Production and characterization of murine models of classic and intermediate maple syrup urine disease

Homanics, Gregg E.; Skvorak, Kristen J.; Ferguson, Carolyn; Watkins, Simon C.; Paul, Harbhajan S.

doi:10.1186/1471-2350-7-33

Cited by 45 publications

(69 citation statements)

References 40 publications

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“…Our data clearly demonstrate that loss of PP2Cm leads to a metabolic and phenotypic abnormality characteristic of intermittent or intermediate types of human MSUD. Homanics et al (35) have generated an MSUD model by genetic targeting of the E2 subunit of BCKD; these mice have severe postnatal developmental problems unless they are rescued by hepatic-specific expression of the human E2 subunit, thus representing a model of the "classic" types of MSUD. In contrast, the PP2Cm -/-mice, reported herein, thrive well under normal conditions, exhibiting no overt developmental issues.…”

Section: Figurementioning

confidence: 99%

Protein phosphatase 2Cm is a critical regulator of branched-chain amino acid catabolism in mice and cultured cells

Lü

Sun²,

She³

et al. 2009

J. Clin. Invest.

184

192

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The branched-chain amino acids (BCAA) are essential amino acids required for protein homeostasis, energy balance, and nutrient signaling. In individuals with deficiencies in BCAA, these amino acids can be preserved through inhibition of the branched-chain-α-ketoacid dehydrogenase (BCKD) complex, the rate-limiting step in their metabolism. BCKD is inhibited by phosphorylation of its E1α subunit at Ser293, which is catalyzed by BCKD kinase. During BCAA excess, phosphorylated Ser293 (pSer293) becomes dephosphorylated through the concerted inhibition of BCKD kinase and the activity of an unknown intramitochondrial phosphatase. Using unbiased, proteomic approaches, we have found that a mitochondrial-targeted phosphatase, PP2Cm, specifically binds the BCKD complex and induces dephosphorylation of Ser293 in the presence of BCKD substrates. Loss of PP2Cm completely abolished substrate-induced E1α dephosphorylation both in vitro and in vivo. PP2Cm-deficient mice exhibited BCAA catabolic defects and a metabolic phenotype similar to the intermittent or intermediate types of human maple syrup urine disease (MSUD), a hereditary disorder caused by defects in BCKD activity. These results indicate that PP2Cm is the endogenous BCKD phosphatase required for nutrient-mediated regulation of BCKD activity and suggest that defects in PP2Cm may be responsible for a subset of human MSUD.

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Section: Figurementioning

confidence: 99%

Protein phosphatase 2Cm is a critical regulator of branched-chain amino acid catabolism in mice and cultured cells

Lü

Sun²,

She³

et al. 2009

J. Clin. Invest.

184

192

View full text Add to dashboard Cite

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“…To overcome this problem, selected target genes can be humanized, that is, the mouse gene can be eliminated and replaced by the corresponding human orthologous gene sequence. Because of the difficulties of using conventional KO technologies to directly replace large mouse genes with their large human genomic counterparts, genetic humanization is currently most often accomplished by the so-called "KO-plus-transgenic humanization" strategy that involves crossing a KO of the mouse gene with a randomly integrated transgenic of the human gene (2)(3)(4)(5). The conceptually more straightforward direct homologous replacement, in which a mouse gene is directly replaced by its human counterpart at the same genetic location ("in situ humanization"), is rarely attempted because of technological difficulties.…”

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confidence: 99%

Precise and in situ genetic humanization of 6 Mb of mouse immunoglobulin genes

Macdonald

Karow

Stevens

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

303

273

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Genetic humanization, which involves replacing mouse genes with their human counterparts, can create powerful animal models for the study of human genes and diseases. One important example of genetic humanization involves mice humanized for their Ig genes, allowing for human antibody responses within a mouse background (HumAb mice) and also providing a valuable platform for the generation of fully human antibodies as therapeutics. However, existing HumAb mice do not have fully functional immune systems, perhaps because of the manner in which they were genetically humanized. Heretofore, most genetic humanizations have involved disruption of the endogenous mouse gene with simultaneous introduction of a human transgene at a new and random location (so-called KO-plus-transgenic humanization). More recent efforts have attempted to replace mouse genes with their human counterparts at the same genetic location (in situ humanization), but such efforts involved laborious procedures and were limited in size and precision. We describe a general and efficient method for very large, in situ, and precise genetic humanization using large compound bacterial artificial chromosome-based targeting vectors introduced into mouse ES cells. We applied this method to genetically humanize 3-Mb segments of both the mouse heavy and κ light chain Ig loci, by far the largest genetic humanizations ever described. This paper provides a detailed description of our genetic humanization approach, and the companion paper reports that the humoral immune systems of mice bearing these genetically humanized loci function as efficiently as those of WT mice.genome engineering | therapeutic antibody | immunoglobulin locus T he laboratory mouse is one of the premier model organisms used by biologists. As a mammal, the mouse is more genetically similar to humans and thus more relevant to human physiology and disease than many other model organisms. Its small size, short generation time, and the availability of a large variety of inbred strains have led to a robust body of classical genetic research on the mouse. The utility of mice as a genetic model is also greatly enhanced by powerful transgenic and knockout technologies, allowing researchers to study the effects of the directed overexpression or deletion of specific genes. However, despite all of its advantages, the mouse remains an imperfect model of human disease and an imperfect platform on which to test potential human therapeutics. One issue is that, although about 99% of human genes have a mouse homolog (1), potential therapeutic agents often do not cross-react, or cross-react only poorly, with the mouse ortholog of the intended human target. To overcome this problem, selected target genes can be humanized, that is, the mouse gene can be eliminated and replaced by the corresponding human orthologous gene sequence. Because of the difficulties of using conventional KO technologies to directly replace large mouse genes with their large human genomic counterparts, genetic humanization is currently mo...

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“…Recently, mice modified in genes pertinent to leucine metabolism were generated by knockout of the gene for the E2 subunit of BCKDH [34] or for BCKDH kinase [35]. These transgenic animals can serve as models for maple syrup urine disease.…”

Section: Branched-chain A-keto Acid Dehydrogenasementioning

confidence: 99%

Metabolic and Regulatory Roles of Leucine in Neural Cells

Murín

Hamprecht

2007

Neurochem Res

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Dietary leucine transported into the brain parenchyma serves several functions. Most prominent is the role of leucine as a metabolic precursor of fuel molecules, alpha-ketoisocaproate and ketone bodies. As alternatives to glucose, these compounds are forwarded by the producing astrocytes to the adjacent neural cells. Leucine furthermore participates in the maintenance of the nitrogen balance in the glutamate/glutamine cycle pertinent to the neurotransmitter glutamate. Leucine also serves as a regulator of the activity of some enzymes important for brain energy metabolism. Another role of leucine as an informational molecule is in mTOR signaling that participates in the regulation of food ingestion. The importance of leucine for brain function is stressed by the fact that inborn errors in its metabolism cause metabolic diseases often associated with neuropathological symptoms. In this overview, the current knowledge on the metabolic and regulatory roles of this essential amino acid in neural cells are briefly summarized.

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Production and characterization of murine models of classic and intermediate maple syrup urine disease

Cited by 45 publications

References 40 publications

Protein phosphatase 2Cm is a critical regulator of branched-chain amino acid catabolism in mice and cultured cells

Protein phosphatase 2Cm is a critical regulator of branched-chain amino acid catabolism in mice and cultured cells

Precise and in situ genetic humanization of 6 Mb of mouse immunoglobulin genes

Metabolic and Regulatory Roles of Leucine in Neural Cells

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