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Transgenerational inheritance of diet-induced genome rearrangements in Drosophila.

Aldrich JC, Maggert KA - PLoS Genet. (2015)

Bottom Line: Pursuing the relationship between rDNA expression and stability, we have discovered that increased dietary yeast concentration, emulating periods of dietary excess during life, results in somatic rDNA instability and copy number reduction.Modulation of Insulin/TOR signaling produces similar results, indicating a role for known nutrient sensing signaling pathways in this process.Furthermore, adults fed elevated dietary yeast concentrations produce offspring with fewer rDNA copies demonstrating that these effects also occur in the germline, and are transgenerationally heritable.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, College of Science, Texas A&M University, College Station, Texas, United States of America.

ABSTRACT
Ribosomal RNA gene (rDNA) copy number variation modulates heterochromatin formation and influences the expression of a large fraction of the Drosophila genome. This discovery, along with the link between rDNA, aging, and disease, high-lights the importance of understanding how natural rDNA copy number variation arises. Pursuing the relationship between rDNA expression and stability, we have discovered that increased dietary yeast concentration, emulating periods of dietary excess during life, results in somatic rDNA instability and copy number reduction. Modulation of Insulin/TOR signaling produces similar results, indicating a role for known nutrient sensing signaling pathways in this process. Furthermore, adults fed elevated dietary yeast concentrations produce offspring with fewer rDNA copies demonstrating that these effects also occur in the germline, and are transgenerationally heritable. This finding explains one source of natural rDNA copy number variation revealing a clear long-term consequence of diet.

No MeSH data available.


Related in: MedlinePlus

Mutations affecting nutrient signaling perturb nucleolar stability.(A) α-Fibrillarin immunofluorescent detection in salivary gland nuclei from wild-type larvae or (B) larvae expressing a hypermorphic insulin receptor allele (InR.R418P) under the control of Ubi-GAl4. (C) Flies expressing InR.R418P were raised on food tainted with 10 µM rapamycin did not exhibit multiple nucleoli. (D) Flies expressing an antimorphic insulin receptor allele (InR.K1409A) did not have multiple nucleoli. In all images, red shows fibrillarin and blue shows DNA. N = total number of nuclei scored, F = percentage of nuclei with multiple nucleoli.
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pgen.1005148.g003: Mutations affecting nutrient signaling perturb nucleolar stability.(A) α-Fibrillarin immunofluorescent detection in salivary gland nuclei from wild-type larvae or (B) larvae expressing a hypermorphic insulin receptor allele (InR.R418P) under the control of Ubi-GAl4. (C) Flies expressing InR.R418P were raised on food tainted with 10 µM rapamycin did not exhibit multiple nucleoli. (D) Flies expressing an antimorphic insulin receptor allele (InR.K1409A) did not have multiple nucleoli. In all images, red shows fibrillarin and blue shows DNA. N = total number of nuclei scored, F = percentage of nuclei with multiple nucleoli.

Mentions: If instability is a consequence of changes in nutrient availability, then we reasoned that modulating known nutrient signaling pathways should produce similar results. In Drosophila, as in Cænorhabditis elegans, mouse, and human, the insulin/insulin-like growth factor signaling (IIS) and TOR signaling networks mediate many cellular responses to nutrient availability, including ribosome biogenesis and rDNA expression [49, 68, 69]. We expressed a constitutively active form of the insulin receptor (InR.R418P) either generally in larvae (using a Ubiquitin promoter to drive GAL4 expression in all cells) or specifically in salivary glands (using the Sgs3 promoter to drive GAL4 expression in larval salivary glands). Because these cells do not undergo cytokinesis, rDNA removed from the chromosomal rDNA array (e.g., as extrachromosomal circles) would not be measurably lost using real-time PCR, thus we used the formation of supernumerary nucleoli as proxy for rDNA instability [23, 25]. In both cases we observed elevated levels of multiple nucleoli (~41% and 28% respectively) (Fig 3A and 3B), indicating that activating the Insulin Receptor was sufficient to induce instability. Raising flies expressing constitutive InR.R418P on food laced with rapamycin mitigated the effect (Fig 3C), suggesting inhibition of rDNA transcription suppressed the nucleolar instability. Expression of an antimorphic allele (InR.K1409A) had no apparent effect (Fig 3D), indicating that either antimorphic receptor expression levels were insufficient to reduce rDNA expression and affect loss rate, or the basal level of nucleolar instability we observe is independent of IIS-mediated rDNA expression.


Transgenerational inheritance of diet-induced genome rearrangements in Drosophila.

Aldrich JC, Maggert KA - PLoS Genet. (2015)

Mutations affecting nutrient signaling perturb nucleolar stability.(A) α-Fibrillarin immunofluorescent detection in salivary gland nuclei from wild-type larvae or (B) larvae expressing a hypermorphic insulin receptor allele (InR.R418P) under the control of Ubi-GAl4. (C) Flies expressing InR.R418P were raised on food tainted with 10 µM rapamycin did not exhibit multiple nucleoli. (D) Flies expressing an antimorphic insulin receptor allele (InR.K1409A) did not have multiple nucleoli. In all images, red shows fibrillarin and blue shows DNA. N = total number of nuclei scored, F = percentage of nuclei with multiple nucleoli.
© Copyright Policy
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC4401788&req=5

pgen.1005148.g003: Mutations affecting nutrient signaling perturb nucleolar stability.(A) α-Fibrillarin immunofluorescent detection in salivary gland nuclei from wild-type larvae or (B) larvae expressing a hypermorphic insulin receptor allele (InR.R418P) under the control of Ubi-GAl4. (C) Flies expressing InR.R418P were raised on food tainted with 10 µM rapamycin did not exhibit multiple nucleoli. (D) Flies expressing an antimorphic insulin receptor allele (InR.K1409A) did not have multiple nucleoli. In all images, red shows fibrillarin and blue shows DNA. N = total number of nuclei scored, F = percentage of nuclei with multiple nucleoli.
Mentions: If instability is a consequence of changes in nutrient availability, then we reasoned that modulating known nutrient signaling pathways should produce similar results. In Drosophila, as in Cænorhabditis elegans, mouse, and human, the insulin/insulin-like growth factor signaling (IIS) and TOR signaling networks mediate many cellular responses to nutrient availability, including ribosome biogenesis and rDNA expression [49, 68, 69]. We expressed a constitutively active form of the insulin receptor (InR.R418P) either generally in larvae (using a Ubiquitin promoter to drive GAL4 expression in all cells) or specifically in salivary glands (using the Sgs3 promoter to drive GAL4 expression in larval salivary glands). Because these cells do not undergo cytokinesis, rDNA removed from the chromosomal rDNA array (e.g., as extrachromosomal circles) would not be measurably lost using real-time PCR, thus we used the formation of supernumerary nucleoli as proxy for rDNA instability [23, 25]. In both cases we observed elevated levels of multiple nucleoli (~41% and 28% respectively) (Fig 3A and 3B), indicating that activating the Insulin Receptor was sufficient to induce instability. Raising flies expressing constitutive InR.R418P on food laced with rapamycin mitigated the effect (Fig 3C), suggesting inhibition of rDNA transcription suppressed the nucleolar instability. Expression of an antimorphic allele (InR.K1409A) had no apparent effect (Fig 3D), indicating that either antimorphic receptor expression levels were insufficient to reduce rDNA expression and affect loss rate, or the basal level of nucleolar instability we observe is independent of IIS-mediated rDNA expression.

Bottom Line: Pursuing the relationship between rDNA expression and stability, we have discovered that increased dietary yeast concentration, emulating periods of dietary excess during life, results in somatic rDNA instability and copy number reduction.Modulation of Insulin/TOR signaling produces similar results, indicating a role for known nutrient sensing signaling pathways in this process.Furthermore, adults fed elevated dietary yeast concentrations produce offspring with fewer rDNA copies demonstrating that these effects also occur in the germline, and are transgenerationally heritable.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, College of Science, Texas A&M University, College Station, Texas, United States of America.

ABSTRACT
Ribosomal RNA gene (rDNA) copy number variation modulates heterochromatin formation and influences the expression of a large fraction of the Drosophila genome. This discovery, along with the link between rDNA, aging, and disease, high-lights the importance of understanding how natural rDNA copy number variation arises. Pursuing the relationship between rDNA expression and stability, we have discovered that increased dietary yeast concentration, emulating periods of dietary excess during life, results in somatic rDNA instability and copy number reduction. Modulation of Insulin/TOR signaling produces similar results, indicating a role for known nutrient sensing signaling pathways in this process. Furthermore, adults fed elevated dietary yeast concentrations produce offspring with fewer rDNA copies demonstrating that these effects also occur in the germline, and are transgenerationally heritable. This finding explains one source of natural rDNA copy number variation revealing a clear long-term consequence of diet.

No MeSH data available.


Related in: MedlinePlus