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Biomedical subjects

T B Shows

Publications and source records attributed to T B Shows.

At least 289 records · Page 16Linked to original sources
PubMed1983

Mucolipidosis II and III. The genetic relationships between two disorders of lysosomal enzyme biosynthesis.

The genetic relationships between the multiple variants of mucolipidosis II (I-cell disease) and mucolipidosis III (pseudo-Hurler polydystrophy) were investigated with a sensitive genetic complementation analysis procedure. These clinically distinct disorders have defects in the synthesis of a recognition marker necessary for the intracellular transport of acid hydrolases into lysosomes. Both disorders are associated with an inherited deficiency of a uridine diphosphate-N-acetyl-glucosamine: lysosomal enzyme precursor N-acetyl-glucosamine-phosphate transferase activity. We had previously shown that both disorders are genetically heterogeneous. Complementation analysis between mucolipidosis II and III fibroblasts indicated an identity of mucolipidosis II with one of the three mucolipidosis III complementation groups (ML IIIA), suggesting a close genetic relationship between these groups. The presence of several instances of complementation within this group suggested an intragenic complementation mechanism. Genetic complementation in heterokaryons resulted in increases in N-acetyl-glucosamine-phosphate transferase activity, as well as in the correction of lysosomal enzyme transport. This resulted in increases in the intracellular levels of several lysosomal enzymes and in the correction of the abnormal electrophoretic mobility pattern of intracellular beta-hexosaminidase. The findings demonstrate that a high degree of genetic heterogeneity exists within these disorders. N-acetyl-glucosamine-phosphate transferase is apparently a multicomponent enzyme with a key role in the biosynthesis and targeting of lysosomal enzymes.

Cell Fusion↗
PubMed1983

Suppression of tumorigenicity in somatic cell hybrids. II. Human chromosomes implicated as suppressors of tumorigenicity in hybrids with Chinese hamster ovary cells.

Nontumorigenic diploid human cells were fused with tumorigenic Chinese hamster ovary cells (CHO), and the hybrids were tested for tumorigenicity to determine if specific human chromosomes are associated with suppression of tumorigenicity in cell hybrids. Chromosome complements of cells of 62 nontumorigenic and 45 tumorigenic hybrids (divided into those of low, medium, and high tumorigenicity) as well as 44 tumors derived from the tumorigenic hybrids were determined by both analysis of banded chromosomes and assays of gene markers. Although no single human chromosome was consistently associated with the suppressed phenotype, chromosome 2 was never found in tumor cells, and chromosomes 9, 10, 11, and 17 were found at very low incidences in tumor cells, which suggested that they carry tumorigenicity suppressor information. Since not all suppressed hybrids contained these chromosomes, it is likely that they suppressed tumorigenicity only in combination with each other or other chromosomes. Nine chromosomes in 12 pairwise combinations of nonhomologous chromosomes were not found in tumor cells and were found at an incidence of 5% or less in hybrids of both medium and high tumorigenicity. Other experiments implicated 11 of these combinations involving only 8 chromosomes (chromosomes 4, 7, 8, 9, 10, 11, 13, and 17) as those primarily involved in suppression. Whether chromosome 2 requires another chromosome to effect suppression could not be determined. Further evaluations of the implicated suppressors, including selection of tumorigenic segregants from a panel of suppressed hybrids, again implicated the same chromosomes and their combinations in suppression. Oncogenes have been mapped to many of these chromosomes, and they are frequently involved in tumor-type-specific numerical or structural abnormalities in human neoplasias. The combined evidence suggests that specific human chromosomes of a normal cell carry genes that can regulate several cell phenotypes necessary for the expression of tumorigenicity.

Animals↗
PubMed1983

Organization of rDNA spacer fragment variants among human acrocentric chromosomes in somatic cell hybrids.

Although the human rDNA gene family is organized in clusters of tandem repeats on five pairs of acrocentric chromosomes, all rDNA genes have undergone a "concerted" evolution resulting in a homogeneous population of genes. Two steps are necessary for a variant to spread to all rDNA genes: dissemination of the variant to all genes in a cluster; and exchange of rDNA genes between nonhomologous chromosomes. To study the organization of rDNA genes, a restriction fragment length polymorphism in the spacer region adjacent to the 28S gene was examined in somatic cell hybrids in which individual human acrocentric chromosomes could be isolated. Human DNA cut with BamHI and analyzed by Southern hybridization yields two to four major bands that hybridize to a 32P-labeled cloned fragment of the 28S gene. Hybrids containing single human acrocentric chromosomes do not recapitulate the parental patterns, but frequently have only one of the parental bands. The data suggest that the quantitative distribution of spacer length variants differs among the human acrocentric chromosomes in hybrids. The frequently observed homogeneity of the rDNA variants on individual acrocentric chromosomes in hybrid cells may reflect the individual rDNA clusters in the parental cell or may be a result of unequal crossing over in the hybrid cell.

Animals↗
PubMed1982

Clustering of leukocyte and fibroblast interferon genes of human chromosome 9.

At least ten leukocyte interferon genes and the single known fibroblast interferon gene have been localized on the pter leads to q12 region of human chromosome 9. Gene mapping was accomplished by blot hybridization of cloned interferon complementary DNA to DNA from human-mouse cell hybrids with a translocation involving human chromosome 9. Supporting evidence suggests these genes are clustered.

Chromosome Mapping↗
PubMed1982

Genetic heterogeneity of I-cell disease is demonstrated by complementation of lysosomal enzyme processing mutants.

I-cell disease (mucolipidosis II) is a fatal childhood disorder affecting the expression of multiple lysosomal acid hydrolases. The disorder is characterized by clinical and biochemical heterogeneity which may reflect different mutants with a similar phenotype. Genetic complementation studies demonstrating genetic heterogeneity within this disorder are described utilizing cultured fibroblasts from 11 different patients. Fibroblasts from I-cell disease (ICD) and from five different lysosomal storage diseases with single structural gene enzyme deficiencies were fused in different combinations, and fractions enriched for multinucleated heterokaryons were isolated and tested for acid hydrolase activity and electrophoretic mobility. In fusions of ICD fibroblasts and various single lysosomal enzyme-deficient fibroblasts, the activity of the deficient enzyme and of the other ICD hydrolases were restored, demonstrating that ICD is not a lysosomal enzyme structural gene defect and that the ICD defect, and not just the single enzyme deficiency, is corrected. In fusions involving only I-cell fibroblasts, at least two complementation groups were identified by the recovery of activities of all lysosomal enzymes tested in heterokaryons. These results demonstrate the existence of genetic heterogeneity within the disorder and suggest that different mutations can result in the I-cell clinical and biochemical phenotype. The data support an altered post-translational processing of lysosomal enzymes as the cause of ICD and suggest that at least two genes participate in this pathway.

Cell Fusion↗
PubMed1982

Human beta-galactosidase and alpha-neuraminidase deficient mucolipidosis: genetic complementation analysis of the neuraminidase deficiency.

Human beta-galactosidase and alpha-neuraminidase deficient mucolipidosis [ML(gal-neur-)] is an inherited lysosomal enzymopathy which recently was designated as a sialidosis. We analyzed the neuraminidase deficiency of this disorder with genetic complementation analyses using a heterokaryon enrichment procedure. The genetic defects of two apparent variants of this disorder complemented the defects of the neuraminidase deficiency diseases, sialidosis I and mucolipidosis I, resulting in the restoration of neuraminidase activity in heterokaryons. The neuraminidase deficiency, therefore, may not be the primary defect in ML(gal-neur-) and is not an appropriate test for determining carrier status. The clinical and biochemical characteristics of this disorder suggest that a post-translational or processing event for these enzymes may be defective. The defect, however, is different from I-cell disease and pseudo-Hurler polydystrophy, two disorders of post-translational lysosomal enzyme biosynthesis, since complementation studies demonstrated recovery of intracellular beta-galactosidase and alpha-neuraminidase levels in heterokaryons. The lack of human beta-galactosidase expression in man-mouse somatic cell hybrids formed from fibroblasts of the infantile onset type disorder suggests that the defect is not corrected by the mouse genome. The ML(gal-neur-) disorder therefore appears to be a distinct subtype of the inherited neuraminidase deficiencies in which the defect mat occur in a post-translational or regulatory step which coordinately affects the expression of lysosomal beta-galactosidase and alpha-neuraminidase.

Animals↗
PubMed1982

Coronavirus 229E susceptibility in man-mouse hybrids is located on human chromosome 15.

Human coronavirus 229E, n enveloped, RNA-containing virus, causes respiratory illness in man and is serologically related to murine coronavirus JHM, which causes acute and chronic demyelination in rodents. 229E displays a species-specific host range restriction whose genetic basis was studied in human-mouse hybrids. 229E replicated in human WI-38 cells but not in three mouse cell lines tested (RAG, LM/TK-, and A9). Human coronavirus sensitivity (HCVS) was expressed as a dominant phenotype in hybrids, indicating that mouse cells do not actively suppress 229E replication. HCVS segregated concordantly with the human chromosome 15 enzyme markers mannose phosphate isomerase (MPI) and the muscle form of pyruvate kinase (PKM2), and analysis of hybrids containing an X/15 translocation [t(X;15)(p11;q11)] localized HCVS to the q11 leads to qter region of chromosome 15. HCVS might code for a specific surface receptor, allowing 229E to be absorbed to and received within the host cell.

Animals↗
PubMed1982

Gene for glutathione S-transferase-1 (GST1) is on human chromosome 11.

The glutathione S-transferases (GST) are a group of related enzymes that can detoxify potentially carcinogenic electrophiles by conjugating them with reduced glutathione (GSH). The chromosomal location of one of the enzyme forms, GST1, reported recently to be polymorphic, was determined utilizing man-mouse somatic cell hybrids segregating human chromosomes. The expression of GST1 by hybrid clones was compared with that of 34 enzyme markers representing 23 chromosomes, and karyotypes of selected cell hybrids were analyzed. The evidence indicated that GST1 is assigned to chromosome 11 in humans. Utilizing and X/11 translocation segregating in hybrids, GST1 was localized to the p13 leads to qter region of chromosome 11.

Animals↗
PubMed1982

Mucolipidosis III is genetically heterogeneous.

Mucolipidosis III (ML III), or pseudo-Hurler polydystrophy, is an inherited childhood disorder characterized biochemically by low activities and abnormal electrophoretic patterns of multiple lysosomal enzymes in fibroblasts. The primary deficiency of ML III has been proposed to be in UDP-N-acetylglucosamine:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase. However, variation in this enzyme and in other biochemical properties of different ML III lines has been observed. Therefore, we investigated genetic heterogeneity within the disorder by complementation analysis. Heterokaryon cell fractions were generated by fusing together ML III fibroblast lines. When pairs of cells complemented, correction of lysosomal enzyme activities and electrophoretic patterns was observed. Twelve fibroblast lines from 10 sibships were analyzed and three distinct complementation groups were characterized. One complementation group represents the classical ML III disorder. A single cell line identifies a second complementation group. The cell lines comprising a third complementation group have a number of biochemical characteristics different from classical ML III and may represent a genetically distinct disorder.

Cell Line↗
PubMed1982

The adrenergic responsiveness of Down syndrome cells.

Platelets and cultured fibroblasts were used to examine the hormonal response of normal diploid and Down syndrome (trisomy 21) cells. An enhanced physiological response to catecholamine hormones was found in the trisomy 21 cells. This effect was specific for the adrenergic agonists since other hormones showed equivalent responses in the normal diploid and trisomy 21 cell types. Radioligand analysis of the alpha-adrenergic receptors in trisomy 21 platelets indicated no significant difference in receptor density or ligand affinity. Enzymatic analysis of the platelet adenylate cyclase activity in vitro showed no major changes in catecholamine sensitivity between the normal and Down syndrome preparations. Somatic cell genetic studies using human-hamster hybrids indicated that a gene coding for the beta-adrenergic receptor was not located on chromosome 21 but on human chromosome 5. These receptor, enzymic, and somatic cell genetic studies argue against a gene-dosage effect involving either the adrenergic hormone receptors or a component of the adenylate cyclase enzyme in the trisomy 21 cells. Identifying the gene(s) on chromosome 21 and the molecular mechanism(s) responsible for the exaggerated response of Down syndrome cells to catecholamines are the current objectives of this research program.

Cells, Cultured↗
PubMed1982

Mapping of aminoacylase-1 and beta-galactosidase-A to homologous regions of human chromosome 3 and mouse chromosome 9 suggests location of additional genes.

Conserved linkage groups have been found on the X and autosomal chromosomes in several mammalian species. The identification of conserved chromosomal regions has potential for predicting gene location in mammals, particularly in humans. The genes for human aminoacylase-1 (ACY1, N-acylamino acid aminohydrolase, E.C.3.5.1.14), an enzyme in amino acid metabolism, and beta-galactosidase-A (GLB1, E.C.3.2.1.23), deficient in GM1-gangliosidosis, have been assigned to human chromosome 3. Using human-mouse somatic cell hybrids segregating translocations of human chromosome 3, expression of both ACY1 and GLB1 correlated with the presence of the p21 leads to q21 region of chromosome 3. In a previous study, assignment of these genes to mouse chromosome 9 used mouse-Chinese hamster somatic cell hybrids, eliminating mouse chromosomes. To approximate the size of the conserved region in the mouse, experiments were performed with recombinant inbred mouse strains. An electrophoretic variant of ACY-1 in mouse strains was used to map the Acy-1 gene 10.7 map U from the beta-galactosidase locus. These data suggest that there is a region of homology within the p21 leads to q21 region of human chromosome 3 and a segment of mouse chromosome 9. Since the mouse transferrin gene (Trf) is closely linked to the aminoacylase and beta-galactosidase loci, we predict that the human transferrin (TF) gene is on chromosome 3.

Amidohydrolases↗
PubMed1981

The prolactin gene is located on chromosome 6 in humans.

The gene for prolactin has been located on chromosome 6 in humans. DNA fragments of 4.8 and 4.0 kilobases containing prolactin gene sequences were identified in human genomic DNA, whereas DNA fragments of 7.4, 3.6, and 3.3 kilobases containing prolactin gene sequences were found in mouse cells. In somatic cell hybrids of human and mouse cells the 7.4-, 3.6-, and 3.3-kilobase mouse fragments were always present, whereas the 4.8- and 4.0-kilobase human fragments were only present when human chromosome 6 was also present. We conclude that the prolactin gene resides on chromosome 6, a different location from those of the genes for the related hormones chorionic somatomammotropin and growth hormone.

Animals↗