Modulation of α-synuclein expression in transgenic animals for modelling synucleinopathies — is the juice worth the squeeze?

Studies of various animal models have made a substantial contribution to the recent progress in understanding the molecular and cellular basis of neurodegenerative disorders. Modelling of neuro-degeneration by genetic alteration of laboratory animals became one of the most powerful tools of modern experimental neurology. The crucial event in pathogenesis of neurodegenerative diseases known as synucleinopathies is modification of α-synuclein metabolism caused by missense mutations, increased expression of the gene, or impaired degradation or intracellular compart-mentalisation of the protein. Therefore, manipulations with expression of α-synuclein in laboratory animals were widely used for creating models of these diseases. In the present review we discuss strong and weak sides of such models, what has been already learned from studies of these animals and what types of models might be useful to further our knowledge about pathogenesis of different synucleinopathies

γ-synuclein is a novel player in the control of body lipid metabolism

Peer reviewedPublisher PD

Molecular cloning and expression pattern of rpr-1, a resiniferatoxin-binding, phosphotriesterase-related protein, expressed in rat kidney tubules1The sequence of rpr-1 has the EMBL accession number X99477.1

AbstractBacterial phosphotriesterases are enzymes that hydrolyse phosphotriester-containing organophosphate pesticides. Resiniferatoxin is a vanilloid that desensitises nociceptive neurons. By screening a rat cDNA library with labelled resiniferatoxin, we unexpectedly isolated a novel rat phosphotriesterase homologue, here named rpr-1, that encodes a 349 amino acid, 39 kDa protein (confirmed by in vitro translation). Northern blotting and in situ hybridisation show expression primarily in proximal tubules of the kidney, in which rpr-1 distribution correlates with resiniferatoxin-binding activity. These results suggest an unsuspected link between the phosphotriesterase enzyme family and resiniferatoxin toxicity and pharmacology

Combinational losses of synucleins reveal their differential requirements for compensating age-dependent alterations in motor behavior and dopamine metabolism

Synucleins are involved in multiple steps of the neurotransmitter turnover but the largely normal synaptic function in young adult animals completely lacking synucleins suggests their roles are dispensable for execution of these processes. Instead, they may be utilized for boosting the efficiency of certain molecular mechanisms in presynaptic terminals, with a deficiency of synuclein proteins sensitizing to or exacerbating synaptic malfunction caused by accumulation of mild alterations, which are commonly associated with aging. Although functional redundancy within the family has been reported, it is unclear whether the remaining synucleins can fully compensate for the deficiency of a lost family member, or whether some functions are specific for a particular member. We assessed several structural and functional characteristics of the nigrostriatal system of mice lacking members of the synuclein family in every possible combination and demonstrated that stabilization of the striatal dopamine level depends on the presence of α-synuclein and cannot be compensated for by other family members, whereas β-synuclein is required for efficient maintenance of animal’s balance and coordination in old age

Disruption of electroencephalogram coherence between cortex/striatum and midbrain dopaminergic regions in the knock-out mice with combined loss of alpha, beta, and gamma synucleins

The malfunctioning of the brain synucleins is associated with pathogenesis of Parkinson’s disease. Synucleins’ ability to modulate various pre-synaptic processes suggests their modifying effects on the electroencephalogram (EEG) recorded from different brain structures. Disturbances in interrelations between them are critical for the onset and evolution of neurodegenerative diseases. Recently, we have shown that, in mice lacking several synucleins, differences between the frequency spectra of EEG from different brain structures are correlated with specificity of synucleins’ combinations. Given that EEG spectra are indirect characteristics of inter-structural relations, in this study, we analyzed a coherence of instantaneous values for EEGs recorded from different structures as a direct measure of “functional connectivity” between them. Methods: EEG data from seven groups of knock-out (KO) mice with combined deletions of alpha, beta, and gamma synucleins versus a group of wild-type (WT) mice were compared. EEG coherence was estimated between the cortex (MC), putamen (Pt), ventral tegmental area (VTA), and substantia nigra (SN) in all combinations. Results: EEG coherence suppression, predominantly in the beta frequency band, was observed in KO mice versus WT littermates. The suppression was minimal in MC-Pt and VTA-SN interrelations in all KO groups and in all inter-structural relations in mice lacking either all synucleins or only beta synuclein. In other combinations of deleted synucleins, significant EEG coherence suppression in KO mice was dominant in relations with VTA and SN. Conclusion: Deletions of the synucleins produced significant attenuation of intra-cerebral EEG coherence depending on the imbalance of different types of synucleins

Synuclein deficiency results in age-related respiratory and cardiovascular dysfunctions in mice

Synuclein (α, β, and γ) proteins are highly expressed in presynaptic terminals, and significant data exist supporting their role in regulating neurotransmitter release. Targeting the gene encoding α-synuclein is the basis of many animal models of Parkinson’s disease (PD). However, the physiological role of this family of proteins in not well understood and could be especially relevant as interfering with accumulation of α-synuclein level has therapeutic potential in limiting PD progression. The long-term effects of their removal are unknown and given the complex pathophysiology of PD, could exacerbate other clinical features of the disease, for example dysautonomia. In the present study, we sought to characterize the autonomic phenotypes of mice lacking all synucleins (α, β, and γ; αβγ−/−) in order to better understand the role of synuclein-family proteins in autonomic function. We probed respiratory and cardiovascular reflexes in conscious and anesthetized, young (4 months) and aged (18–20 months) αβγ−/− male mice. Aged mice displayed impaired respiratory responses to both hypoxia and hypercapnia when breathing activities were recorded in conscious animals using whole-body plethysmography. These animals were also found to be hypertensive from conscious blood pressure recordings, to have reduced pressor baroreflex gain under anesthesia, and showed reduced termination of both pressor and depressor reflexes. The present data demonstrate the importance of synuclein in the normal function of respiratory and cardiovascular reflexes during aging

Generation of mouse lines with conditionally or constitutively inactivated Snca gene and Rosa26-stop-lacZ reporter located in cis on the mouse chromosome 6

α-Synuclein is involved in many important molecular processes in neuronal cells and their synapses, and its malfunction has been linked to the development of Parkinson’s and certain other neurodegenerative diseases. Animal models allowing tightly monitored conditional inactivation of the encoding gene, Snca, are indispensible for studies aimed at understanding normal function of α-synuclein in various neuronal populations and its role in pathogenesis of neurodegenerative diseases. We have recently reported the production of several novel mouse lines for manipulating expression of the endogenous Snca gene, including a line for Cre-recombinase-driven conditional inactivation of the gene (mice with floxed Snca) and a new line with a constitutive knockout of α-synuclein. Rosa26-stop-lacZ reporter cassette is commonly used for monitoring efficiency of Cre-recombination but in mouse genome Snca and Rosa26 loci are located on the same chromosome. Here we describe production of lines with a modified Snca locus, either floxed or constitutively inactivated and the Rosa26-stop-lacZ reporter cassette located in cis on the mouse chromosome 6. These new mouse lines are invaluable for fast identification of cells with inactivation of Snca by Cre-recombination and represent useful tools for in vivo studies of α-synuclein function and dysfunctio

Selective pattern of motor system damage in gamma-synuclein transgenic mice mirrors the respective pathology in amyotrophic lateral sclerosis

AbstractAmyotrophic lateral sclerosis (ALS) is characterised by substantial loss of both upper and lower motor neuron function, with sensory and cognitive systems less affected. Though heritable forms of the disease have been described, the vast majority of cases are sporadic with poorly defined underlying pathogenic mechanisms. Here we demonstrate that the neurological pathology induced in transgenic mice by overexpression of γ-synuclein, a protein not previously associated with ALS, recapitulates key features of the disease, namely selective damage and loss of discrete populations of upper and lower motor neurons and their axons, contrasted by limited effects upon the sensory system

Triple-knockout, synuclein-free mice display compromised lipid pattern

Recent studies have implicated synucleins in several reactions during the biosynthesis of lipids and fatty acids in addition to their recognised role in membrane lipid binding and synaptic functions. These are among aspects of decreased synuclein functions that are still poorly acknowledged especially in regard to pathogenesis in Parkinson’s disease. Here, we aimed to add to existing knowledge of synuclein deficiency (i.e., the lack of all three family members), with respect to changes in fatty acids and lipids in plasma, liver, and two brain regions in triple synuclein-knockout (TKO) mice. We describe changes of long-chain polyunsaturated fatty acids (LCPUFA) and palmitic acid in liver and plasma, reduced triacylglycerol (TAG) accumulation in liver and non-esterified fatty acids in plasma of synuclein free mice. In midbrain, we observed counterbalanced changes in the relative concentrations of phosphatidylcholine (PC) and cerebrosides (CER). We also recorded a notable reduction in ethanolamine plasmalogens in the midbrain of synuclein free mice, which is an important finding since the abnormal ether lipid metabolism usually associated with neurological disorders. In summary, our data demonstrates that synuclein deficiency results in alterations of the PUFA synthesis, storage lipid accumulation in the liver, and the reduction of plasmalogens and CER, those polar lipids which are principal compounds of lipid rafts in many tissues. An ablation of all three synuclein family members causes more profound changes in lipid metabolism than changes previously shown to be associated with γ-synuclein deficiency alone. Possible mechanisms by which synuclein deficiency may govern the reported modifications of lipid metabolism in TKO mice are proposed and discussed