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Biomedical subjects

M E Pembrey

Publications and source records attributed to M E Pembrey.

At least 73 records · Page 4Linked to original sources
PubMed1987

A girl with the Weaver syndrome.

A female with the Weaver syndrome is reported. In addition to the characteristic manifestations of overgrowth and advanced bone age, the facies were typical, with a broad forehead, hypertelorism, a long philtrum, micrognathia, and large ears. Like most other patients with Weaver syndrome, she was developmentally delayed, hypertonic, and had a hoarse voice. Other clinical features included prominent finger pads, narrow hyperconvex nails, small and narrow chest, unilateral dislocated distal ulna, and abnormal thoracic vertebrae.

Abnormalities, Multiple↗
PubMed1987

Osteogenesis imperfecta type IIA: evidence for dominant inheritance.

Thirty cases of radiologically proven type IIA osteogenesis imperfecta (OI) have been ascertained. All were isolated with 19 unaffected foreborn and 19 unaffected afterborn sibs. Two sets of parents, both Asian, were consanguineous. There was a significant parental age effect, most marked for paternal age. It is concluded that most cases of type IIA OI result from new dominant mutations.

Consanguinity↗
PubMed1987

Recurrence risks and prognosis in severe sporadic osteogenesis imperfecta.

A study was carried out in the United Kingdom of patients with severe osteogenesis imperfecta (OI), born with fractures to normal parents, in order to determine recurrence risks. A total of 105 cases from 98 families survived the perinatal period and 60 cases from 57 families were stillborn or died during the first week of life. The majority of the perinatal survivors correspond to the overlapping group of Sillence type III and sporadic type IV OI. In 40 of these, the radiograph at birth was available and in 37 it showed a characteristic appearance similar to that described previously for type III OI. The other three cases had radiological type IIB OI at birth and died before 26 months of age. The patients with perinatally lethal OI were subdivided on radiological appearance into Sillence type IIA (30 cases, described in the previous paper), type IIB (12 cases from 11 families), and type IIC (three cases from three families), and in five cases from three families the radiological appearance was the same as that of the 37 perinatal survivors described above. Ten cases from 10 families were not classified because their radiographs were unavailable. To analyse the empirical recurrence risks, patients were grouped according to radiological appearance at birth. Those with a type III-like pattern numbered 42 cases and they were grouped with the other cases of severe deforming OI who survived the perinatal period, for whom no x ray at birth was available, making a total of 107 cases. Taking one affected child per family as the proband, there were 98 probands. They had 146 sibs, of whom 10 were affected, giving an empirical recurrence risk of 6.9%. This is consistent with the disease arising as a new dominant mutation in about three quarters of families and as a recessive in about one quarter in this heterogeneous group. It is reasonable to give a recurrence risk of up to 25% in cases with parental consanguinity and a risk of 4.4% in cases with unrelated parents. Fifteen patients (14 probands) with Sillence type IIB OI had 13 sibs, one affected, giving an empirical recurrence risk of 7.7%. The parents were consanguineous in three families and the evidence for autosomal recessive inheritance for the majority in this group is probably stronger. The three patients with type IIC OI had three healthy sibs and the 10 unclassifiable perinatally lethal cases had 22 sibs, all normal. The radiological appearance at birth predicts prognosis to some extent; essentially, the better the bone morphology and mineralisation the longer the survival.

Consanguinity↗
PubMed1986

Analysis of linkage relationships between genetic markers around the fragile X locus with special reference to the daughters of normal transmitting males.

Genetic linkage data from loci around the fragile X locus at Xq27.3 are analysed in the light of the hypothesis of Pembrey et al. (1985) concerning the generation of the fragile X mutation. Recombination between the four loci 52A, F9, fragile X, and ST14 is significantly decreased in meioses giving rise to the affected grandsons of normal transmitting males, when compared to families where there are no apparent normal transmitting males. There are at least two possible explanations for this phenomenon. Either the established fragile site at Xq27.3 promotes increased recombination in the distal part of the X chromosome as a secondary event, unrelated to the mechanism of formation of the fragile site itself, or an event involving recombination at or around Xq27.3 is the mechanism of formation of the full fragile X mutation, and the decreased recombination seen amongst flanking marker loci in meioses giving rise to the affected grandsons of normal transmitting males is the result of interference.

Chromosome Mapping↗
PubMed1986

Applications and limitations of direct DNA analysis in genetic prediction.

Direct analysis of DNA has enormous potential for improved carrier detection or exclusion and early prenatal diagnosis in monogenic diseases. The strategy adopted in practice is determined by the fact that in most diseases allelic genetic heterogeneity precludes elucidation of the mutation in all families. Gene tracking asks the question--has a relative or fetus inherited the same relevant chromosome region as a previously affected family member?--and requires a gene-specific or closely linked DNA probe that reveals a restriction fragment length polymorphism (RFLP) in order to do a linkage study within the family. Gene tracking is independent of allelic heterogeneity in the disease, but is limited to those families in which key relatives are heterozygous for an RFLP.

Chromosome Deletion↗
PubMed1985

First trimester prenatal diagnosis and detection of carriers of haemophilia A using the linked DNA probe DX13.

Although the use of a gene specific deoxyribonucleic acid (DNA) probe is the method of choice for detecting carriers of genes for rare genetic disorders, there will always be families in which such probes cannot be used because key subjects are not informative for restriction fragment length polymorphisms in or around the gene. In these cases closely linked DNA markers have to be used. An X chromosome specific DNA probe, DX13, which is closely linked to the haemophilia A locus on the X chromosome, was used for early prenatal diagnosis in two cases and to detect carriers in a series of nine possible heterozygote women. The first reported crossover between DX13 and the factor VIII:C locus was observed in this study. There are complexities inherent in using any linked DNA probe for assignment of genes, but such techniques are clinically important.

Female↗
PubMed1985

A premutation that generates a defect at crossing over explains the inheritance of fragile X mental retardation.

The view that the Martin-Bell syndrome (X-linked mental retardation with fragile site at Xq27/8) is inherited in a regular X-linked fashion is becoming untenable with the increasing number of reports of transmission through phenotypically normal males. Analysis of the published pedigrees containing such males shows that their heterozygous daughters are never mentally retarded, and have either no fragile site or very few indeed. By contrast, in the next generation, a third of the female heterozygotes are mentally subnormal with an average of 29% fragile sites. These data suggest a premutation that generates the definitive mutation only when transmitted by a female. We propose an inherited sub-microscopic chromosome rearrangement involving the Xq27/8 region that causes no ill effect per se, but generates a significant genetic imbalance when involved in a recombination event with the other X chromosome. This hypothesis explains many of the puzzling genetic aspects of the Martin-Bell syndrome, but it also complicates the interpretation of linkage analysis with genetic markers.

Crossing Over, Genetic↗
PubMed1985

Amniotic bands in connective tissue disorders.

Amniotic bands are described in two children with Ehlers-Danlos syndrome type IV and in one with severe osteogenesis imperfecta. Since the basic defect in both of these disorders rests in collagen, which constitutes the main component of the load bearing amnion, it is proposed that these cases provide further insight into the pathogenesis of amniotic bands.

Adult↗
PubMed1985

Trigonocephaly and the Opitz C syndrome.

We present 12 cases of trigonocephaly of which six were associated with other malformations. On the basis of this experience we examine the diagnostic criteria for the presumed autosomal recessive trigonocephaly C syndrome.

Abnormalities, Multiple↗
PubMed1985

Prenatal diagnosis of ornithine carbamoyl transferase deficiency using a gene specific probe.

A gene specific DNA probe has been used to predict the genotype of two fetuses in families at risk for ornithine carbamoyl transferase deficiency. Although the probe does not detect the mutation directly, prediction was possible by examining restriction fragment length polymorphisms of the parents and sibs to identify the X chromosome carrying the mutation. It is suggested that in all pregnancies, regardless of the predicted outcome, the biochemical status of carrier mothers should be monitored because hyperammonaemia and arginine deficiency may have a deleterious effect on the fetus.

Amino Acid Metabolism, Inborn Errors↗
PubMed1984

A clinically useful DNA probe closely linked to haemophilia A.

Genetic linkage studies were done in families segregating for haemophilia A with an X-chromosome-specific probe, DX13, which has been localised to band Xq28. When DNA is digested with the restriction enzyme Bg1 II, this probe recognises a restriction fragment length polymorphism, for which 50% of females are heterozygous. No crossovers were seen between the haemophilia A locus and the DX13 locus (lod score = 5.4 at recombination fraction [theta] 0.0; 95% confidence limits of theta, 0-12%). This indicates that the DX13 probe is closely linked to the haemophilia A locus and is likely to prove useful in carrier detection and prenatal diagnosis.

Alleles↗
PubMed1984

Use of a chromosome 21 cloned DNA probe for the analysis of non-disjunction in Down syndrome.

A recombinant clone was isolated containing a sequence which occurs only on human chromosome 21 and defines a two-allele restriction fragment length polymorphism showing Mendelian inheritance. Forty seven percent of the London population are heterozygous for the polymorphism. The chromosomal location of the DNA sequence homologous to the probe was confirmed using rodent-human somatic cell hybrids. DNA from persons with Down syndrome and from their parents was analysed. It was possible to confirm trisomy 21 by dosage hybridisation to Southern blots, and to determine the origin of the supernumerary chromosome. The technique will be of use for determination of the paternal or maternal origin of nondisjunction in cases of Down syndrome which are not informative using existing markers.

Adult↗
PubMed1984

Clinical use of DNA markers linked to the gene for Duchenne muscular dystrophy.

Seventy families with Duchenne muscular dystrophy (DMD) known to the Institute of Child Health fall into three categories with respect to potential linkage analysis with the X chromosome DNA markers RC8 and L1.28 that bridge the DMD gene. Families in which there is at least one obligatory female heterozygote (n = 13). Here 'prediction' and 'exclusion' of DMD gene transmission may be possible, the accuracy being dependent on the closeness of the linkage of the DNA marker(s) to the DMD gene; an illustrative case is reported. Families in which there is a single affected boy, who also has one or more healthy brothers (n = 26). Given an informative restriction fragment length polymorphism (RFLP), the probability that the boy represents a new mutation can be reassessed; it is also possible to 'exclude' the DMD gene in a sister. Families with a single affected boy with no brother (n = 30). Here 'exclusion' of the DMD gene in a sister may be possible. Only in one family was there no possibility of useful linkage analysis. The linkage analysis required is described, and the need to check DMD families for informative RFLPs is stressed.

Base Sequence↗
PubMed1983

The estimation of fetal haemoglobin in healthy adults by radioimmunoassay.

A radioimmunoassay (RIA) for the measurement of fetal haemoglobin (HbF) was established and used to determine the distribution of HbF in 2463 British adults between the ages of 18 and 65 years. Although a range in HbF values was similar in both genders a shift towards higher values is seen in females and the mean HbF% is higher, in females, at all ages between 18 and 55. A significant and different fall in HbF over the age range studied was noted between females (47%) and males (23%). The difference in mean HbF between the genders was less marked after age 40 years and a small rise in HbF production was measured in females between ages 50 and 54 years.

Adolescent↗