An integrated genetic, radiation hybrid, physical and transcription map of a region of distal mouse chromosome 12, including an imprinted locus and the 'Legs at odd angles' (Loa) mutation

Cytoplasmic dynein heavy chain: the servant of many masters

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The cytoplasmic dynein complex is the main retrograde motor in all eukaryotic cells.

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This complex is built around a dimer of cytoplasmic dynein heavy chains (DYNC1H1).

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Mouse DYNC1H1 mutants have sensory defects, but motor defects have been controversial.

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Now human DYNC1H1 mutations with sensory, motor, and cognitive deficits are being found.

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The study of these mutations will give us new insight into DYNC1H1 function in the nervous system.

Cytoplasmic dynein is the main retrograde motor in all eukaryotic cells. This complex comprises different subunits assembled on a cytoplasmic dynein heavy chain 1 (DYNC1H1) dimer. Cytoplasmic dynein is particularly important for neurons because it carries essential signals and organelles from distal sites to the cell body. In the past decade, several mouse models have helped to dissect the numerous functions of DYNC1H1. Additionally, several DYNC1H1 mutations have recently been found in human patients that give rise to a broad spectrum of developmental and midlife-onset disorders. Here, we discuss the effects of mutations of mouse and human DYNC1H1 and how these studies are giving us new insight into the many critical roles DYNC1H1 plays in the nervous system.

Molecular biology of amyotrophic lateral sclerosis: insights from genetics

Amyotrophic lateral sclerosis (ALS) is a paralytic disorder caused by motor neuron degeneration. Mutations in more than 50 human genes cause diverse types of motor neuron pathology. Moreover, defects in five Mendelian genes lead to motor neuron disease, with two mutations reproducing the ALS phenotype. Analyses of these genetic effects have generated new insights into the diverse molecular pathways involved in ALS pathogenesis. Here, we present an overview of the mechanisms for motor neuron death and of the role of non-neuronal cells in ALS.

Genetic analysis of the cytoplasmic dynein subunit families

Cytoplasmic dyneins, the principal microtubule minus-end-directed motor proteins of the cell, are involved in many essential cellular processes. The major form of this enzyme is a complex of at least six protein subunits, and in mammals all but one of the subunits are encoded by at least two genes. Here we review current knowledge concerning the subunits, their interactions, and their functional roles as derived from biochemical and genetic analyses. We also carried out extensive database searches to look for new genes and to clarify anomalies in the databases. Our analysis documents evolutionary relationships among the dynein subunits of mammals and other model organisms, and sheds new light on the role of this diverse group of proteins, highlighting the existence of two cytoplasmic dynein complexes with distinct cellular roles.

Prion disease incubation time is not affected in mice heterozygous for a dynein mutation

A mechanism for transmission of the infectious prions from the peripheral nerve ends to the central nervous system is thought to involve neuronal anterograde and retrograde transport systems. Cytoplasmic dynein is the major retrograde transport molecular motor whose function is impaired in the Legs at odd angles (Loa) mouse due to a point mutation in the cytoplasmic dynein heavy chain subunit. Loa is a dominant trait which causes neurodegeneration and progressive motor function deficit in the heterozygotes. To investigate the role of cytoplasmic dynein in the transmission of prions within neurons, we inoculated heterozygous Loa and wild type littermates with mouse-adapted scrapie prions intracerebrally and intraperitonially, and determined the incubation period to onset of clinical prion disease. Our data indicate that the dynein mutation in the heterozygous state does not affect prion disease incubation time or its neuropathology in Loa mice.

Mutations in dynein link motor neuron degeneration to defects in retrograde transport

Degenerative disorders of motor neurons include a range of progressive fatal diseases such as amyotrophic lateral sclerosis (ALS), spinal-bulbar muscular atrophy (SBMA), and spinal muscular atrophy (SMA). Although the causative genetic alterations are known for some cases, the molecular basis of many SMA and SBMA-like syndromes and most ALS cases is unknown. Here we show that missense point mutations in the cytoplasmic dynein heavy chain result in progressive motor neuron degeneration in heterozygous mice, and in homozygotes this is accompanied by the formation of Lewy-like inclusion bodies, thus resembling key features of human pathology. These mutations exclusively perturb neuron-specific functions of dynein.