Papers by Garth Nicholson
Acetylcholine receptor antibody in the diagnosis of myasthenia gravis
The Medical Journal of Australia, Nov 1, 1983
The acetylcholine receptor (AchR) antibody assay has a key role in the diagnosis of myasthenia gr... more The acetylcholine receptor (AchR) antibody assay has a key role in the diagnosis of myasthenia gravis. In this article, the role of AchR antibody assay in the diagnosis of ocular and generalized myasthenia gravis is reviewed, and compared to standard means of diagnosing the disease by clinical and electrophysiological methods.
Clinical Chemistry, 2007
Background: X-linked Charcot-Marie-Tooth type 1 disease has been associated with 280 mutations in... more Background: X-linked Charcot-Marie-Tooth type 1 disease has been associated with 280 mutations in the GJB1 [gap junction protein, beta 1, 32kDa (connexin 32, Charcot-Marie-Tooth neuropathy, X-linked)] gene. High-resolution melting analysis with an automated instrument can be used to scan DNA for alterations, but its use in X-linked disorders has not been described. Methods: A 96-well LightScanner for high resolution melting analysis was used to scan amplicons of the GJB1 gene. All mutations reported in this study had been confirmed previously by sequence analysis. DNA samples were amplified with the double-stranded DNAbinding dye LC Green Plus. Melting curves were analyzed as fluorescence difference plots. The shift and curve shapes of melting profiles were used to distinguish controls from patient samples. Results: The method detected each of the 23 mutations used in this study. Eighteen known mutations provided validation of the high-resolution melting method and a further 5 mutations were identified in a blind study. Altered fluorescence difference curves for all the mutations were easily distinguished from the wild-type melting profile. Conclusion: High-resolution melting analysis is a simple, sensitive, and cost-efficient alternative method to scan for gene mutations in the GJB1 gene. The technology has the potential to reduce sequencing burden and would be suitable for mutation screening of exons of large multiexon genes that have been discovered to be associated with Charcot Marie Tooth neuropathy.
Mutational origin of Machado-Joseph disease in the Australian Aboriginal communities of Groote Eylandt and Yirrkala
Arch Neurol 69 746 751, Feb 20, 2012
To determine whether the presence of Machado-Joseph disease (MJD, also spinocerebellar ataxia typ... more To determine whether the presence of Machado-Joseph disease (MJD, also spinocerebellar ataxia type 3 [SCA3]) among Australian aborigines was caused by a new mutational event or by the introduction of expanded alleles from other populations. We sequenced a region of 4 kilobases (kb), encompassing the CAG repeat within the ATXN3 gene, in 2 affected Australian aboriginal families and compared them with the Joseph and Machado lineages described before. Full-extended haplotypes (including also more distant single-nucleotide polymorphisms and flanking short tandem repeats) were assessed by segregation and allele-specific amplification. A phylogenetic tree was inferred from genetic distances, and age of the Australasian Joseph-derived lineage was estimated. The aboriginal communities of Groote Eylandt and Yirrkala, in the Northern Territories, Australia (local ethics institutional permission was granted, and both community and individual informed consent was obtained). A convenience sample of 19 patients and unaffected relatives, from 2 Australian aboriginal families affected with MJD; 40 families with MJD of multiethnic origins and 50 unrelated Asian control subjects. The 2 aboriginal families shared the same full haplotype, including 20 single-nucleotide polymorphisms:TTGATCGAGC-(CAG)(Exp)-CACCCAGCGC, that is, the Joseph lineage with a G variant in rs56268847.Among 33 families with the Joseph lineage, this derived haplotype was found only in 5 of 16 Taiwanese, all 3 Indian,and 1 of 3 Japanese families analyzed. A related-extended MJD haplotype shared by Australian aborigines and some Asian families (a Joseph-derived lineage) suggests a common ancestor for all, dating back more than 7000 years.
Archives of Neurology, Mar 1, 2003
H ereditary sensory neuropathies (HSNs) are rare disorders characterized by progressive distal se... more H ereditary sensory neuropathies (HSNs) are rare disorders characterized by progressive distal sensory loss, predominantly affecting the lower limbs. Foot ulcers, severe skin and bone infections, arthropathy, and amputations are frequent and feared complications. Occasionally, patients complain of spontaneous shooting or lancinating pain. Autonomic fibers can be affected to a variable degree. Patients with HSN can also have severe distal weakness, and some HSN variants have therefore been classified among the hereditary motor and sensory neuropathies (HMSNs). Molecular genetic studies of autosomal dominant inherited neuropathies with prominent sensory loss and ulceromutilating features have assigned the genetic loci for HMSN type 2B (Charcot-Marie-Tooth syndrome type 2B) and HSN type 1 to chromosomes 3q13-22 and 9q22.1-22.3, respectively. However, some families with HSN have been excluded for linkage to these loci, suggesting further genetic heterogeneity. Recently, disease-causing mutations in the SPTLC1 gene have been identified in patients with HSN type 1. In this review, we discuss the hallmark features associated with the distinct genetic subtypes of autosomal dominant inherited HSN and provide genotype-phenotype correlations.
The American Journal of Human Genetics, Aug 10, 2010
Acetylcholine receptor antibodies in the diagnosis and management of myasthenia gravis
Clinical and Experimental Neurology, Feb 1, 1981
The relationship of acetylcholine receptor (AchR) antibodies to disease activity in myasthenia gr... more The relationship of acetylcholine receptor (AchR) antibodies to disease activity in myasthenia gravis (MG) is controversial. Some authors claim a direct correlation with disease activity and treatment, in particular plasmapheresis therapy, whereas others have commented on the poor overall correlation of antibody levels with clinical state. Antibody levels were examined in a population of MG patients and correlated with disease activity and response to treatment. Antibodies to skeletal muscle AchR were found in most patients with generalised MG (24/25) and in about half of the patients with purely ocular MG (6/10) and in neither of 2 patients with congenital MG. There was scant correlation with disease activity or response to treatment. It is concluded that the assay is more useful for diagnosis than for management of MG.
A Reassessment of Genetic Diversity in Icelanders: Strong Evidence from Multiple Loci for Relative Homogeneity Caused by Genetic Drift
Annals of Human Genetics, Jul 1, 2003
There has been some controversy in the literature concerning whether Icelanders are genetically h... more There has been some controversy in the literature concerning whether Icelanders are genetically homogenous or heterogeneous relative to other European populations. We reassess this question in the light of large data sets spanning 83 autosomal SNP loci, 14 serogenetic loci, 6622 Y-chromosomes and 3214 sequences from mtDNA hypervariable segments 1 and 2 (HVS1 and HVS2). Our results strongly support the hypothesis that genetic drift, with a consequent loss of variation, has had a greater impact on Icelanders than most other Europeans. We also analyse 7245 HVS1 sequences from 25 European populations. In line with other studies, we observe a deficit of rare HVS1 haplotypes and an excess of intermediate frequency haplotypes in Icelanders compared to most European populations, with some measures of genetic diversity indicating relative heterogeneity and others indicating relative homogeneity of Icelanders. Simulations indicate that genetic drift, and not admixture (as proposed by Arnason, 2003) is the most likely cause of the atypical Icelandic HVS1 frequency spectrum. These simulations reveal that gene diversity (heterozygosity) and mean pairwise differences are largely insensitive to events in recent population history, while statistics based on the number of haplotypes or segregating sites are much more sensitive. Overall, our analyses strongly indicate that the Icelandic gene pool is less heterogeneous than those of most other European populations.
Genetic basis of hindlimb loss in a naturally occurring vertebrate model
Biology Open, 2016
Here we genetically characterise pelvic finless, a naturally occurring model of hindlimb loss in ... more Here we genetically characterise pelvic finless, a naturally occurring model of hindlimb loss in zebrafish that lacks pelvic fin structures, which are homologous to tetrapod hindlimbs, but displays no other abnormalities. Using a hybrid positional cloning and next generation sequencing approach, we identified mutations in the nuclear localisation signal (NLS) of T-box transcription factor 4 (Tbx4) that impair nuclear localisation of the protein, resulting in altered gene expression patterns during pelvic fin development and the failure of pelvic fin development. Using a TALEN-induced tbx4 knockout allele we confirm that mutations within the Tbx4 NLS (A78V; G79A) are sufficient to disrupt pelvic fin development. By combining histological, genetic, and cellular approaches we show that the hindlimb initiation gene tbx4 has an evolutionarily conserved, essential role in pelvic fin development. In addition, our novel viable model of hindlimb deficiency is likely to facilitate the elucidation of the detailed molecular mechanisms through which Tbx4 functions during pelvic fin and hindlimb development.
MORC2 mutations cause axonal Charcot-Marie-Tooth disease with pyramidal signs
Annals of Neurology, 2015
To use linkage analysis and whole exome sequencing to identify the genetic mutation in a multigen... more To use linkage analysis and whole exome sequencing to identify the genetic mutation in a multigenerational Australian family with Charcot-Marie-Tooth type 2 (CMT2) and pyramidal signs. Genome-wide linkage analysis was performed to map the locus. Whole exome sequencing was undertaken on selected individuals (3 affected, one normal) and segregation analysis and mutation screening was carried out using high resolution melt analysis. The GEM.app database was queried to identify additional families with mutations. Significant linkage (2 point LOD score ≥ +3) and haplotype analysis mapped a new locus for CMT2 and pyramidal signs to a 6.6-Mb interval on chromosome 22q12.1-q12.3. Whole exome sequencing identified a novel mutation (p.R252W) in the Microrchidia CW-type zinc finger 2 (MORC2) gene mapping within the linkage region. The mutation fully segregated with the disease phenotype in the family. Screening additional families and querying unsolved CMT2 exomes we identified the p.R252W mutation in two unrelated early onset CMT2 families and a second mutation p.E236G in two unrelated CMT2 families. Both the mutations occurred at highly conserved amino acid residues and were absent in the normal population. We have identified a new locus in which MORC2 mutations are the likely pathogenic cause of CMT2 and pyramidal signs in these families. MORC2 encodes the human CW-type zinc finger 2 protein which is a chromatin modifier involved in the regulation of DNA repair as well as gene transcription. This article is protected by copyright. All rights reserved.
PloS one, 2014
FUS mutations can occur in familial amyotrophic lateral sclerosis (fALS), a neurodegenerative dis... more FUS mutations can occur in familial amyotrophic lateral sclerosis (fALS), a neurodegenerative disease with cytoplasmic FUS inclusion bodies in motor neurons. To investigate FUS pathology, we generated transgenic zebrafish expressing GFP-tagged wild-type or fALS (R521C) human FUS. Cell cultures were made from these zebrafish and the subcellular localization of human FUS and the generation of stress granule (SG) inclusions examined in different cell types, including differentiated motor neurons. We demonstrate that mutant FUS is mislocalized from the nucleus to the cytosol to a similar extent in motor neurons and all other cell types. Both wild-type and R521C FUS localized to SGs in zebrafish cells, demonstrating an intrinsic ability of human FUS to accumulate in SGs irrespective of the presence of disease-associated mutations or specific cell type. However, elevation in relative cytosolic to nuclear FUS by the R521C mutation led to a significant increase in SG assembly and persistenc...
Australian Journal of Physiotherapy, 2006
A Sensitive Assay for Creatine Kinase in Serum Samples Dried on Paper: Enhanced Thermal Stability of the Dried Enzyme
A new bioluminescent creatine kinase (CK) assay using purified luciferase was used to analyse CK ... more A new bioluminescent creatine kinase (CK) assay using purified luciferase was used to analyse CK activity in serum samples dried on filter paper. Enzyme activity was preserved for over 1 wk on paper stored at room temperature. At 60 degrees C, CK activity in liquid serum samples was rapidly inactivated, but the activity of enzyme stored on paper was preserved for at least 2 days.
A Combination of Linkage Analysis and Exome Sequencing Identifies a New Gene for X-linked Charcot-Marie-Tooth Neuropathy (S26.007)
Neurology, Feb 12, 2013
Mutation analysis of genes within the dynactin complex in a cohort of hereditary peripheral neuropathies
Clinical Genetics, 2015
The cytoplasmic dynein-dynactin genes are attractive candidates for neurodegenerative disorders g... more The cytoplasmic dynein-dynactin genes are attractive candidates for neurodegenerative disorders given their functional role in retrograde transport along neurons. The cytoplasmic dynein heavy chain (DYNC1H1) gene has been implicated in various neurodegenerative disorders, and dynactin 1 (DCTN1) genes have been implicated in a wide spectrum of disorders including motor neuron disease, Parkinson's disease, spinobulbar muscular atrophy and hereditary spastic paraplegia. However, the involvement of other dynactin genes with inherited peripheral neuropathies (IPN) namely, hereditary sensory neuropathy, hereditary motor neuropathy and Charcot-Marie-Tooth disease is under reported. We screened eight genes; DCTN1-6 and ACTR1A and ACTR1B in 136 IPN patients using whole exome sequencing (WES) and high resolution melt (HRM) analysis. Eight nonsynonymous variants (including one novel variant) and three synonymous variants were identified. Four variants have been reported previously in other studies, however segregation analysis within family members excluded them from causing IPN in these families. No variants of disease-significance were identified in this study suggesting the dynactin genes are unlikely to be a common cause of IPNs. However, with the ease of querying gene variants from exome data, these genes remain worthwhile candidates to assess unsolved IPN families for variants that may affect the function of the proteins.
Although many genetic diseases are caused by the presence of point mutations in respective genes,... more Although many genetic diseases are caused by the presence of point mutations in respective genes, an increasing number of diseases are known to be caused by gene copy number changes. We report the develop- ment of a rapid and reliable PCR-based method for quantitation of gene copy number with sufficient sen- sitivity to detect single copy changes without the use
Use of Whole-Exome Sequencing for Diagnosis of Limb-Girdle Muscular Dystrophy: Outcomes and Lessons Learned
JAMA neurology, Jan 5, 2015
To our knowledge, the efficacy of transferring next-generation sequencing from a research setting... more To our knowledge, the efficacy of transferring next-generation sequencing from a research setting to neuromuscular clinics has never been evaluated. To translate whole-exome sequencing (WES) to clinical practice for the genetic diagnosis of a large cohort of patients with limb-girdle muscular dystrophy (LGMD) for whom protein-based analyses and targeted Sanger sequencing failed to identify the genetic cause of their disorder. We performed WES on 60 families with LGMDs (100 exomes). Data analysis was performed between January 6 and December 19, 2014, using the xBrowse bioinformatics interface (Broad Institute). Patients with LGMD were ascertained retrospectively through the Institute for Neuroscience and Muscle Research Biospecimen Bank between 2006 and 2014. Enrolled patients had been extensively investigated via protein studies and candidate gene sequencing and remained undiagnosed. Patients presented with more than 2 years of muscle weakness and with dystrophic or myopathic change...
Novel TBK1 truncating mutation in a familial amyotrophic lateral sclerosis patient of Chinese origin
Neurobiology of Aging, 2015
Missense and frameshift mutations in TRAF family member-associated NF-kappa-B activator (TANK)-bi... more Missense and frameshift mutations in TRAF family member-associated NF-kappa-B activator (TANK)-binding kinase 1 (TBK1) have been reported in European sporadic and familial amyotrophic lateral sclerosis (ALS) cohorts. To assess the role of TBK1 in ALS patient cohorts of wider ancestry, we have analyzed whole-exome sequence data from an Australian cohort of familial ALS (FALS) patients and controls. We identified a novel TBK1 deletion (c.1197delC) in a FALS patient of Chinese origin. This frameshift mutation (p.L399fs) likely results in a truncated protein that lacks functional domains required for adapter protein binding, as well as protein activation and structural integrity. No novel or reported TBK1 mutations were identified in FALS patients of European ancestry. This is the first report of a TBK1 mutation in an ALS patient of Asian origin and indicates that sequence variations in TBK1 are a rare cause of FALS in Australia.
Nature genetics, 2001
Hereditary sensory neuropathy type I (HSN1) is the most common hereditary disorder of peripheral ... more Hereditary sensory neuropathy type I (HSN1) is the most common hereditary disorder of peripheral sensory neurons. HSN1 is an autosomal dominant progressive degeneration of dorsal root ganglia and motor neurons with onset in the second or third decades. Initial symptoms are sensory loss in the feet followed by distal muscle wasting and weakness. Loss of pain sensation leads to chronic skin ulcers and distal amputations. The HSN1 locus has been mapped to chromosome 9q22.1-22.3 (refs. 3,4). Here we map the gene SPTLC1, encoding serine palmitoyltransferase, long chain base subunit-1, to this locus. Mutation screening revealed 3 different missense mutations resulting in changes to 2 amino acids in all affected members of 11 HSN1 families. We found two mutations to be located in exon 5 (C133Y and C133W) and one mutation to be located in exon 6 of SPTLC1 (V144D). All families showing definite or probable linkage to chromosome 9 had mutations in these two exons. These mutations are associat...
Brain, 2015
Hereditary spastic paraplegias are heterogeneous neurological disorders characterized by a pyrami... more Hereditary spastic paraplegias are heterogeneous neurological disorders characterized by a pyramidal syndrome with symptoms predominantly affecting the lower limbs. Some limited pyramidal involvement also occurs in patients with an autosomal recessive neurocutaneous syndrome due to ALDH18A1 mutations. ALDH18A1 encodes delta-1-pyrroline-5-carboxylate synthase (P5CS), an enzyme that catalyses the first and common step of proline and ornithine biosynthesis from glutamate. Through exome sequencing and candidate gene screening, we report two families with autosomal recessive transmission of ALDH18A1 mutations, and predominant complex hereditary spastic paraplegia with marked cognitive impairment, without any cutaneous abnormality. More interestingly, we also identified monoallelic ALDH18A1 mutations segregating in three independent families with autosomal dominant pure or complex hereditary spastic paraplegia, as well as in two sporadic patients. Low levels of plasma ornithine, citrulline, arginine and proline in four individuals from two families suggested P5CS deficiency. Glutamine loading tests in two fibroblast cultures from two related affected subjects confirmed a metabolic block at the level of P5CS in vivo. Besides expanding the clinical spectrum of ALDH18A1-related pathology, we describe mutations segregating in an autosomal dominant pattern. The latter are associated with a potential trait biomarker; we therefore suggest including amino acid chromatography in the clinico-genetic work-up of hereditary spastic paraplegia, particularly in dominant cases, as the associated phenotype is not distinct from other causative genes.
Neurotoxicity Research, 2015
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the pr... more Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the progressive degeneration of brain and spinal cord motor neurons. Ubiquitin-proteasome system (UPS) dysfunction and oxidative stress have been implicated in ALS pathogenesis.
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Papers by Garth Nicholson