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Altering a histone H3K4 methylation pathway in glomerular podocytes promotes a chronic disease phenotype.

Lefevre GM, Patel SR, Kim D, Tessarollo L, Dressler GR - PLoS Genet. (2010)

Bottom Line: Loss of PTIP resulted in subtle changes in gene expression patterns prior to the onset of a renal disease phenotype.Chromatin immunoprecipitation showed a loss of PTIP binding and lower H3K4 methylation at the Ntrk3 (neurotrophic tyrosine kinase receptor, type 3) locus, whose expression was significantly reduced and whose function may be essential for podocyte foot process patterning.These data demonstrate that alterations or mutations in an epigenetic regulatory pathway can alter the phenotypes of differentiated cells and lead to a chronic disease state.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, University of Michigan, Ann Arbor, Michigan, United States of America.

ABSTRACT
Methylation of specific lysine residues in core histone proteins is essential for embryonic development and can impart active and inactive epigenetic marks on chromatin domains. The ubiquitous nuclear protein PTIP is encoded by the Paxip1 gene and is an essential component of a histone H3 lysine 4 (H3K4) methyltransferase complex conserved in metazoans. In order to determine if PTIP and its associated complexes are necessary for maintaining stable gene expression patterns in a terminally differentiated, non-dividing cell, we conditionally deleted PTIP in glomerular podocytes in mice. Renal development and function were not impaired in young mice. However, older animals progressively exhibited proteinuria and podocyte ultra structural defects similar to chronic glomerular disease. Loss of PTIP resulted in subtle changes in gene expression patterns prior to the onset of a renal disease phenotype. Chromatin immunoprecipitation showed a loss of PTIP binding and lower H3K4 methylation at the Ntrk3 (neurotrophic tyrosine kinase receptor, type 3) locus, whose expression was significantly reduced and whose function may be essential for podocyte foot process patterning. These data demonstrate that alterations or mutations in an epigenetic regulatory pathway can alter the phenotypes of differentiated cells and lead to a chronic disease state.

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Related in: MedlinePlus

Podocyte Viability and Glomerular Morphology.A) After immunostaining with WT1 and Nephrin antibodies, podocyte nuclei were counted in mid-cross sections through glomeruli whose vascular and proximal tubular poles were visible. Glomerular surface area for mid-cross sections was measured by morphometry and is expressed in relative units. B) Immunostaining for WT1 (pink) and Nephrin (green) at 3 months of age shows little significant difference between PTIP+ and PTIP− glomeruli. However, Podocin staining (green, lower panels) appears less and discontinuous in PTIP− glomeruli. Nuclei were counterstained with DAPI. By 12 months, large regions cleared of Nephrin positive staining were evident within the glomerular tufts of PTIP− animals.
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pgen-1001142-g003: Podocyte Viability and Glomerular Morphology.A) After immunostaining with WT1 and Nephrin antibodies, podocyte nuclei were counted in mid-cross sections through glomeruli whose vascular and proximal tubular poles were visible. Glomerular surface area for mid-cross sections was measured by morphometry and is expressed in relative units. B) Immunostaining for WT1 (pink) and Nephrin (green) at 3 months of age shows little significant difference between PTIP+ and PTIP− glomeruli. However, Podocin staining (green, lower panels) appears less and discontinuous in PTIP− glomeruli. Nuclei were counterstained with DAPI. By 12 months, large regions cleared of Nephrin positive staining were evident within the glomerular tufts of PTIP− animals.

Mentions: Glomerular pathology and increased albuminuria can be the direct result of podocyte death [29]. Thus, we used a variety of markers to characterize the glomerular architecture and the numbers of podocyte cells at various ages to insure that the phenotype of the PTIP− mice was not just the result of early podocyte cell death. Immunostaining with WT1, Nephrin, and Podocin antibodies enabled us to determine the podocyte numbers, as average per mid-cross section, and to indirectly assess the integrity of the slit diaphragm (Figure 3). The number of WT1 positive podocytes was not significantly different between PTIP+ and PTIP− glomeruli at 1 or 3 months of age. At 6 months, PTIP− glomeruli had slightly fewer podocytes and by 12 months, the number of podocytes was half that of the PTIP+ littermates. Immunostainings for podocyte markers such as WT1, Nephrin, and Podocin did not reveal dramatic differences at 1 or 3 months, despite the increase in proteinuria, although some discontinuous staining could be seen with Podocin antibodies in PTIP− glomeruli (Figure 3B). Consistent with this data, TUNEL staining for apoptosis did not reveal differences between PTIP+ and PTIP− kidneys at 1 or 3 months of age (data not shown). Thus, the breakdown of the filtration barrier was not due to simple podocyte depletion at these early times. However by 12 months of age, the extensive network of Nephrin staining was partially depleted in PTIP− glomeruli (Figure 3B).


Altering a histone H3K4 methylation pathway in glomerular podocytes promotes a chronic disease phenotype.

Lefevre GM, Patel SR, Kim D, Tessarollo L, Dressler GR - PLoS Genet. (2010)

Podocyte Viability and Glomerular Morphology.A) After immunostaining with WT1 and Nephrin antibodies, podocyte nuclei were counted in mid-cross sections through glomeruli whose vascular and proximal tubular poles were visible. Glomerular surface area for mid-cross sections was measured by morphometry and is expressed in relative units. B) Immunostaining for WT1 (pink) and Nephrin (green) at 3 months of age shows little significant difference between PTIP+ and PTIP− glomeruli. However, Podocin staining (green, lower panels) appears less and discontinuous in PTIP− glomeruli. Nuclei were counterstained with DAPI. By 12 months, large regions cleared of Nephrin positive staining were evident within the glomerular tufts of PTIP− animals.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2965754&req=5

pgen-1001142-g003: Podocyte Viability and Glomerular Morphology.A) After immunostaining with WT1 and Nephrin antibodies, podocyte nuclei were counted in mid-cross sections through glomeruli whose vascular and proximal tubular poles were visible. Glomerular surface area for mid-cross sections was measured by morphometry and is expressed in relative units. B) Immunostaining for WT1 (pink) and Nephrin (green) at 3 months of age shows little significant difference between PTIP+ and PTIP− glomeruli. However, Podocin staining (green, lower panels) appears less and discontinuous in PTIP− glomeruli. Nuclei were counterstained with DAPI. By 12 months, large regions cleared of Nephrin positive staining were evident within the glomerular tufts of PTIP− animals.
Mentions: Glomerular pathology and increased albuminuria can be the direct result of podocyte death [29]. Thus, we used a variety of markers to characterize the glomerular architecture and the numbers of podocyte cells at various ages to insure that the phenotype of the PTIP− mice was not just the result of early podocyte cell death. Immunostaining with WT1, Nephrin, and Podocin antibodies enabled us to determine the podocyte numbers, as average per mid-cross section, and to indirectly assess the integrity of the slit diaphragm (Figure 3). The number of WT1 positive podocytes was not significantly different between PTIP+ and PTIP− glomeruli at 1 or 3 months of age. At 6 months, PTIP− glomeruli had slightly fewer podocytes and by 12 months, the number of podocytes was half that of the PTIP+ littermates. Immunostainings for podocyte markers such as WT1, Nephrin, and Podocin did not reveal dramatic differences at 1 or 3 months, despite the increase in proteinuria, although some discontinuous staining could be seen with Podocin antibodies in PTIP− glomeruli (Figure 3B). Consistent with this data, TUNEL staining for apoptosis did not reveal differences between PTIP+ and PTIP− kidneys at 1 or 3 months of age (data not shown). Thus, the breakdown of the filtration barrier was not due to simple podocyte depletion at these early times. However by 12 months of age, the extensive network of Nephrin staining was partially depleted in PTIP− glomeruli (Figure 3B).

Bottom Line: Loss of PTIP resulted in subtle changes in gene expression patterns prior to the onset of a renal disease phenotype.Chromatin immunoprecipitation showed a loss of PTIP binding and lower H3K4 methylation at the Ntrk3 (neurotrophic tyrosine kinase receptor, type 3) locus, whose expression was significantly reduced and whose function may be essential for podocyte foot process patterning.These data demonstrate that alterations or mutations in an epigenetic regulatory pathway can alter the phenotypes of differentiated cells and lead to a chronic disease state.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, University of Michigan, Ann Arbor, Michigan, United States of America.

ABSTRACT
Methylation of specific lysine residues in core histone proteins is essential for embryonic development and can impart active and inactive epigenetic marks on chromatin domains. The ubiquitous nuclear protein PTIP is encoded by the Paxip1 gene and is an essential component of a histone H3 lysine 4 (H3K4) methyltransferase complex conserved in metazoans. In order to determine if PTIP and its associated complexes are necessary for maintaining stable gene expression patterns in a terminally differentiated, non-dividing cell, we conditionally deleted PTIP in glomerular podocytes in mice. Renal development and function were not impaired in young mice. However, older animals progressively exhibited proteinuria and podocyte ultra structural defects similar to chronic glomerular disease. Loss of PTIP resulted in subtle changes in gene expression patterns prior to the onset of a renal disease phenotype. Chromatin immunoprecipitation showed a loss of PTIP binding and lower H3K4 methylation at the Ntrk3 (neurotrophic tyrosine kinase receptor, type 3) locus, whose expression was significantly reduced and whose function may be essential for podocyte foot process patterning. These data demonstrate that alterations or mutations in an epigenetic regulatory pathway can alter the phenotypes of differentiated cells and lead to a chronic disease state.

Show MeSH
Related in: MedlinePlus