Elevated levels of erythrocyte hypoxanthine phosphoribosyltransferase associated with allelic variation of murine Hprt

Johnson, Gregory L.; Larsen, Teresa A.; Blakely, Patricia; Chapman, Verne M.

doi:10.1021/bi00340a019

Cited by 14 publications

(4 citation statements)

References 43 publications

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“…In vivo differences in stability may parallel those seen in the heat stability experiments or may be the result of other variation that affects the turnover of GPI-1 molecules in blood. Beutler (1983) has argued for differential sensitivity to proteases and Johnson and colleagues have discussed differences in turnover of mouse hypoxanthine phosphoribosyltransferase variants during reticulocyte maturation (Johnson & Chapman, 1987;Johnson et al 1985Johnson et al , 1988.…”

Section: Discussionmentioning

confidence: 99%

Non-additive inheritance of glucose phosphate isomerase activity in mice heterozygous at theGpi-1sstructural locus

West

Flockhart

1989

Genet. Res.

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The activity of blood glucose phosphate isomerase (GPI-1) in mice heterozygous for various alleles at the Gpi-\s structural locus (heterozygotes a/b, a/c and b/c) was significantly higher than expected, on the basis of additive inheritance, from the levels in parental homozygotes. Moreover, the GPI-1 activity was higher in a/b heterozygotes than in either parent (heterosis). Studies of heat stability with kidney homogenates revealed that the relative stabilities of GPI-1 dimers was AA > AB > BB > AC ^ BC > CC. Differences in dimer stabilities in vivo would affect the total GPI-1 levels in heterozygotes and could account for non-additive inheritance but would be insufficient to explain heterosis for GPI-1 activity. Other possible contributing factors include unequal production or stability of monomers, or higher catalytic activity of heterodimers. Monomers could also associate non-randomly but this would not be sufficient to explain heterosis. It is clear that non-additive inheritance patterns may be produced by variants of either structural or regulatory genes.

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Section: Discussionmentioning

confidence: 99%

Non-additive inheritance of glucose phosphate isomerase activity in mice heterozygous at theGpi-1sstructural locus

West

Flockhart

1989

Genet. Res.

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“…C57BL/6 male and female mice were used for the analysis of DNA methylation in adult tissues. Crosses between the ES cell-derived Hprt-m3 animals (BM3) (20,45) and a C57BL/6-Hprta Pgk-la congenic strain (AT29) (13) or Mus spretus (Hprla) (23) were established. Two 6-thioguanine-resistant (TG') cell lines, HOBMSL2 (shortened to BML-2) (unpublished data) and HOMSKI (11) CGGTATGGTTAGTA7TA-3') and Hm-aII (5'-ACTCTA GAAAAATCCCCTTAACTCACCAC-3') were used in our study to produce a 371-bp fragment from the upper strand of Hprt.…”

Section: Methodsmentioning

confidence: 99%

CpG island promoter region methylation patterns of the inactive-X-chromosome hypoxanthine phosphoribosyltransferase (Hprt) gene.

Park¹,

Chapman²

1994

Mol. Cell. Biol.

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Inactive-X-chromosome genes in mammalian females have methylated CpG islands. We have questioned whether there are variable levels of cytosine methylation at different CpG sites within the island that might indicate the presence of primary sites of methylation which may be critical for the maintenance of gene repression and candidate sites for the initiation of inactivation. To address these questions, we have analyzed the methylation patterns of 32 CpG sites of the X-linked hypoxanthine phosphoribosyltransferase (Hprt) gene on the active and inactive X chromosomes of mouse tissues and cell lines, using genomic sequencing of bisulfite-treated genomic DNA. Cytosine is deaminated by bisulfite, but methylcytosine is not affected. Cell lines that were heterozygous for the Hprt deletion mutation (Hprt1-m3) and a functional Hprt allele were selected with 6-thioguanine. The resulting cell populations uniformly carry the intact Hprt allele on the inactive X chromosome. The methylation of these CpG sites was determined either by the direct sequence analysis of bisulfite-treated and amplified DNA or by the sequence analysis of clones derived from the amplified DNA. No CpG methylation was detected on the active Hprt genes from either males or the active X chromosome of females. On average, 22 CpGs were methylated in the other 50% of female DNA, and the level of methylation at individual sites varied from 42 to 100%o. Analysis of the inactive Hprt gene in two cell lines showed that averages of 14 and 18 CpGs were methylated and that the frequency of methylation at 32 individual sites ranged from 3 to 100%0. The highest frequency of methylation in cell lines coincided with the sequences flanking transcription initiation sites. These results suggest that methylation patterns are heterogeneous within a tissue and even in clonal cell populations and that specific subsets of CpG sites sustain high methylation frequencies which may be critical for the maintenance of X-chromosome inactivation. The bisulfite method identified which CpG sites were methylated on the inactive X chromosome, and it provided a quantitative estimate of the frequency of methylation of these sites in genomic DNA.Cytosine methylation in mammalian cells has been established as a regulatory feature in genomic imprinting (3, 27), fragile X syndrome (44), and the process of X-chromosome inactivation (16). This methylation is typically found in CpG island-associated promoters that are normally free of methylation when a gene is expressed (5). DNA methylation of X-chromosome genes is correlated with an inactive X chromosome (Xi) in female mammals (16,33). One of the two X chromosomes in somatic cells of females becomes inactive during early embryonic development, and, once the inactive state of a chromosome is established, it becomes somatically heritable in a cell lineage. The onset of DNA methylation on the Xi may occur after the inactive condition is established, although the timing of this may vary with different sites and genes on the X chromosome.Treatment o...

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“…After electrophoresis, proteins in the gel were electroblotted onto nitrocellulose membranes for 12-24 h at 100 mV. Membranes were then incubated with 1% bovine serum albumin for 60 rnin to saturate nonspecific protein binding sites and exposed for 12-24 h to a polyclonal rabbit antiserum raised against HPRT purified from mouse brain (Johnson et al, 1985). The antiserum was diluted 1:2,000 with 0.2% Triton X-100, 1% bovine serum albumin, and 100 mM Tris buffer, pH 7.5.…”

Section: Western Analysismentioning

confidence: 99%

Brain Purines in a Genetic Mouse Model of Lesch‐Nyhan Disease

Jinnah

Page

Friedmann

1993

Journal of Neurochemistry

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Mice carrying a mutation in the gene encoding the purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT) have recently been produced to provide an animal model for Lesch-Nyhan disease. The current studies were conducted to characterize the consequences of the mutation on the expression of HPRT and to characterize potential changes in brain purine content in these mutants. Our results indicate that the mutant animals have no detectable HPRT-immunoreactive material on western blots and no detectable HPRT enzyme activity in brain tissue homogenates, confirming that they are completely HPRT deficient (HPRT-). Despite the absence of HPRT-mediated purine salvage, the animals have apparently normal brain purine content. However, de novo purine synthesis, as measured by [14C]formate incorporation into brain purines, is accelerated four- to fivefold in the mutant animals. This increase in the synthesis of purines may protect the HPRT- mice from potential depletion of brain purines despite complete impairment of HPRT-mediated purine salvage.

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Elevated levels of erythrocyte hypoxanthine phosphoribosyltransferase associated with allelic variation of murine Hprt

Cited by 14 publications

References 43 publications

Non-additive inheritance of glucose phosphate isomerase activity in mice heterozygous at theGpi-1sstructural locus

Non-additive inheritance of glucose phosphate isomerase activity in mice heterozygous at theGpi-1sstructural locus

CpG island promoter region methylation patterns of the inactive-X-chromosome hypoxanthine phosphoribosyltransferase (Hprt) gene.

Brain Purines in a Genetic Mouse Model of Lesch‐Nyhan Disease

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