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Toxoplasma gondii infection specifically increases the levels of key host microRNAs.

Zeiner GM, Norman KL, Thomson JM, Hammond SM, Boothroyd JC - PLoS ONE (2010)

Bottom Line: We show that both the primary transcripts for miR-17 approximately 92 and miR-106b approximately 25 and the pivotal miRNAs that are derived from miR-17 approximately 92 display increased abundance in Toxoplasma-infected primary human cells; a Toxoplasma-dependent up-regulation of the miR-17 approximately 92 promoter is at least partly responsible for this increase.Altered levels of miR-17 approximately 92 and miR-106b approximately 25 are known to play crucial roles in mammalian cell regulation and have been implicated in numerous hyperproliferative diseases although the mechanisms driving their altered expression are unknown.Hence, in addition to the implications of these findings on the host-pathogen interaction, Toxoplasma may represent a powerful probe for understanding the normal mechanisms that regulate the levels of key host miRNAs.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America.

ABSTRACT

Background: The apicomplexan parasite Toxoplasma gondii can infect and replicate in virtually any nucleated cell in many species of warm-blooded animals; thus, it has evolved the ability to exploit well-conserved biological processes common to its diverse hosts. Here we have investigated whether Toxoplasma modulates the levels of host microRNAs (miRNAs) during infection.

Methodology/principal findings: Using microarray profiling and a combination of conventional molecular approaches we report that Toxoplasma specifically modulates the expression of important host microRNAs during infection. We show that both the primary transcripts for miR-17 approximately 92 and miR-106b approximately 25 and the pivotal miRNAs that are derived from miR-17 approximately 92 display increased abundance in Toxoplasma-infected primary human cells; a Toxoplasma-dependent up-regulation of the miR-17 approximately 92 promoter is at least partly responsible for this increase. The abundance of mature miR-17 family members, which are derived from these two miRNA clusters, remains unchanged in host cells infected with the closely related apicomplexan Neospora caninum; thus, the Toxoplasma-induced increase in their abundance is a highly directed process rather than a general host response to infection.

Conclusions/significance: Altered levels of miR-17 approximately 92 and miR-106b approximately 25 are known to play crucial roles in mammalian cell regulation and have been implicated in numerous hyperproliferative diseases although the mechanisms driving their altered expression are unknown. Hence, in addition to the implications of these findings on the host-pathogen interaction, Toxoplasma may represent a powerful probe for understanding the normal mechanisms that regulate the levels of key host miRNAs.

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Related in: MedlinePlus

MiRNA microarray profiling reveals that Toxoplasma infection increases the levels of miR-17-, miR-18- and miR-19-family members.(A) Sequence alignment of miR-17 family members. The 6-nucleotide seed region that defines the miR-17 family is indicated in yellow. Nucleotide differences from the miR-17 sequence are shown in boldface blue type. (B) Genomic organization of the miR-17∼92, miR-106b∼25 and miR-106a∼363 clusters. Colors of each miRNA indicate the miRNA family to which each belongs; miR-17 = yellow; miR-18 = green; miR-19 = blue; miR-25 = red. miR-17∼92 and miR-106b∼25 are encoded in the 3rd intron of C13ORF25 and the 13th intron of MCM7, respectively; for these genes, exons are indicated as boxes, and introns are lines. (C) Microarray profiling of host miRNAs during Toxoplasma infection. From left to right, columns are from individual microarrays hybridized with RNA extracted from uninfected HFFs at 6, 12 or 24 hours and with RNA samples derived from HFFs infected with Toxoplasma at 6, 12 or 24 hours. The data were normalized with the default settings in the Stanford Microarray Database software package. The scale of the heat-map is presented as fold-change from the median value. The rows are the averaged data from all probes that are predicted to hybridize to members of the indicated miRNA families; these families represent all miRNAs encoded by the miR-17∼92, miR-106a∼363 and miR-106b∼25 clusters. Shown for comparison is miR-21 which is a highly expressed miRNA in HFFs and is derived from an independent intergenic locus.
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pone-0008742-g001: MiRNA microarray profiling reveals that Toxoplasma infection increases the levels of miR-17-, miR-18- and miR-19-family members.(A) Sequence alignment of miR-17 family members. The 6-nucleotide seed region that defines the miR-17 family is indicated in yellow. Nucleotide differences from the miR-17 sequence are shown in boldface blue type. (B) Genomic organization of the miR-17∼92, miR-106b∼25 and miR-106a∼363 clusters. Colors of each miRNA indicate the miRNA family to which each belongs; miR-17 = yellow; miR-18 = green; miR-19 = blue; miR-25 = red. miR-17∼92 and miR-106b∼25 are encoded in the 3rd intron of C13ORF25 and the 13th intron of MCM7, respectively; for these genes, exons are indicated as boxes, and introns are lines. (C) Microarray profiling of host miRNAs during Toxoplasma infection. From left to right, columns are from individual microarrays hybridized with RNA extracted from uninfected HFFs at 6, 12 or 24 hours and with RNA samples derived from HFFs infected with Toxoplasma at 6, 12 or 24 hours. The data were normalized with the default settings in the Stanford Microarray Database software package. The scale of the heat-map is presented as fold-change from the median value. The rows are the averaged data from all probes that are predicted to hybridize to members of the indicated miRNA families; these families represent all miRNAs encoded by the miR-17∼92, miR-106a∼363 and miR-106b∼25 clusters. Shown for comparison is miR-21 which is a highly expressed miRNA in HFFs and is derived from an independent intergenic locus.

Mentions: Although miRNAs were first identified due to their regulatory roles in sculpting metazoan development [21], [22], miRNA dysregulation also plays a central role in cancer and infection [20], [23]-[28]. The dysregulation of several miRNAs have been experimentally demonstrated to promote oncogenesis [20], [28]. Examples relevant to the present work are four families of miRNAs (miR-17, miR-18, miR-19 and miR-25) that are encoded by three paralogous loci; these related loci, which are miR-17∼92, miR-106b∼25 and miR-106a∼363 (see Figure 1B), produce primary transcripts that are post-transcriptionally processed to yield mature miR-17, miR-18, miR-19 and miR-25 family members. MiR-17∼92 is also known by the synonym OncomiR-1 due to the observed acceleration of lymphomagenesis when these miRNAs are over-expressed in Eµ-Myc mice [29].


Toxoplasma gondii infection specifically increases the levels of key host microRNAs.

Zeiner GM, Norman KL, Thomson JM, Hammond SM, Boothroyd JC - PLoS ONE (2010)

MiRNA microarray profiling reveals that Toxoplasma infection increases the levels of miR-17-, miR-18- and miR-19-family members.(A) Sequence alignment of miR-17 family members. The 6-nucleotide seed region that defines the miR-17 family is indicated in yellow. Nucleotide differences from the miR-17 sequence are shown in boldface blue type. (B) Genomic organization of the miR-17∼92, miR-106b∼25 and miR-106a∼363 clusters. Colors of each miRNA indicate the miRNA family to which each belongs; miR-17 = yellow; miR-18 = green; miR-19 = blue; miR-25 = red. miR-17∼92 and miR-106b∼25 are encoded in the 3rd intron of C13ORF25 and the 13th intron of MCM7, respectively; for these genes, exons are indicated as boxes, and introns are lines. (C) Microarray profiling of host miRNAs during Toxoplasma infection. From left to right, columns are from individual microarrays hybridized with RNA extracted from uninfected HFFs at 6, 12 or 24 hours and with RNA samples derived from HFFs infected with Toxoplasma at 6, 12 or 24 hours. The data were normalized with the default settings in the Stanford Microarray Database software package. The scale of the heat-map is presented as fold-change from the median value. The rows are the averaged data from all probes that are predicted to hybridize to members of the indicated miRNA families; these families represent all miRNAs encoded by the miR-17∼92, miR-106a∼363 and miR-106b∼25 clusters. Shown for comparison is miR-21 which is a highly expressed miRNA in HFFs and is derived from an independent intergenic locus.
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getmorefigures.php?uid=PMC2806928&req=5

pone-0008742-g001: MiRNA microarray profiling reveals that Toxoplasma infection increases the levels of miR-17-, miR-18- and miR-19-family members.(A) Sequence alignment of miR-17 family members. The 6-nucleotide seed region that defines the miR-17 family is indicated in yellow. Nucleotide differences from the miR-17 sequence are shown in boldface blue type. (B) Genomic organization of the miR-17∼92, miR-106b∼25 and miR-106a∼363 clusters. Colors of each miRNA indicate the miRNA family to which each belongs; miR-17 = yellow; miR-18 = green; miR-19 = blue; miR-25 = red. miR-17∼92 and miR-106b∼25 are encoded in the 3rd intron of C13ORF25 and the 13th intron of MCM7, respectively; for these genes, exons are indicated as boxes, and introns are lines. (C) Microarray profiling of host miRNAs during Toxoplasma infection. From left to right, columns are from individual microarrays hybridized with RNA extracted from uninfected HFFs at 6, 12 or 24 hours and with RNA samples derived from HFFs infected with Toxoplasma at 6, 12 or 24 hours. The data were normalized with the default settings in the Stanford Microarray Database software package. The scale of the heat-map is presented as fold-change from the median value. The rows are the averaged data from all probes that are predicted to hybridize to members of the indicated miRNA families; these families represent all miRNAs encoded by the miR-17∼92, miR-106a∼363 and miR-106b∼25 clusters. Shown for comparison is miR-21 which is a highly expressed miRNA in HFFs and is derived from an independent intergenic locus.
Mentions: Although miRNAs were first identified due to their regulatory roles in sculpting metazoan development [21], [22], miRNA dysregulation also plays a central role in cancer and infection [20], [23]-[28]. The dysregulation of several miRNAs have been experimentally demonstrated to promote oncogenesis [20], [28]. Examples relevant to the present work are four families of miRNAs (miR-17, miR-18, miR-19 and miR-25) that are encoded by three paralogous loci; these related loci, which are miR-17∼92, miR-106b∼25 and miR-106a∼363 (see Figure 1B), produce primary transcripts that are post-transcriptionally processed to yield mature miR-17, miR-18, miR-19 and miR-25 family members. MiR-17∼92 is also known by the synonym OncomiR-1 due to the observed acceleration of lymphomagenesis when these miRNAs are over-expressed in Eµ-Myc mice [29].

Bottom Line: We show that both the primary transcripts for miR-17 approximately 92 and miR-106b approximately 25 and the pivotal miRNAs that are derived from miR-17 approximately 92 display increased abundance in Toxoplasma-infected primary human cells; a Toxoplasma-dependent up-regulation of the miR-17 approximately 92 promoter is at least partly responsible for this increase.Altered levels of miR-17 approximately 92 and miR-106b approximately 25 are known to play crucial roles in mammalian cell regulation and have been implicated in numerous hyperproliferative diseases although the mechanisms driving their altered expression are unknown.Hence, in addition to the implications of these findings on the host-pathogen interaction, Toxoplasma may represent a powerful probe for understanding the normal mechanisms that regulate the levels of key host miRNAs.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America.

ABSTRACT

Background: The apicomplexan parasite Toxoplasma gondii can infect and replicate in virtually any nucleated cell in many species of warm-blooded animals; thus, it has evolved the ability to exploit well-conserved biological processes common to its diverse hosts. Here we have investigated whether Toxoplasma modulates the levels of host microRNAs (miRNAs) during infection.

Methodology/principal findings: Using microarray profiling and a combination of conventional molecular approaches we report that Toxoplasma specifically modulates the expression of important host microRNAs during infection. We show that both the primary transcripts for miR-17 approximately 92 and miR-106b approximately 25 and the pivotal miRNAs that are derived from miR-17 approximately 92 display increased abundance in Toxoplasma-infected primary human cells; a Toxoplasma-dependent up-regulation of the miR-17 approximately 92 promoter is at least partly responsible for this increase. The abundance of mature miR-17 family members, which are derived from these two miRNA clusters, remains unchanged in host cells infected with the closely related apicomplexan Neospora caninum; thus, the Toxoplasma-induced increase in their abundance is a highly directed process rather than a general host response to infection.

Conclusions/significance: Altered levels of miR-17 approximately 92 and miR-106b approximately 25 are known to play crucial roles in mammalian cell regulation and have been implicated in numerous hyperproliferative diseases although the mechanisms driving their altered expression are unknown. Hence, in addition to the implications of these findings on the host-pathogen interaction, Toxoplasma may represent a powerful probe for understanding the normal mechanisms that regulate the levels of key host miRNAs.

Show MeSH
Related in: MedlinePlus