Molecular genetic analysis of the APEX nuclease gene in amyotrophic lateral sclerosis.

We analyzed genomic DNA from ALS patients for mutations in the apurinic/apyrimidinic endonuclease (APEX nuclease) gene. We identified three rare polymorphisms in the untranslated region of the gene and one common two-allele polymorphism (D148E). The allelic frequency D148E was significantly different in sporadic ALS patients compared with controls. A conserved amino acid change and a 4-base pair deletion were also identified in sporadic ALS patients. These data suggest that APEX nuclease may contribute to the etiology of ALS.

Issues in implementing prenatal screening for cystic fibrosis: results of a working conference.

PURPOSE: To summarize a conference convened to examine how cystic fibrosis screening might appropriately be introduced into routine prenatal practice. METHODS: Participants included experts from various relevant disciplines. Systematic reviews and data from individual trials were presented; issues were identified and discussed. RESULTS: Judged by published criteria, prenatal cystic fibrosis screening is suitable for introduction. Screening can be performed cost-effectively by identifying racial/ethnic groups at sufficient risk and then using either of two models for delivering laboratory services. Validated educational materials exist. Ethical issues are not unique. CONCLUSIONS: Once adequate facilities for patient and provider education, testing, counseling, quality control, and monitoring are in place, individual programs can begin prenatal screening for cystic fibrosis.

Attitudes of general practitioners to screening for cystic fibrosis.

OBJECTIVE: To ascertain the views of general practitioners (GPs) about screening for cystic fibrosis. To find out whether and under what conditions they might play a part in the delivery of such programmes. SETTING: All GP practices within the Lothian Health Board area. METHODS: A self administered questionnaire was sent to each of the 532 GPs in the area. RESULTS: 334 (63%) GPs participated in the study. Only 23% of these claimed to have no professional or personal experience of the disorder. 77% of GPs were aware of the existence of a programme of antenatal screening for cystic fibrosis (CF), which had been running in Edinburgh for the past six years, with only 2% unfavourably disposed to it. However, when asked to rank CF screening against antenatal screening for spina bifida and Down's syndrome, or cervical and breast screening, 55% gave it the lowest priority. There was fairly equal support for the screening site being an antenatal clinic, a genetic centre, a family planning clinic, or a GP surgery, but little enthusiasm for programmes in schools or the workplace. Surprisingly, only 13% of GPs thought that screening should be offered to those with a negative family history of the disorder. Although the idea of involvement in screening was favoured, GPs claimed that any aspect of delivery that they undertook would need to be supported. There were no significant differences between the responses of fundholding GPs and non-fundholders. CONCLUSIONS: The low ranking by GPs of CF screening against other programmes, together with the need for support if they were to be involved, suggests that it is currently impractical to move the programme from its existing site in antenatal clinics.

The incidence of cystic fibrosis in Scotland calculated from heterozygote frequencies.

The incidence of cystic fibrosis (CF) has previously been calculated from epidemiological surveys and from neonatal screening. With the cloning of the CF gene it has become possible to derive incidence figures from heterozygote frequencies, provided that the distribution of mutant alleles among healthy carriers is the same as among affected people. We have estimated the allele frequencies for four CF mutations, AF508, G551D, G542X and R117H, in 14360 unselected women undergoing antenatal heterozygote screening. The proportion of R117H, an allele of known mild effect, was much greater for heterozygotes than for homozygotes. The incidence of CF was therefore calculated from the heterozygote frequencies of AF508, G551D and G542X in a larger cohort of 27 161 successively screened women. The point estimate for the incidence of CF in the Scottish population was 1 in 1984, with 95% confidence intervals of 1 in 1692 to 1 in 2336.

P67L: a cystic fibrosis allele with mild effects found at high frequency in the Scottish population.

Only three mutant cystic fibrosis (CF) alleles have to date been established as conferring a dominant mild effect on affected subjects who are compound heterozygotes. We now add a fourth, P67L, which occurs on about 1.4% of Scottish CF chromosomes. Among 13 patients (12 unrelated) with this allele, the average age at diagnosis was 22.5 +/- 11.3 years. None of the cases had consistently raised sweat chloride concentrations, the average value being 57 +/- 9 mmol/l; 77% of the patients were pancreatic sufficient. When compared to three other established mild CF alleles, R117H, A455E, and 3849 + 10kb C-T, a compound heterozygote for P67L has minimal disease and clinical suspicions are unlikely to be confirmed other than by DNA typing.

Marfan Database (third edition): new mutations and new routines for the software.

The Marfan database is a software that contains routines for the analysis of mutations identified in the FBN1 gene that encodes fibrillin-1. Mutations in this gene are associated not only with Marfan syndrome but also with a spectrum of overlapping disorders. The third version of the Marfan database contains 137 entries. The software has been modified to accommodate four new routines and is now accessible on the World Wide Web at http://www.umd.necker.fr

Prenatal screening for cystic fibrosis carriers: does the method of testing affect the longer-term understanding and reproductive behaviour of women?

A comparative study of women who underwent prenatal cystic fibrosis (CF) carrier screening by either the 'two-step method' or the 'couple method' was carried out 2-4 years after testing. Recall of the screening test and test result, understanding of the implications of the test result, and reproductive intentions and behaviour were compared. Women screened by the two-step method were significantly better informed on the genetic implications of the test result and the significance of being a single gene carrier than their couple screen counterparts. Regardless of the method of screening, a majority of those who had received a negative test result erroneously believed that they were definitely not a carrier. However, women who intended having further children were significantly more likely to understand correctly that a negative test result meant that they were unlikely to be a CF carrier. The method of testing had no influence on reproductive intentions or behaviour. Differences in emphasis, content and presentation of pre-screening information and counselling between the two methods of screening are identified. Reasons for variation in the long-term understanding between women screened by the two methods are discussed.

Evidence for a familial pregnancy-induced hypertension locus in the eNOS-gene region.

Pregnancy-induced hypertension may be regarded as a manifestation of endothelial-cell dysfunction. The role of the eNOS gene in the development of a familial pregnancy-induced hypertension was evaluated by analysis of linkage among affected sisters and in multiplex families (n = 50). Markers from a 4-cM region encoding the eNOS gene showed distortion from the expected allele sharing among affected sisters (P = .001-.05), and the statistic obtained from the multilocus application of the affected-pedigree-member method also showed distortion (T[f(P)=sqrt(P)] = 3.53; P < .001). A LOD score of 3.36 was obtained for D7S505 when a best-fitting model derived from genetic epidemiological data was used, and LOD scores of 2.54-4.03 were obtained when various other genetic models were used. Estimates of recombination rate, rather than maximum LOD-score values, were affected by changes in the genetic parameters. The transmission-disequilibrium test, a model-free estimate of linkage, showed strongest association and linkage with a microsatellite within intron 13 of the eNOS gene (P = .005). These results support the localization of a familial pregnancy-induced hypertension-susceptibility locus in the region of chromosome 7q36 encoding the eNOS gene.

Mutation screening of all 65 exons of the fibrillin-1 gene in 60 patients with Marfan syndrome: report of 12 novel mutations.

Mutations in the fibrillin-1 gene on chromosome 15q21.1 have been found to cause Marfan syndrome, a dominantly inherited disorder characterised by clinically variable skeletal, ocular, and cardiovascular abnormalities. In this study we screened all 65 exons of the fibrillin-1 gene in 20 Marfan syndrome families where at least two affected individuals were characterised and available for analysis, another 30 families with only one affected member available for analysis, and in 10 sporadic cases. In large well-characterised families with more than four affected individuals, the detection rate for mutations rose to 78% (7/9), in families with either two or three affected members 27% (3/11). In families where only one affected family member was available, the mutation detection rate was 17% (5/30), and in sporadic cases it was 20% (2/10). In addition, we found eight neutral polymorphisms. Twelve of the 17 disease-causing mutations identified have not been previously described, thus raising the total number of different fibrillin-1 mutations reported to 85 in 94 unrelated cases.

Marfan Database (second edition): software and database for the analysis of mutations in the human FBN1 gene.

Fibrillin is the major component of extracellular microfibrils. Mutations in the fibrillin gene on chromosome 15 (FBN1) were described at first in the heritable connective tissue disorder, Marfan syndrome (MFS). More recently, FBN1 has also been shown to harbor mutations related to a spectrum of conditions phenotypically related to MFS. These mutations are private, essentially missense, generally non-recurrent and widely distributed throughout the gene. To date no clear genotype/phenotype relationship has been observed excepted for the localization of neonatal mutations in a cluster between exons 24 and 32. The second version of the computerized Marfan database contains 89 entries. The software has been modified to accomodate new functions and routines.

Fibrillin-1 mutations in Marfan syndrome and other type-1 fibrillinopathies.

Fibrillin is the major component of extracellular microfibrils and is widely distributed in connective tissue throughout the body. Mutations in the fibrillin-1 (FBN1) gene, on chromosome 15q21.1, have been found to cause Marfan syndrome, a dominantly inherited disorder characterised by clinically variable skeletal, ocular, and cardiovascular abnormalities. Fibrillin-1 mutations have also been found in several other related connective tissue disorders, such as severe neonatal Marfan syndrome, dominant ectopia lentis, familial ascending aortic aneurysm, isolated skeletal features of Marfan syndrome, and Shprintzen-Goldberg syndrome. Mutations are spread throughout the gene and, with the exception of neonatal Marfan syndrome, show no obvious clustering or phenotypic association.

Population screening for cystic fibrosis.

In the 7 years since the cystic fibrosis (CF) gene has been cloned, many experimental trials of population screening for CF heterozygotes have been reported. Targeting young adults near reproductive age has shown that the method in which screening is offered is a major determinant of acceptance rates: personal invitations produce high rates of acceptance, whereas offers made by mail or leaflet produce disappointing results. In contrast, trials of screening during pregnancy have been more satisfactory. Two models have been tested. In sequential screening, women are screened first and their partners are tested only if the women are found positive for CF alleles. This can lead to anxiety during the period when women who have tested positive await their partner's results. In couple screening both partners agree to be treated as a unit and are reported to be "high risk" only if both results are positive. In all other situations, the results are reported to be negative. Couple screening has turned out to be efficient, trouble-free, and consumer-friendly and may be the method of choice for integration into routine health care.

A general method for the detection of large CAG repeat expansions by fluorescent PCR.

The expansion of a tandemly repeated trinucleotide sequence, CAG, is the mutational mechanism for several human genetic diseases. We present a generally applicable PCR amplification method using a fluorescently labelled locus specific primer flanking the CAG repeat together with paired primers amplifying from multiple priming sites within the CAG repeat. Triplet repeat primed PCR (TP PCR) gives a characteristic ladder on the fluorescence trace enabling the rapid identification of large pathogenetic CAG repeats that cannot be amplified using flanking primers. We used our method to test a cohort of 183 people from myotonic dystrophy families including unaffected subjects and spouses. Eighty five clinically affected subjects with expanded alleles on Southern blot analysis were all correctly identified by TP PCR. This method is applicable for any human diseases involving CAG repeat expansions.

Psychological impact of population-based carrier testing for cystic fibrosis: 3-year follow-up. UK Cystic Fibrosis Follow-Up Study Group.

BACKGROUND: The objective of this study was to show the long-term psychological effects of population-based screening for cystic fibrosis. METHODS: The sample comprised all carriers (n = 435) and, for each carrier, two matched screen-negative individuals (n = 870) detected during screening programmes for cystic fibrosis in the general population and in antenatal populations carried out a median of 3 years earlier in six UK centres. Questionnaires were sent to all eligible participants, with reminders sent to non-responders. The main endpoints were understanding of test results, degree of anxiety, perceptions of health, and reproductive intentions, and behaviour. FINDINGS: 746 (62%) of 1201 questionnaires were returned. Recall of the meaning of test results was accurate in 225 (80%) of 280 carriers but only 200 (43%) of 466 screen-negative individuals. 46 (16%) of 280 proven carriers believed that their result meant that they were only likely, rather than definitely, to be a carrier; 232 (50%) of 466 of those with a screen-negative result erroneously believed that the result meant that they were definitely not carriers. There was no significant difference between carriers and screen-negative individuals in degree of general anxiety, although 16% of carriers reported feeling worried about their test results. Carriers had a poorer perception of their current health than did non-carriers, even though they had been told that carrier status confers no disadvantages to their own health. There were no differences between carriers and screen-negative individuals in reproductive intentions or behaviour. INTERPRETATION: We have shown that in the long-term, retention of the meaning of test results from cystic fibrosis screening is poor. Further research is needed to improve the performance of test-related counselling programmes to ensure that the main objectives of these programmes, to provide information on carrier status and to allow informed reproductive decisions, are met.

Friedreich's ataxia, with retained lower limb tendon reflexes, in a Saudi Arabian family.

Friedreich's ataxia (FA) was studied in a large inbred Arab family living near Jeddah, Saudi Arabia, in which DNA linkage studies localised the disease gene to 9q13-q21.1. Five siblings (aged 19-35 years), and their 27 year old cousin, had the typical features of FA, however in two patients, tendon reflexes were retained and were indeed brisk in the lower limbs, 13 and 19 years respectively after onset of symptoms: retention of lower limb tendon reflexes is exceptional in FA. Another 6 deceased individuals from two related families are presumed to have had FA.

Prenatal screening for cystic fibrosis: 5 years' experience reviewed.

BACKGROUND: Although several programmes of prenatal screening for cystic fibrosis have been completed and reported, there are still uncertainties about rates of take up and also about the action of parents identified as having a one-in-four risk of an affected child. I report 5 years' experience with the two-step and couple models of prenatal screening of cystic fibrosis. METHODS: Screening has been available at two antenatal clinics in Edinburgh, UK, since January, 1992, first on a research basis and then routinely. 25,000 couples have been screened. FINDINGS: Take-up rates for the two-step and couple models of delivery are very similar at about 70%. Take-up rates did not change when screening moved from a research to a routine service. Of 22 high-risk couples identified entirely through screening, 20 (91%) opted for prenatal diagnosis. Four couples returned for second and two for third monitored pregnancies. In all eight cases where affected fetuses were identified, pregnancy was terminated. INTERPRETATION: These data remove one of the few remaining obstacles to a general implementation of prenatal screening for cystic fibrosis.

Huntington's disease in a Sudanese family from Khartoum.

Typical Huntington's disease (HD) was studied in a 40-year-old Sudanese man from Khartoum. He had 51 CAG repeats in the Huntington's gene. It is suspected that his mother and his 16-year-old son (both deceased) were also affected. Up to now, there had only been anecdotal evidence of HD in the Sudanese.