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Lewit-Mendes MF, Lowe GC, Lewis S, Corben LA, Delatycki MB. Young People Living at Risk of Huntington's Disease: The Lived Experience. J Huntingtons Dis 2019; 7:391-402. [PMID: 30372686 DOI: 10.3233/jhd-180308] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND For young people in families with Huntington's disease (HD) the challenge of having an affected family member (AFM) compounds challenges related to being at risk of HD themselves. OBJECTIVE This study aimed to quantitatively examine the experiences of young people in families with HD, adding to existing qualitative studies regarding teenagers and young adults in families with HD. METHODS The experiences of young people with living in a family with HD were captured by an online anonymous questionnaire, available worldwide through the Huntington's Disease Youth Organization. The questionnaire contained mostly forced choice questions. RESULTS Most participants (n = 84/101, 83.2%) provide assistance to an AFM and 46.4% (n = 39/84) wish they didn't have to look after their AFM. Many participants (n = 64/78, 82.1%) reported feeling anxious about being at risk; 64.9% (n = 50/77) agreed it is a barrier in their life. Over one third (n = 29/76, 38.2%) of participants disagreed that they have support in relation to being at risk, despite 85.5% (n = 65/76) agreeing it is important to have support and ongoing follow up. CONCLUSIONS Young people in families with HD endure considerable emotional, social and practical burden secondary to having an AFM and being at risk themselves. Without increased support and services, the effects of being a young caregiver and living at risk are likely to have long term impacts on the well-being of these young people.
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Massie RJ, Delatycki MB. The Guttmacher-Lancet Commission on sexual and reproductive health and rights: how does Australia measure up? Med J Aust 2019; 211:381-381.e1. [PMID: 31630406 DOI: 10.5694/mja2.50350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Keage M, Delatycki MB, Dyer J, Corben LA, Vogel AP. Changes detected in swallowing function in Friedreich ataxia over 12 months. Neuromuscul Disord 2019; 29:786-793. [DOI: 10.1016/j.nmd.2019.08.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 07/08/2019] [Accepted: 08/23/2019] [Indexed: 12/20/2022]
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Delatycki MB, Bidichandani SI. Friedreich ataxia- pathogenesis and implications for therapies. Neurobiol Dis 2019; 132:104606. [PMID: 31494282 DOI: 10.1016/j.nbd.2019.104606] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 08/08/2019] [Accepted: 09/04/2019] [Indexed: 01/01/2023] Open
Abstract
Friedreich ataxia is the most common of the hereditary ataxias. It is due to homozygous/compound heterozygous mutations in FXN. This gene encodes frataxin, a protein largely localized to mitochondria. In about 96% of affected individuals there is homozygosity for a GAA repeat expansion in intron 1 of the FXN gene. Studies of people with Friedreich ataxia and of animal and cell models, have provided much insight into the pathogenesis of this disorder. The expanded GAA repeat leads to transcriptional deficiency of the FXN gene. The consequent deficiency of frataxin protein leads to reduced iron-sulfur cluster biogenesis and mitochondrial ATP production, elevated mitochondrial iron, and oxidative stress. More recently, a role for inflammation has emerged as being important in the pathogenesis of Friedreich ataxia. These findings have led to a number of potential therapies that have been subjected to clinical trials or are being developed toward human studies. Therapies that have been proposed include pharmaceuticals that increase frataxin levels, protein and gene replacement therapies, antioxidants, iron chelators and modulators of inflammation. Whilst no therapies have yet been approved for Friedreich ataxia, there is much optimism that the advances in the understanding of the pathogenesis of this disorder since the discovery its genetic basis, will result in approved disease modifying therapies in the near future.
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Tiller J, Morris S, Rice T, Barter K, Riaz M, Keogh L, Delatycki MB, Otlowski M, Lacaze P. Correction to: Genetic discrimination by Australian insurance companies: a survey of consumer experiences. Eur J Hum Genet 2019; 28:137. [PMID: 31358952 DOI: 10.1038/s41431-019-0475-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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Quarrell OW, Delatycki MB, Clarke AJ, Lahiri N, Craufurd D, Miedzybrodzka Z, MacLeod R, Renwick P, Tomlinson C. Letter in Response to Tibben et al., Risk Assessment for Huntington's Disease for (Future) Offspring Requires Offering Preconceptional CAG Analysis to Both Partners. J Huntingtons Dis 2019; 8:357-359. [PMID: 31282428 DOI: 10.3233/jhd-190360] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Rafehi H, Szmulewicz DJ, Bennett MF, Sobreira NLM, Pope K, Smith KR, Gillies G, Diakumis P, Dolzhenko E, Eberle MA, Barcina MG, Breen DP, Chancellor AM, Cremer PD, Delatycki MB, Fogel BL, Hackett A, Halmagyi GM, Kapetanovic S, Lang A, Mossman S, Mu W, Patrikios P, Perlman SL, Rosemergy I, Storey E, Watson SRD, Wilson MA, Zee DS, Valle D, Amor DJ, Bahlo M, Lockhart PJ. Bioinformatics-Based Identification of Expanded Repeats: A Non-reference Intronic Pentamer Expansion in RFC1 Causes CANVAS. Am J Hum Genet 2019; 105:151-165. [PMID: 31230722 PMCID: PMC6612533 DOI: 10.1016/j.ajhg.2019.05.016] [Citation(s) in RCA: 146] [Impact Index Per Article: 29.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 05/21/2019] [Indexed: 01/28/2023] Open
Abstract
Genomic technologies such as next-generation sequencing (NGS) are revolutionizing molecular diagnostics and clinical medicine. However, these approaches have proven inefficient at identifying pathogenic repeat expansions. Here, we apply a collection of bioinformatics tools that can be utilized to identify either known or novel expanded repeat sequences in NGS data. We performed genetic studies of a cohort of 35 individuals from 22 families with a clinical diagnosis of cerebellar ataxia with neuropathy and bilateral vestibular areflexia syndrome (CANVAS). Analysis of whole-genome sequence (WGS) data with five independent algorithms identified a recessively inherited intronic repeat expansion [(AAGGG)exp] in the gene encoding Replication Factor C1 (RFC1). This motif, not reported in the reference sequence, localized to an Alu element and replaced the reference (AAAAG)11 short tandem repeat. Genetic analyses confirmed the pathogenic expansion in 18 of 22 CANVAS-affected families and identified a core ancestral haplotype, estimated to have arisen in Europe more than twenty-five thousand years ago. WGS of the four RFC1-negative CANVAS-affected families identified plausible variants in three, with genomic re-diagnosis of SCA3, spastic ataxia of the Charlevoix-Saguenay type, and SCA45. This study identified the genetic basis of CANVAS and demonstrated that these improved bioinformatics tools increase the diagnostic utility of WGS to determine the genetic basis of a heterogeneous group of clinically overlapping neurogenetic disorders.
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Corben LA, Yiu EM, Tai G, Milne SC, Lynch B, Delatycki MB. Probing the multifactorial source of hand dysfunction in Friedreich ataxia. J Clin Neurosci 2019; 64:71-76. [DOI: 10.1016/j.jocn.2019.04.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 03/22/2019] [Accepted: 04/12/2019] [Indexed: 11/29/2022]
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Amor DJ, Stephenson SE, Mustapha M, Mensah MA, Ockeloen CW, Lee WS, Tankard RM, Phelan DG, Shinawi M, de Brouwer AP, Pfundt R, Dowling C, Toler TL, Sutton VR, Agolini E, Rinelli M, Capolino R, Martinelli D, Zampino G, Dumić M, Reardon W, Shaw-Smith C, Leventer RJ, Delatycki MB, Kleefstra T, Mundlos S, Mortier G, Bahlo M, Allen NJ, Lockhart PJ. Pathogenic Variants in GPC4 Cause Keipert Syndrome. Am J Hum Genet 2019; 104:914-924. [PMID: 30982611 DOI: 10.1016/j.ajhg.2019.02.026] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 02/25/2019] [Indexed: 12/22/2022] Open
Abstract
Glypicans are a family of cell-surface heparan sulfate proteoglycans that regulate growth-factor signaling during development and are thought to play a role in the regulation of morphogenesis. Whole-exome sequencing of the Australian family that defined Keipert syndrome (nasodigitoacoustic syndrome) identified a hemizygous truncating variant in the gene encoding glypican 4 (GPC4). This variant, located in the final exon of GPC4, results in premature termination of the protein 51 amino acid residues prior to the stop codon, and in concomitant loss of functionally important N-linked glycosylation (Asn514) and glycosylphosphatidylinositol (GPI) anchor (Ser529) sites. We subsequently identified seven affected males from five additional kindreds with novel and predicted pathogenic variants in GPC4. Segregation analysis and X-inactivation studies in carrier females provided supportive evidence that the GPC4 variants caused the condition. Furthermore, functional studies of recombinant protein suggested that the truncated proteins p.Gln506∗ and p.Glu496∗ were less stable than the wild type. Clinical features of Keipert syndrome included a prominent forehead, a flat midface, hypertelorism, a broad nose, downturned corners of mouth, and digital abnormalities, whereas cognitive impairment and deafness were variable features. Studies of Gpc4 knockout mice showed evidence of the two primary features of Keipert syndrome: craniofacial abnormalities and digital abnormalities. Phylogenetic analysis demonstrated that GPC4 is most closely related to GPC6, which is associated with a bone dysplasia that has a phenotypic overlap with Keipert syndrome. Overall, we have shown that pathogenic variants in GPC4 cause a loss of function that results in Keipert syndrome, making GPC4 the third human glypican to be linked to a genetic syndrome.
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Bowman-Smart H, Savulescu J, Mand C, Gyngell C, Pertile MD, Lewis S, Delatycki MB. 'Is it better not to know certain things?': views of women who have undergone non-invasive prenatal testing on its possible future applications. JOURNAL OF MEDICAL ETHICS 2019; 45:231-238. [PMID: 30679192 PMCID: PMC6582742 DOI: 10.1136/medethics-2018-105167] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 12/13/2018] [Accepted: 12/21/2018] [Indexed: 05/21/2023]
Abstract
Non-invasive prenatal testing (NIPT) is at the forefront of prenatal screening. Current uses for NIPT include fetal sex determination and screening for chromosomal disorders such as trisomy 21 (Down syndrome). However, NIPT may be expanded to many different future applications. There are a potential host of ethical concerns around the expanding use of NIPT, as examined by the recent Nuffield Council report on the topic. It is important to examine what NIPT might be used for before these possibilities become consumer reality. There is limited research exploring views of women on possible future uses of NIPT, particularly those of women who have undergone NIPT. In this study, we examined the views of women who undertook NIPT previously on the acceptability of and interest levels in using NIPT for a number of current and possible future applications. These included several medical conditions encompassing psychiatric, neurodevelopmental and adult-onset conditions as well as non-medical traits such as intelligence. One thousand women were invited to participate and 235 eligible surveys were received. Women generally reported an interest in using NIPT for medical conditions that severely impacted quality of life and with an onset earlier in life and stressed the importance of the accuracy of the test. Concerns were raised about the use of NIPT for non-medical traits. Respondents indicated that termination of pregnancy was not their only reason for testing, particularly in the case of sex. These results can further inform the ethical debate around the increasing integration of NIPT into healthcare systems.
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McLaren CE, Chen WP, Bertalli NA, Delatycki MB, Giles GG, English DR, Hopper JL, Allen KJ, Gurrin LC. Bivariate mixture models for the joint distribution of repeated serum ferritin and transferrin saturation measured 12 years apart in a cohort of healthy middle-aged Australians. PLoS One 2019; 14:e0214196. [PMID: 30913256 PMCID: PMC6435128 DOI: 10.1371/journal.pone.0214196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 03/10/2019] [Indexed: 11/25/2022] Open
Abstract
Homozygosity for the p.C282Y substitution in the HFE protein encoded by the hemochromatosis gene on chromosome 6p (HFE) is a common genetic trait that increases susceptibility to iron overload. McLaren et al. used bivariate mixture modeling to analyze the joint population distribution of transferrin saturation (TS) and serum ferritin concentration (SF) measured for participants in the Hemochromatosis and Iron Overload Screening (HEIRS) Study. They identified four components (C1, C2, C3, and C4) with successively increasing means for TS and SF. They demonstrated that bivariate mixture modeling in TS and SF reflect the genetic locus of HFE and may isolate p.C282Y homozygotes from the general population. In the current study we used data from the another large cohort, the Australian HealthIron study of genetic and environmental modifiers of hereditary hemochromatosis, to validate the component analysis approach, to examine stability of component proportions over time and to determine if TS and SF values from an individual move between components at baseline and follow-up. Because sampling fractions from each p.C282Y / p.H63D genotype stratum are not equal, we used frequency weights based on the inverse of the probability of selection for invitation to participate. In the weighted female analytic cohorts, C4 captured most of C282Y homozygotes, and C2 was the largest component. We identified four components from the weighted male analytic cohort and C4 captured most of p.C282Y homozygotes. The bivariate mixture modeling approach suggested that the model is transferable from one white population to another, although estimated means within components may differ.
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Hayhurst H, de Coo IFM, Piekutowska-Abramczuk D, Alston CL, Sharma S, Thompson K, Rius R, He L, Hopton S, Ploski R, Ciara E, Lake NJ, Compton AG, Delatycki MB, Verrips A, Bonnen PE, Jones SA, Morris AA, Shakespeare D, Christodoulou J, Wesol-Kucharska D, Rokicki D, Smeets HJM, Pronicka E, Thorburn DR, Gorman GS, McFarland R, Taylor RW, Ng YS. Leigh syndrome caused by mutations in MTFMT is associated with a better prognosis. Ann Clin Transl Neurol 2019; 6:515-524. [PMID: 30911575 PMCID: PMC6414492 DOI: 10.1002/acn3.725] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 12/21/2018] [Accepted: 12/26/2018] [Indexed: 12/18/2022] Open
Abstract
Objectives Mitochondrial methionyl‐tRNA formyltransferase (MTFMT) is required for the initiation of translation and elongation of mitochondrial protein synthesis. Pathogenic variants in MTFMT have been associated with Leigh syndrome (LS) and mitochondrial multiple respiratory chain deficiencies. We sought to elucidate the spectrum of clinical, neuroradiological and molecular genetic findings of patients with bi‐allelic pathogenic variants in MTFMT. Methods Retrospective cohort study combining new cases and previously published cases. Results Thirty‐eight patients with pathogenic variants in MTFMT were identified, including eight new cases. The median age of presentation was 14 months (range: birth to 17 years, interquartile range [IQR] 4.5 years), with developmental delay and motor symptoms being the most frequent initial manifestation. Twenty‐nine percent of the patients survived into adulthood. MRI headings in MTFMT pathogenic variants included symmetrical basal ganglia changes (62%), periventricular and subcortical white matter abnormalities (55%), and brainstem lesions (48%). Isolated complex I and combined respiratory chain deficiencies were identified in 31% and 59% of the cases, respectively. Reduction of the mitochondrial complex I and complex IV subunits was identified in the fibroblasts (13/13). Sixteen pathogenic variants were identified, of which c.626C>T was the most common. Seventy‐four percent of the patients were alive at their last clinical review (median 6.8 years, range: 14 months to 31 years, IQR 14.5 years). Interpretation Patients that harbour pathogenic variants in MTFMT have a milder clinical phenotype and disease progression compared to LS caused by other nuclear defects. Fibroblasts may preclude the need for muscle biopsy, to prove causality of any novel variant.
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Bowman-Smart H, Savulescu J, Mand C, Gyngell C, Pertile MD, Lewis S, Delatycki MB. 'Small cost to pay for peace of mind': Women's experiences with non-invasive prenatal testing. Aust N Z J Obstet Gynaecol 2019; 59:649-655. [PMID: 30724335 PMCID: PMC6850570 DOI: 10.1111/ajo.12945] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 12/09/2018] [Indexed: 01/17/2023]
Abstract
Background Non‐invasive prenatal testing (NIPT) has been available in Australia on a user‐pays basis since 2012. Since its introduction, it has grown in popularity as a screening method for fetal aneuploidy and may become publicly funded. Aims To assess the motivations and experiences of women who have undergone NIPT in a user‐pays system in Australia. Materials and methods One thousand women who had undergone NIPT through the Victorian Clinical Genetics Services in Melbourne, Australia were contacted and asked to complete a mixed‐methods survey. The number of eligible responses received was 235. Quantitative data analysis was performed in STATA IC 15.1, and qualitative data were examined using content analysis. Results Women reported generally positive experiences with NIPT and 95% of respondents indicated they would undergo NIPT in a future pregnancy. Most respondents received a low‐risk result, with 2.2% receiving a high‐risk result. Respondents viewed NIPT favourably compared to invasive testing and cited reassurance as a key reason they sought it. However, a small minority of women reported negative experiences with the testing process. Women were also supportive of NIPT becoming publicly funded, with 93% of respondents indicating support. Pre‐ and post‐test counselling were identified as possible areas for improvement to ensure informed consent. Conclusion In support of the existing literature, these results indicate that Australian women generally report positive experiences with NIPT. As NIPT becomes more common, with possible integration into public healthcare, further qualitative research would be valuable to examine the motivations and experiences of women undergoing NIPT.
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Wallis MJ, Boys A, Tassano E, Delatycki MB. Small interstitial 9p24.3 deletions principally involving KANK1 are likely benign copy number variants. Eur J Med Genet 2019; 63:103618. [PMID: 30684669 DOI: 10.1016/j.ejmg.2019.01.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 11/14/2018] [Accepted: 01/19/2019] [Indexed: 11/24/2022]
Abstract
A small heterozygous deletion involving KANK1 was originally reported in 2005 to cause cerebral palsy in one large Israeli family of Jewish Moroccan origin. There were nine affected children over two generations to five unaffected fathers. All of these children had congenital hypotonia that evolved into spastic quadriplegia over the first year of life, along with intellectual impairment and brain atrophy. The subsequent clinical depictions of other individuals with neurological disease harbouring a comparable KANK1 deletion have been extremely variable and most often quite dissimilar to the original family. The reported pathogenicity of these deletions has also been variable, due to an inconsistent nature of reported disease associations and limited data. We therefore sought to perform a review of the significance of small distal interstitial chromosome 9p24.3 deletions principally involving KANK1, including data from the VCGS cytogenetics laboratory. We found that carrier parents do not appear to display an increased frequency of neurological disease, individuals with a small KANK1 deletion have sometimes been found to have an alternate genetic diagnosis that explained their neurological condition, and small KANK1 deletions can be seen with approximate equal frequency in case and control populations. These data led us to conclude that small deletions involving KANK1 do not cause a highly-penetrant influence of large effect size and they are unlikely to contribute significantly to the aetiology of disease in patients with development delay, intellectual disability, autism or cerebral palsy. We recommend searching for an alternate explanation for disease in individuals with a neurological disorder found to have a small deletion involving KANK1.
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Ward PGD, Harding IH, Close TG, Corben LA, Delatycki MB, Storey E, Georgiou-Karistianis N, Egan GF. Longitudinal evaluation of iron concentration and atrophy in the dentate nuclei in friedreich ataxia. Mov Disord 2019; 34:335-343. [PMID: 30624809 DOI: 10.1002/mds.27606] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 11/26/2018] [Accepted: 12/06/2018] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND Friedreich ataxia is a recessively inherited, progressive neurological disease characterized by impaired mitochondrial iron metabolism. The dentate nuclei of the cerebellum are characteristic sites of neurodegeneration in the disease, but little is known of the longitudinal progression of abnormalities in these structures. METHODS Using in vivo magnetic resonance imaging, including quantitative susceptibility mapping, we investigated changes in iron concentration and volume in the dentate nuclei in individuals with Friedreich ataxia (n = 20) and healthy controls (n = 18) over a 2-year period. RESULTS The longitudinal rate of iron concentration was significantly elevated bilaterally in participants with Friedreich ataxia relative to healthy controls. Atrophy rates did not differ significantly between groups. Change in iron concentration and atrophy both correlated with baseline disease severity or duration, indicating sensitivity of these measures to disease stage. Specifically, atrophy was maximal in individuals early in the disease course, whereas the rate of iron concentration increased with disease progression. CONCLUSIONS Progressive dentate nucleus abnormalities are evident in vivo in Friedreich ataxia, and the rates of change of iron concentration and atrophy in these structures are sensitive to the disease stage. The findings are consistent with an increased rate of iron concentration and atrophy early in the disease, followed by iron accumulation and stable volume in later stages. This pattern suggests that iron dysregulation persists after loss of the vulnerable neurons in the dentate. The significant changes observed over a 2-year period highlight the utility of quantitative susceptibility mapping as a longitudinal biomarker and staging tool. © 2019 International Parkinson and Movement Disorder Society.
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Catford SR, O'Bryan MK, McLachlan RI, Delatycki MB, Rombauts L. Germ cell arrest associated with aSETX mutation in ataxia oculomotor apraxia type 2. Reprod Biomed Online 2019; 38:961-965. [PMID: 30642639 DOI: 10.1016/j.rbmo.2018.12.042] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 12/17/2018] [Accepted: 12/18/2018] [Indexed: 11/19/2022]
Abstract
Ataxia with oculomotor apraxia type 2 (AOA2) is a rare autosomal recessive neurodegenerative disorder characterized by cerebellar atrophy, peripheral neuropathy and oculomotor apraxia. It is caused by mutations in the SETX gene that encodes senataxin, a ubiquitously expressed protein that mediates processes, including transcription, transcription termination, DNA repair, RNA processing, DNA-RNA hybrid (R-loop) elimination and telomere stability. In mice, senataxin is essential for male germ cell development and fertility through its role in meiotic recombination and sex chromosome inactivation. AOA2 is associated with hypogonadism in women, but there are no reports of hypogonadism or infertility in men. We describe the first case of human male infertility caused by germ cell arrest in a man with AOA2. Our patient has a homozygous mutation in the SETX gene (NC_000009.11:g.135158775dup), which results in a frameshift and premature protein termination (NM_015046.6:c.6422dup, p.[Ser2142Glufs*23]). In accordance with the murine phenotype, testis histology revealed disrupted seminiferous tubules with spermatogonia and primary spermatocytes, but absent spermatids. Collectively, these data support an essential role of senataxin in human spermatogenesis, and provide a compelling case that men with AOA2 should be counselled at diagnosis about the possibility of infertility.
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Peverill RE, Donelan L, Corben LA, Delatycki MB. Differences in the determinants of right ventricular and regional left ventricular long-axis dysfunction in Friedreich ataxia. PLoS One 2018; 13:e0209410. [PMID: 30596685 PMCID: PMC6312254 DOI: 10.1371/journal.pone.0209410] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2018] [Accepted: 12/05/2018] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative condition which also has effects on the heart. In 96% of affected individuals FRDA is due to homozygosity of a GAA repeat expansion in intron 1 of the frataxin (FXN) gene. The number of GAA repeats have been shown to relate to disease severity in FRDA, this thought to be via an inverse relationship of GAA repeat number and cellular frataxin levels. We investigated the effects of FRDA on regional long axis function of the left and right ventricles, and also the relationship of long axis systolic (s`) and early diastolic (e`) peak velocities with GAA repeat number on the shorter (GAA1) and longer FXN alleles (GAA2). METHODS The study group of 78 adult subjects (age 32±9 years) with FRDA and normal left ventricular (LV) ejection fraction were compared to 54 healthy control subjects of similar age, sex and body size. Tissue Doppler imaging (TDI) signals were recorded at the mitral annulus for measurement of s`and e`of the septal, lateral, anterior and inferior walls and at the tricuspid annulus for measurement of right ventricular (RV) s`and e`. RESULTS All the regional LV s`and e`, and both RV s`and RV e`, were lower in individuals with FRDA compared to controls (p<0.001 for all). On multivariate analysis, which included LV septal wall thickness (SWT), RV s`and RV e`were both inversely correlated with GAA1 (β = -0.32 & -0.33, respectively, p = 0.01), but not with GAA2, whereas anterior and lateral s`were both inversely correlated with GAA2 (β = -0.25 and β = -0.28, p = 0.02) but not with GAA1. Increasing SWT was the most consistent LV structural correlate of lower s`and e`, whereas age was a consistent inverse correlate of e`but not of s`. CONCLUSION There are generalized abnormalities of both LV regional and RV long axis function in FRDA, but there are also regional differences in the association of this dysfunction with the smaller and larger GAA repeats in the FXN gene.
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Tankard RM, Bennett MF, Degorski P, Delatycki MB, Lockhart PJ, Bahlo M. Detecting Expansions of Tandem Repeats in Cohorts Sequenced with Short-Read Sequencing Data. Am J Hum Genet 2018; 103:858-873. [PMID: 30503517 PMCID: PMC6288141 DOI: 10.1016/j.ajhg.2018.10.015] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 10/16/2018] [Indexed: 10/27/2022] Open
Abstract
Repeat expansions cause more than 30 inherited disorders, predominantly neurogenetic. These can present with overlapping clinical phenotypes, making molecular diagnosis challenging. Single-gene or small-panel PCR-based methods can help to identify the precise genetic cause, but they can be slow and costly and often yield no result. Researchers are increasingly performing genomic analysis via whole-exome and whole-genome sequencing (WES and WGS) to diagnose genetic disorders. However, until recently, analysis protocols could not identify repeat expansions in these datasets. We developed exSTRa (expanded short tandem repeat algorithm), a method that uses either WES or WGS to identify repeat expansions. Performance of exSTRa was assessed in a simulation study. In addition, four retrospective cohorts of individuals with eleven different known repeat-expansion disorders were analyzed with exSTRa. We assessed results by comparing the findings to known disease status. Performance was also compared to three other analysis methods (ExpansionHunter, STRetch, and TREDPARSE), which were developed specifically for WGS data. Expansions in the assessed STR loci were successfully identified in WES and WGS datasets by all four methods with high specificity and sensitivity. Overall, exSTRa demonstrated more robust and superior performance for WES data than did the other three methods. We demonstrate that exSTRa can be effectively utilized as a screening tool for detecting repeat expansions in WES and WGS data, although the best performance would be produced by consensus calling, wherein at least two out of the four currently available screening methods call an expansion.
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Lynch DR, Farmer J, Hauser L, Blair IA, Wang QQ, Mesaros C, Snyder N, Boesch S, Chin M, Delatycki MB, Giunti P, Goldsberry A, Hoyle C, McBride MG, Nachbauer W, O'Grady M, Perlman S, Subramony SH, Wilmot GR, Zesiewicz T, Meyer C. Safety, pharmacodynamics, and potential benefit of omaveloxolone in Friedreich ataxia. Ann Clin Transl Neurol 2018; 6:15-26. [PMID: 30656180 PMCID: PMC6331199 DOI: 10.1002/acn3.660] [Citation(s) in RCA: 97] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 09/05/2018] [Indexed: 12/12/2022] Open
Abstract
Objective Previous studies have demonstrated that suppression of Nrf2 in Friedreich ataxia tissues contributes to excess oxidative stress, mitochondrial dysfunction, and reduced ATP production. Omaveloxolone, an Nrf2 activator and NF-kB suppressor, targets dysfunctional inflammatory, metabolic, and bioenergetic pathways. The dose-ranging portion of this Phase 2 study assessed the safety, pharmacodynamics, and potential benefit of omaveloxolone in Friedreich ataxia patients (NCT02255435). Methods Sixty-nine Friedreich ataxia patients were randomized 3:1 to either omaveloxolone or placebo administered once daily for 12 weeks. Patients were randomized in cohorts of eight patients, at dose levels of 2.5-300 mg/day. Results Omaveloxolone was well tolerated, and adverse events were generally mild. Optimal pharmacodynamic changes (noted by changes in ferritin and GGT) were observed at doses of 80 and 160 mg/day. No significant changes were observed in the primary outcome, peak work load in maximal exercise testing (0.9 ± 2.9 W, placebo corrected). At the 160 mg/day dose, omaveloxolone improved the secondary outcome of the mFARS by 3.8 points versus baseline (P = 0.0001) and by 2.3 points versus placebo (P = 0.06). Omaveloxolone produced greater improvements in mFARS in patients that did not have musculoskeletal foot deformity (pes cavus). In patients without this foot deformity, omaveloxolone improved mFARS by 6.0 points from baseline (P < 0.0001) and by 4.4 points versus placebo (P = 0.01) at the 160 mg/day. Interpretation Treatment of Friedreich ataxia patients with omaveloxolone at the optimal dose level of 160 mg/day appears to improve neurological function. Therefore, omaveloxolone treatment is being examined in greater detail at 150 mg/day for Friedreich ataxia.
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Knight KW, Stephenson SE, West S, Delatycki MB, Jones CA, Little MH, Patton GC, Sawyer SM, Skinner SR, Telfer MM, Wake M, North KN, Oberklaid F. The kids are OK: it is discrimination not same-sex parents that harms children. Med J Aust 2018; 207:374-375. [PMID: 29092695 DOI: 10.5694/mja17.00943] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 11/02/2017] [Indexed: 12/17/2022]
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Ravenscroft G, Pannell S, O'Grady G, Ong R, Ee HC, Faiz F, Marns L, Goel H, Kumarasinghe P, Sollis E, Sivadorai P, Wilson M, Magoffin A, Nightingale S, Freckmann ML, Kirk EP, Sachdev R, Lemberg DA, Delatycki MB, Kamm MA, Basnayake C, Lamont PJ, Amor DJ, Jones K, Schilperoort J, Davis MR, Laing NG. Variants in ACTG2 underlie a substantial number of Australasian patients with primary chronic intestinal pseudo-obstruction. Neurogastroenterol Motil 2018; 30:e13371. [PMID: 29781137 DOI: 10.1111/nmo.13371] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 04/09/2018] [Indexed: 12/13/2022]
Abstract
BACKGROUND Primary chronic intestinal pseudo-obstruction (CIPO) is a rare, potentially life-threatening disorder characterized by severely impaired gastrointestinal motility. The objective of this study was to examine the contribution of ACTG2, LMOD1, MYH11, and MYLK mutations in an Australasian cohort of patients with a diagnosis of primary CIPO associated with visceral myopathy. METHODS Pediatric and adult patients with primary CIPO and suspected visceral myopathy were recruited from across Australia and New Zealand. Sanger sequencing of the genes encoding enteric gamma-actin (ACTG2) and smooth muscle leiomodin (LMOD1) was performed on DNA from patients, and their relatives, where available. MYH11 and MYLK were screened by next-generation sequencing. KEY RESULTS We identified heterozygous missense variants in ACTG2 in 7 of 17 families (~41%) diagnosed with CIPO and its associated conditions. We also identified a previously unpublished missense mutation (c.443C>T, p.Arg148Leu) in one family. One case presented with megacystis-microcolon-intestinal hypoperistalsis syndrome in utero with subsequent termination of pregnancy at 28 weeks' gestation. All of the substitutions identified occurred at arginine residues. No likely pathogenic variants in LMOD1, MYH11, or MYLK were identified within our cohort. CONCLUSIONS AND INFERENCES ACTG2 mutations represent a significant underlying cause of primary CIPO with visceral myopathy and associated phenotypes in Australasian patients. Thus, ACTG2 sequencing should be considered in cases presenting with hypoperistalsis phenotypes with suspected visceral myopathy. It is likely that variants in other genes encoding enteric smooth muscle contractile proteins will contribute further to the genetic heterogeneity of hypoperistalsis phenotypes.
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Hamedani AG, Hauser LA, Perlman S, Mathews K, Wilmot GR, Zesiewicz T, Subramony SH, Ashizawa T, Delatycki MB, Brocht A, Lynch DR. Longitudinal analysis of contrast acuity in Friedreich ataxia. NEUROLOGY-GENETICS 2018; 4:e250. [PMID: 30065952 PMCID: PMC6066362 DOI: 10.1212/nxg.0000000000000250] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/23/2017] [Accepted: 05/22/2018] [Indexed: 11/15/2022]
Abstract
Objective To determine the natural history of contrast acuity in Friedreich ataxia. Methods In the Friedreich Ataxia–Clinical Outcome Measures Study, participants (n = 764) underwent binocular high- and low-contrast visual acuity testing at annual study visits. Mixed-effects linear regression was used to model visual acuity as a function of time, with random intercepts and slopes to account for intraindividual correlation of repeated measurements. A time-varying covariate was used to adjust for diabetes, and interaction terms were used to assess for effect modification by GAA repeat length, disease duration, and other variables. Results Across a median of 4.4 years of follow-up, visual acuity decreased significantly at 100% contrast (−0.37 letters/y, 95% confidence interval [CI]: −0.52 to −0.21), 2.5% contrast (−0.81 letters/year, 95% CI: −0.99 to −0.65), and 1.25% contrast (−1.12 letters/y, 95% CI: −1.29 to −0.96 letters/year). There was a significant interaction between time and GAA repeat length such that the rate of decrease in visual acuity was greater for patients with higher GAA repeat lengths at 2.5% contrast (p = 0.018) and 1.25% contrast (p = 0.043) but not 100% contrast. There was no effect modification by age at onset after adjusting for GAA repeat length. Conclusions Low-contrast visual acuity decreases linearly over time in Friedreich ataxia, and the rate of decrease is greater at higher GAA repeat lengths. Contrast sensitivity has the potential to serve as a biomarker and surrogate outcome in future studies of Friedreich ataxia.
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Bahlo M, Bennett MF, Degorski P, Tankard RM, Delatycki MB, Lockhart PJ. Recent advances in the detection of repeat expansions with short-read next-generation sequencing. F1000Res 2018; 7:F1000 Faculty Rev-736. [PMID: 29946432 PMCID: PMC6008857 DOI: 10.12688/f1000research.13980.1] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/07/2018] [Indexed: 11/20/2022] Open
Abstract
Short tandem repeats (STRs), also known as microsatellites, are commonly defined as consisting of tandemly repeated nucleotide motifs of 2-6 base pairs in length. STRs appear throughout the human genome, and about 239,000 are documented in the Simple Repeats Track available from the UCSC (University of California, Santa Cruz) genome browser. STRs vary in size, producing highly polymorphic markers commonly used as genetic markers. A small fraction of STRs (about 30 loci) have been associated with human disease whereby one or both alleles exceed an STR-specific threshold in size, leading to disease. Detection of repeat expansions is currently performed with polymerase chain reaction-based assays or with Southern blots for large expansions. The tests are expensive and time-consuming and are not always conclusive, leading to lengthy diagnostic journeys for patients, potentially including missed diagnoses. The advent of whole exome and whole genome sequencing has identified the genetic cause of many genetic disorders; however, analysis pipelines are focused primarily on the detection of short nucleotide variations and short insertions and deletions (indels). Until recently, repeat expansions, with the exception of the smallest expansion (SCA6), were not detectable in next-generation short-read sequencing datasets and would have been ignored in most analyses. In the last two years, four analysis methods with accompanying software (ExpansionHunter, exSTRa, STRetch, and TREDPARSE) have been released. Although a comprehensive comparative analysis of the performance of these methods across all known repeat expansions is still lacking, it is clear that these methods are a valuable addition to any existing analysis pipeline. Here, we detail how to assess short-read data for evidence of expansions, reviewing all four methods and outlining their strengths and weaknesses. Implementation of these methods should lead to increased diagnostic yield of repeat expansion disorders for known STR loci and has the potential to detect novel repeat expansions.
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Morrison PJ, Delatycki MB. Ameliorating the age at onset and disease progression in Huntington disease. Neurology 2018; 90:1087-1088. [DOI: 10.1212/wnl.0000000000005670] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Ejaz R, Chen S, Isaacs CJ, Carnevale A, Wilson J, George K, Delatycki MB, Perlman SL, Mathews KD, Wilmot GR, Hoyle JC, Subramony SH, Zesiewicz T, Farmer JM, Lynch DR, Yoon G. Impact of Mobility Device Use on Quality of Life in Children With Friedreich Ataxia. J Child Neurol 2018; 33:397-404. [PMID: 29607705 DOI: 10.1177/0883073818764941] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
OBJECTIVE To determine how mobility device use impacts quality of life in children with Friedreich ataxia. STUDY DESIGN Data from 111 pediatric patients with genetically confirmed Friedreich ataxia were collected from a prospective natural history study utilizing standardized clinical evaluations, including health-related quality of life using the Pediatric Quality of Life Inventory (PedsQL) 4.0 Generic Core Module. RESULTS Mobility device use was associated with worse mean PedsQL total, physical, emotional, social, and academic subscores, after adjusting for gender, age of disease onset, and Friedreich Ataxia Rating Scale score. The magnitude of the difference was greatest for the physical subscore (-19.5 points, 95% CI = -30.00, -8.99, P < .001) and least for the emotional subscore (-10.61 points, 95% CI = -20.21, -1.02, P = .03). Transition to or between mobility devices trended toward worse physical subscore (-16.20 points, 95% CI = -32.07, -0.33, P = .05). CONCLUSIONS Mobility device use is associated with significant worsening of all domains of quality of life in children with Friedreich ataxia.
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