The new genetics. Implications for clinical services in Britain and the United States.
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Awareness↗
Biomedical subjects
M Bobrow
Publications and source records attributed to M Bobrow.
Dystrophins in vertebrates and invertebrates.
Members of the dystrophin family of proteins perform a critical but incompletely characterized role in the maintenance of membrane-associated complexes at points of intercellular contact in many vertebrate cell types. They interact with, amongst others, the transmembrane laminin receptor dystroglycan, cytoskeletal actin and, indirectly, the intracellular membrane-associated signalling enzyme neuronal nitric oxide synthase (nNOS). Here we describe sequences of a range of dystrophin-related proteins from vertebrate and invertebrate animals (including the important model organism Drosophila melanogaster ) and infer an evolutionary history of this family and its relationship to the distantly related dystrobrevins. It appears that most metazoa possess sequences encoding a single highly conserved dystrophin-like protein in addition to a presumed distinct dystrobrevin, derived from an early duplication of an ancestral gene. In the vertebrates (but not the protochordate Amphioxus), the single invertebrate dystrophin-like gene has undergone serial duplication to generate at least three distinct genes encoding proteins which have adopted specialized roles. It is hoped that this broadening of the biology of the dystrophins will afford further opportunities for the advancement of our understanding of the fundamental defect underlying the variety of human genetic disorders which result from aberrant or absent dystrophin-associated complexes.
Animals↗
Objectives of genetic counselling: differing views of purchasers, providers and users.
BACKGROUND: This study aimed to compare the views of purchasers, providers and users about the objectives of genetic counselling. METHODS: A modified Delphi technique was used, incorporating two postal questionnaires that were sent to six study groups with a three-month interval: purchasers (public health doctors (n = 37) and regional advisers in general practice (n = 35)); providers (clinical geneticists (n = 33) and genetic counsellors (n = 25)); and users (out-patients (n = 36) and members of genetic support groups (n = 32)). The response rate for the first questionnaire was 115/198 (58 per cent) and for the second, 102/198 (52 per cent). The first questionnaire asked an open-ended question about what the objectives of genetic counselling should be and asked respondents to rank order them. The second questionnaire summarized the views expressed in the first questionnaire and asked respondents to rank order the most frequently cited and most highly ranked five objectives. RESULTS: The five most frequently cited and highly ranked objectives from Questionnaire One were, in descending order: provide information, give support, facilitate decision-making, assess risk and achieve understanding. In response to Questionnaire Two, purchasers differed from providers and users in rating 'facilitate decision-making' more highly than did providers and users. By contrast, providers and users rated 'give information' more highly than did purchasers. CONCLUSIONS: Purchasers hold different views from providers and users about what the objectives of genetic counselling should be. This raises two questions: (1) Which views are or should be most influential in the future development of genetic counselling? (2) By what processes can more than one view on genetic counselling be integrated?
Attitude of Health Personnel↗
Expression of the dystrophin-related protein 2 (Drp2) transcript in the mouse.
We have recently characterised a new member of the dystrophin gene family, DRP2, and its murine counterpart, Drp2, which encode dystrophin-related protein 2 (DRP2). DRP2 is predicted to resemble certain short C-terminal isoforms of dystrophin and dystrophin-related protein 1 (DRP1 or utrophin). We describe here a comprehensive survey of Drp2 expression in the mouse by RT-PCR, and compare the expression profile of Drp2 with that of the related genes Dmd, Drp1 and Dag1 that encode all the known isoforms of dystrophin, DRP1/utrophin and a component of the dystrophin-associated protein complex, dystroglycan, respectively. Drp2 was shown to be expressed throughout the central nervous system (CNS) and in several peripheral tissues including the eye, kidney, teeth, oesophagus, colon, epididymis and ovary. The expression of Drp2 in the CNS was then further defined by in situ hybridization. Overall, the pattern of Drp2 expression corresponds to a subset of the brain regions known to express Dag1, and shows substantial overlap with regions that express various isoforms of dystrophin (particularly in the cerebral cortex, hippocampus and cerebellum). These data define the distribution of Drp2 expression in the mouse, and raise the possibility that in the CNS it may be an important component in neuronal dystrophin-associated complexes.
Animals↗
Evaluation of mitochondrial function after cold preservation of pancreatic islet cells from donors treated with pefloxacin.
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4-Quinolones↗
Clinical, cytogenetic, and molecular analysis of three families with FRAXE.
The probe StB12.3 has been used to screen the FMR-1 gene in 42 pedigrees with a distal Xq fragile site for expansion of the CCG repeat and aberrant methylation of the FRAXA locus. Four families did not have a FRAXA mutation and were investigated further. Fluorescent in situ hybridisation (FISH) and molecular analyses showed that three of these families had an expansion at FRAXE and one at FRAXE. Detailed psychiatric, psychological, and behavioural features of three families with FRAXE identified in the study are presented. All the males who expressed FRAXE had a large methylated CCG repeat at FRAXF. All males with the mutation had some degree of mental handicap. This study illustrates the need for the FRAXE phenotype to be defined further.
Adult↗
Genetic counselling: the psychological impact of meeting patients' expectations.
We know little about patients' expectations of genetic counselling, the extent to which these are met, and whether meeting expectations is associated with improved patient outcome. This study describes 131 consultations of patients referred to a regional genetics centre, and documents their expectations, the extent to which these are met, and the predictors and consequences of expectations being met. The outcomes assessed were state anxiety, concern about the problem for which the patient was referred, and satisfaction with information given. Patients came to genetic counselling expecting information (79%), explanation (63%), reassurance (50%), advice (50%), and help in making decisions (30%). The majority got what they were expecting: 74% had their expectation for information met, 56% had their expectation for explanation met, 60% had their expectation for reassurance met, 61% had their expectation for advice met, and 73% had their expectation for help with making decisions met. Patient expectations, and whether or not these were met, were not predicted by any of the patient or counsellor variables measured. When patients' expectations for reassurance and advice were met, patients were less concerned and their anxiety level was more reduced than when such expectations were not met. Meeting patients' expectations for information, explanation, or help with decision making were not associated with better outcomes. Explanations for these results and implications for the practice of genetic counselling are discussed.
Adult↗
Nondirectiveness in genetic counseling: an empirical study.
Nondirectiveness is considered an essential part of genetic counseling, yet there is no generally accepted definition nor data documenting its impact on counselees. This study is an empirical investigation of directiveness, using ratings from transcripts of consultations and comparing these with counselor-reported and counselee-reported directiveness. Rated directiveness was defined as advice, expressed views about or selective reinforcement of counselees' behavior, thoughts, or emotions (advice, evaluation, and reinforcement). Analysis of 131 transcripts revealed a mean of 5.8 advice statements per consultation, 5.8 evaluative statements, and 1.7 reinforcing statements. When asked to describe their counseling style, none of the 11 counselors rated it as "not at all" directive. Half the counselees who faced a decision felt steered by the counselor. Items of rated directiveness showed satisfactory interrater reliability (kappa = .63). Factor analysis revealed that they formed one factor (eigenvalue 1.72). There were no associations either between counselor-reported, counselee-reported, and rated directiveness or between these measures and counselee anxiety and concern, satisfaction with information, or the meeting of counselees' expectations. Rated directiveness was the only measure to be associated with other process measures of the consultation, being associated with longer consultations, more blocks of speech, more social and emotional issues being raised, and fewer concerns being followed up. Advice was more likely to be given to counselees of lower socioeconomic status and to counselees judged by counselors to be highly concerned. Evaluative statements were more likely to be made by counselors who had received counseling training. These results show that genetic counseling was not characterized--by counselors, counselees, or a standardized rating scale--as uniformly nondirective.
Genetic Counseling↗
Sequence and chromosomal location of a human homologue of LRPR1, an FSH primary response gene.
The rat gene Leucine-Rich Primary Response Gene-1 (LRPR1) has been proposed to encode a protein involved in the response of gonadal tissues to follicle-stimulating hormone. We have characterized a human transcript that probably encodes the orthologue of the rat protein, exhibiting 72% identity at the amino acid level. The gene from which the transcript is derived maps to human chromosomal region Xq22 and therefore becomes a potential candidate for human X-linked disorders of gonadal development.
Amino Acid Sequence↗
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.
Adult↗
Characterization of DRP2, a novel human dystrophin homologue.
The currently recognised dystrophin protein family comprises the archetype, dystrophin, its close relative, utrophin or dystrophin-related protein (DRP), and a distantly related protein known as the 87K tyrosine kinase substrate. During the course of a phylogenetic study of sequences encoding the characteristic C-terminal domains of dystrophin-related proteins, we identified an unexpected novel class of vertebrate dystrophin-related sequences. We term this class dystrophin-related protein 2 (DRP2), and suggest that utrophin/DRP be renamed DRP1 to simplify future nomenclature. DRP2 is a relatively small protein, encoded in man by a 45 kb gene localized to Xq22. It is expressed principally in the brain and spinal cord, and is similar in overall structure to the Dp116 dystrophin isoform. The discovery of a novel relative of dystrophin substantially broadens the scope for study of this interesting group of proteins and their associated glycoprotein complexes.
Amino Acid Sequence↗
Parents' responses to predictive genetic testing in their children: report of a single case study.
There is a widely held view among health professionals that predictive genetic testing of children for late onset diseases is not desirable clinical practice. Yet, little is known about the views of parents, or their responses, to predictive genetic testing in their children. Since such testing is being carried out in some genetic centres, the opportunity was taken to conduct a single case study of the parents of 2 and 4 year old sisters who were tested for the gene for familial adenomatous polyposis. Interviews before testing, after, and 15 months later showed a stable attitude, that parental responsibility included making decisions about such testing, and that the role of health professionals should be one of information giving rather than decision making. These parents had no regrets about having their children tested and reported no changes in their behaviour towards either the child who tested positively or the child who tested negatively. Using standardised scales, mood was found to be within the normal range both before and after testing in the mother and father. This case study is a first step towards systematic empirical studies determining the consequences of acquiescing to parents' requests for genetic testing in their children.
Adenomatous Polyposis Coli↗
Accurate diagnosis of carriers of deletions and duplications in Duchenne/Becker muscular dystrophy by fluorescent dosage analysis.
We have developed a semiautomated approach to amplify 25 exons of the dystrophin gene using two fluorescent multiplex PCR assays which detect over 98% of reported deletions and 90% of duplications causing Duchenne/Becker muscular dystrophy. The 5' multiplex detects 11 exons from the proximal deletion hotspot of the gene while the 3' multiplex detects 14 exons from the central deletion hotspot. The PCR products are accurately sized and quantified by a fluorescent DNA sequencer after only 18 cycles of amplification. The amount of product amplified from each exon in a multiplex is divided by that from each of the other exons, and this ratio is compared with those from control samples to obtain a series of dosage quotients (DQ), from which the copy number of each exon is determined. No overlap was observed between the DQ values obtained from single and double copy loci. The assays can be used to screen both affected males and at risk female relatives for a mutation. The method has been evaluated as a female carrier test by conducting a blind trial on 150 coded samples. Sixty-three deletion carriers, two duplication carriers, and 84 normal female controls were all correctly identified, showing that carrier diagnosis is possible even in families where the nature of the mutation is unknown. Additionally the analysis showed a non-pathogenic duplication involving the muscle specific promoter and exon 1. Together these two multiplex assays detect over 70% of all mutations in the dystrophin gene, greatly simplifying and partly automating molecular diagnosis in Duchenne and Becker muscular dystrophy.
Automation↗
Detection of 12 novel mutations in the collagenous domain of the COL4A5 gene in Alport syndrome patients.
A population of 35 Alport syndrome patients, defined by strict diagnostic criteria, was screened for mutations in 23 exons of the COL4A5 gene by SSCP analysis. Mobility shifts were observed in 12 out of 35 patients and were shown to represent genuine mutations. 9 of these were glycine substitutions in the collagenous domain (in exons 20, 25, 26, 29, 31, and 41), 2 were small deletions resulting in frameshifts (in exons 21 and 31), and one was a splice site mutation (in exon 12).
Base Sequence↗
Identification of Btk mutations in 20 unrelated patients with X-linked agammaglobulinaemia (XLA).
X-linked agammaglobulinaemia (XLA) is an inherited immunodeficiency resulting from mutations in the gene for a cytoplasmic protein tyrosine kinase (Btk). We have utilised reverse-transcription-based PCR in combination with the chemical cleavage and mismatch technique (CCM) to screen for Btk mutations in 42 unrelated patients having classical XLA or 'leaky' XLA-like phenotypes. A variety of mutations, including point mutations, large deletions and splicing defects were detected using this strategy. In total, 20 mutations were found in these patients. All the mutations were different with the exception of three unrelated patients who all showed the same Arg-->His amino acid substitution (R641H) at a highly-conserved residue in the kinase domain. We have also used structural modelling of the Btk kinase domain to predict how two different amino acid substitution mutations at highly-conserved residues are likely to affect the Btk kinase activity.
Agammaglobulinaemia Tyrosine Kinase↗
Down's syndrome births and pregnancy terminations in 1989 to 1993: preliminary findings.
OBJECTIVE: To investigate changes in the numbers of Down's syndrome births and terminations of pregnancies from 1989 to 1993. DESIGN: Data from a national register of cytogenetic diagnoses of karyotypes associated with Down's syndrome were analysed to obtain observed numbers of births and terminations of pregnancies known to be affected. Allowance was made for those cases diagnosed prenatally for whom the eventual outcome of the pregnancies had not yet been ascertained. RESULTS: There has been an increase over the study years in the number of cytogenetic diagnoses of Down's syndrome from 1063 in 1989 to 1137 in 1993, despite an overall fall in births in England and Wales. This is largely due to the increase in antenatal screening and diagnosis, but in part also due to the rise in numbers of pregnancies at increased maternal ages. The rise in prenatally diagnosed cases, of which 92% end in termination, has been accompanied by a fall in both the estimated numbers of affected live births, from 764 in 1989 to 615 in 1993, and the rate per 1000 total live births in the same years from 1.1 to 0.9. CONCLUSIONS: Better and speedier information on the outcome of prenatally diagnosed cases of congenital anomalies such as Down's syndrome would improve the quality of information available for those auditing genetic services or those planning for the care of survivors.
Abortion, Legal↗
Public attitudes towards the selection of desirable characteristics in children.
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Abortion, Legal↗
A rapid, non-radioactive screening test for fragile X mutations at the FRAXA and FRAXE loci.
Screening of referrals for the mutations associated with the fragile X syndrome constitutes a significant workload in many genetics laboratories. Since the great majority of these referrals will be negative, there is a need for a rapid and inexpensive screening test. We have developed an assay which allows simultaneous amplification of the triplet repeat sequences at the FRAXA and FRAXE loci by polymerase chain reaction, and detection of the products on non-denaturing gels stained with ethidium bromide. Alleles of normal size are detected, leaving a small minority of samples to be tested by Southern blotting. A PCR based assay for detection of methylation at the CpG island upstream of the FMR-1 gene has also been devised.
Alleles↗