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Biomedical subjects

K E Davies

Publications and source records attributed to K E Davies.

At least 19 recordsLinked to original sources
PubMed1995

Expression of utrophin and its mRNA in denervated mdx mouse muscle.

Utrophin is a large cytoskeletal protein which shows high homology to dystrophin. In contrast to the sarcolemmal distribution of dystrophin, utrophin accumulates at the postsynaptic membrane of the neuromuscular junction. Because of its localization within this compartment of muscle fibers, expression of utrophin may be significantly influenced by the presence of the motor nerve. We tested this hypothesis by denervating muscles of mdx mouse and monitoring levels of utrophin and its mRNA by immunofluorescence, immunoblotting and RT-PCR. A significant increase in the number of utrophin positive fibers was observed by immunofluorescence 3 to 21 days after sectioning of the sciatic nerve. Quantitative analyses of utrophin and its transcripts in hindlimb muscles denervated for two weeks showed only a moderate increase in the levels of both utrophin (approximately 2-fold) and its transcript (approximately 60 to 90%). The present data suggest that although utrophin is a component of the postsynaptic membrane, its neural regulation is distinct from that of the acetylcholine receptor.

Animals↗
PubMed1995

Mapping of retrotransposon sequences in the unstable region surrounding the spinal muscular atrophy locus in 5q13.

The mutation that underlies the autosomal recessive disorder spinal muscular atrophy (SMA) is located on chromosome 5q13. Recent studies show that SMA patients frequently have deletions and rearrangements in this region compared to normal controls. During the isolation of candidate cDNAs for the disease, we identified a sequence that shows high homology to the THE-1 retrotransposon gene family. Using YAC fragmentation techniques, we have refined the localization of this sequence to the domain known to show instability in SMA patients. The implication of these results for the mechanism of the mutation in SMA is discussed.

Base Sequence↗
PubMed1995

Deletions in the survival motor neuron gene on 5q13 in autosomal recessive spinal muscular atrophy.

Autosomal recessive spinal muscular atrophy is a motor neuron disease which affects about 1 in 10,000 births. Recent evidence shows that the candidate region contains multiple copies of genes and pseudogenes and is characterised by genome instability. We have analysed the frequency of deletions in a recently characterised candidate survival motor neuron (SMN) gene. Our data confirm previous analyses and show that this gene is disrupted by deletion in SMA patients. The same deletion frequency is observed in the milder variants of the disease as in patients with the severe form. In addition, we observed one case of a new mutation in a family previously thought not to be segregating for a chromosome 5 linked form of SMA. This assay is a very good diagnostic for SMA although no direct correlation between phenotype and genotype is apparent and carrier status cannot be determined. The implications for the identification of the gene or genes causing the disease are discussed.

Chromosomes, Human, Pair 5↗
PubMed1992

Utrophin, the autosomal homologue of dystrophin, is widely-expressed and membrane-associated in cultured cell lines.

Utrophin, the autosomal dystrophin-related protein (DRP), is expressed in HeLa cells, smooth muscle-like BC3H1 cells from mouse brain, COS monkey kidney cells, the P388D1 monocyte-macrophage cell line and untransformed human skin fibroblasts, as well as in rat C6 glioma and Schwannoma cells. It was undetectable, however, in the Sp2/O mouse myeloma cell line and in hybridoma lines derived from it. Dystrophin was not detected in any of these cell lines. Although all utrophin-containing cells were capable of forming monolayers in culture, no major effects of either attachment to substratum or length of time in culture (2-17 days) on utrophin levels were observed. After subcellular fractionation of BC3H1 or glioma cells, nearly all of the utrophin was found in the Triton-soluble fraction, suggesting an association with cell membranes.

Animals↗
PubMed1992

Retroviral-mediated transfer of a dystrophin minigene into mdx mouse myoblasts in vitro.

We have demonstrated expression of a 6.3 kb Becker muscular dystrophy (BMD) human dystrophin cDNA following retroviral-mediated transduction of cultured myoblasts from the dystrophin-deficient mdx mouse. The truncated dystrophin protein was localised to the sarcolemma of differentiated myotubes by antibodies against the C-terminus of the molecule, and produced an identical immunostaining pattern to that observed in control myotubes expressing normal endogenous dystrophin. These results indicate that retroviral-mediated gene transfer may be useful for experimental in vivo studies on the complementation of dystrophin gene mutations.

Animals↗
PubMed1992

Localisation of the gene for Norrie disease to between DXS7 and DXS426 on Xp.

A highly informative microsatellite marker, DXS426, which maps proximal to DXS7 in the interval Xp11.4-Xp11.23, has been used to refine further the localisation of the gene for Norrie disease (NDP). The results from a multiply informative crossover localize the NDP gene proximal to DXS7. In conjunction with information from 2 NDP patients who have a deletion for DXS7 but not for DSX426, our data indicate that the NDP gene lies between DXS7 and DXS426 on proximal Xp.

Base Sequence↗
PubMed1992

Genotype mosaicism in fragile X fetal tissues.

The fragile X syndrome is one of the most common familial causes of mental retardation. It is associated with the expression of a fragile site at Xq27.3, although not all individuals carrying the mutation are fragile-X-positive. Recently, the mutation causing this disease has been identified as the amplification of, or insertion into, a CGG repeat sequence at the fragile site. The mutated chromosome can be recognised by the decrease in mobility of the EcoRI fragment that covers the mutated region. Analysis of lymphocytes of affected males often gives a number of different sized fragments indicating somatic heterogeneity. We have investigated this mosaicism in various tissues of an affected fetus in order to determine the extent of the variation between tissues, and to ascertain how to interpret the results in lymphocytes. Our results suggest that the heterogeneity occurs in all fetal tissues, but that the pattern of fragments observed varies between tissues. Methylation across the region also varies. These differences may be reflected in the cellular phenotypes and may influence the ultimate expression of the clinical phenotype.

Blotting, Southern↗
PubMed1992

Three DNA markers for hypophosphataemic rickets.

This paper presents three markers, 16D/E, pHMAI (DXS208), and CRI-L1391 (DXS274), that show close linkage for X-linked hypophosphataemic rickets (HYP). DXS274 is closely linked to HYP (theta max = 0.00, Zmax = 4.20), and DXS41 (99.6), (theta max = 0.00, Zmax = 5.20). Marker 16D/E maps distal to the disease locus (theta max = 0.05, Zmax = 3.11). The pHMAI probe recognises the same restriction fragment length polymorphism (RFLP) as 99.6. Multipoint analysis suggests that the most probable order of loci is Xpter-(DXS43, 16D/E)-HYP-DXS274-(DXS208, DXS41)-Xcen. The location of DXS274 distal to HYP cannot be excluded, as no recombinants were observed between DXS274 and HYP, or between DXS274 and DXS41/DXS208. One of the families contains a large number of recombinants, four of which are double recombinants. This most probably means that the disease in this family maps elsewhere on the X chromosome or on an autosome, indicating locus heterogeneity.

Blotting, Southern↗
PubMed1992

Molecular analysis of the fragile X syndrome.

The molecular analysis of human X-linked disease has progressed rapidly over the last few years owing to advances in power of mapping techniques. Physical DNA maps covering more than 5 million base pairs have been constructed for several chromosomal regions. Many of these regions have now also been cloned into overlapping cosmid and YAC contigs facilitating the search for disease genes. The recent identification of the mutation in the fragile X syndrome is such an example of the power of YAC technology in the characterization of human genetic disease mutations.

Chromosome Mapping↗
PubMed1992

Bending and fracture of the femoral component in cemented total hip replacement.

A computer method was used to make 41 measurements on the geometry of insertion of the femoral component in 200 Charnley total hip replacements. Surgery had been performed at least 12 years before, giving results which were classified as: success (90); fracture (56); or loose (54), according to rigid selection criteria. Fracture was associated with heavier patients in which there was poor proximal fixation of the femoral component but adequate distal fixation. Stems with a medial disposition proximally were more common in the fracture group than in the successful or loose groups. Sequential measurements of bending and subsequent fracture were made on the follow-up radiographs of 24 of the 200 cases (6 fracture and 18 successful). These measurements allowed bending to be detected at an earlier stage than by simple inspection of the radiographs.

Aged↗
PubMed1992

Aseptic loosening of the femoral component in cemented total hip replacement.

The purpose of this study was to identify factors which predispose to aseptic loosening of the femoral component in cemented total hip replacement. Its design was based on rigid selection criteria, so that successful and loose replacements which employed the same surgical technique were compared. Measurements of patient anatomy and of the insertion of the femoral component were made, by an accurate computer technique, on initial post-operative radiographs. Loosening was associated with heavier patients with a wider medullary canal which was flared proximally. This difference in anatomy led to differing distributions of cement in the successful and loose replacements. Medial cement-bone demarcation, at the mid-stem level, was also associated with loosening. These findings indicate the importance of optimizing the size of the prosthesis with respect to the femoral morphology.

Bone Cements↗
PubMed1992

Mapping of FMR1, the gene implicated in fragile X-linked mental retardation, on the mouse X chromosome.

A genetic map of the Cf-9 to Dmd region of the mouse X chromosome has been established by typing 100 offspring from a Mus musculus x Mus spretus interspecific backcross for the four loci Cf-9, Cdr, Gabra3, and Dmd. The following order and genetic distances in centimorgans were determined: (Cf-9)-2.4 +/- 1.7-(Cdr)-2.0 +/- 1.4-(Gabra3)-4.1 +/- 2.0-(Dmd). Six backcross offspring carrying X chromosomes with recombination events in the Cdr-Dmd region were identified. These recombination events were used to define the position of Fmr-1, the murine homologue of FMR1, which is the gene implicated in the fragile X syndrome in man, and that of DXS296h, the murine homologue of DXS296. Both Fmr-1 and DXS296h were mapped into the same recombination interval as Gabra3 on the mouse X chromosome. These findings provide strong support for the concept that the order of loci lying in the Cf-9 to Gabra3 segment of the X chromosome is highly conserved between human and mouse.

Animals↗
PubMed1992

The dystrophin-related protein, utrophin, is expressed on the sarcolemma of regenerating human skeletal muscle fibres in dystrophies and inflammatory myopathies.

Utrophin is the 400 kDa protein product of an autosomal homologue (DMDL) of the dystrophin gene. In normal skeletal muscle, utrophin is expressed in vascular smooth muscle, endothelium and nerves but not in mature muscle fibres except at the neuromuscular junction. We have examined the expression of utrophin in a wide range of human skeletal muscle diseases using monoclonal antibodies against three C-terminal epitopes. Utrophin is consistently expressed in all basophilic, regenerating fibres irrespective of the underlying disease or expression of dystrophin. It is also found in regenerating fibres from a normal volunteer. In Duchenne and Becker dystrophies, as well as in dermatomyositis, sarcolemmal staining for utrophin is also seen in larger fibres which are not obviously regenerating. These studies do not support the idea that utrophin occupies membrane attachment sites only when dystrophin is absent or reduced, but would be consistent with utrophin expression as part of an activated foetal programme during regeneration.

Adolescent↗