Dicer-dependent pathways regulate chondrocyte proliferation and differentiation

Abstract

Small noncoding RNAs, microRNAs (miRNAs), bind to messenger RNAs through base pairing to suppress gene expression. Despite accumulating evidence that miRNAs play critical roles in various biological processes across diverse organisms, their roles in mammalian skeletal development have not been demonstrated. Here, we show that Dicer, an essential component for biogenesis of miRNAs, is essential for normal skeletal development. Dicer-null growth plates show a progressive reduction in the proliferating pool of chondrocytes, leading to severe skeletal growth defects and premature death of mice. The reduction of proliferating chondrocytes in Dicer-null growth plates is caused by two distinct mechanisms: decreased chondrocyte proliferation and accelerated differentiation into postmitotic hypertrophic chondrocytes. These defects appear to be caused by mechanisms downstream or independent of the Ihh-PTHrP signaling pathway, a pivotal signaling system that regulates chondrocyte proliferation and differentiation. Microarray analysis of Dicer-null chondrocytes showed limited expression changes in miRNA-target genes, suggesting that, in the majority of cases, chondrocytic miRNAs do not directly regulate target RNA abundance. Our results demonstrate the critical role of the Dicer-dependent pathway in the regulation of chondrocyte proliferation and differentiation during skeletal development.microRNA ͉ skeletal development E ndochondral bone development is composed of the initial formation of a cartilage template and its subsequent replacement by mineralized bone. Longitudinal bone growth is driven by regulated proliferation and differentiation of chondrocytes in the growth plate cartilage. In developing growth plates, periarticular chondrocytes proliferate and differentiate into flat columnar chondrocytes that proliferate further to form orderly columns. Columnar chondrocytes stop proliferating and then differentiate into postmitotic hypertrophic chondrocytes. This process is tightly controlled by multiple layers of regulatory mechanisms, thus allowing persistent longitudinal bone growth.Regulation of gene expression is the major mechanism to control a variety of cellular functions, including proliferation and differentiation. Small noncoding microRNAs (miRNAs) encoded in the genome regulate gene expression at the posttranscriptional level. Genetic ablation of miRNA genes has demonstrated that loss of single miRNAs can results in significant physiological consequences in mice (1-4). In addition, germ-line ablation of genes encoding components for miRNA biogenesis results in embryonic or perinatal lethality in mice (5-7). These examples suggest that posttranscriptional gene regulation by miRNAs plays a critical role in regulating fundamental cellular functions in mice. miRNAs are generated from long primary transcripts (primiRNAs) through multiple processing steps (8). primiRNAs are cleaved into small-hairpin premiRNAs by the microprocessor complex containing Drosha and DGCR8. premiRNAs are exported into the cytoplasm, where ...

MicroRNAs as regulators of bone homeostasis and bone metastasis

“…5 Similarly, Dicer knockout in chondrocytes, using Col2a1-Cre mice, modulated proliferation and differentiation. 6 These transgenic mice presented with significant skeletal defects that were associated with the differentiation of cells into postmitotic hypertrophic chondrocytes featuring decreased proliferation. Subsequent analysis has revealed the expression of several hundred miRNAs within chondrocytes under physiological conditions.…”

MiR‐455‐3p regulates early chondrogenic differentiation via inhibiting Runx2

“…miRNAs have been reported to have important roles in multiple biological processes, including the process of cartilage differentiation and degradation [1,[3][4][5][6][7][38][39][40]. Dicer is an essential component for the biogenesis of miRNAs, and Dicer-null growth plates showed a progressive reduction in the proliferation of chondrocytes and the acceleration of hypertrophy, leading to severe skeletal growth defects and premature death in mice [8]. MiR-335-5p was significantly increased during mouse mesenchymal stem cell (MSC) chondrogenesis, and it could up-regulate the expression of chondrogenic marker genes by targeting negative regulators of SRY (sex-determining region Y)-box 9 (Sox9), including Daam1 and ROCK1 [9].…”

MicroRNA‐199a‐3p, microRNA‐193b, and microRNA‐320c are correlated to aging and regulate human cartilage metabolism

“…2 Abnormalities in cartilage development have been observed in Dicer gene dysfunction models, and miRNA is known to play a key role in cartilage differentiation. 3 miRNA plays a key role in differentiation and growth in organs and tissues, 2 and miRNAs expressed specifically in cartilage [4][5][6][7][8] have been reported. Till date, miR21, 4 miR22, 9 miR27a, 6 miR140, 10 and miR146 8 have been reported as miRNAs that are associated with cartilage metabolism.…”