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Emma L Williams

Publications and source records attributed to Emma L Williams.

5 recordsLinked to original sources
PubMed2006

Reconstruction of human hepatocyte glyoxylate metabolic pathways in stably transformed Chinese-hamster ovary cells.

Failure to detoxify the intermediary metabolite glyoxylate in human hepatocytes underlies the metabolic pathology of two potentially lethal hereditary calcium oxalate kidney stone diseases, PH (primary hyperoxaluria) types 1 and 2. In order to define more clearly the roles of enzymes involved in the metabolism of glyoxylate, we have established singly, doubly and triply transformed CHO (Chinese-hamster ovary) cell lines, expressing all combinations of normal human AGT (alanine:glyoxylate aminotransferase; the enzyme deficient in PH1), GR/HPR (glyoxylate/hydroxypyruvate reductase; the enzyme deficient in PH2), and GO (glycolate oxidase). We have embarked on the preliminary metabolic analysis of these transformants by studying the indirect toxicity of glycolate as a simple measure of the net intracellular production of glyoxylate. Our results show that glycolate is toxic only to those cells expressing GO and that this toxicity is diminished when AGT and/or GR/HPR are expressed in addition to GO. This finding indicates that we have been able to reconstruct the glycolate-->glyoxylate, glyoxylate-->glycine, and glyoxylate-->glycolate metabolic pathways, catalysed by GO, AGT, and GR/HPR respectively, in cells that do not normally express them. These results are compatible with the findings in PH1 and PH2, in which AGT and GR/HPR deficiencies lead to increased oxalate synthesis, due to the failure to detoxify its immediate precursor glyoxylate. These CHO cell transformants have a potential use as a cell-based bioassay for screening small molecules that stabilize AGT or GR/HPR and might have use in the treatment of PH1 or PH2.

Alcohol Oxidoreductases↗
PubMed2006

A de novo mutation in the AGXT gene causing primary hyperoxaluria type 1.

Primary hyperoxaluria type 1 is caused by mutations in the alanine-glyoxylate aminotransferase (AGXT) gene. In cases in which no mutation was identified, linkage analysis can be used to confirm or exclude the diagnosis in other siblings. We present a family in which a sibling of the index case predicted to have primary hyperoxaluria type 1 by means of linkage analysis failed to show hyperoxaluria during the following 7 years, putting the diagnosis into question. Whole-gene sequence analysis identified 2 causative mutations in the index case, of which only 1, c.646A (Gly216Arg), was inherited. The other sequence change, c.33_34insC, was a de novo mutation occurring on the paternal allele. This particular mutation is a relatively common cause of primary hyperoxaluria type 1. It occurs in a run of 8 cytosines and therefore potentially is susceptible to polymerase slippage. This case illustrates 2 important points. First, biochemical confirmation of a genetic diagnosis should always be made in siblings diagnosed by using genetic tests. Second, de novo mutations should be considered as a potential, albeit rare, cause of primary hyperoxaluria type 1.

Child, Preschool↗
PubMed2005

Nitric oxide and metastatic cell behaviour.

Nitric oxide (NO) is a pleiotropic signalling molecule that subserves a wide variety of basic cellular functions and also manifests itself pathophysiologically. As regards cancer and its progression, however, the reported role of NO appears surprisingly inconsistent. In this review, we focus on metastasis, the process of cancer cell spread and secondary tumour formation. In a 'reductionist' approach, we consider the metastatic cascade to be made up of a series of basic cellular behaviours (such as proliferation, apoptosis, adhesion, secretion migration, invasion and angiogenesis). We evaluate how NO controls such behaviours, in comparison with normal cells. The available information suggests strongly that NO signalling would be expected to regulate these behaviours both positively and negatively and this probably leads to the observed apparent variability in the NO status of cancer cells and tissues. Thus, the role of NO in cancer is more complex than previously thought. A number of suggestions are made, including consideration of novel mechanisms, such as ion channels, in order to achieve a more consistent and integrated understanding of NO signalling in cancer and to realise its clinical potential.

Animals↗
PubMed2003

Molecular analysis of the glyoxylate reductase (GRHPR) gene and description of mutations underlying primary hyperoxaluria type 2.

Primary hyperoxaluria type 2, an inherited autosomal recessive disorder of endogenous oxalate overproduction, is caused by mutations in the GRHPR gene encoding the glyoxylate/hydroxypyruvate reductase enzyme. The GRHPR genes from nineteen unrelated patients with PH2 were analysed for mutations using a combination of PCR-SSCP and sequence analysis of genomic and cDNA. Eleven mutations were identified, seven of which are novel. The mutations included five point mutations: c.84-2A>G, c.295C>T (R99X), c.494G>A (G165D), and c.904C>T (R302C) as well as six minor deletions: c.103delG, c.375delG, c.403_405+2 delAAGT, c.540delT, c.608_609delCT and a more complex mutation in intron 1: c.84-13_c.84-12del; c.84-8_c.84-5del. Aberrant transcripts were demonstrated in hepatic mRNA as a result of the c.403_405+2 delAAGT and c.84-2A>G mutations. In addition, a splice variant lacking 28 bp of exon 1 was expressed in a number of tissues but is of unknown function. Two polymorphisms, c.579A>G in exon 6 and a (CT)(n) microsatellite in intron 8 were identified. Expression studies showed that the G165D and R302C mutants had glyoxylate reductase activity 1.5 and 5.6% respectively of the wild type protein. Both mutant proteins were unstable on purification. Although there is wide expression of the GRHPR mRNA demonstrated by northern blot analysis, our study shows that GRHPR protein distribution is predominantly hepatic and concludes that PH2, like the related type 1 disease, is primarily a disorder affecting hepatic glyoxylate metabolism.

Alcohol Oxidoreductases↗