Biomedical subjects

Elizabeth M C Fisher

Publications and source records attributed to Elizabeth M C Fisher.

At least 19 recordsLinked to original sources

PubMed2025

Generation of C9orf72 repeat knock-in iPSC lines for modelling ALS and FTD.

Induced pluripotent stem cell (iPSC) models are powerful tools for neurodegenerative disease modelling, as they allow mechanistic studies in a human genetic environment and they can be differentiated into a range of neuronal and non-neuronal cells. However, these models come with inherent challenges due to line-to-line and clonal variability. To combat this issue, the iPSC Neurodegenerative Disease Initiative (iNDI) has generated an iPSC repository using a single clonal reference line, KOLF2.1J, into which disease-causing mutations and revertants are introduced via gene editing. Here we describe the generation and validation of lines carrying the most common causative mutation for amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), a repeat expansion in the C9orf72 gene, for the iNDI collection of neurodegenerative iPSC models. We demonstrate that these C9orf72 knock-in lines differentiate efficiently into neurons and display characteristic C9orf72-associated pathologies, including reduced C9orf72 levels and the presence of dipeptide repeat proteins (DPRs) and RNA foci, which increase in abundance over time in culture. These pathologies are not present in revertant cells lacking the repeat expansion. These repeat expansion and revertant cell lines are now available to academic and for-profit institutions through the JAX iPS cell repository and will help to facilitate and standardise iPSC-based ALS/FTD research.

Journal Article↗

PubMed2006

New techniques to understand chromosome dosage: mouse models of aneuploidy.

Aberrations in human chromosome copy number and structure are common and extremely deleterious. Their downstream effects on phenotype are caused by aberrant dosage of sequences in the affected regions. However, we know little about why the abnormal gene copy number causes disease or why specific features result from deficits in specific chromosomes. Mice are the organism of choice to help us try to tease apart the complex relationships between genotype and phenotype in aneuploidy and segmental aneusomy syndromes. As new technologies such as chromosome engineering and the creation of transchromosomic mice become routine, these will help us identify individual dosage-sensitive genes that are causative in specific syndromes and will enable us to produce mouse models to accurately recapitulate human chromosomal disorders.

Aneuploidy↗

PubMed2006

No association of DYNC1H1 with sporadic ALS in a case-control study of a northern European derived population: a tagging SNP approach.

The cytoplasmic dynein-dynactin complex has been implicated in the aetiology of motor neuron degeneration in both mouse models and human forms of motor neuron disease. We have previously shown that mutations in the cytoplasmic dynein 1 heavy chain 1 gene (Dync1h1) are causal in a mouse model of late-onset motor neuron degeneration but have found no association of the homologous sites in human DYNC1H1 with human motor neuron disease. Here we extend these analyses to investigate the DYNC1H1 genomic locus to determine if it is associated with sporadic amyotrophic lateral sclerosis (ALS) in a northern European-derived population. Among the 16 single nucleotide polymorphisms (SNPs) we examined, just two SNPs (rs2251644 and rs941793) were sufficient to tag the majority of haplotypic variation (r2 > or = 0.85) and these were tested in a case-control association study with 266 North American sporadic ALS patients and 225 matched controls. We found no association between genetic variation at DYNC1H1 and sporadic ALS (rs2251644; p = 0.538, rs941793; p = 0.204, haplotype; p = 0.956). In addition we investigated patterns of diversity at DYNC1H1 in Japanese and Cameroonian populations to establish the evolutionary history for this gene and observed reduced genetic diversity in the northern Europeans suggestive of selection at this locus.

Amyotrophic Lateral Sclerosis↗

PubMed2006

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.

Animals↗

PubMed2005

Cytoplasmic dynein nomenclature.

A variety of names has been used in the literature for the subunits of cytoplasmic dynein complexes. Thus, there is a strong need for a more definitive consensus statement on nomenclature. This is especially important for mammalian cytoplasmic dyneins, many subunits of which are encoded by multiple genes. We propose names for the mammalian cytoplasmic dynein subunit genes and proteins that reflect the phylogenetic relationships of the genes and the published studies clarifying the functions of the polypeptides. This nomenclature recognizes the two distinct cytoplasmic dynein complexes and has the flexibility to accommodate the discovery of new subunits and isoforms.

Animals↗

PubMed2005

An aneuploid mouse strain carrying human chromosome 21 with Down syndrome phenotypes.

Aneuploidies are common chromosomal defects that result in growth and developmental deficits and high levels of lethality in humans. To gain insight into the biology of aneuploidies, we manipulated mouse embryonic stem cells and generated a trans-species aneuploid mouse line that stably transmits a freely segregating, almost complete human chromosome 21 (Hsa21). This "transchromosomic" mouse line, Tc1, is a model of trisomy 21, which manifests as Down syndrome (DS) in humans, and has phenotypic alterations in behavior, synaptic plasticity, cerebellar neuronal number, heart development, and mandible size that relate to human DS. Transchromosomic mouse lines such as Tc1 may represent useful genetic tools for dissecting other human aneuploidies.

Aneuploidy↗

PubMed2005

Mutations in the endosomal ESCRTIII-complex subunit CHMP2B in frontotemporal dementia.

We have previously reported a large Danish pedigree with autosomal dominant frontotemporal dementia (FTD) linked to chromosome 3 (FTD3). Here we identify a mutation in CHMP2B, encoding a component of the endosomal ESCRTIII complex, and show that it results in aberrant mRNA splicing in tissue samples from affected members of this family. We also describe an additional missense mutation in an unrelated individual with FTD. Aberration in the endosomal ESCRTIII complex may result in FTD and neurodegenerative disease.

Dementia↗

PubMed2005

A mutation in dynein rescues axonal transport defects and extends the life span of ALS mice.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative condition characterized by motoneuron degeneration and muscle paralysis. Although the precise pathogenesis of ALS remains unclear, mutations in Cu/Zn superoxide dismutase (SOD1) account for approximately 20-25% of familial ALS cases, and transgenic mice overexpressing human mutant SOD1 develop an ALS-like phenotype. Evidence suggests that defects in axonal transport play an important role in neurodegeneration. In Legs at odd angles (Loa) mice, mutations in the motor protein dynein are associated with axonal transport defects and motoneuron degeneration. Here, we show that retrograde axonal transport defects are already present in motoneurons of SOD1(G93A) mice during embryonic development. Surprisingly, crossing SOD1(G93A) mice with Loa/+ mice delays disease progression and significantly increases life span in Loa/SOD1(G93A) mice. Moreover, there is a complete recovery in axonal transport deficits in motoneurons of these mice, which may be responsible for the amelioration of disease. We propose that impaired axonal transport is a prime cause of neuronal death in neurodegenerative disorders such as ALS.

Amyotrophic Lateral Sclerosis↗

PubMed2005

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.

Animals↗

PubMed2005

The origins and uses of mouse outbred stocks.

Outbred mouse stocks, often used in genetics, toxicology and pharmacology research, have been generated in rather haphazard ways. Understanding the characteristics of these stocks and their advantages and disadvantages is important for experimental design. In many studies these mice are used inappropriately, wasting animals' lives and resources on suboptimal experiments. Recently, however, researchers from the field of complex trait analysis have capitalized on the genetics of outbred stocks to refine the identification of quantitative trait loci. Here we assess the most widely used outbred stocks of mice and present guidelines for their use.

Animals↗

PubMed2005

The SOD1 transgene in the G93A mouse model of amyotrophic lateral sclerosis lies on distal mouse chromosome 12.

The SOD1G93A transgenic mouse strain which carries a human mutant Cu/Zn superoxide dismutase transgene array is a widely studied model of amyotrophic lateral sclerosis. These mice have been used in many breeding experiments to look for interactions with other loci, including transgenic and gene targeted mutations. Therefore, we decided to map the site of the transgene insertion as this may affect the outcome of such breeding experiments. In a fluorescence in situ hybridization experiment we determined that the SOD1G93A transgene insertion site lies on distal mouse chromosome 12. This chromosome also carries the 'Legs at odd angles' locus, which is an entirely unrelated mutation in the dynein heavy chain gene that we have been studying. We have analysed data from a SOD1G93AxLoa cross and determined that the site of the transgene insertion lies proximal of the dynein heavy chain gene on mouse chromosome 12.

Amyotrophic Lateral Sclerosis↗

PubMed2004

Identification and characterization of a novel mouse prion gene allele.

The major determinant of prion disease incubation time in mice is thought to be the amino acid sequence of the prion protein. Two alleles of the mouse prion gene ( Prnp) have been described, where Prnp(a) (Leu-108, Thr-189) and Prnp(b) (Phe-108, Val-189) are associated with short and long incubation times, to defined prion strains, respectively. As part of a survey of inbred mouse lines, the prion gene open reading frame was sequenced and revealed a new allele, Prnp(c) (Phe-108, Thr-189), in the strain MAI/Pas. To study the influence of Prnp(c) independently of the MAI/Pas genetic background, we generated a congenic line in which Prnp(c) was bred onto the C57BL/6JOlaHsd background. Following intracerebral inoculation with Chandler/RML scrapie prions, the congenic mice showed an increased mean incubation time relative to C57BL/6JOlaHsd, of over 100 days. However, no differences were observed in the intensity and pattern of PrP immunoreactivity deposition or spongiosis. We conclude that the new allele, Prnp(c), modulates incubation time but not neuropathology and that the previous classification of mice into two distinct groups based on incubation time and Prnp genotype should now be revised.

Alleles↗

PubMed2004

Towards a mutant map of the mouse--new models of neurological, behavioural, deafness, bone, renal and blood disorders.

With the completion of the first draft of the human genome sequence, the next major challenge is assigning function to genes. One approach is genome-wide random chemical mutagenesis, followed by screening for mutant phenotypes of interest and subsequent mapping and identification of the mutated genes in question. We (a consortium made up of GlaxoSmithKline, the MRC Mammalian Genetics Unit and Mouse Genome Centre, Harwell, Imperial College, London, and the Royal London Hospital) have used ENU mutagenesis in the mouse for the rapid generation of novel mutant phenotypes for use as animal models of human disease and for gene function assignment (Nolan et al., 2000). As of 2003, 35,000 mice have been produced to date in a genome-wide screen for dominant mutations and screened using a variety of screening protocols. Nearly 200 mutants have been confirmed as heritable and added to the mouse mutant catalogue and, overall, we can extrapolate that we have recovered over 700 mutants from the screening programme. For further information on the project and details of the data, see http://www.mgu.har.mrc.ac.uk/mutabase.

Animals↗

PubMed2003

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.

Animals↗

PubMed2003

Balancing selection at the prion protein gene consistent with prehistoric kurulike epidemics.

Kuru is an acquired prion disease largely restricted to the Fore linguistic group of the Papua New Guinea Highlands, which was transmitted during endocannibalistic feasts. Heterozygosity for a common polymorphism in the human prion protein gene (PRNP) confers relative resistance to prion diseases. Elderly survivors of the kuru epidemic, who had multiple exposures at mortuary feasts, are, in marked contrast to younger unexposed Fore, predominantly PRNP 129 heterozygotes. Kuru imposed strong balancing selection on the Fore, essentially eliminating PRNP 129 homozygotes. Worldwide PRNP haplotype diversity and coding allele frequencies suggest that strong balancing selection at this locus occurred during the evolution of modern humans.

Adult↗

PubMed2003

Microcell-mediated chromosome transfer (MMCT): small cells with huge potential.

Microcell-mediated chromosome transfer (MMCT) is a technique that has been in use since the 1970s for the fusion of microcells, containing single or a small number of chromosomes, with whole cells, and the subsequent selection of the hybrids. MMCT can be carried out with somatic cells, embryonic carcinoma (EC) or embryonic stem (ES) cell recipients, to study in vitro or in vivo effects of the transferred genetic material. These effects may be unpredictable--do the transferred genes function normally while in the regulatory milieu of the host cell? Will epigenetic effects become apparent, and how will these alter gene expression? What happens to the host cell phenotype? Here, we present a review of MMCT in which we argue that, although this is an old technique, its adaptability and efficiency make it an excellent method for the dissection of gene function and dysfunction in a very wide range of current systems.

Animals↗

PubMed2003

No association with common Caucasian genotypes in exons 8, 13 and 14 of the human cytoplasmic dynein heavy chain gene (DNCHC1) and familial motor neuron disorders.

We have shown in a mouse model of motor neuron disease, the legs-at-odd-angles (Loa) mutant, and that mutations in the cytoplasmic dynein heavy chain gene (Dnchc1) cause motor neuron degeneration. Mice exhibiting the Loa phenotype suffer progressive loss of locomotor function and homozygous animals have neuronal inclusion bodies that are positive for SOD1, CDK5, neurofilament and ubiquitin proteins. As this phenotype models some aspects of human motor neuron degeneration disorders, we think there is a reasonable likelihood that dynein may be a causative gene or susceptibility factor in human motor neuron disease. Therefore we have screened exons of this gene in a set of human patients with familial forms of disparate motor neuron degeneration diseases, affecting both upper and lower motor neurons: amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), and hereditary spastic paraplegia. As part of this study, we have determined that DNCHC1 is a large gene of 78 exons spanning 86 kb genomic length. We have focused on the exons known to be mutated in Loa, and in a very similar mouse mutation, cramping 1 (Cra1); both mutations result in loss of anterior horn cells. The exons studied are highly conserved in a wide range of eukaryotes. We screened our patient samples by sequencing and although we detect single nucleotide polymorphisms, our results show these occur at the same frequency in our patient group as in control samples of unaffected individuals. Therefore we do not find any association between familial motor neuron disease and the genotypes presented here in the exons screened.

DNA Mutational Analysis↗

PubMed2003

Paradigms for the identification of new genes in motor neuron degeneration.

It is estimated that between 10-20% of amyotrophic lateral sclerosis (ALS) is familial and these cases encompass recessive and dominant modes of inheritance. So far, mutations in three genes, superoxide dismutase 1 (SOD1), the p150 subunit of dynactin (DCTN1), and alsin have been shown to be directly causal for motor neuron degeneration in humans. However, clearly the disorder is genetically heterogeneous and other causal genes remain to be found that explain the vast majority of familial ALS cases. Human genetics can be problematical in that it is difficult to detect linkage in disorders in which multiple loci give similar phenotypes and where families are often small. In addition, the vertical collection of generations is often not possible with late onset disorders. An excellent genetic model of humans is provided by the mouse. We can use mouse models of neurodegeneration to find new genes in the human population. These models are not exact replicas of the human condition, but are the mouse equivalent and are incredibly valuable resources for highlighting genes and biochemical pathways disrupted in ALS and other diseases. In addition mouse models give us access to both control and affected tissues, at all stages of development and disease, thus greatly facilitating our understanding of pathogenesis. They also provide us with model systems for testing new therapies. Here we describe the approach taken to the characterization of new models of motor neuron disease and illustrate this with examples, including a recently characterized mouse model, Legs at odd angles (Loa).

Amyotrophic Lateral Sclerosis↗