower motor neurons located in the brain, brainstem, and spinal cord. ALS can be broadly categorized into two main types: sporadic ALS (sALS), which constitutes approximately 90% of all cases, and familial ALS (fALS), which represents the remaining 10% of cases. Transforming growth factor type-β (TGF-β) is a cytokine involved in various cellular processes and pathological contexts, including inflammation and fibrosis. Elevated levels of TGF-β have been observed in the plasma and cerebrospinal fluid (CSF) of both ALS patients and mouse models. In this perspective, we explore the impact of the TGF-β signaling pathway using a transient zebrafish model for ALS. Our findings reveal that the knockdown of tgfb1a lead to a partial prevention of motor axon abnormalities and locomotor deficits in a transient ALS zebrafish model at 48 h post-fertilization (hpf). In this context, we delve into the proposed distinct roles of TGF-β in the progression of ALS. Indeed, some evidence suggests a dual role for TGF-β in ALS progression. Initially, it seems to exert a neuroprotective effect in the early stages, but paradoxically, it may contribute to disease progression in later stages. Consequently, we suggest that the TGF-β signaling pathway emerges as an attractive therapeutic target for treating ALS. Nevertheless, further research is crucial to comprehensively understand the nuanced role of TGF-β in the pathological context.

Neuromuscular Junction Dysfunction in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurological disorder characterized by progressive degeneration of motor neurons leading to skeletal muscle denervation. Earlier studies have shown that motor neuron degeneration begins in motor cortex and descends to the neuromuscular junction (NMJ) in a dying forward fashion. However, accumulating evidences support that ALS is a distal axonopathy where early pathological changes occur at the NMJ, prior to onset of clinical symptoms and propagates towards the motor neuron cell body supporting "dying back" hypothesis. Despite several evidences, series of events triggering NMJ disassembly in ALS are still obscure. Neuromuscular junction is a specialized tripartite chemical synapse which involves a well-coordinated communication among the presynaptic motor neuron, postsynaptic skeletal muscle, and terminal Schwann cells. This review provides comprehensive insight into the role of NMJ in ALS pathogenesis. We have emphasized the molecular alterations in cellular components of NMJ leading to loss of effective neuromuscular transmission in ALS. Further, we provide a preview into research involved in exploring NMJ as potential target for designing effective therapies for ALS.

Association of Single Nucleotide Polymorphism at rs2275294 in the ZNF512B Gene with Prognosis in Amyotrophic Lateral Sclerosis

The aim of this study is to explore whether the single nucleotide polymorphism rs2275294 in the ZNF512B gene is related to the length of survival of patients with amyotrophic lateral sclerosis (ALS). This prospective study examined 212 patients with ALS, who were genotyped at the rs2275294 locus in ZNF512B using the ligase method. Genotype was compared with clinical data and survival. Kaplan-Meier survival analysis and Cox hazard regression were used to identify risk factors of shorter survival. Our results were meta-analyzed together with previous work in order to examine the potential association between the rs2275294-C allele and survival. Of the 212 patients, 166 carried the CC + CT genotype at the rs2275294 locus, while 46 carried the TT genotype. Patients with the C allele showed significantly shorter survival than those without it (34.13 ± 1.9 vs. 45.32 ± 5.7 months, p = 0.036). Cox analysis identified the C allele and time from symptom onset to diagnosis as risk factors for shorter survival. Meta-analysis of 447 patients in China and Japan confirmed the rs2275294-C allele to be an independent risk factor of shorter survival in ALS patients. The C allele at the rs2275294 locus in ZNF512B is a risk factor for shorter survival in patients with ALS.

Multiple Roles of Transforming Growth Factor Beta in Amyotrophic Lateral Sclerosis

Transforming growth factor beta (TGFB) is a pleiotropic cytokine known to be dysregulated in many neurodegenerative disorders and particularly in amyotrophic lateral sclerosis (ALS). This motor neuronal disease is non-cell autonomous, as it affects not only motor neurons but also the surrounding glial cells, and the target skeletal muscle fibers. Here, we analyze the multiple roles of TGFB in these cell types, and how TGFB signaling is altered in ALS tissues. Data reported support a crucial involvement of TGFB in the etiology and progression of ALS, leading us to hypothesize that an imbalance of TGFB signaling, diminished at the pre-symptomatic stage and then increased with time, could be linked to ALS progression. A reduced stimulation of the TGFB pathway at the beginning of disease blocks its neuroprotective effects and promotes glutamate excitotoxicity. At later disease stages, the persistent activation of the TGFB pathway promotes an excessive microglial activation and strengthens muscular dysfunction. The therapeutic potential of TGFB is discussed, in order to foster new approaches to treat ALS.

Massive transcriptome sequencing of human spinal cord tissues provides new insights into motor neuron degeneration in ALS

ALS is a devastating and debilitating human disease characterized by the progressive death of upper and lower motor neurons. Although much effort has been made to elucidate molecular determinants underlying the onset and progression of the disorder, the causes of ALS remain largely unknown. In the present work, we have deeply sequenced whole transcriptome from spinal cord ventral horns of post-mortem ALS human donors affected by the sporadic form of the disease (which comprises ~90% of the cases but which is less investigated than the inherited form of the disease). We observe 1160 deregulated genes including 18 miRNAs and show that down regulated genes are mainly of neuronal derivation while up regulated genes have glial origin and tend to be involved in neuroinflammation or cell death. Remarkably, we find strong deregulation of SNAP25 and STX1B at both mRNA and protein levels suggesting impaired synaptic function through SNAP25 reduction as a possible cause of calcium elevation and glutamate excitotoxicity. We also note aberrant alternative splicing but not disrupted RNA editing.

TGF-β Family Signaling in Neural and Neuronal Differentiation, Development, and Function

Signaling by the transforming growth factor β (TGF-β) family is necessary for proper neural development and function throughout life. Sequential waves of activation, inhibition, and reactivation of TGF-β family members regulate numerous elements of the nervous system from the earliest stages of embryogenesis through adulthood. This review discusses the expression, regulation, and function of TGF-β family members in the central nervous system at various developmental stages, beginning with induction and patterning of the nervous system to their importance in the adult as modulators of inflammatory response and involvement in degenerative diseases.

Reactive Astrocytes Promote ALS-like Degeneration and Intracellular Protein Aggregation in Human Motor Neurons by Disrupting Autophagy through TGF-β1

Amyotrophic lateral sclerosis (ALS) is a fatal and rapidly progressing motor neuron disease. Astrocytic factors are known to contribute to motor neuron degeneration and death in ALS. However, the role of astrocyte in promoting motor neuron protein aggregation, a disease hallmark of ALS, remains largely unclear. Here, using culture models of human motor neurons and primary astrocytes of different genotypes (wild-type or SOD1 mutant) and reactive states (non-reactive or reactive), we show that reactive astrocytes, regardless of their genotypes, reduce motor neuron health and lead to moderate neuronal loss. After prolonged co-cultures of up to 2 months, motor neurons show increased axonal and cytoplasmic protein inclusions characteristic of ALS. Reactive astrocytes induce protein aggregation in part by releasing transforming growth factor β1 (TGF-β1), which disrupts motor neuron autophagy through the mTOR pathway. These results reveal the important contribution of reactive astrocytes in promoting aspects of ALS pathology independent of genetic influences.

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Reactive astrocytes induce ALS-like protein aggregation in human motor neurons

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Reactive astrocytes have increased secretion of TGF-β1

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TGF-β1 induces axonal and cytoplasmic protein aggregation in hMNs

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TGF-β1 activates PI3K/AKT/mTOR pathway and impairs autophagy in hMNs

ALS skeletal muscle shows enhanced TGF-β signaling, fibrosis and induction of fibro/adipogenic progenitor markers

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease in which upper and lower motoneurons degenerate leading to muscle wasting, paralysis and eventually death from respiratory failure. Several studies indicate that skeletal muscle contributes to disease progression; however the molecular mechanisms remain elusive. Fibrosis is a common feature in skeletal muscle under chronic damage conditions such as those caused by muscular dystrophies or denervation. However, the exact mechanisms of fibrosis induction and the cellular bases of this pathological response are unknown. We show that extracellular matrix (ECM) components are augmented in skeletal muscles of symptomatic hSOD1^G93A mice, a widely used murine model of ALS. These mice also show increased TGF-β1 mRNA levels, total Smad3 protein levels and p-Smad3 positive nuclei. Furthermore, platelet-derived growth factor receptor-α (PDGFRα), Tcf4 and α-smooth muscle actin (α-SMA) levels are augmented in the skeletal muscle of symptomatic hSOD1^G93A mice. Additionally, the fibro/adipogenic progenitors (FAPs), which are the main producers of ECM constituents, are also increased in these pathogenic conditions. Therefore, FAPs and ECM components are more abundant in symptomatic stages of the disease than in pre-symptomatic stages. We present evidence that fibrosis observed in skeletal muscle of symptomatic hSOD1^G93A mice is accompanied with an induction of TGF-β signaling, and also that FAPs might be involved in triggering a fibrotic response. Co-localization of p-Smad3 positive cells together with PDGFRα was observed in the interstitial cells of skeletal muscles from symptomatic hSOD1^G93A mice. Finally, the targeting of pro-fibrotic factors such as TGF-β, CTGF/CCN2 and platelet-derived growth factor (PDGF) signaling pathway might be a suitable therapeutic approach to improve muscle function in several degenerative diseases.

Transforming Growth Factor Beta (TGF-β) Is a Muscle Biomarker of Disease Progression in ALS and Correlates with Smad Expression

We recently identified Smads1, 5 and 8 as muscle biomarkers in human ALS. In the ALS mouse, these markers are elevated and track disease progression. Smads are signal transducers and become activated upon receptor engagement of ligands from the TGF-β superfamily. Here, we sought to characterize ligands linked to activation of Smads in ALS muscle and their role as biomarkers of disease progression. RNA sequencing data of ALS muscle samples were mined for TGF-β superfamily ligands. Candidate targets were validated by qRT-PCR in a large cohort of human ALS muscle biopsy samples and in the G93A SOD1 mouse. Protein expression was evaluated by Western blot, ELISA and immunohistochemistry. C2C12 muscle cells were used to assess Smad activation and induction. TGF-β1, 2 and 3 mRNAs were increased in ALS muscle samples compared to controls and correlated with muscle strength and Smads1, 2, 5 and 8. In the G93A SOD1 mouse, the temporal pattern of TGF-β expression paralleled the Smads and increased with disease progression. TGF-β1 immunoreactivity was detected in mononuclear cells surrounding muscle fibers in ALS samples. In muscle cells, TGF-β ligands were capable of activating Smads. In conclusion, TGF-β1, 2 and 3 are novel biomarkers of ALS in skeletal muscle. Their correlation with weakness in human ALS and their progressive increase with advancing disease in the ALS mouse suggest that they, as with the Smads, can track disease progression. These ligands are capable of upregulating and activating Smads and thus may contribute to the Smad signaling pathway in ALS muscle.

Dysregulated expression of death, stress and mitochondrion related genes in the sciatic nerve of presymptomatic SOD1(G93A) mouse model of Amyotrophic Lateral Sclerosis

Schwann cells are the main source of paracrine support to motor neurons. Oxidative stress and mitochondrial dysfunction have been correlated to motor neuron death in Amyotrophic Lateral Sclerosis (ALS). Despite the involvement of Schwann cells in early neuromuscular disruption in ALS, detailed molecular events of a dying-back triggering are unknown. Sciatic nerves of presymptomatic (60-day-old) SOD1(G93A) mice were submitted to a high-density oligonucleotide microarray analysis. DAVID demonstrated the deregulated genes related to death, stress and mitochondrion, which allowed the identification of Cell cycle, ErbB signaling, Tryptophan metabolism and Rig-I-like receptor signaling as the most representative KEGG pathways. The protein-protein interaction networks based upon deregulated genes have identified the top hubs (TRAF2, H2AFX, E2F1, FOXO3, MSH2, NGFR, TGFBR1) and bottlenecks (TRAF2, E2F1, CDKN1B, TWIST1, FOXO3). Schwann cells were enriched from the sciatic nerve of presymptomatic mice using flow cytometry cell sorting. qPCR showed the up regulated (Ngfr, Cdnkn1b, E2f1, Traf2 and Erbb3, H2afx, Cdkn1a, Hspa1, Prdx, Mapk10) and down-regulated (Foxo3, Mtor) genes in the enriched Schwann cells. In conclusion, molecular analyses in the presymptomatic sciatic nerve demonstrated the involvement of death, oxidative stress, and mitochondrial pathways in the Schwann cell non-autonomous mechanisms in the early stages of ALS.

Characterization of the Contribution of Genetic Background and Gender to Disease Progression in the SOD1 G93A Mouse Model of Amyotrophic Lateral Sclerosis: A Meta-Analysis

Background: The SOD1 G93A mouse model of amyotrophic lateral sclerosis (ALS) is the most frequently used model to examine ALS pathophysiology. There is a lack of homogeneity in usage of the SOD1 G93A mouse, including differences in genetic background and gender, which could confound the field’s results.

Objective: In an analysis of 97 studies, we characterized the ALS progression for the high transgene copy control SOD1 G93A mouse on the basis of disease onset, overall lifespan, and disease duration for male and female mice on the B6SJL and C57BL/6J genetic backgrounds and quantified magnitudes of differences between groups.

Methods: Mean age at onset, onset assessment measure, disease duration, and overall lifespan data from each study were extracted and statistically modeled as the response of linear regression with the sex and genetic background factored as predictors. Additional examination was performed on differing experimental onset and endpoint assessment measures.

Results: C57BL/6 background mice show delayed onset of symptoms, increased lifespan, and an extended disease duration compared to their sex-matched B6SJL counterparts. Female B6SJL generally experience extended lifespan and delayed onset compared to their male counterparts, while female mice on the C57BL/6 background show delayed onset but no difference in survival compared to their male counterparts. Finally, different experimental protocols (tremor, rotarod, etc.) for onset determination result in notably different onset means.

Conclusions: Overall, the observed effect of sex on disease endpoints was smaller than that which can be attributed to the genetic background. The often-reported increase in lifespan for female mice was observed only for mice on the B6SJL background, implicating a strain-dependent effect of sex on disease progression that manifests despite identical mutant SOD1 expression.

Smad3 deficiency increases cortical and hippocampal neuronal loss following traumatic brain injury

Transforming growth factor-β (TGF-β) signaling is involved in pathological processes following brain injury. TGF-β signaling through Smad3 contributes significantly to the immune response and glial scar formation after brain injury. However, TGF-β is also neuroprotective, suggesting that Smad3 signaling may also be involved in neuroprotection after injury. We found expression of the TGF-β type II receptor (TβRII) and Smad3 protein to be strongly and rapidly induced in neurons in the ipsilateral cortex and CA1 region of the hippocampus after stab wound injury. In contrast, astrocytic expression of TβRII and Smad3 was induced more slowly. Comparison of the response of wild-type and Smad3 null mice to cortical stab wound injury showed a more pronounced loss of neuronal viability in Smad3 null mice. Neuronal density was more strongly reduced in Smad3 null mice than in wild-type mice at 1 and 3days post lesion in both the ipsilateral cortex and hippocampal CA1 region. Fluoro-Jade B, TUNEL staining, and cleaved caspase-3 staining also demonstrated increased neuronal degeneration at early time points after injury in the ipsilateral hemisphere in Smad3 null mice. Taken together, our results suggest that TGF-β cytokine family signaling through Smad3 protects neurons in the damaged cortex and hippocampus at early time points after injury.

A multilevel screening strategy defines a molecular fingerprint of proregenerative olfactory ensheathing cells and identifies SCARB2, a protein that improves regenerative sprouting of injured sensory spinal axons

Olfactory ensheathing cells (OECs) have neuro-restorative properties in animal models for spinal cord injury, stroke, and amyotrophic lateral sclerosis. Here we used a multistep screening approach to discover genes specifically contributing to the regeneration-promoting properties of OECs. Microarray screening of the injured olfactory pathway and of cultured OECs identified 102 genes that were subsequently functionally characterized in cocultures of OECs and primary dorsal root ganglion (DRG) neurons. Selective siRNA-mediated knockdown of 16 genes in OECs (ADAMTS1, BM385941, FZD1, GFRA1, LEPRE1, NCAM1, NID2, NRP1, MSLN, RND1, S100A9, SCARB2, SERPINI1, SERPINF1, TGFB2, and VAV1) significantly reduced outgrowth of cocultured DRG neurons, indicating that endogenous expression of these genes in OECs supports neurite extension of DRG neurons. In a gain-of-function screen for 18 genes, six (CX3CL1, FZD1, LEPRE1, S100A9, SCARB2, and SERPINI1) enhanced and one (TIMP2) inhibited neurite growth. The most potent hit in both the loss- and gain-of-function screens was SCARB2, a protein that promotes cholesterol secretion. Transplants of fibroblasts that were genetically modified to overexpress SCARB2 significantly increased the number of regenerating DRG axons that grew toward the center of a spinal cord lesion in rats. We conclude that expression of SCARB2 enhances regenerative sprouting and that SCARB2 contributes to OEC-mediated neuronal repair.

Intricate interplay between astrocytes and motor neurons in ALS

ALS results from the selective and progressive degeneration of motor neurons. Although the underlying disease mechanisms remain unknown, glial cells have been implicated in ALS disease progression. Here, we examine the effects of glial cell/motor neuron interactions on gene expression using the hSOD1(G93A) (the G93A allele of the human superoxide dismutase gene) mouse model of ALS. We detect striking cell autonomous and nonautonomous changes in gene expression in cocultured motor neurons and glia, revealing that the two cell types profoundly affect each other. In addition, we found a remarkable concordance between the cell culture data and expression profiles of whole spinal cords and acutely isolated spinal cord cells during disease progression in the G93A mouse model, providing validation of the cell culture approach. Bioinformatics analyses identified changes in the expression of specific genes and signaling pathways that may contribute to motor neuron degeneration in ALS, among which are TGF-β signaling pathways.

ZNF512B gene is a prognostic factor in patients with amyotrophic lateral sclerosis

Recently, Iida et al. discovered a new single-nucleotide polymorphism (SNP) in the ZNF512B gene associated with susceptibility to amyotrophic lateral sclerosis (ALS). The ZNF512B gene was found to be a transcription factor promoting the expression of a downstream gene in the signal transduction pathway of the transforming growth factor-β (TGF-β), which is essential for the protection and survival of neurons but the influence of the new SNP (rs2275294) in actual ALS patients remained unknown. The objective of our study was to examine whether the new SNP in the ZNF512B gene might influence the phenotype of ALS. We conducted a retrospective analysis of the ZNF512B gene in 176 patients diagnosed as having ALS at our hospital. Evaluation of the prognosis after the onset using Kaplan-Meier survival curves in patients with versus without the risk allele (C allele: CC and CT genotypes) revealed a significantly lower survival probability in those with the risk allele (log-rank test, P<0.01), independent of the other prognostic factors in ALS. Our study revealed the influence of the new SNP in actual ALS patients. It would be clinically reasonable to suggest that the ZNF512B gene is a new prognostic factor in ALS. This study is the first, as per our knowledge, to indicate that the association between the new susceptibility gene for ALS and its pathway could be identified.

Ablation of proliferating cells in the CNS exacerbates motor neuron disease caused by mutant superoxide dismutase

Proliferation of glia and immune cells is a common pathological feature of many neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). Here, to investigate the role of proliferating cells in motor neuron disease, SOD1(G93A) transgenic mice were treated intracerebroventicularly (i.c.v.) with the anti-mitotic drug cytosine arabinoside (Ara-C). I.c.v. delivery of Ara-C accelerated disease progression in SOD1(G93A) mouse model of ALS. Ara-C treatment caused substantial decreases in the number of microglia, NG2+ progenitors, Olig2+ cells and CD3+ T cells in the lumbar spinal cord of symptomatic SOD1(G93A) transgenic mice. Exacerbation of disease was also associated with significant alterations in the expression inflammatory molecules IL-1β, IL-6, TGF-β and the growth factor IGF-1.

TGF-beta2 alters the characteristics of the neuromuscular junction by regulating presynaptic quantal size

The amount of neurotransmitter released from a presynaptic terminal is the product of the quantal content (number of vesicles) and the presynaptic quantal size (QSpre, amount of transmitter per vesicle). QSpre varies with synaptic use, but its regulation is poorly understood. The motor nerve terminals at the neuromuscular junction (NMJ) contain TGF-beta receptors. We present evidence that TGF-beta2 regulates QSpre at the NMJ. Application of TGF-beta2 to the rat diaphragm NMJ increased the postsynaptic response to both spontaneous and evoked release of acetylcholine, whereas antibodies to TGF-beta2 or its receptor had the converse effect. L-vesamicol and bafilomycin blocked the actions of TGF-beta2, indicating that TGF-beta2 acts by altering the extent of vesicular filling. Recordings of the postsynaptic currents from the diaphragm were consistent with TGF-beta2 having this presynaptic action and a lesser postsynaptic effect on input resistance. TGF-beta2 also decreased quantal content by an atropine-sensitive pathway, indicating that this change is secondary to cholinergic feedback on vesicular release. Consequently, the net actions of TGF-beta2 at the NMJ were to amplify the postsynaptic effects of spontaneous transmission and to diminish the number of vesicles used per evoked stimulus, without diminishing the amount of acetylcholine released.

Phosphorylated Smad2/3 immunoreactivity in sporadic and familial amyotrophic lateral sclerosis and its mouse model

Phosphorylated Smad2/3 (pSmad2/3), the central mediators of transforming growth factor (TGF)-beta signaling, were recently identified in tau-positive inclusions in certain neurodegenerative disorders. To clarify whether the localization of pSmad2/3 is altered in amyotrophic lateral sclerosis (ALS), we immunohistochemically examined spinal cords from sporadic ALS (SALS), from familial ALS (FALS) patients with the A4V mutation in their Cu/Zn superoxide dismutase (SOD1) gene, and from G93A mutant SOD1 transgenic (mSOD1 Tg) mice. In control spinal cords, pSmad2/3 immunoreactivity was observed exclusively in neuronal and glial nuclei. In SALS and FALS patients the nuclei showed increased immunoreactivity for pSmad2/3. Noticeably, round hyaline inclusions (RHIs) and skein-like inclusions of SALS patients were immunoreactive for pSmad2/3. Double immunofluorescence staining for pSmad2/3 and transactive response-DNA-binding protein (TDP)-43 revealed co-localization of these proteins within RHIs. In contrast, Bunina bodies in SALS and Lewy body-like hyaline inclusions (LBHIs) in FALS were devoid of labeling for pSmad2/3. Similarly, in the mSOD1 Tg mice pSmad2/3 immunoreactivity was increased in the nuclei, while LBHIs were not labeled. These findings suggest increased TGF-beta-Smad signaling in SALS, FALS, and mSOD1 Tg mice, as well as impaired TGF-beta signal transduction in RHI-bearing neurons of SALS patients, presumably at the step of pSmad2/3 translocation into the nucleus. The pathomechanisms, including the process of inclusion development, appears to be different between SALS and mSOD1-related FALS or Tg mice.

Muscle-derived but not centrally derived transgene GDNF is neuroprotective in G93A-SOD1 mouse model of ALS

Glial cell line-derived neurotrophic factor (GDNF) is a potent survival factor for motoneurons (MNs), and is considered a potential agent for the treatment of amyotrophic lateral sclerosis (ALS) and other MN diseases. The effectiveness of GDNF may depend significantly upon its route of delivery to MNs. In this study we tested the neuroprotective effects of target-derived and centrally derived GDNF in the G93A-SOD1 mouse model of ALS using a transgenic approach. We found that overexpression of GDNF in the skeletal muscle (Myo-GDNF mice) significantly delayed the onset of disease and increased the life span of G93A-SOD1 mice by 17 days. The duration of disease also increased by 8.5 days, indicating that GDNF slowed down the progression of disease. Locomotor performance in Myo-GDNF/G93A-SOD1 mice was also significantly improved. The behavioral improvement correlated well with anatomical and histological data. We demonstrated that muscle-derived GDNF resulted in increased survival of spinal MNs, and twice as many MNs survived in end-stage double transgenic mice compared to end-stage G93A-SOD1 mice. Muscle-derived GDNF also had profound effects on muscle innervation and axonal degeneration. Significantly higher numbers of completely or partially innervated NMJs and large caliber myelinated axons were found in double transgenic mice. In contrast, we demonstrated that overexpression of GDNF in astrocytes in the CNS (GFAP-GDNF mice) failed to demonstrate any neuroprotective effects in G93A-SOD1 mice both on behavioral and histological levels. These data indicate that retrograde transport and signaling of GDNF is more physiological and effective for ALS treatment than anterogradely transported GDNF.

Transforming growth factor beta2 haploinsufficient mice develop age-related nigrostriatal dopamine deficits

The transforming growth factor-betas (TGF-betas) regulate the induction of dopaminergic neurons and are elevated in the CSF of Parkinson's patients. We report here that mice with TGF-beta2 haploinsufficiency (TGF-beta2+/-) have subclinical defects in the dopaminergic neurons of their substantia nigra pars compacta. At 6 weeks of age, the TGF-beta2+/- mice had 12% fewer dopaminergic neurons than wild-type littermates. No additional loss of neurons occurred during the next 5 months, although striatal dopamine declined to 70% of normal. The level of 3,4-dihydroxphenylacetic acid was normal in the TGF-beta2+/- mice, indicating that a compensatory mechanism maintains dopamine stimulation of their striatum. The TGF-beta2+/- mice had normal sensitivity to the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, despite having reduced levels of monoamine oxidase-B. These results raise the possibility that people with naturally low levels of TGF-beta2 may have less functional reserve in their nigrostriatal pathway, causing them to be at increased risk of developing Parkinson disease.