The Mouse Transketolase (TKT) Gene: Cloning, Characterization, and Functional Promoter Analysis

Salamon, Csaba; Chervenak, Matthew; Piatigorsky, Joram; Sax, Christina M.

doi:10.1006/geno.1997.5187

Cited by 19 publications

(14 citation statements)

References 62 publications

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“…Finally, our results are consistent with mouse TKT being encoded in a single-copy gene (24) expressed at a threshold level for normal homeostasis. Similarly, a small decrease in TKT activity in tobacco results in decreased ribulose-1,5-diphosphate, photosynthesis, sugars, aromatic amino acids, phenylpropenoid metabolism, chlorophyll, and carotene (8).…”

Section: Discussionsupporting

confidence: 79%

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Transketolase Haploinsufficiency Reduces Adipose Tissue and Female Fertility in Mice

Zhengping

Wawrousek

Piatigorsky

2002

Molecular and Cellular Biology

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Transketolase (TKT) is a ubiquitous enzyme used in multiple metabolic pathways. We show here by gene targeting that TKT-null mouse embryos are not viable and that disruption of one TKT allele can cause growth retardation (Ϸ35%) and preferential reduction of adipose tissue (Ϸ77%). Other TKT ؉/؊ tissues had moderate (Ϸ33%; liver, gonads) or relatively little (Ϸ7 to 18%; eye, kidney, heart, brain) reductions in mass. These mice expressed a normal level of growth hormone and reduced leptin levels. No phenotype was observed in the TKT ؉/؊ cornea, where TKT is especially abundant in wild-type mice. The small female TKT ؉/؊ mice mated infrequently and had few progeny (with a male/female ratio of 1.4:1) when pregnant. Thus, TKT in normal mice appears to be carefully balanced at a threshold level for well-being. Our data suggest that TKT deficiency may have clinical significance in humans and raise the possibility that obesity may be treated by partial inhibition of TKT in adipose tissue.Transketolase (EC 2.2.1.1) (TKT) is a thiamine diphosphate-dependent enzyme linking the nonoxidative branch of the pentose phosphate pathway (PPP) to the glycolytic pathway. The PPP generates sugar phosphates for intermediary biosynthesis and nucleic acid synthesis and NADPH for reductive biosynthesis (26,31). Fatty acid biosynthesis and steroid biosynthesis utilize large amounts of NADPH. TKT is expressed in most tissues throughout the animal and plant kingdoms (27). It is prevalent in proliferating tumor cells, and its repression can inhibit tumor cell growth (2).Our interest in TKT was stimulated by its abundance in the cornea of mice (25) and rabbits (9). In mice, TKT comprises approximately 10% (25) and aldehyde dehydrogenase class 3 (ALDH3) comprises approximately 40% (4, 16) of the watersoluble protein of the corneal epithelial cells. By analogy with the use of enzymes as lens crystallins, we have speculated that the abundant metabolic enzymes in the cornea may serve a structural as well as metabolic role (4,21,22).In the present investigation we disrupted the TKT gene by homologous recombination to test whether corneal clarity is dependent on the concentration of this enzyme. We were only able to obtain viable TKT ϩ/Ϫ mice. While their corneas appeared normal, the TKT haploinsufficient mice were often smaller and the small females were relatively infertile. The sizes of the organs were differentially affected, with adipose tissue being markedly reduced in the TKT ϩ/Ϫ mice. It thus appears that in mice, as found earlier in plants (8), a reduction in TKT leads to multiple phenotypes and metabolic disturbances. Moreover, our results suggest that TKT haploinsufficiency or a reduction in TKT activity may have clinical implications in humans. MATERIALS AND METHODS Generation and mating of TKT؉/؊ mice. A 12.5-kb genomic clone containing the mouse TKT gene was isolated from a 129Sv library (Stratagene, La Jolla, Calif.). The targeting construct was created by replacing a 2.8-kb BamHI-BamHI fragment (24) with a 1.6-kb PGK/neo cassette for...

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Section: Discussionsupporting

confidence: 79%

“…We replaced part of intron 2 and exon 3 of the mouse TKT gene (24) with the neomycin resistance gene cassette (neo) in ES cells (Fig. 1A), made chimeric mice, and verified the recombination event in F 1 progeny by Southern blot analysis of genomic DNA (Fig.…”

Section: Creation and Mating Of Tktmentioning

confidence: 99%

Transketolase Haploinsufficiency Reduces Adipose Tissue and Female Fertility in Mice

Zhengping

Wawrousek

Piatigorsky

2002

Molecular and Cellular Biology

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“…Thus the observed up-regulation of cysD and sseA could be due to a starvation-type response resulting from the limited availability of sulphur within the macrophage environment. The tkt gene (clone 1) is upregulated in the mouse cornea upon exposure to oxidative stress such as the presence of hydrogen peroxide (Salamon et al, 1998) and thus up-regulation of the M. tuberculosis homologue could be due to the stress response encountered by the bacterium during residence within the macrophage. Furthermore, the tkt gene product has the ability to compensate for the loss of superoxide dismutase in Saccharomyces cerevisiae (Slekar et al, 1996), a protein which appears to play an important role in the cell's defence against toxic oxygen metabolites generated by phagocytic cells in an attempt to eliminate pathogenic invaders (Miller & Britigan, 1997).…”

Section: Discussionmentioning

confidence: 99%

Use of fluorescence induction and sucrose counterselection to identify Mycobacterium tuberculosis genes expressed within host cells

Triccas¹,

Berthet²,

Pelicic³

et al. 1999

Microbiology

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“…ALDH3 expression is very low in the limbal stem cells of the cornea as well as in other tissues of the mouse (slight expression in stomach and other tissues). By contrast, TKT is expressed highly in the limbal stem cells and in the central corneal epithelial cells, and is present at typical enzymatic levels in many other tissues (28)(29)(30).…”

Section: Abundant Proteins In Corneal Epithelial Cells Of Vertebratesmentioning

confidence: 84%

Review: A Case for Corneal Crystallins

Piatigorsky

2000

Journal of Ocular Pharmacology and Therapeutics

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It is established that the diverse, multifunctional crystallins are responsible for the optical properties of the cellular, transparent lens of the complex eyes of vertebrates and invertebrates. Lens crystallins often differ among species and may be enzymes or stress proteins. I present here the idea that abundant water-soluble enzymes and other proteins may also be used for cellular transparency in the epithelial cells and, possibly, stromal keratocytes of the cornea. Aldehyde dehydrogenases and transketolase are among the putative "corneal crystallins" in mammals, and gelsolin may be a corneal crystallin in the zebrafish. In invertebrates, the glutathione S-transferase-related S-crystallins of the lens appear to be used also as corneal crystallins in the squid, and an aldehyde dehydrogenase-related protein is the crystallin in the lens and, possibly, cornea of the scallop. The use of abundant, taxon-specific water-soluble proteins as crystallins for cellular transparency in the cornea would provide a new conceptual link between this tissue and the lens.

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The Mouse Transketolase (TKT) Gene: Cloning, Characterization, and Functional Promoter Analysis

Cited by 19 publications

References 62 publications

Transketolase Haploinsufficiency Reduces Adipose Tissue and Female Fertility in Mice

Transketolase Haploinsufficiency Reduces Adipose Tissue and Female Fertility in Mice

Use of fluorescence induction and sucrose counterselection to identify Mycobacterium tuberculosis genes expressed within host cells

Review: A Case for Corneal Crystallins

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