James N. Macpherson

Population studies of the fragile X: a molecular approach.

The fragile X mutation can now be recognised by a variety of molecular techniques. We report a pilot screening survey of a population of children with mental impairment in which we used Southern blotting methods to detect the fragile X mutation, augmented by cytogenetic studies on children whose phenotype suggested a possible chromosome abnormality. There were 873 children with special educational needs in our survey and 310 fulfilled our criteria for testing. A sample was obtained from 254, of whom four were found to have a full fra(X) mutation (delta L) and none to have a premutation. The number of CGG repeats in our population of X chromosomes was measured by PCR analysis and the genotype at the closely linked polymorphic locus FRAXAC1 established. The distribution of CGG repeat numbers was very similar to that of the control population reported by Fu et al and the distribution of FRAXAC1 alleles almost identical to that of the control population reported by Richards et al. Among the non-fragile X chromosomes, we found a very significant correlation between the size of the CGG repeat and the FRAXAC1 genotype. There was a dearth of A and D genotypes in subjects with a small number of CGG repeats and an excess of the A genotype in those with a large number of CGG repeats. These observations are considered in the light of the reported disequilibrium between the A (and possibly also the D) genotype and the fra(X) mutation.

Observation of an excess of fragile-X premutations in a population of males referred with spinocerebellar ataxia

Premutations of the fragile-X (FRAXA) gene were thought to have no clinical effects until recent reports of an increased incidence of premature ovarian failure in females and a late-onset neurological disorder in males. These patients were identified from families including typical fragile-X males with a full mutation. By analysing a cohort of patients with neurodegenerative disorders referred for genetic analysis of spinocerebellar ataxia genes, we have found that 3 of 59 males carry the premutation. Our patients extend the phenotype associated with the FRAXA premutation and indicate that it may account for a proportion of undiagnosed neurodegenerative disorders.

Cirugía del aneurisma de aorta abdominal en pacientes octogenarios

Objetivo. Analizar las caracteristicas de los pacientes octogenarios sometidos a cirugia convencional y valorar la experiencia y los resultados de este tipo de tratamiento en nuestro servicio. Pacientes y metodos. Estudio retrospectivo de todos los pacientes consecutivos mayores de 80 anos con un aneurisma de aorta abdominal (AAA) tratados de forma quirurgica convencional desde enero de 1993 hasta diciembre de 2006 en nuestro centro. Resultados. Se incluyeron 45 pacientes, con una edad media de 83,4 ± 3,4 anos. La mayoria eran varones (40 pacientes, 88,9%). Veintiocho pacientes (62,2%) fueron clasificados como ASA (Asociacion Americana de Anestesiologia) IV. La media del diametro de los AAA fue de 6,9 ± 2·cm. Se trato de forma urgente a 29 pacientes (64,4%), de los cuales, en 22 casos, la indicacion fue por rotura aneurismatica. Destaco entre los factores de riesgo cardiovascular la hipertension, presente en 30 pacientes (66,7%). Treinta y un pacientes (68,9%) padecian alguna cardiopatia. La mortalidad operatoria fue del 6,3% en los pacientes tratados de forma electiva, mientras que en los tratados de forma urgente la mortalidad ascendio a 41,4% (p = 0,01). La presencia de ictus previo (11,1%) a la intervencion quirurgica se asocio a mayor mortalidad (p = 0,02). Conclusiones. Basandonos en estos resultados, el tratamiento quirurgico electivo de los pacientes octogenarios parece justificado en nuestro centro cuando no existe una opcion terapeutica alternativa menos invasiva. [ANGIOLOGIA 2008; 60: 103-8J

Intermediate sized CGG repeats are not a common cause of idiopathic premature ovarian failure

BACKGROUND It is recognized that FMR1 premutation expansions are associated with premature ovarian failure (POF), but the role of smaller repeats at the boundary of premutation and normal is less clear. METHODS We have therefore investigated the incidence of these intermediate sized FMR1 CGG repeats (35-58 repeats) in a series of 366 women ascertained because of menopause before the age of 40. RESULTS We found no significant difference in the incidence of intermediates in cases compared with controls. Thus, we were unable to replicate previous studies showing a positive association, despite a significantly larger sample size. CONCLUSIONS We therefore conclude that intermediate sized FMR1 CGG repeat alleles should not be considered a high-risk factor for POF based on current evidence.

Editorial comment: Significance of linkage disequilibrium between the fragile X locus and its flanking markers

The identification of several microsatellite markers flanking the FRAXA locus was instrumental in the positional cloning of the FMR1 gene. These markers can still be valuable in family studies, e.g., as additional evidence in prenatal diagnosis. Additionally, they were employed to verify the presence of any significant gametic disequilibrium between the fragile X mutation and some haplotypes, although the high mutation rate predicted from early segregation studies implied that new mutants would arise on almost every chromosomal background. Thus, the discovery of linkage disequilibrium encompassing the fragile X locus has been surprising. Here, we review the available evidence of such gametic association and underline its implications for the mutational mechanism. 50 refs., 1 fig., 2 tabs.

Population-based estimates of the prevalence of FMR1 expansion mutations in women with early menopause and primary ovarian insufficiency

Purpose:Primary ovarian insufficiency before the age of 40 years affects 1% of the female population and is characterized by permanent cessation of menstruation. Genetic causes include FMR1 expansion mutations. Previous studies have estimated mutation prevalence in clinical referrals for primary ovarian insufficiency, but these are likely to be biased as compared with cases in the general population. The prevalence of FMR1 expansion mutations in early menopause (between the ages of 40 and 45 years) has not been published.Methods:We studied FMR1 CGG repeat number in more than 2,000 women from the Breakthrough Generations Study who underwent menopause before the age of 46 years. We determined the prevalence of premutation (55–200 CGG repeats) and intermediate (45–54 CGG repeats) alleles in women with primary ovarian insufficiency (n = 254) and early menopause (n = 1,881).Results:The prevalence of the premutation was 2.0% in primary ovarian insufficiency, 0.7% in early menopause, and 0.4% in controls, corresponding to odds ratios of 5.4 (95% confidence interval = 1.7–17.4; P = 0.004) for primary ovarian insufficiency and 2.0 (95% confidence interval = 0.8–5.1; P = 0.12) for early menopause. Combining primary ovarian insufficiency and early menopause gave an odds ratio of 2.4 (95% confidence interval = 1.02–5.8; P = 0.04). Intermediate alleles were not significant risk factors for either early menopause or primary ovarian insufficiency.Conclusion:FMR1 premutations are not as prevalent in women with ovarian insufficiency as previous estimates have suggested, but they still represent a substantial cause of primary ovarian insufficiency and early menopause.Genet Med 16 1, 19–24.

New neuropathological findings in Unverricht–Lundborg disease: neuronal intranuclear and cytoplasmic inclusions

Unverricht–Lundborg disease (EPM1A), also known as Baltic myoclonus, is the most common form of progressive myoclonic epilepsy. It is inherited as an autosomal recessive trait, due to mutations in the Cystatin-B gene promoter region. Although there is much work on rodent models of this disease, there is very little published neuropathology in patients with EPM1A. Here, we present the neuropathology of a patient with genetically confirmed EPM1A, who died at the age of 76. There was atrophy and gliosis affecting predominantly the cerebellum, frontotemporal cortex, hippocampus and thalamus. We have identified neuronal cytoplasmic inclusions containing the lysosomal proteins, Cathepsin-B and CD68. These inclusions also showed immunopositivity to both TDP-43 and FUS, in some cases associated with an absence of normal neuronal nuclear TDP-43 staining. There were also occasional ubiquitinylated neuronal intranuclear inclusions, some of which were FUS immunopositive. This finding is consistent with neurodegeneration in EPM1A as at least a partial consequence of lysosomal damage to neurons, which have reduced Cystatin-B-related neuroprotection. It also reveals a genetically defined neurodegenerative disease with both FUS and TDP-43 related pathology.

Molecular re-investigation of patients with Huntington's disease in Wessex reveals a family with dentatorubral and pallidoluysian atrophy

Dentatorubral and pallidoluysian atrophy (DRPLA), a neurological disorder thought to be rare in European populations, is caused by a triplet repeat expansion in the B37 gene on chromosome 12. This disorder can phenotypically mimic Huntingtons disease (HD) which is also caused by a repeat expansion. We have analysed 139 affected individuals for the HD triplet repeat expansion and found 132 patients had one normal and one expanded allele. Two patients had an expansion on both chromosomes and five patients had two normal-size alleles. Of these five patients, two were considered to be atypical. Two patients who were father and daughter were found to have an expansion of the DRPLA triplet repeat. This therefore constitutes the second such family described in the United Kingdom.

9th international workshop on fragile X syndrome and X-linked mental retardation.

Jean-Pierre Fryns,1 Martine Borghgraef,1 Ted W. Brown,2 Jamel Chelly,3 Gene S. Fisch,4 Ben Hamel,5 André Hanauer,6 Didier Lacombe,7 Ligun Luo,8 James N. MacPherson,9 Jean-Louis Mandel,6 Claude Moraine,10 John Mulley,11 David Nelson,12 Ben Oostra,13 Michael Partington,14 Ger J.A. Ramakers,15 Hans-Hilger Ropers,16 François Rousseau,17 Charles Schwartz,18 Peter Steinbach,19 Claude Stoll,20 Lisbeth Tranebjaerg,21 Gillian Turner,22 Hans Van Bokhoven,5 Angela Vianna-Morgante,23 Laurent Villard,24 and Stephen T. Warren25 1Clinical Genetics Unit/Center for Human Genetics, University Hospital of Leuven, Leuven, Belgium 2New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York 3ICGM-INSERM U129, CHU-Cochin-Port-Royal, Paris, France 4General Clinical Research Center, Yale University, New Haven, Connecticut 5Department of Human Genetics, University Hospital Nijmegen, Nijmegen, the Netherlands 6IGBMC, Illkirch, France 7Department of Medical Genetics, CHU-Pellegrin Enfants, Bordeaux, France 8Biological Sciences, Stanford University, Stanford, California 9Wessex Regional Genetics Laboratory, Salisbury District Hospital, Salisbury Wiltshire, United Kingdom 10Service Génétique, Hôpital Bretonneau, Tours, France 11Cytogenetics and Molecular Genetics, Women’s and Children’s Hospital, North Adelaide, Australia 12Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 13Clinical Genetics Department, Erasmus University, Rotterdam, the Netherlands 14Newcastle, New South Wales, Australia 15Neurons and Networks Group, Netherlands Institute for Brain Research, Amsterdam, the Netherlands 16Max-Planck Institut für Molekulare Genetik, Berlin-Dalhem, Germany 17URGHM, Université Laval Québec, Québec, Canada 18Center for Molecular Studies, J.C. Self Research Institute, Greenwood Genetics Center, Greenwood, South Carolina 19Department of Medical Genetics, Universitätsklinikum Ulm, Ulm, Germany 20Service de Génétique Médicale, Hôpital de Hautepierre, Strasbourg, France 21Department of Medical Genetics, University Hospital of Tromso, Tromso, Norway 22Fragile X Department, Hunter Genetics, Waratah, New South Wales, Australia 23Department de Biologia, Instituto de Biociencias, Universidade de São Paulo, São Paulo, Brazil 24INSERM U491, Faculté de Médecine La Timone, Marseille, France 25Department of Biochemistry, Rollins Research Center, HHMI/Emory University, Atlanta, Georgia

Development of Genetic Testing for Fragile X Syndrome and Associated Disorders, and Estimates of the Prevalence of FMR1 Expansion Mutations

The identification of a trinucleotide (CGG) expansion as the chief mechanism of mutation in Fragile X syndrome in 1991 heralded a new chapter in molecular diagnostic genetics and generated a new perspective on mutational mechanisms in human genetic disease, which rapidly became a central paradigm (“dynamic mutation”) as more and more of the common hereditary neurodevelopmental disorders were ascribed to this novel class of mutation. The progressive expansion of a CGG repeat in the FMR1 gene from “premutation” to “full mutation” provided an explanation for the “Sherman paradox,” just as similar expansion mechanisms in other genes explained the phenomenon of “anticipation” in their pathogenesis. Later, FMR1 premutations were unexpectedly found associated with two other distinct phenotypes: primary ovarian insufficiency and tremor-ataxia syndrome. This review will provide a historical perspective on procedures for testing and reporting of Fragile X syndrome and associated disorders, and the population genetics of FMR1 expansions, including estimates of prevalence and the influence of AGG interspersions on the rate and probability of expansion.