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S Malcolm

Publications and source records attributed to S Malcolm.

At least 19 recordsLinked to original sources
PubMed1995

A case of Pelizaeus-Merzbacher disease showing increased dosage of the proteolipid protein gene.

Clinical, neuropathological and molecular genetic studies in a 9 month old boy with Pelizaeus-Merzbacher disease are described. The principal clinical features were developmental delay, nystagmus, stridor and seizures. Both brain and spinal cord showed almost complete absence of stainable central myelin, while cranial and spinal root myelin was preserved. Probes for cDNA in the boy and his asymptomatic mother indicated an increase in the dosage of proteolipid protein gene (of at least twofold) compared with controls.

DNA Probes↗
PubMed1992

Female twin with Hunter disease due to nonrandom inactivation of the X-chromosome: a consequence of twinning.

We report the occurrence of Hunter disease (mucopolysaccharidosis type II) in a karyotypically normal girl who was one of identical twins. Molecular studies showed nonrandom X-inactivation in both her fibroblasts and lymphocytes, while her normal twin showed equal usage of both X chromosomes. In view of previous reports of 7 pairs of identical female twins in which one had Duchenne muscular dystrophy, it seems that twinning may be strongly associated with nonrandom X-inactivation, and is not specific to the properties of the disease causing gene.

DNA Probes↗
PubMed1992

Further evidence for dominant inheritance at the chromosome 15q11-13 locus in familial Angelman syndrome.

Eleven patients with Angelman syndrome (AS) and their parents from 5 families have been studied with high resolution chromosome analysis and molecular probes from region 15q11-13 in an attempt to elucidate the mode of inheritance in familial AS. No deletions were detected. All families were informative with a combination of different short arm cytogenetic markers. All sets of sibs inherited the same maternal chromosome 15, but in 3 families sibs inherited different paternal 15s. Analysis of 6 polymorphic DNA markers supported the conclusion that AS sibs inherit the same maternal 15, but often different paternal 15s. These data make autosomal recessive inheritance at a 15q11-13 locus very unlikely and support the hypothesis that familial AS is due to maternal transmission of a mutation within 15q11-13.

Angelman Syndrome↗
PubMed1992

Duplication of part of chromosome 17 is commonly associated with hereditary motor and sensory neuropathy type I (Charcot-Marie-Tooth disease type 1).

Hereditary motor and sensory neuropathy type I (HMSNI), also known as Charcot-Marie-Tooth disease type 1 (CMT1), has been shown to be genetically heterogeneous. A major gene maps to chromosome 17 (CMT1A). A set of loci, D17S122, D17S125, and D17S124, show tight linkage to the CMT1A locus, and a duplication of D17S122 has been detected in some families. We show that the locus D17S122 is duplicated in affected individuals from 7 informative families with HMSNI. The duplication was demonstrated either by differences in hybridization densities between two bands of a restriction fragment length polymorphism or by the presence of all three alleles. No normal individual had the duplication. A single recombinant exists between the MspI polymorphism of D17S122 and the duplicated band, suggesting that the duplication is of considerable size. Patients with HMSN type II do not show the duplication. These findings will have considerable impact on the diagnosis of chronic demyelinating neuropathies, in patients with or without similarly affected relatives.

Charcot-Marie-Tooth Disease↗
PubMed1992

Maternal origin of deletion 15q11-13 in 25/25 cases of Angelman syndrome.

About half of the cases of Angelman syndrome arise from deletions of chromosome band 15q12. In 25 cases we have been able to determine the parental origin of the deletion and, in line with other reported cases, we have found the deletion to be of maternal origin. There were no exceptions. The parental origin was determined using cytogenetic markers in 13 of the cases, in nine by using the pattern of inheritance of restriction fragment length polymorphisms, and in three using both techniques.

Abnormalities, Multiple↗
PubMed1992

Identification of CpG islands around the DXS178 locus in the region of the X-linked agammaglobulinaemia gene locus in Xq22.

The X-linked agammaglobulinaemia (XLA) gene locus has previously been mapped to Xq22. Genetic linkage analysis has shown tight linkage between the disease and the DXS178 locus and that DXS3 and DXS94 are the closet proximal and distal flanking markers, respectively, separated by a genetic distance of 10-12 cM. We attempted to construct a physical map of Xq22 using pulsed field gel electrophoresis (PFGE) and rare-cutting restriction enzymes in order to obtain a finite physical value for the distance between DXS3 and DXS94. However, these attempts were hampered by the large number of rare-cutting restriction enzyme sites around the DXS178 locus, indicative of the presence of CpG rich regions of DNA. We were able to construct a physical map of the sites close to DXS178 that suggests the presence of at least three, and perhaps as many as five, CpG islands. These are arranged on either side of DXS178, extending over about 550kb of genomic DNA. Each of these regions must be considered as being associated with a potential "candidate" gene sequence for the XLA gene and we have initiated a chromosome walk from DXS178 to the nearest of these islands.

Agammaglobulinemia↗
PubMed1992

Molecular detection of altered X-inactivation patterns in the diagnosis of genetic disease.

It is widely assumed that when a female carrier of a genetic disorder exhibits clinical signs of the disorder it is due to chance non-random X-inactivation in particular tissues. Recently molecular methods have become available for the analysis of X-chromosome inactivation status. These are based either on the methylation patterns of DNA from the active and inactive chromosomes or on the rescue of active X chromosomes in somatic cell hybrids. As a consequence of the molecular studies, it has become obvious that there are some special cases of non-random X-inactivation patterns. These include females carrying X-linked immunodeficiencies and, sometimes, one of a pair of identical female twins.

Diseases in Twins↗
PubMed1992

Effect of varying the type of fat in a semi-purified AIN-76A diet on cellular proliferation in the mammary gland and intestinal crypts in female Swiss Webster mice.

Young virgin female Swiss Webster mice were fed AIN-76A semi-purified diets containing equal weights of different fats for approximately 30 days. Using [3H]thymidine radioautography, it was established that mice fed 100% lard or high levels of fish oils (menhaden oil or cod liver oil) developed elevated cellular proliferation in the duct cells of the mammary gland and an increased number of labeled cells/crypt in the crypts of the colo-rectum accompanied by an increase in the size of the proliferative compartment. A possible inverse correlation between the level of [3H]thymidine labeling in the mammary gland, but not in the colo-rectum, and the linoleic acid content of individual diets may help to explain the significance of these observations. The effect of adding an antioxidant mixture to these diets was to reduce the excess proliferation induced in the intestinal crypts by lard or fish oil to the level induced by soybean oil, but only partially so in the duct cells of the mammary gland.

Animals↗
PubMed1992

Angelman syndrome with a chromosomal inversion 15 inv(p11q13) accompanied by a deletion in 15q11q13.

A family is described in which an inversion of chromosome 15, 15 inv(p11q13), is segregating. All family members are healthy except the proband who is a 10 year old boy with Angelman syndrome. Although the chromosomal inversion has been passed from the grandfather to both his son and his daughter with no ill effect, passage from daughter to grandson has resulted in a deletion of chromosome 15 material which is presumed to be the cause of Angelman syndrome in this boy. The probabilities of an inversion of this type being instrumental in causing the syndrome are discussed.

Angelman Syndrome↗
PubMed1992

Confirmation of an association between RFLPs at the transforming growth factor-alpha locus and non-syndromic cleft lip and palate.

Three RFLPs at the TGFA locus were studied in 60 unrelated British Caucasian subjects with non-syndromic cleft lip/palate and 60 controls. A highly significant association between the TaqI RFLP and the occurrence of clefting was found (chi 2 = 15.04, p = less than 0.001). No significant association was found with the two other RFLPs studied (BamHI and RsaI). Haplotypes derived from the three RFLPs at the TGFA locus also showed an over-representation of the C2A2B2 haplotype in cases compared to controls. Analyses of genotypes according to type of cleft and the presence or absence of a family history of clefting were also carried out. These results provide further support for the role of TGFA as a gene of major effect in the development of orofacial clefts in humans.

Alleles↗
PubMed1992

No evidence of linkage between the transforming growth factor-alpha gene in families with apparently autosomal dominant inheritance of cleft lip and palate.

Eight families have been identified with cleft lip, with or without cleft palate (CL/P), inherited in an apparently autosomal dominant manner. Transforming growth factor-alpha (TGFA) has been tested as a candidate gene for clefting in these families. Negative lod scores were generated in an autosomal dominant model with 80% penetrance (Z = -3.152 at theta = 0.05 and Z = -2.49 at theta = 0.05 with only affected subjects scored). After testing with a reduced penetrance of 28%, less negative lod scores were generated (Z = -0.157 at theta = 0.00), but there was still no evidence of linkage. An autosomal recessive model with a penetrance of 35% was also tested. Regardless of the model used there was little evidence of linkage between TGFA and the CL/P phenotype, which is in contrast to the previously published findings of an association between TGFA and CL/P in unrelated subjects.

Cleft Lip↗
PubMed1992

Clinical and genetic heterogeneity in X-linked deafness.

The use of molecular techniques in respect of the rare X-linked non-syndromic form of genetic deafness demonstrates that this is a genetically heterogeneous disorder, with evidence for at least two separate gene loci on the X chromosome. Audiological heterogeneity in this condition is emphasized by the observation of both mixed deafness and sensorineural deafness in pedigrees showing evidence for linkage to Xq13-q21. The importance and shortcomings of the audiogram in assessing females who are known gene carriers is discussed.

Adolescent↗
PubMed1992

Pelizaeus-Merzbacher disease: detection of mutations Thr181----Pro and Leu223----Pro in the proteolipid protein gene, and prenatal diagnosis.

A family with an apparent history of X-linked Pelizaeus-Merzbacher disease presented for genetic counseling, requesting carrier detection and prenatal diagnosis. RFLP analysis using the proteolipid protein (PLP) gene probe was uninformative in this family. A prenatal diagnosis on a chorionic villus sample (CVS) was carried out using single-strand conformation polymorphism (SSCP) analysis of a variant in exon 4 of the PLP gene. The fetus was predicted to be unaffected. Sequencing of the exon from the CVS, the predicted-carrier mother, and the obligate-carrier grandmother revealed an A-to-C change at nucleotide 541 in the two women but not in the fetus. As this change results in a Thr-to-Pro change at amino acid 181 in a region of the gene predicted to be part of a transmembrane segment, it was concluded that this was the mutation causing the disease in this family. In addition, in a second family, an exon 5 variant band pattern on SSCP analysis was shown by sequencing to be due to a T-to-C change at nucleotide 668. This results in a Leu-to-Pro change in a carrier mother and in her two affected sons. These results provide further examples of mutations in PLP that cause Pelizaeus-Merzbacher disease and illustrate the value of SSCP in genetic analysis.

Amino Acid Sequence↗