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J F Clayton

Publications and source records attributed to J F Clayton.

At least 19 recordsLinked to original sources
PubMed1992

A likelihood approach to HLA serology.

A likelihood approach to HLA serology has been developed in which the aim is not to define a recognition set for a serum but to describe the serum's ability to react with each and every antigen in the test cells, this ability being quantified in terms of the probability of a positive reaction. For a given set of probabilities, one for each antigen, it is possible to derive the probability of the observed set of reactions (the likelihood of the set of probabilities). The maximum possible value of the likelihood for any possible combination of the probability set can then be sought, but this requires a maximization of likelihood with respect to 60-100 independent parameters. Theoretical considerations of the shape of the likelihood surface prove that, in this particular case, this is a feasible proposition. This approach allows the recognition of three groups of antigens: those for which there is considerable evidence of a specificity, those for which there is either no specificity or a very weak specificity, and those for which there is insufficient evidence on which to base a conclusion. The existence of a specificity can be tested using a log likelihood ratio as a statistic, but the usual assumption of a chi 2 distribution of this statistic cannot automatically be made in this situation. Therefore, the distribution is estimated by simulation. A serologist using this approach would receive considerably more information as to the serum's reaction patterns and valid statistics for the existence, or not, of a specificity.

HLA Antigens↗
PubMed1988

DNA polymorphism and the study of disease associations.

Recombinant DNA approaches to disease analysis may be as applicable to studies of disease association as they are to the analysis and diagnosis of single-gene defects. Population and/or family association analyses, using restriction fragment length polymorphisms around candidate genes as markers, have been employed to study conditions such as atherosclerosis and disease with an HLA-association. Progress made to date in disease-association studies using recombinant DNA methodology is reviewed, the rationale behind such studies is examined and associated problems and pitfalls discussed.

Alleles↗
PubMed1988

Linkage heterogeneity and fragile X.

A multipoint test of heterogeneity on published data from 57 families with the fragile X syndrome has been undertaken. The hypothesis being tested was that there are two loci coding for fragile X expression, mutations at either of which can produce the phenotype. No predivision of the families was undertaken, as the test used an admixture parameter. Maximum likelihoods of the hypothesis have been calculated and compared with those produced on assuming a single locus for fragile X. The data do not suggest that there are two such loci within the interval between probes 52a and St14. In particular, the large kindred published by Camerino et al. (1983) does not supply convincing evidence of heterogeneity under this test. It is argued that the observed heterogeneity between factor IX and fragile X must have another explanation. There is some evidence for a second locus for fragile X outside the interval noted above; this locus being most probably proximal to these probes. The majority of the data suggesting this result comes from a family published by Davies et al. (1985).

Fragile X Syndrome↗
PubMed1987

Ten families with fragile X syndrome: linkage relationships with four DNA probes from distal Xq.

We present clinical, cytogenetic, and linkage data of four DNA probes from the terminal long arm of the X chromosome in ten new families with fragile X syndrome. A prior/posterior method of multipoint linkage analysis is employed to combine these results with published data to refine the linkage map of terminal Xq. Ten possible probe/disease orderings were tested. The order with the greatest posterior probability (0.78) of the five loci is 52a-F9-fragile X gene-DX13-St14, although the order with reversal of the positions of 52a and F9 has a posterior probability 0.15. The mean estimates of the distances between the probes and the fragile X gene are 38 cM and 33 cM for the proximal probes 52a and F9, and 8 cM and 12 cM for the distal probes DX13 and St14. Although the current method of choice in the prenatal diagnosis and carrier detection of the fragile X syndrome remains detailed cytogenetic analysis, consideration is given to the potential role of these DNA probes, both singly and in pairs.

Chromosome Banding↗
PubMed1987

Multipoint linkage analysis of steroid sulfatase (X-linked ichthyosis) and distal Xp markers.

Six families with steroid sulfatase deficiency (STS; X-linked ichthyosis) have been studied with the Xg blood group (XG) and the DNA markers dic56 (DXS143), 782 (DXS85), pD2 (DXS43), and GMGX9. Carrier status of females was determined by assay of STS in hair roots. GMGX9 detects a frequent restriction fragment length polymorphism and also identifies a deletion in the majority of families with STS deficiency, including five of the six reported here. The linkage relationship of this marker to the others was studied in normal three-generation families yielding 32 phase-known meioses informative for two or more markers. No recombinants were observed between STS and GMGX9, giving a maximum lod score of 8.73 at zero recombination. Multipoint linkage analysis taking STS and GMGX9 as a single locus and incorporating two-point marker data and STS-XG data from published studies gave the map (Sequence: see text). This order was 2.4 times more likely than with (STS,GMGX9) and dic56 reversed and is supported by our findings in a male with steroid sulfatase deficiency due to a deletion of Xp22.3 which encompasses the XG locus. He is deleted for GMGX9 but shows normal hybridization to dic56 and 782.

Chromosome Mapping↗
PubMed1987

Mortality and causes of death in females with extra X chromosomes and males with extra Y chromosomes.

A prospective study of mortality in females with extra X chromosomes and males with extra Y chromosomes is reported. Among the 94 females who survived infancy and were then observed on average for 16 years there were 24 deaths compared with an expected mortality of 10.7. The greater than twofold increase is highly significant (p less than 0.005). The deaths were due to a variety of diseases but no significant increase from any single cause could be identified. Among 136 males with extra Y chromosomes observed on average for 12 years there were 10 deaths. This number is not significantly greater than the expected 6.4. No increase in mortality from a single cause was observed.

Adolescent↗
PubMed1987

Studies of genetic linkage between adult polycystic kidney disease and three markers on chromosome 16.

Adult polycystic kidney disease (APKD) is a common genetic disorder that is inherited as an autosomal dominant trait. Recent reports show that, in some families, the APKD gene shows close genetic linkage to two chromosome 16 specific genetic markers. We have been conducting a genetic linkage study using 29 polymorphic isoenzyme and antigenic markers in 184 members of 12 APKD families. We present here the results of linkage analysis using three of these markers which have also been reported to be located on chromosome 16: phosphoglycolate phosphatase (PGP), glutamate pyruvate transaminase (GPT), and haptoglobin (HP). The results show that APKD is closely linked to the PGP locus on the short arm of chromosome 16 (16p13----p12), which is consistent with the previously reported linkage both to PGP and to the alpha globin locus. The genetic distance between PGP and APKD shows a maximum likelihood value of the recombination fraction at zero with a lod score of 5 X 5. There is no evidence of linkage between APKD and either GPT or HP. The PGP polymorphism potentially provides a useful predictive test to complement the use of alpha globin probes in genetic counselling. These tests should provide an efficient means of primary screening of family members at risk, as well as introducing the possibility of prenatal diagnosis.

Alanine Transaminase↗
PubMed1987

Linkage relationships between X-linked retinitis pigmentosa and nine short-arm markers: exclusion of the disease locus from Xp21 and localization to between DXS7 and DXS14.

Linkage data between X-linked retinitis pigmentosa (XLRP) and nine X-chromosomal markers are reported. To test the assignment of XLRP to the Xp21 region (as considered at Human Gene Mapping 8), an analysis of XLRP and six markers flanking this region was undertaken. The XLRP locus was found to be excluded from the chromosome distal to ornithine transcarbamylase (OTC) (P = 6.5 X 10(-5]. Further data were accumulated with three more probes proximal to DXS7 (L1.28), the closest linked probe. Multipoint analysis of these data suggests a posterior probability of .94 that XLRP is proximal to DXS7 (L1.28), which has been mapped to the region Xp11.3.

Chromosome Mapping↗
PubMed1986

Genetic linkage between X-linked retinitis pigmentosa and DNA probe DXS7 (L1.28): further linkage data, heterogeneity testing, and risk estimation.

Further linkage data relating X-linked retinitis pigmentosa and DNA probe DXS7 (L1.28) is presented in this paper. The current mean estimate of the recombination fraction (theta) including this and all published data, is 0.09, with confidence limits 0.04 to 0.17 (maximum Lod score of 14.01 at a theta of 0.08). There is no evidence for heterogeneity of recombination fraction between the 13 families for which data are available. However, it is argued that heterogeneity should be assumed to exist for the purposes of risk estimation. Mean estimates and variances of risk are calculated for hypothetical families each with different linkage data. In families in which no recombination has been observed, the mean and variance of risk are sufficiently small for the clinical use of this probe to be acceptable to many.

DNA↗
PubMed1986

A study into possible deviation from the Hardy-Weinberg equilibrium by the alleles of the hypervariable sequence in the region of the human insulin gene.

A number of studies have reported on possible relationships between a hypervariable sequence near the 5' end of the insulin gene and some common diseases. Control populations within these studies appear to disobey the Hardy-Weinberg equilibrium. In this study we have ascertained the allele frequencies in 181 random individuals. The chi-squared statistic comparing this population with a theoretical Hardy-Weinberg population was 0.61. This makes it unlikely that in the general population the Hardy-Weinberg rule is disobeyed. Possible reasons for the discrepancy between our study and the studies of others are discussed.

Adolescent↗
PubMed1986

Mortality ratios, life expectancy, and causes of death in patients with Turner's syndrome.

In a prospective study of 156 female patients with Turner's syndrome who had survived infancy and been followed up for an average of 17 years there were 15 deaths. The expected mortality was 3.6. Sixteen of the patients had a congenital heart anomaly and five of the deaths occurred in this group. The 10 deaths in the remaining 140 were three times as many as expected. The reduction in life expectation was 12.5 years at age 1 year, 11 years at age 20, and 10 years at age 40. Deaths were due to a broad spectrum of diseases. In the sample as a whole there were eight deaths from diseases of the circulatory system. This number is significantly greater than expected, but four were due to congenital heart disease. When patients with congenital heart disease were omitted from the sample the mortality from circulatory disorders was not significantly increased. Within the category of circulatory disorders there were three deaths from dissection of the aorta, a number which is greatly in excess of the expected. Two of these patients had no previous evidence of heart disease.

Female↗
PubMed1986

A genetic linkage study of choroideremia.

One hundred and twenty-two members of 15 choroideremia families have been used in a genetic linkage study of choroideremia (TCD) using four DNA probes situated on the X chromosome. Linkage was analysed using DNA probes DXS14 (p58-1), DXYS1 (pDP 34), DXS178 (p212) and DXS177 (lambda 2.7). Statistically significant linkage was demonstrated with DXYS1 (theta = 0.00, lod 4.95), in agreement with the findings of Nussbaum et al. (1985). Evidence consistent with loose linkage to TCD was also found with DXS14 (theta = 0.31, lod 0.23), DXS178 (theta = 0.18, lod 1.41) and DXS177 (theta = 0.27, lod 0.20). The results suggest that TCD is located in the region Xq13-q21. Probe DXYS1 is likely to prove useful in the prenatal diagnosis of this condition.

Choroid↗
PubMed1985

A genetic linkage study of a kindred with X-linked retinitis pigmentosa.

A large kindred with X-linked retinitis pigmentosa (XLRP) was investigated clinically and by means of genetic linkage with a view to developing methods of carrier detection and early diagnosis. A restriction fragment length polymorphism, identified by recombinant DNA probe L1.28, showed close genetic linkage to XLRP in this kindred and is a potentially useful marker for the purposes of genetic counselling.

Adolescent↗
PubMed1985

Mortality ratios and life expectancy in X chromatin positive males.

In a prospective study of 466 X chromatin positive males an increase in mortality of about 50% has been observed. The increase is associated with a loss of about five years in life span. There is no convincing evidence that the increase is concentrated at any particular age group but this possibility could not be excluded. No effect of mode of ascertainment could be demonstrated. From this study we conclude that it is likely that the mortality experienced by chromatin positive males in general is at least 115% of that experienced by normal men and could be more than 200%.

Adolescent↗
PubMed1985

Causes of death in X chromatin positive males (Klinefelter's syndrome).

The causes of death in 466 X chromatin positive males (Klinefelter's syndrome) studied prospectively over the last 25 years have been analysed. We have previously reported the overall mortality to be increased by 50% and life expectancy reduced by about five years. A highly significant increase in mortality from cerebrovascular disease was observed in the sub group considered to be most representative of X chromatin positive males in general. In the age group up to 45 years this increase could be attributed to deaths from subarachnoid haemorrhage. An increase in mortality from respiratory diseases was observed in those ascertained in psychiatric hospitals. In the sample as a whole there were small but highly significant numbers of deaths from carcinoma of the breast and aortic valve disease. The deaths from carcinoma of the breast were comparable with those expected if female mortality rates were applied.

Adolescent↗