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S Cottrell

Publications and source records attributed to S Cottrell.

27 records · Page 2Linked to original sources
PubMed1992

Yeast artificial chromosomes for the molecular analysis of the familial polyposis APC gene region.

Two yeast artificial chromosomes (YACs) spanning a total distance of 1.1 megabase pairs of DNA around the MCC (for mutated in colorectal carcinoma) and APC (for adenomatous polyposis coli) genes at 5q21 have been isolated and characterized. Starting from the MCC gene, a strategy was undertaken to identify constitutional submicroscopic deletions in familial adenomatous polyposis patients that might considerably narrow down the position of the APC gene. To this end, YACs identified by the MCC gene were screened across a chromosome 5-specific cosmid library to provide a source of DNA probes for genomic scanning. The cosmids isolated from these experiments were used to screen a panel of somatic cell hybrids containing chromosome 5 segregated from patients suspected to carry putative interstitial deletions. This screening approach led to the confirmation of a small heterozygous deletion in a polyposis patient that overlaps one of the two isolated YACs. This YAC has been shown to contain the entire APC gene, in addition to a significant portion of DNA flanking the 5' end of the gene, and should therefore prove a valuable resource for functional studies by transfer to colorectal tumor-derived cell lines.

Adenomatous Polyposis Coli↗
PubMed1991

Fine mapping of probes in the adenomatous polyposis coli region of chromosome 5 by in situ hybridization.

The gene for adenomatous polyposis coli has been localized to 5q21-22. We have mapped six probes from this region using isotopic or nonisotopic in situ hybridization. Using tritium-labeled probes we localized II227 (D5S37) to 5q14-15 and ECB27 (D5S98) to 5q21. Following hybridization with biotin-labeled probes, the positions of signals along the chromosomes were measured as fractional length relative to the length of the chromosome arm from centromere to qter (FLcen-qter). Ninety-five percent confidence limits, compared with standard karyotypes, provided the corresponding band localization. By this method we localized Cllpll (D5S71) to FLcen-qter 0.407-0.452 (5q21.1-21.3), ECB27 to FLcen-qter 0.426-0.473 (5q21.3), YN5.48 (D5S81) to FLcen-qter 0.459-0.496 (5q21.3-22.2), and ECB134 (D5S97) to FLcen-qter 0.509-0.533 (5q22.3-23.1). ECB220 had three sites of hybridization, a major site at FLcen-qter 0.460-0.492 (5q21.3-22.1) and minor sites at FLcen-qter 0.299-0.339 (5q14.3-15) and FLcen-qter 0.629-0.691 (5q23.3-31.2). We have shown that the chromosome 5 breakpoint in a t(5;15) translocation from a patient with Gardner's syndrome (GM03314) is between Cllpll and ECB27. Linkage data are presented suggesting that ECB27 is located on the same side of the APC locus as II227. These and published results including data on several constitutional deletions (M, SD, and brothers PW and ND) give a probable order of [cen] - [II227, proximal SD breakpoint] - [Cllpll] - [proximal PW/ND, M breakpoint(s), GM03314 breakpoint] - [ECB27] - [APC] - [YN5.48] - [distal PW/ND breakpoint] - [ECB134] - [distal M breakpoint] - [qter]. The major site of ECB220 appears to be between ECB27 and the distal PW/ND breakpoint; the distal SD breakpoint is distal to YN5.48.

Adenomatous Polyposis Coli↗
PubMed1990

Studies on the cytochrome P-450 of avocado (Persea [corrected] americana) mesocarp microsomal fraction.

1. Because of the low concentration of cytochrome P-450 in avocado fruit, microsomal fractions were prepared using polyethylene glycol aggregation and low-speed centrifugation, thus avoiding the need for high-speed centrifugation of large volumes of post-mitochondrial supernatant. Recoveries of cytochrome P-450 by this means (0.29 nmol/g tissue) were similar to those after the usual high-speed centrifugation preparation (0.26 nmol/g). The cytochrome P-450 content of tulip bulb (0.30 nmol/g) was similar to that of avocado, but both plant tissues had much lower P-450 contents than did rat liver (13.0 nmol/g). 2. Spectral studies indicate that cytochrome P-450 of avocado mesocarp microsomal fraction binds fewer substrates than does the rat liver enzyme system. Type I binding spectra are given by fatty acids (C7-C14), aryl hydrocarbons (C7-C12), p-chloro-N-methylaniline and N,N-dimethylaniline. Type II binding is seen with inhibitors of mammalian cytochrome P-450 such as metyrapone, and with the imidazole antifungal agents such as clotrimazole. 3. These binding spectra provide a rapid method for identifying possible substrates and inhibitors of avocado cytochrome P-450, and also provide information concerning the nature of the active site of avocado cytochrome P-450. 4. Avocado cytochrome P-450 catalysed the N-demethylation of N,N-dimethylaniline (17.1 nmol/min per nmol P-450) and p-chloro-N-methylaniline (13.1 nmol/min per nmol P-450), and the hydroxylation of lauric (dodecanoic) acid (1.1 nmol/min per nmol P-450).

Aniline Compounds↗
PubMed1989

CpG island clones from a deletion encompassing the gene for adenomatous polyposis coli.

Adenomatous polyposis coli (APC), a dominantly inherited disorder, has been mapped to chromosome 5q15-q21 by family linkage studies. Cells from patients with deletions in this region, in one case associated with polyposis in a family, have been used to construct human hamster hybrid cell lines that retain either the normal or deleted chromosome 5. These lines have been used to identify markers from the region of the polyposis gene obtained by cloning the ends of 0.5- to 2-megabase BssHII fragments purified by pulsed-field gel electrophoresis. Three markers are described that map within the deletions and must therefore be close to the APC gene.

Adenoma↗
PubMed1989

Genetic analysis of colorectal cancer.

Adenomatous polyposis, mainly of the colon, (APC) is a rare dominantly inherited susceptibility to colon cancer in which individuals develop hundreds of polyps mainly in their large bowel. The APC gene has been localised to chromosome 5q21 by following up a case report of an individual with an interstitial deletion on chromosome 5q who had multiple developmental abnormalities together with adenomatous polyposis. A DNA marker (D5S71) was found to be closely linked to APC in family studies and localised to 5q21 by in situ annealing. Material from further patients with deletions in this region of chromosome 5 has been used, by a combination of somatic cell hybrid and long-range DNA analysis, to identify new DNA markers close to the APC gene. These and other markers now provide the basis for genetic counselling of nearly all families with APC. These studies are being extended, together with other approaches for analysing DNA clones around the APC gene, in the search for the gene itself. Allele loss in tumour as compared to normal tissue from sporadic cases of colorectal carcinomas has clearly implicated the APC gene in at least 25 to 40% of all cases of colorectal carcinomas. Similar studies by Vogelstein and others as well as ourselves have further implicated recessive changes on chromosomes 17 and 18 in the development of colorectal carcinomas. Following the demonstration by Vogelstein of the role of p53 mutations in connection with the chromosome 17 changes, we have now shown, using monoclonal antibodies to the mutant p53 products and by other approaches, that changes in the p53 gene may occur in up to 50% or more of colorectal carcinomas. Frequent mutations of the K-ras dominant oncogene, as well as changes in the expression of human leucocyte antigen (HLA)-A, B, C determinants, are further genetic changes that appear commonly to be involved in the progression of colorectal carcinomas. The latter have important implications for T cell immune response to tumours and its manipulation for treatment and even prevention of colorectal cancer. We may soon be approaching a situation when it will become possible to identify all the genetic steps and their sequence during tumour progression, as well as their functional significance largely through the induction of inappropriate growth and the suppression of differentiation.

Adenomatous Polyposis Coli↗