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NIAM-deficient mice are predisposed to the development of proliferative lesions including B-cell lymphomas.

Reed SM, Hagen J, Muniz VP, Rosean TR, Borcherding N, Sciegienka S, Goeken JA, Naumann PW, Zhang W, Tompkins VS, Janz S, Meyerholz DK, Quelle DE - PLoS ONE (2014)

Bottom Line: It is a novel activator of the ARF-Mdm2-Tip60-p53 tumor suppressor pathway as well as other undefined pathways important for genome maintenance.Unexpectedly, basal p53 expression and activity was largely unaffected by NIAM loss in isolated splenic B cells.In sum, NIAM down-regulation in vivo results in a significant predisposition to developing benign tumors or early stage cancers.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, University of Iowa, Iowa City, Iowa, United States of America; Medical Scientist Training Program, University of Iowa, Iowa City, Iowa, United States of America.

ABSTRACT
Nuclear Interactor of ARF and Mdm2 (NIAM, gene designation Tbrg1) is a largely unstudied inhibitor of cell proliferation that helps maintain chromosomal stability. It is a novel activator of the ARF-Mdm2-Tip60-p53 tumor suppressor pathway as well as other undefined pathways important for genome maintenance. To examine its predicted role as a tumor suppressor, we generated NIAM mutant (NIAM(m/m)) mice homozygous for a β-galactosidase expressing gene-trap cassette in the endogenous gene. The mutant mice expressed significantly lower levels of NIAM protein in tissues compared to wild-type animals. Fifty percent of aged NIAM deficient mice (14 to 21 months) developed proliferative lesions, including a uterine hemangioma, pulmonary papillary adenoma, and a Harderian gland adenoma. No age-matched wild-type or NIAM(+/m) heterozygous animals developed lesions. In the spleen, NIAM(m/m) mice had prominent white pulp expansion which correlated with enhanced increased reactive lymphoid hyperplasia and evidence of systemic inflammation. Notably, 17% of NIAM mutant mice had splenic white pulp features indicating early B-cell lymphoma. This correlated with selective expansion of marginal zone B cells in the spleens of younger, tumor-free NIAM-deficient mice. Unexpectedly, basal p53 expression and activity was largely unaffected by NIAM loss in isolated splenic B cells. In sum, NIAM down-regulation in vivo results in a significant predisposition to developing benign tumors or early stage cancers. These mice represent an outstanding platform for dissecting NIAM's role in tumorigenesis and various anti-cancer pathways, including p53 signaling.

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Generating and verifying NIAM gene disruption in mice.A. The targeted NIAM gene locus for the conditional-ready mouse knockout model. Cre-recombinase LoxP sites and Flippase targeted FRT sites are shown, as are locations for the PCR primers to detect the endogenous NIAM allele (a+b) or the mutant allele (a+c). Ex, exon. B. PCR amplification of the mutant (mut) allele results in a 380 bp product whereas the 548 bp product reflects the wild-type (WT) NIAM allele. DNA standards are shown in lane 4. C. Number of mice with each genotype (+/+, +/m, m/m) from heterozygous mouse crossings. Chi-square analysis shows a statistically significant difference from the Mendelian distribution of 1∶2∶1.
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pone-0112126-g002: Generating and verifying NIAM gene disruption in mice.A. The targeted NIAM gene locus for the conditional-ready mouse knockout model. Cre-recombinase LoxP sites and Flippase targeted FRT sites are shown, as are locations for the PCR primers to detect the endogenous NIAM allele (a+b) or the mutant allele (a+c). Ex, exon. B. PCR amplification of the mutant (mut) allele results in a 380 bp product whereas the 548 bp product reflects the wild-type (WT) NIAM allele. DNA standards are shown in lane 4. C. Number of mice with each genotype (+/+, +/m, m/m) from heterozygous mouse crossings. Chi-square analysis shows a statistically significant difference from the Mendelian distribution of 1∶2∶1.

Mentions: A NIAM gene targeting construct was inserted between exon 1 (which contains the ATG start site) and exon 2 in C57BL/6N embryonic stem cells by the Knockout Mouse Project (KOMP) (Fig. 2A). The cassette contains a poly (A) adenylation site, a neomycin resistance gene (Neo), and β-galactosidase trap for tracking normal NIAM expression patterns in tissues. It also contains FRT sites for removal of neomycin and β-galactosidase cassettes by flippase, which would restore normal gene function of NIAM. Two intronic LoxP sites enable conditional deletion of exon 2 using Cre-expressing mice should the cassette not lead to sufficient loss of the NIAM gene. This construct is predicted to interfere with splicing or, at minimum, generate a severely truncated chimeric protein containing only 48 N-terminal residues of NIAM.


NIAM-deficient mice are predisposed to the development of proliferative lesions including B-cell lymphomas.

Reed SM, Hagen J, Muniz VP, Rosean TR, Borcherding N, Sciegienka S, Goeken JA, Naumann PW, Zhang W, Tompkins VS, Janz S, Meyerholz DK, Quelle DE - PLoS ONE (2014)

Generating and verifying NIAM gene disruption in mice.A. The targeted NIAM gene locus for the conditional-ready mouse knockout model. Cre-recombinase LoxP sites and Flippase targeted FRT sites are shown, as are locations for the PCR primers to detect the endogenous NIAM allele (a+b) or the mutant allele (a+c). Ex, exon. B. PCR amplification of the mutant (mut) allele results in a 380 bp product whereas the 548 bp product reflects the wild-type (WT) NIAM allele. DNA standards are shown in lane 4. C. Number of mice with each genotype (+/+, +/m, m/m) from heterozygous mouse crossings. Chi-square analysis shows a statistically significant difference from the Mendelian distribution of 1∶2∶1.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231569&req=5

pone-0112126-g002: Generating and verifying NIAM gene disruption in mice.A. The targeted NIAM gene locus for the conditional-ready mouse knockout model. Cre-recombinase LoxP sites and Flippase targeted FRT sites are shown, as are locations for the PCR primers to detect the endogenous NIAM allele (a+b) or the mutant allele (a+c). Ex, exon. B. PCR amplification of the mutant (mut) allele results in a 380 bp product whereas the 548 bp product reflects the wild-type (WT) NIAM allele. DNA standards are shown in lane 4. C. Number of mice with each genotype (+/+, +/m, m/m) from heterozygous mouse crossings. Chi-square analysis shows a statistically significant difference from the Mendelian distribution of 1∶2∶1.
Mentions: A NIAM gene targeting construct was inserted between exon 1 (which contains the ATG start site) and exon 2 in C57BL/6N embryonic stem cells by the Knockout Mouse Project (KOMP) (Fig. 2A). The cassette contains a poly (A) adenylation site, a neomycin resistance gene (Neo), and β-galactosidase trap for tracking normal NIAM expression patterns in tissues. It also contains FRT sites for removal of neomycin and β-galactosidase cassettes by flippase, which would restore normal gene function of NIAM. Two intronic LoxP sites enable conditional deletion of exon 2 using Cre-expressing mice should the cassette not lead to sufficient loss of the NIAM gene. This construct is predicted to interfere with splicing or, at minimum, generate a severely truncated chimeric protein containing only 48 N-terminal residues of NIAM.

Bottom Line: It is a novel activator of the ARF-Mdm2-Tip60-p53 tumor suppressor pathway as well as other undefined pathways important for genome maintenance.Unexpectedly, basal p53 expression and activity was largely unaffected by NIAM loss in isolated splenic B cells.In sum, NIAM down-regulation in vivo results in a significant predisposition to developing benign tumors or early stage cancers.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, University of Iowa, Iowa City, Iowa, United States of America; Medical Scientist Training Program, University of Iowa, Iowa City, Iowa, United States of America.

ABSTRACT
Nuclear Interactor of ARF and Mdm2 (NIAM, gene designation Tbrg1) is a largely unstudied inhibitor of cell proliferation that helps maintain chromosomal stability. It is a novel activator of the ARF-Mdm2-Tip60-p53 tumor suppressor pathway as well as other undefined pathways important for genome maintenance. To examine its predicted role as a tumor suppressor, we generated NIAM mutant (NIAM(m/m)) mice homozygous for a β-galactosidase expressing gene-trap cassette in the endogenous gene. The mutant mice expressed significantly lower levels of NIAM protein in tissues compared to wild-type animals. Fifty percent of aged NIAM deficient mice (14 to 21 months) developed proliferative lesions, including a uterine hemangioma, pulmonary papillary adenoma, and a Harderian gland adenoma. No age-matched wild-type or NIAM(+/m) heterozygous animals developed lesions. In the spleen, NIAM(m/m) mice had prominent white pulp expansion which correlated with enhanced increased reactive lymphoid hyperplasia and evidence of systemic inflammation. Notably, 17% of NIAM mutant mice had splenic white pulp features indicating early B-cell lymphoma. This correlated with selective expansion of marginal zone B cells in the spleens of younger, tumor-free NIAM-deficient mice. Unexpectedly, basal p53 expression and activity was largely unaffected by NIAM loss in isolated splenic B cells. In sum, NIAM down-regulation in vivo results in a significant predisposition to developing benign tumors or early stage cancers. These mice represent an outstanding platform for dissecting NIAM's role in tumorigenesis and various anti-cancer pathways, including p53 signaling.

Show MeSH
Related in: MedlinePlus