Conversations with French medical geneticists. A personal perspective on the origins and early years of medical genetics in France.

The history of the beginnings of medical genetics in France is discussed, based on the personal perspective provided by recorded interviews with 16 early French workers in the field. The weakness of French genetics overall up to the beginning of the Second World War meant that post-war medical genetics had to start from new, with its origins largely derived from the medical fields of child health and the prevention of genetic disorders, rather than from basic science. The key people responsible for initiating these developments were Robert Debré and Maurice Lamy at Hôpital Necker in Paris and those interviewed included a number of their colleagues and successors, including Jean Frézal, Pierre Maroteaux, Josué Feingold, André and Joelle Boué, and Jean-Claude Kaplan. A separate group of paediatricians, originally at Hôpital Trousseau under Raymond Turpin, including Jérôme Lejeune, Marthe Gautier and Roland Berger, was responsible for major advances in human cytogenetics. Outside Paris, workers were interviewed from Marseille, Strasbourg and Nancy, although not from Lyon, where Jacques-Michel Robert was an early pioneer, particularly of genetic counselling. Challenges in the development of medical genetics in France included the advent of prenatal diagnosis with its ethical issues, the emergence of medical genetics as a distinct specialty from paediatrics, and its spread from Paris across France. These and other aspects are described by those interviewed from their own experiences, given in Appendix S1, while the fully edited transcripts for most interviews are accessible on the Web: www.genmedhist.org/interviews.

A case of multiple cutaneous schwannomas; schwannomatosis or neurofibromatosis type 2?

A 54 year old man presented with numerous cutaneous schwannomas, cranial nerve lesions, and spinal cord lesions, but no evidence of vestibular nerve involvement. There was no family history of neurocutaneous lesions. To help discriminate between the various possible diagnoses in this patient, molecular analysis of two cutaneous schwannomas was undertaken. An identical point mutation in the NF2 gene in the two anatomically distinct tumours was found, confirming this as a case of NF2 mosaicism.

Population based study of late onset cerebellar ataxia in south east Wales.

OBJECTIVE: To determine the prevalence and causation of late onset cerebellar ataxia (LOCA) in south east Wales, United Kingdom. METHODS: A population based study of LOCA was conducted in a defined geographical region with a total population of 742,400. Multiple sources of ascertainment were used to identify all cases prevalent on 1 January 2001. The inclusion criteria were: a predominantly progressive cerebellar ataxia with onset of symptoms at age > or = 18 years; and disease duration of > or = 1 year. Cases with known acquired ataxias, ataxic syndromes with associated prominent autonomic dysfunction and/or atypical parkinsonism suggestive of multiple system atrophy and disorders with ataxia as a minor feature were excluded. RESULTS: We identified 76 index cases of LOCA, of whom 63 were sporadic, idiopathic LOCA (ILOCA) and 13 were familial LOCA, of whom six had either spinocerebellar ataxia type 6, Friedreich's ataxia or dominant episodic ataxia. The mean annual incidence rate for the period 1999-2001 was 0.3/100,000 population/year. The crude prevalence rates were 8.4 per 100,000 (95% CI 7.2 to 11.6) for ILOCA and 1.8 per 100,000 (95% CI 0.8 to 2.7) for inherited LOCA. Of the 54/63 (85.7%) patients with ILOCA who were assessed, mean (SD) age at onset of symptoms was 53.8 (14.1) years (range 19 to 78) with a male:female ratio of 2.1:1. The mean disease duration was 8.7 (6.3) years (range 1 to 31). The most frequent presenting complaint was disturbance in gait (90.7%). One-third had a relatively pure cerebellar syndrome (33.3%) and two-thirds (66.7%) had additional extracerebellar neurological features. The majority (92%) were ambulant but only 9.3% were independently self-caring. CONCLUSION: This population based study provides insight into LOCA within a defined region and will inform decisions about the rational use of healthcare resources for patients with LOCA.

Familial motor neurone disease with dementia: phenotypic variation and cerebellar pathology.

OBJECTIVES: To characterise the neuropathological phenotypes of two affected individuals from a family with an unusual clinical phenotype resembling motor neurone disease and dementia. METHODS: Histological sections of cerebral cortex, basal ganglia, brain stem, cerebellum, and spinal cord were stained with haematoxylin-eosin, luxol fast blue, silver stains, anti-tau, anti-ubiquitin, anti-alpha-synuclein, and anti-neurofilament. RESULTS: Numerous ubiquitin positive, tau and alpha-synuclein negative intraneuronal inclusions were present in the cerebral cortex (particularly within the dentate gyrus), cerebellar cortex, brain stem, and spinal cord. The cerebellar ubiquitinated inclusions were located in the proximal dendrite of the Purkinje cells. Loss of Purkinje cells and occasional silver and neurofilament positive axonal swellings (torpedoes) were also seen within the cerebellar cortex. The main difference between the two cases was the severity of the spinal cord involvement: no significant pathology was present within one, but obvious motor neurone disease within the other. CONCLUSIONS: The clinical and neuropathological findings in this family are best described as an example of familial motor neurone disease with dementia. Intraneuronal ubiquitin inclusions together with agyrophilic, neurofilament positive torpedoes were present within the cerebellar cortex, both previously unrecognised findings in this group of diseases.

Clinical and genetic heterogeneity in peroneal muscular atrophy associated with vocal cord weakness.

BACKGROUND: The peroneal muscular atrophy syndrome is the most common inherited disorder of the peripheral nervous system and has extensive clinical and genetic heterogeneity. Cranial nerve involvement is rare, though there are distinct peroneal muscular atrophy syndromes in which vocal cord paralysis is a characteristic feature. Among these dHMN-VII and HMSN-IIC are clinically similar but are differentiated by sensory involvement in HMSN-IIC. The gene for dHMN-VII, designated DHMNVP, has been localised to chromosome 2q14, but the location of the gene for HMSN-IIC is currently unknown. It has been suggested that dHMN-VII and HMSN II-C are allelic disorders. OBJECTIVE: To assess the contribution of the dHMN-VII predisposition gene to peroneal muscular atrophy syndromes associated with vocal cord weakness. METHODS: Linkage analysis of microsatellite markers at chromosome 2q14 was undertaken on two families, one affected by HMSN-IIC and a second manifesting vocal cord paralysis and sensorineural deafness in addition to distal muscular atrophy. RESULTS: Two-point LOD scores at chromosome 2q14 markers encompassing the DHMNVP gene were negative in both families. CONCLUSIONS: These results suggest that at least one further gene predisposing to distal muscular weakness in association with vocal cord paralysis is likely to exist, and that dHMN-VII and HMSN-IIC are unlikely to be allelic disorders. Analyses of further HMSN-IIC families are required to confirm this.

Developing a quality scoring system for epidemiological surveys of genetic disorders.

A prototype database of published articles containing data on the frequency of human inherited disorders has been developed for use in clinical contexts, in medical research, for epidemiological studies, and in the planning of genetic services. It can be accessed at http://www.uwcm.ac.uk/uwcm/mg/fidd/. The information available in the literature comes from a wide range of publications, not all can be described primarily as epidemiological surveys. A preliminary assessment indicated that the quality of published articles was highly variable. Very few published articles describe quality-scoring systems for epidemiological surveys in general. We have developed a new scoring system to assess the quality of published articles on genetic disease frequency based on five main criteria and nine component scores. We carried out a first pilot study, to test its feasibility, usefulness and reproducibility. Eleven assessors scored six papers on the epidemiology of Huntington disease. As a result of these findings, we modified the scoring system to define each component more clearly. This was then evaluated in a second pilot study, which utilized six assessors to score 20 papers. The consensus between assessors remained relatively poor. We feel that while it may be possible to improve the scoring system further, the degree of improvement attainable may be limited by the poor standards of content and presentation of published surveys, which led to confusion and uncertainty by assessors. This pilot exercise has shown the need to raise the awareness of researchers and clinicians about the basic quality standards to be required of epidemiological genetic surveys.

Mutational analysis in X-linked spondyloepiphyseal dysplasia tarda.

Spondyloepiphyseal dysplasia tarda (SEDT) is an X-linked recessive disorder characterized by short stature due to defective growth of the vertebral bodies. In addition, deformities of the femoral heads result in early onset secondary osteoarthritis of the hips. The disorder affects males only with heterozygous female carriers showing no consistent abnormalities. The gene causing SEDT, which is located on Xp22.12-p22.31, consists of 6 exons of which only exons 3, 4, 5, and 6 are translated to yield an 140 amino acid protein, referred to as SEDLIN. SEDLIN mutations have been observed in SEDT patients, and we have undertaken studies to characterize such mutations in four unrelated SEDT kindreds by DNA sequence analysis. We identified two nonsense and two intragenic deletional frameshift mutations. The nonsense mutations occurred in exons 4 (TGG-->TGA, Trp70Stop) and 6 (CGA-->TGA, Arg122Stop). Both of the intragenic deletions, which were approximately 750 bp and 1300-1445 bp in size, involved intron 5 and part of exon 6 and resulted in frameshifts that lead to premature termination (Stop) signals. Thus, all four mutations are predicted to result in truncated proteins. The results of our study expand the spectrum of SEDLIN mutations associated with SEDT, and this will help to elucidate further the role of this novel protein in the etiology of this form of osteochondrodysplasia.

Localization of the gene for distal hereditary motor neuronopathy VII (dHMN-VII) to chromosome 2q14.

Distal hereditary motor neuronopathy type VII (dHMN-VII) is an autosomal dominant disorder characterized by distal muscular atrophy and vocal cord paralysis. We performed a genomewide linkage search in a large Welsh pedigree with dHMN-VII and established linkage to chromosome 2q14. Analyses of a second family with dHMN-VII confirmed the location of the gene and provided evidence for a founder mutation segregating in both pedigrees. The maximum three-point LOD score in the combined pedigree was 7.49 at D2S274. Expansion of a polyalanine tract in Engrailed-1, a transcription factor strongly expressed in the spinal cord, was excluded as the cause of dHMN-VII.

The frequency of inherited disorders database: prevalence of Huntington disease.

A database of the frequency of human inherited disorders is being established for use in a clinical context, in medical research, for epidemiological studies, and in the planning of genetic services. Each entry includes the disease name categorized by organ system, an Online Mendelian Inheritance in Man (OMIM) number, the mode of inheritance, the population origin, a prevalence and/or incidence rate and a literature reference. The Frequency of Inherited Disorders Database (FIDD) currently contains 1,580 entries relating to 280 different Mendelian disorders. FIDD will be prospectively maintained and can be accessed at http://www.uwcm.ac.uk/uwcm/mg/fidd/. A more refined and systematic literature search that will serve to expand the size, scope and scale of the database is currently in progress. The coverage of neurological and neuromuscular disorders is however considered to be nearly complete. In this first description of FIDD, Huntington disease was used to illustrate the structure and scope of the database as well as its potential scientific utility. A total of 100 published articles on the prevalence of Huntington disease were appraised. Prevalence and incidence rates varied between different ethnic groups and between different countries. Possible reasons for this variation are discussed.

Variation in the vitreous phenotype of Stickler syndrome can be caused by different amino acid substitutions in the X position of the type II collagen Gly-X-Y triple helix.

Stickler syndrome is a dominantly inherited disorder characterized by arthropathy, midline clefting, hearing loss, midfacial hypoplasia, myopia, and retinal detachment. These features are highly variable both between and within families. Mutations causing the disorder have been found in the COL2A1 and COL11A1 genes. Premature termination codons in COL2A1 that result in haploinsufficiency of type II collagen are a common finding. These produce a characteristic congenital "membranous" anomaly of the vitreous of all affected individuals. Experience has shown that vitreous slit-lamp biomicroscopy can distinguish between patients with COL2A1 mutations and those with dominant negative mutations in COL11A1, who produce a different "beaded" vitreous phenotype. Here we characterize novel dominant negative mutations in COL2A1 that result in Stickler syndrome. Both alter amino acids in the X position of the Gly-X-Y triple-helical region. A recurrent R365C mutation occurred in two unrelated sporadic cases and resulted in the membranous vitreous anomaly associated with haploinsufficiency. In a large family with linkage to COL2A1, with a LOD score of 2.8, a unique L467F mutation produced a novel "afibrillar" vitreous gel devoid of all normal lamella structure. These data extend the mutation spectrum of the COL2A1 gene and help explain the basis for the different vitreous phenotypes seen in Stickler syndrome.

Ten years of presymptomatic testing for Huntington's disease: the experience of the UK Huntington's Disease Prediction Consortium.

Data on all presymptomatic genetic tests for Huntington's disease (HD) in the UK have been collected over the 10 year period since testing became available as a service. A total of 2937 completed tests have been performed up to the end of 1997, 2502 based on specific mutation testing, feasible since late 1993.A total of 93.1% of these were at 50% prior risk, with a significant excess of females (58.3%); 41.4% of results were abnormal or high risk, including 29.4% in subjects aged 60 or over. The trend in test numbers has currently levelled out at around 500 per year. Almost all presymptomatic tests are carried out in National Health Service genetics centres, with a defined genetic counselling protocol and with availability now in all regions of the UK. The introduction and establishment of HD presymptomatic testing shows that this form of predictive medicine for Mendelian disorders can be successfully incorporated into National Health Service structures. The comprehensive collection of simple data allows trends in demand and outcomes to be monitored and has also been the foundation for more detailed specific studies. A comparable approach to data collection in other genetic disorders will be important as presymptomatic testing becomes more generally feasible.

Psychological Model for Presymptomatic Test Interviews: Lessons Learned from Huntington Disease.

This paper reflects on experience gained from presymptomatic testing for Huntington disease. An approach is presented which considers the role of the clinician and aims of the interview. Irrespective of the disease being tested for, it is suggested that the psychological aim of presymptomatic testing is to foster emotional insight and understanding that will help clients in their decision-making process about testing and their subsequent adjustment to the result. Based on these aims the process of presymptomatic testing, counseling is considered in terms of clarification, consideration, education, and reflection, followed by decision making. Practical approaches are discussed and illustrated with clinical examples.