RESUMO
MicroRNAs (miRs) and Hox transcription factors have decisive roles in postnatal bone formation and homeostasis. In silico analysis identified extensive interaction between HOXA cluster mRNA and microRNAs from the miR-23a cluster. However, Hox regulation by the miR-23a cluster during osteoblast differentiation remains undefined. We examined this regulation in preosteoblasts and in a novel miR-23a cluster knockdown mouse model. Overexpression and knockdown of the miR-23a cluster in preosteoblasts decreased and increased, respectively, the expression of the proteins HOXA5, HOXA10, and HOXA11; these proteins' mRNAs exhibited significant binding with the miR-23a cluster miRNAs, and miRNA 3'-UTR reporter assays confirmed repression. Importantly, during periods correlating with development and differentiation of bone cells, we found an inverse pattern of expression between HoxA factors and members of the miR-23a cluster. HOXA5 and HOXA11 bound to bone-specific promoters, physically interacted with transcription factor RUNX2, and regulated bone-specific genes. Depletion of HOXA5 or HOXA11 in preosteoblasts also decreased cellular differentiation. Additionally, stable overexpression of the miR-23a cluster in osteoblasts decreased the recruitment of HOXA5 and HOXA11 to osteoblast gene promoters, significantly inhibiting histone H3 acetylation. Heterozygous miR-23a cluster knockdown female mice (miR-23a ClWT/ZIP) had significantly increased trabecular bone mass when compared with WT mice. Furthermore, miR-23a cluster knockdown in calvarial osteoblasts of these mice increased the recruitment of HOXA5 and HOXA11, with a substantial enrichment of promoter histone H3 acetylation. Taken together, these findings demonstrate that the miR-23a cluster is required for maintaining stage-specific HoxA factor expression during osteogenesis.
Assuntos
Regiões 3' não Traduzidas , Diferenciação Celular , Proteínas de Homeodomínio/metabolismo , MicroRNAs/metabolismo , Família Multigênica , Osteoblastos/metabolismo , Fosfoproteínas/metabolismo , Acetilação , Animais , Subunidade alfa 1 de Fator de Ligação ao Core/genética , Subunidade alfa 1 de Fator de Ligação ao Core/metabolismo , Células HEK293 , Histonas/genética , Histonas/metabolismo , Proteínas de Homeodomínio/genética , Humanos , Camundongos , MicroRNAs/genética , Osteoblastos/citologia , Osteogênese , Fosfoproteínas/genética , Fatores de TranscriçãoRESUMO
Janthinobacterium sp. Ant5-2-1, isolated from the Schirmacher Oasis of East Antarctica, produces a purple-violet pigment, manifests diverse energy metabolism abilities, and tolerates cold, ultraviolet radiation, and other environmental stressors. We report here the 6.19-Mb draft genome of strain Ant5-2-1, which will help understand its survival mechanisms in extreme Antarctic ecosystems.
RESUMO
Studies of proteins involved in microRNA (miRNA) processing, maturation, and silencing have indicated the importance of miRNAs in skeletogenesis, but the specific miRNAs involved in this process are incompletely defined. Here, we identified miRNA 665 (miR-665) as a potential repressor of odontoblast maturation. Studies with cultured cell lines and primary embryonic cells showed that miR-665 represses the expression of early and late odontoblast marker genes and stage-specific proteases involved in dentin maturation. Notably, miR-665 directly targeted Dlx3 mRNA and decreased Dlx3 expression. Furthermore, RNA-induced silencing complex (RISC) immunoprecipitation and biotin-labeled miR-665 pulldown studies identified Kat6a as another potential target of miR-665. KAT6A interacted physically and functionally with RUNX2, activating tissue-specific promoter activity and prompting odontoblast differentiation. Overexpression of miR-665 reduced the recruitment of KAT6A to Dspp and Dmp1 promoters and prevented KAT6A-induced chromatin remodeling, repressing gene transcription. Taken together, our results provide novel molecular evidence that miR-665 functions in an miRNA-epigenetic regulatory network to control dentinogenesis.