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- Jee, Youn Hee, et al.
(författare)
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Mir-374-5p, mir-379-5p, and mir-503-5p regulate proliferation and hypertrophic differentiation of growth plate chondrocytes in male rats
- 2018
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Ingår i: Endocrinology. - Cary, NC, USA : Oxford University Press. - 0013-7227 .- 1945-7170. ; 159:3, s. 1469-1478
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Tidskriftsartikel (refereegranskat)abstract
- Growth plate chondrocytes undergo sequential differentiation to form the resting (RZ), proliferative (PZ), and hypertrophic zones (HZ). The important role of microRNAs (miRNAs) in the growth plate was previously revealed by cartilage-specific ablation of Dicer, an enzyme essential for biogenesis of many miRNAs. To identify specific miRNAs that regulate differentiation of PZ chondrocytes to HZ chondrocytes, we microdissected individual growth plate zones from juvenile rats and performed miRNA profiling using a solution hybridization method and also miRNA-seq. Thirty-four miRNAs were differentially expressed between PZ and HZ and we hypothesized that some of the miRNAs that are preferentially expressed in PZ may serve to promote proliferation and inhibit hypertrophic differentiation. Consistent with this hypothesis, transfection of inhibitors for four of these miRNAs (mir-369-3p, mir-374-5p, mir-379-5p, mir-503-5p) decreased proliferation in primary epiphyseal chondrocytes. The inhibitors for three of these miRNAs (mir-374-5p, mir-379-5p, mir-503-5p) also increased expression of multiple genes that are associated with chondrocyte hypertrophic differentiation. We next hypothesized that preferential expression of these miRNAs in PZ is driven by the PTHrP concentration gradient across the growth plate. Consistent with this hypothesis, treatment of primary chondrocytes with a PTH/PTHrP receptor agonist, PTH1-34, increased expression of mir-374-5p, mir-379-5p, and mir-503-5p. Taken together, our findings suggest that the PTHrP concentration gradient across the growth plate induces differential expression of mir-374-5p, mir-379-5p and mir-503-5p between PZ and HZ. In PZ, the higher expression levels of these miRNAs promote proliferation and inhibit hypertrophic differentiation. In HZ, downregulation of these miRNAs inhibits proliferation and promotes hypertrophic differentiation.
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| 2. |
- Jee, Youn Hee, et al.
(författare)
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New developments in the genetic diagnosis of short stature
- 2018
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Ingår i: Current opinion in pediatrics. - : Lippincott Williams & Wilkins. - 1040-8703 .- 1531-698X. ; 30:4, s. 541-547
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Forskningsöversikt (refereegranskat)abstract
- Purpose of review: Genome-wide approaches including genome-wide association studies as well as exome and genome sequencing represent powerful new approaches that have improved our ability to identify genetic causes of human disorders. The purpose of this review is to describe recent advances in the genetic causes of short stature.Recent findings: In addition to SHOX deficiency which is one of the most common causes of isolated short stature, PAPPA2, ACAN, NPPC, NPR2, PTPN11 (and other rasopathies), FBN1, IHH and BMP2 have been identified in isolated growth disorders with or without other mild skeletal findings. In addition, novel genetic causes of syndromic short stature have been discovered, including pathogenic variants in BRCA1, DONSON, AMMECR1, NFIX, SLC25A24, and FN1.Summary: Isolated growth disorders are often monogenic. Specific genetic causes typically have specific biochemical and/or phenotype characteristics which are diagnostically helpful. Identification of additional subjects with a specific genetic cause of short stature often leads to a broadening of the known clinical spectrum for that condition. The identification of novel genetic causes of short stature has provided important insights into the underlying molecular mechanisms of growth failure.
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| 3. |
- Lui, Julian C., et al.
(författare)
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Ezh2 mutations found in the Weaver overgrowth syndrome cause a partial loss of H3K27 histone methyltransferase activity
- 2018
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Ingår i: Journal of Clinical Endocrinology and Metabolism. - Cary, NC, United States : Oxford University Press. - 0021-972X .- 1945-7197. ; 103:4, s. 1470-1478
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Tidskriftsartikel (refereegranskat)abstract
- Context: Weaver syndrome is characterized by tall stature, advanced bone age, characteristic facies, and variable intellectual disability. It is caused by heterozygous mutations in EZH2, a histone methyltransferase responsible for H3K27 trimethylation. However, no early truncating mutations have been identified, suggesting that null mutations do not cause Weaver syndrome.Objective: To test alternative hypotheses that EZH2 variants found in Weaver syndrome either cause a gain of function or a partial loss of function.Design: Exome sequencing was performed in a boy with tall stature, advanced bone age, and mild dysmorphic features. Mutant or wild-type EZH2 protein was expressed in mouse growth plate chondrocytes with or without endogenous EZH2, and enzymatic activity was measured. A mouse model was generated, and histone methylation was assessed in heterozygous and homozygous embryos.Results: A de novo missense EZH2 mutation (c.1876G>A (p.Val626Met)) was identified in the proband. When expressed in growth plate chondrocytes, the mutant protein showed decreased histone methyltransferase activity. A mouse model carrying this EZH2 mutation was generated using CRISPR/Cas9. Homozygotes showed perinatal lethality while heterozygotes were viable, fertile, and showed mild overgrowth. Both homozygous and heterozygous embryos showed decreased H3K27 methylation.Conclusion: We generated a mouse model with the same mutation as our patient and found that it recapitulates the Weaver overgrowth phenotype, and demonstrated that EZH2 mutations found in Weaver syndrome cause a partial loss of function.
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