Mutations In Dynein Research Articles

Structures of human dynein in complex with the lissencephaly 1 protein, LIS1.

The lissencephaly 1 protein, LIS1, is mutated in type-1 lissencephaly and is a key regulator of cytoplasmic dynein-1. At a molecular level, current models propose that LIS1 activates dynein by relieving its autoinhibited form. Previously we reported a 3.1 Å structure of yeast dynein bound to Pac1, the yeast homologue of LIS1, which revealed the details of their interactions (Gillies et al., 2022). Based on this structure, we made mutations that disrupted these interactions and showed that they were required for dynein's function in vivo in yeast. We also used our yeast dynein-Pac1 structure to design mutations in human dynein to probe the role of LIS1 in promoting the assembly of active dynein complexes. These mutations had relatively mild effects on dynein activation, suggesting that there may be differences in how dynein and Pac1/LIS1 interact between yeast and humans. Here, we report cryo-EM structures of human dynein-LIS1 complexes. Our new structures reveal the differences between the yeast and human systems, provide a blueprint to disrupt the human dynein-LIS1 interactions more accurately, and map type-1 lissencephaly disease mutations, as well as mutations in dynein linked to malformations of cortical development/intellectual disability, in the context of the dynein-LIS1 complex.

Using Budding Yeast as a Model to Understand Dynein-Mediated Cargo Transport.

Cytoplasmic dynein-1 is a minus end-directed microtubule motor that transports numerous cargoes in cell types throughout the evolutionary spectrum. Dynein is regulated by various motor-intrinsic and motor-extrinsic factors that enhance its processivity, recruit it to various cellular sites, or otherwise promote or restrict its activity. Studying dynein activity in higher eukaryotes is complicated by various factors, including the myriad functions in which this motor participates, and the consequential pleotropic effects associated with disrupting its activity. Budding yeast has long been a powerful model system for understanding this enormous motor protein complex, which is highly conserved between yeast and humans at the primary sequence and structural levels. Studies in budding yeast are simplified by the fact that dynein only performs one known function in this organism: to position the mitotic spindle at the site of cell division. Monitoring dynein-mediated spindle movements in budding yeast provides a powerful tool for the quantitative measurements of various motility parameters, and a system with which to assess the consequence of mutations in dynein or its regulators. Here, we provide detailed protocols to perform quantitative measurements of dynein activity in live cells using a combination of fluorescence microscopy and computational methods to track and quantitate dynein-mediated spindle movements. These methods are broadly applicable to anyone that wishes to perform fluorescence microscopy on budding yeast.

Leigh Syndrome in a Filipino Child: A Case Report

Introduction: Leigh disease and Leigh-like syndrome are a heterogenous group of neurodegenerative disorders involving any level of the neuraxis and may present with a variety of clinical presentations, prominent among them is psychomotor regression. Despite the remarkable number of established disease genes and novel mutations being discovered, many cases of Leigh syndrome remain without a genetic diagnosis, indicating that there are still more disease genes to be identified. Case: Here we present a case of a two and a half-year-old girl who presented with delayed acquisition of developmental milestones with subsequent regression, ataxia, and dyskinesia. Her work-up showed raised blood lactate levels and lactate peak in MR spectroscopy. Mitochondria genome showed absence of mitochondrial DNA mutation, while whole exome sequence analysis revealed a novel dynein gene variant, p.A1577S. Her parents underwent genetic testing as well, and her father also had the same dynein mutation, however, is non-symptomatic. She had an older brother who initially presented with ophthalmoplegia and eventually developed psychomotor regression. He subsequently expired from respiratory failure after almost 2 years from initial presentation. Both siblings were diagnosed with Leigh syndrome. Conclusion: The diagnosis of Leigh syndrome remains based on characteristic clinical and radiologic findings. However, a specific defect must be identified if reliable genetic counseling is to be provided.

LIS1 and NDEL1 Regulate Axonal Trafficking of Mitochondria in Mature Neurons.

Defective mitochondrial dynamics in axons have been linked to both developmental and late-onset neurological disorders. Axonal trafficking is in large part governed by the microtubule motors kinesin-1 and cytoplasmic dynein 1 (dynein). Dynein is the primary retrograde transport motor in axons, and mutations in dynein and many of its regulators also cause neurological diseases. Depletion of LIS1, famous for linking dynein deregulation to lissencephaly (smooth brain), in adult mice leads to severe neurological phenotypes, demonstrating post-developmental roles. LIS1 stimulates retrograde transport of acidic organelles in cultured adult rat dorsal root ganglion (DRG) axons but findings on its role in mitochondrial trafficking have been inconsistent and have not been reported for adult axons. Here we report that there is an increased number of mitochondria in cross-sections of sciatic nerve axons from adult LIS1+/– mice. This is probably related to reduced dynein activity as axons from adult rat nerves exposed to the dynein inhibitor, ciliobrevin D also had increased numbers of mitochondria. Moreover, LIS1 overexpression (OE) in cultured adult rat DRG axons stimulated retrograde mitochondrial transport while LIS1 knockdown (KD) or expression of a LIS1 dynein-binding mutant (LIS1-K147A) inhibited retrograde transport, as did KD of dynein heavy chain (DHC). These findings are consistent with our report on acidic organelles. However, KD of NDEL1, a LIS1 and dynein binding protein, or expression of a LIS1 NDEL1-binding mutant (LIS1-R212A) also dramatically impacted retrograde mitochondrial transport, which was not the case for acidic organelles. Manipulations that disrupted retrograde mitochondrial transport also increased the average length of axonal mitochondria, suggesting a role for dynein in fusion or fission events. Our data point to cargo specificity in NDEL1 function and raise the possibility that defects in the LIS1/NDEL1 dynein regulatory pathway could contribute to mitochondrial diseases with axonal pathologies.

Structural basis for cytoplasmic dynein-1 regulation by Lis1.

The lissencephaly 1 gene, LIS1, is mutated in patients with the neurodevelopmental disease lissencephaly. The Lis1 protein is conserved from fungi to mammals and is a key regulator of cytoplasmic dynein-1, the major minus-end-directed microtubule motor in many eukaryotes. Lis1 is the only dynein regulator known to bind directly to dynein's motor domain, and by doing so alters dynein's mechanochemistry. Lis1 is required for the formation of fully active dynein complexes, which also contain essential cofactors: dynactin and an activating adaptor. Here, we report the first high-resolution structure of the yeast dynein-Lis1 complex. Our 3.1 Å structure reveals, in molecular detail, the major contacts between dynein and Lis1 and between Lis1's ß-propellers. Structure-guided mutations in Lis1 and dynein show that these contacts are required for Lis1's ability to form fully active human dynein complexes and to regulate yeast dynein's mechanochemistry and in vivo function.

Molecular basis for dyneinopathies reveals insight into dynein regulation and dysfunction.

Cytoplasmic dynein plays critical roles within the developing and mature nervous systems, including effecting nuclear migration, and retrograde transport of various cargos. Unsurprisingly, mutations in dynein are causative of various developmental neuropathies and motor neuron diseases. These 'dyneinopathies' define a broad spectrum of diseases with no known correlation between mutation identity and disease state. To circumvent complications associated with dynein studies in human cells, we employed budding yeast as a screening platform to characterize the motility properties of seventeen disease-correlated dynein mutants. Using this system, we determined the molecular basis for several classes of etiologically related diseases. Moreover, by engineering compensatory mutations, we alleviated the mutant phenotypes in two of these cases, one of which we confirmed with recombinant human dynein. In addition to revealing molecular insight into dynein regulation, our data provide additional evidence that the type of disease may in fact be dictated by the degree of dynein dysfunction.

Mutations in Outer Dynein Arm Heavy Chain DNAH9 Cause Motile Cilia Defects and Situs Inversus

Motile cilia move body fluids and gametes and the beating of cilia lining the airway epithelial surfaces ensures that they are kept clear and protected from inhaled pathogens and consequent respiratory infections. Dynein motor proteins provide mechanical force for cilia beating. Dynein mutations are a common cause of primary ciliary dyskinesia (PCD), an inherited condition characterized by deficient mucociliary clearance and chronic respiratory disease coupled with laterality disturbances and subfertility. Using next-generation sequencing, we detected mutations in the ciliary outer dynein arm (ODA) heavy chain gene DNAH9 in individuals from PCD clinics with situs inversus and in one case male infertility. DNAH9 and its partner heavy chain DNAH5 localize to type 2 ODAs of the distal cilium and in DNAH9-mutated nasal respiratory epithelial cilia we found a loss of DNAH9/DNAH5-containing type 2 ODAs that was restricted to the distal cilia region. This confers a reduced beating frequency with a subtle beating pattern defect affecting the motility of the distal cilia portion. 3D electron tomography ultrastructural studies confirmed regional loss of ODAs from the distal cilium, manifesting as either loss of whole ODA or partial loss of ODA volume. Paramecium DNAH9 knockdown confirms an evolutionarily conserved function for DNAH9 in cilia motility and ODA stability. We find that DNAH9 is widely expressed in the airways, despite DNAH9 mutations appearing to confer symptoms restricted to the upper respiratory tract. In summary, DNAH9 mutations reduce cilia function but some respiratory mucociliary clearance potential may be retained, widening the PCD disease spectrum.

A novel mouse model carrying a human cytoplasmic dynein mutation shows motor behavior deficits consistent with Charcot-Marie-Tooth type 2O disease

Charcot-Marie-Tooth disease (CMT) is a peripheral neuromuscular disorder in which axonal degeneration causes progressive loss of motor and sensory nerve function. The loss of motor nerve function leads to distal muscle weakness and atrophy, resulting in gait problems and difficulties with walking, running, and balance. A mutation in the cytoplasmic dynein heavy chain (DHC) gene was discovered to cause an autosomal dominant form of the disease designated Charcot-Marie-Tooth type 2 O disease (CMT2O) in 2011. The mutation is a single amino acid change of histidine into arginine at amino acid 306 (H306R) in DHC. In order to understand the onset and progression of CMT2, we generated a knock-in mouse carrying the corresponding CMT2O mutation (H304R/+). We examined H304R/+ mouse cohorts in a 12-month longitudinal study of grip strength, tail suspension, and rotarod assays. H304R/+ mice displayed distal muscle weakness and loss of motor coordination phenotypes consistent with those of individuals with CMT2. Analysis of the gastrocnemius of H304R/+ male mice showed prominent defects in neuromuscular junction (NMJ) morphology including reduced size, branching, and complexity. Based on these results, the H304R/+ mouse will be an important model for uncovering functions of dynein in complex organisms, especially related to CMT onset and progression.

Cytoplasmic dynein and its regulatory proteins in Golgi pathology in nervous system disorders.

The Golgi apparatus is a dynamic organelle involved in processing and sorting of lipids and proteins. In neurons, the Golgi apparatus is important for the development of axons and dendrites and maintenance of their highly complex polarized morphology. The motor protein complex cytoplasmic dynein has an important role in Golgi apparatus positioning and function. Together, with dynactin and other regulatory factors it drives microtubule minus-end directed motility of Golgi membranes. Inhibition of dynein results in fragmentation and dispersion of the Golgi ribbon in the neuronal cell body, resembling the Golgi abnormalities observed in some neurodegenerative disorders, in particular motor neuron diseases. Mutations in dynein and its regulatory factors, including the dynactin subunit p150Glued, BICD2 and Lis-1, are associated with several human nervous system disorders, including cortical malformation and motor neuropathy. Here we review the role of dynein and its regulatory factors in Golgi function and positioning, and the potential role of dynein malfunction in causing Golgi apparatus abnormalities in nervous system disorders.

Mechanism and regulation of cytoplasmic dynein.

Until recently, dynein was the least understood of the cytoskeletal motors. However, a wealth of new structural, mechanistic, and cell biological data is shedding light on how this complicated minus-end-directed, microtubule-based motor works. Cytoplasmic dynein-1 performs a wide array of functions in most eukaryotes, both in interphase, in which it transports organelles, proteins, mRNAs, and viruses, and in mitosis and meiosis. Mutations in dynein or its regulators are linked to neurodevelopmental and neurodegenerative diseases. Here, we begin by providing a synthesis of recent data to describe the current model of dynein's mechanochemical cycle. Next, we discuss regulators of dynein, with particular focus on those that directly interact with the motor to modulate its recruitment to microtubules, initiate cargo transport, or activate minus-end-directed motility.

Disruption of axonal transport perturbs bone morphogenetic protein (BMP)--signaling and contributes to synaptic abnormalities in two neurodegenerative diseases.

Formation of new synapses or maintenance of existing synapses requires the delivery of synaptic components from the soma to the nerve termini via axonal transport. One pathway that is important in synapse formation, maintenance and function of the Drosophila neuromuscular junction (NMJ) is the bone morphogenetic protein (BMP)-signaling pathway. Here we show that perturbations in axonal transport directly disrupt BMP signaling, as measured by its downstream signal, phospho Mad (p-Mad). We found that components of the BMP pathway genetically interact with both kinesin-1 and dynein motor proteins. Thick vein (TKV) vesicle motility was also perturbed by reductions in kinesin-1 or dynein motors. Interestingly, dynein mutations severely disrupted p-Mad signaling while kinesin-1 mutants showed a mild reduction in p-Mad signal intensity. Similar to mutants in components of the BMP pathway, both kinesin-1 and dynein motor protein mutants also showed synaptic morphological defects. Strikingly TKV motility and p-Mad signaling were disrupted in larvae expressing two human disease proteins; expansions of glutamine repeats (polyQ77) and human amyloid precursor protein (APP) with a familial Alzheimer's disease (AD) mutation (APPswe). Consistent with axonal transport defects, larvae expressing these disease proteins showed accumulations of synaptic proteins along axons and synaptic abnormalities. Taken together our results suggest that similar to the NGF-TrkA signaling endosome, a BMP signaling endosome that directly interacts with molecular motors likely exist. Thus problems in axonal transport occurs early, perturbs BMP signaling, and likely contributes to the synaptic abnormalities observed in these two diseases.

A microscopy-based screen employing multiplex genome sequencing identifies cargo-specific requirements for dynein velocity

The timely delivery of membranous organelles and macromolecules to specific locations within the majority of eukaryotic cells depends on microtubule-based transport. Here we describe a screening method to identify mutations that have a critical effect on intracellular transport and its regulation using mutagenesis, multicolor-fluorescence microscopy, and multiplex genome sequencing. This screen exploits the filamentous fungus Aspergillus nidulans, which has many of the advantages of yeast molecular genetics but uses long-range microtubule-based transport in a manner more similar to metazoan cells. Using this method, we identified seven mutants that represent novel alleles of components of the intracellular transport machinery: specifically, kinesin-1, cytoplasmic dynein, and the dynein regulators Lis1 and dynactin. The two dynein mutations identified in our screen map to dynein's AAA+ catalytic core. Single-molecule studies reveal that both mutations reduce dynein's velocity in vitro. In vivo these mutants severely impair the distribution and velocity of endosomes, a known dynein cargo. In contrast, another dynein cargo, the nucleus, is positioned normally in these mutants. These results reveal that different dynein functions have distinct stringencies for motor performance.

Mutations in cytoplasmic dynein and its regulators cause malformations of cortical development and neurodegenerative diseases

Neurons are highly specialized for the processing and transmission of electrical signals and use cytoskeleton-based motor proteins to transport different vesicles and cellular materials. Abnormalities in intracellular transport are thought to be a critical factor in the degeneration and death of neurons in both the central and peripheral nervous systems. Several recent studies describe disruptive mutations in the minus-end-directed microtubule motor cytoplasmic dynein that are directly linked to human motor neuropathies, such as SMA (spinal muscular atrophy) and axonal CMT (Charcot-Marie-Tooth) disease or malformations of cortical development, including lissencephaly, pachygyria and polymicrogyria. In addition, genetic defects associated with these and other neurological disorders have been found in multifunctional adaptors that regulate dynein function, including the dynactin subunit p150(Glued), BICD2 (Bicaudal D2), Lis-1 (lissencephaly 1) and NDE1 (nuclear distribution protein E). In the present paper we provide an overview of the disease-causing mutations in dynein motors and regulatory proteins that lead to a broad phenotypic spectrum extending from peripheral neuropathies to cerebral malformations.

New mutations in flagellar motors identified by whole genome sequencing in Chlamydomonas

BackgroundThe building of a cilium or flagellum requires molecular motors and associated proteins that allow the relocation of proteins from the cell body to the distal end and the return of proteins to the cell body in a process termed intraflagellar transport (IFT). IFT trains are carried out by kinesin and back to the cell body by dynein.MethodsWe used whole genome sequencing to identify the causative mutations for two temperature-sensitive flagellar assembly mutants in Chlamydomonas and validated the changes using reversion analysis. We examined the effect of these mutations on the localization of IFT81, an IFT complex B protein, the cytoplasmic dynein heavy chain (DHC1b), and the dynein light intermediate chain (D1bLIC).ResultsThe strains, fla18 and fla24, have mutations in kinesin-2 and cytoplasmic dynein, respectively. The fla18 mutation alters the same glutamic acid (E24G) mutated in the fla10-14 allele (E24K). The fla18 strain loses flagella at 32?C more rapidly than the E24K allele but less rapidly than the fla10-1 allele. The fla18 mutant loses its flagella by detachment rather than by shortening. The fla24 mutation falls in cytoplasmic dynein and changes a completely conserved amino acid (L3243P) in an alpha helix in the AAA5 domain. The fla24 mutant loses its flagella by shortening within 6 hours at 32?C. DHC1b protein is reduced by 18-fold and D1bLIC is reduced by 16-fold at 21?C compared to wild-type cells. We identified two pseudorevertants (L3243S and L3243R), which remain flagellated at 32?C. Although fla24 cells assemble full-length flagella at 21?C, IFT81 protein localization is dramatically altered. Instead of localizing at the basal body and along the flagella, IFT81 is concentrated at the proximal end of the flagella. The pseudorevertants show wild-type IFT81 localization at 21?C, but proximal end localization of IFT81 at 32?C.ConclusionsThe change in the AAA5 domain of the cytoplasmic dynein in fla24 may block the recycling of IFT trains after retrograde transport. It is clear that different alleles in the flagellar motors reveal different functions and roles. Multiple alleles will be important for understanding structure-function relationships.

Dynein mutations associated with hereditary motor neuropathies impair mitochondrial morphology and function with age

Mutations in the DYNC1H1 gene encoding for dynein heavy chain cause two closely related human motor neuropathies, dominant spinal muscular atrophy with lower extremity predominance (SMA–LED) and axonal Charcot–Marie–Tooth (CMT) disease, and lead to sensory neuropathy and striatal atrophy in mutant mice. Dynein is the molecular motor carrying mitochondria retrogradely on microtubules, yet the consequences of dynein mutations on mitochondrial physiology have not been explored. Here, we show that mouse fibroblasts bearing heterozygous or homozygous point mutation in Dync1h1, similar to human mutations, show profoundly abnormal mitochondrial morphology associated with the loss of mitofusin 1. Furthermore, heterozygous Dync1h1 mutant mice display progressive mitochondrial dysfunction in muscle and mitochondria progressively increase in size and invade sarcomeres. As a likely consequence of systemic mitochondrial dysfunction, Dync1h1 mutant mice develop hyperinsulinemia and hyperglycemia and progress to glucose intolerance with age. Similar defects in mitochondrial morphology and mitofusin levels are observed in fibroblasts from patients with SMA–LED. Last, we show that Dync1h1 mutant fibroblasts show impaired perinuclear clustering of mitochondria in response to mitochondrial uncoupling. Our results show that dynein function is required for the maintenance of mitochondrial morphology and function with aging and suggest that mitochondrial dysfunction contributes to dynein-dependent neurological diseases, such as SMA–LED.

Establishing a novel knock‐in mouse line for studying neuronal cytoplasmic dynein under normal and pathologic conditions

Cytoplasmic dynein plays important roles in mitosis and the intracellular transport of organelles, proteins, and mRNAs. Dynein function is particularly critical for survival of neurons, as mutations in dynein are linked to neurodegenerative diseases. Dynein function is also implicated in neuronal regeneration, driving the active transport of signaling molecules following injury of peripheral neurons. To enhance our understanding of dynein function and regulation in neurons, we established a novel knock-in mouse line in which the neuron-specific cytoplasmic dynein 1 intermediate chain 1 (IC-1) is tagged with both GFP and a 3xFLAG tag at its C-terminus. The fusion gene is under the control of IC-1's endogenous promoter and is integrated at the endogenous locus of the IC-1-encoding gene Dync1i1. The IC-1-GFP-3xFLAG fusion protein is incorporated into the endogenous dynein complex, and movements of GFP-labeled dynein expressed at endogenous levels can be observed in cultured neurons for the first time. The knock-in mouse line also allows isolation and analysis of dynein-bound proteins specifically from neurons. Using this mouse line we have found proteins, including 14-3-3 zeta, which physically interact with dynein upon injury of the brain cortex. Thus, we have created a useful tool for studying dynein function in the central nervous system under normal and pathologic conditions.

ZKSCAN3 Is a Master Transcriptional Repressor of Autophagy

Autophagy constitutes a major cell-protective mechanism that eliminates damaged components and maintains energy homeostasis via recycling nutrients under normal/stressed conditions. Although the core components of autophagy have been well studied, regulation of autophagy at the transcriptional level is poorly understood. Herein, we establish ZKSCAN3, a zinc finger family DNA-binding protein, as a transcriptional repressor of autophagy. Silencing of ZKSCAN3 induced autophagy and increased lysosome biogenesis. Importantly, we show that ZKSCAN3 represses transcription of a large gene set (>60) integral to, or regulatory for, autophagy and lysosome biogenesis/function and that a subset of these genes, including Map1lC3b and Wipi2, represent direct targets. Interestingly, ZKSCAN3 and TFEB are oppositely regulated by starvation and in turn oppositely regulate lysosomal biogenesis and autophagy, suggesting that they act in conjunction. Altogether, our study uncovers an autophagy master switch regulating the expression of a transcriptional network of genes integral to autophagy and lysosome biogenesis/function.

Analyses of Dynein Heavy Chain Mutations Reveal Complex Interactions Between Dynein Motor Domains and Cellular Dynein Functions

Cytoplasmic dynein transports cargoes for a variety of crucial cellular functions. However, since dynein is essential in most eukaryotic organisms, the in-depth study of the cellular function of dynein via genetic analysis of dynein mutations has not been practical. Here, we identify and characterize 34 different dynein heavy chain mutations using a genetic screen of the ascomycete fungus Neurospora crassa, in which dynein is nonessential. Interestingly, our studies show that these mutations segregate into five different classes based on the in vivo localization of the mutated dynein motors. Furthermore, we have determined that the different classes of dynein mutations alter vesicle trafficking, microtubule organization, and nuclear distribution in distinct ways and require dynactin to different extents. In addition, biochemical analyses of dynein from one mutant strain show a strong correlation between its in vitro biochemical properties and the aberrant intracellular function of that altered dynein. When the mutations were mapped to the published dynein crystal structure, we found that the three-dimensional structural locations of the heavy chain mutations were linked to particular classes of altered dynein functions observed in cells. Together, our data indicate that the five classes of dynein mutations represent the entrapment of dynein at five separate points in the dynein mechanochemical and transport cycles. We have developed N. crassa as a model system where we can dissect the complexities of dynein structure, function, and interaction with other proteins with genetic, biochemical, and cell biological studies.

A mouse neurodegenerative dynein heavy chain mutation alters dynein motility and localization in Neurospora crassa

Cytoplasmic dynein is responsible for the transport and delivery of cargoes in organisms ranging from humans to fungi. Dysfunction of dynein motor machinery due to mutations in dynein or its activating complex dynactin can result in one of several neurological diseases in mammals. The mouse Legs at odd angles (Loa) mutation in the tail domain of the dynein heavy chain has been shown to lead to progressive neurodegeneration in mice. The mechanism by which the Loa mutation affects dynein function is just beginning to be understood. In this work, we generated the dynein tail mutation observed in Loa mice into the Neurospora crassa genome and utilized cell biological and complementing biochemical approaches to characterize how that tail mutation affected dynein function. We determined that the Loa mutation exhibits several subtle defects upon dynein function in N. crassa that were not seen in mice, including alterations in dynein localization, impaired velocity of vesicle transport, and in the biochemical properties of purified motors. Our work provides new information on the role of the tail domain on dynein function and points out areas of future research that will be of interest to pursue in mammalian systems.

A mutation in the dynein heavy chain gene compensates for energy deficit of mutant SOD1 mice and increases potentially neuroprotective IGF-1

BackgroundAmyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by a progressive loss of motor neurons. ALS patients, as well as animal models such as mice overexpressing mutant SOD1s, are characterized by increased energy expenditure. In mice, this hypermetabolism leads to energy deficit and precipitates motor neuron degeneration. Recent studies have shown that mutations in the gene encoding the dynein heavy chain protein are able to extend lifespan of mutant SOD1 mice. It remains unknown whether the protection offered by these dynein mutations relies on a compensation of energy metabolism defects.ResultsSOD1(G93A) mice were crossbred with mice harboring the dynein mutant Cramping allele (Cra/+ mice). Dynein mutation increased adipose stores in compound transgenic mice through increasing carbohydrate oxidation and sparing lipids. Metabolic changes that occurred in double transgenic mice were accompanied by the normalization of the expression of key mRNAs in the white adipose tissue and liver. Furthermore, Dynein Cra mutation rescued decreased post-prandial plasma triglycerides and decreased non esterified fatty acids upon fasting. In SOD1(G93A) mice, the dynein Cra mutation led to increased expression of IGF-1 in the liver, increased systemic IGF-1 and, most importantly, to increased spinal IGF-1 levels that are potentially neuroprotective.ConclusionsThese findings suggest that the protection against SOD1(G93A) offered by the Cramping mutation in the dynein gene is, at least partially, mediated by a reversal in energy deficit and increased IGF-1 availability to motor neurons.