A novel microRNA targeting HDAC5 regulates osteoblast differentiation in mice and contributes to primary osteoporosis in humans

Abstract

MicroRNAs (miRNAs) interfere with translation of specific target mRNAs and are thought to thereby regulate many cellular processes. Recent studies have suggested that miRNAs might play a role in osteoblast differentiation and bone formation. Here, we identify a new miRNA (miR-2861) in primary mouse osteoblasts that promotes osteoblast differentiation by repressing histone deacetylase 5 (HDAC5) expression at the posttranscriptional level. miR-2861 was found to be transcribed in ST2 stromal cells during bone morphogenetic protein 2-induced (BMP2-induced) osteogenesis, and overexpression of miR-2861 enhanced BMP2-induced osteoblastogenesis, whereas inhibition of miR-2861 expression attenuated it. HDAC5, an enhancer of runtrelated transcription factor 2 (Runx2) degradation, was confirmed to be a target of miR-2861. In vivo silencing of miR-2861 in mice reduced Runx2 protein expression, inhibited bone formation, and decreased bone mass. Importantly, miR-2861 was found to be conserved in humans, and a homozygous mutation in pre-miR-2861 that blocked expression of miR-2861 was shown to cause primary osteoporosis in 2 related adolescents. Consistent with the mouse data, HDAC5 levels were increased and Runx2 levels decreased in bone samples from the 2 affected individuals. Thus, our studies show that miR-2861 plays an important physiological role in osteoblast differentiation and contributes to osteoporosis via its effect on osteoblasts.

MicroRNAs and post-transcriptional regulation of skeletal development

“…Interestingly, other clusters have also been studied, such as the auto-regulatory feedback loops controlling Runx2 expression. miR-3960/-2861 is transactivated by Runx2 in vitro, thereby maintaining its own levels of expression by blocking the expression of Hoxa and Hdac5, negative regulators of osteoblast differentiation (Kanzler et al 1998, Dobreva et al 2006, Li et al 2009a, Hu et al 2011. Furthermore, an in vivo approach has demonstrated that Satb2 is also targeted by miR-34s, affecting osteoblast proliferation mainly by means of miR-34b and miR-34c.…”

“…The 3 0 -UTR of the ACVR1/ALK2 gene has recently been studied in vitro to elucidate miRNAs that when expressed induce BMP signaling alterations in fibrodysplasia ossificans progressiva (Mura et al 2012). Several additional BMP-modulated miRNAs have been identified (Li et al 2008, 2009a, Lin et al 2009, Bae et al 2012, Gamez et al 2013, generally as a result of high-throughput expression analysis but without precise information on their transcriptional control and function.…”

“…It has also been suggested that a decrease in miR-2861 expression contributes to OP. miR-2861 has already been shown to be a BMP-induced miRNA, targeting Hdac5 and therefore involved in Runx2 degradation (Li et al 2009a, Hu et al 2011. Li et al (2009a) have shown that inhibition of miR-2861, using a specific antisense oligonucleotide introduced by a single tail vein injection, leads to decreased bone mass, reduced osteoblast activity, and osteoblast marker alteration in mice.…”

Epigenetic Aspects of Osteoporosis

“…Экспрессия кластера подавляется RUNX2 в остеобла-стах. мкРНК2861 и мкРНК-3960, наоборот, опосредованно стимулируют экспрессию RUNX2, подавляя его ингибито-ры HDAC5 и HOXA2 и, соответственно, тем самым способ-ствуя дифференцировке остеобластов [45,46]. В определенной степени, остерикс (OSX) -транс-крипционный фактор, необходимый для формирования костной ткани, находится под контролем мкРНК, образуя уникальную ауторегуляторную петлю обратной связи с мкРНК93.…”

“…При изучении клинического случая редкой формы се-мейного остеопороза у 2 пациентов подросткового возрас-та была выявлена мутация мкРНК2861 [45]. Увеличение интенсивности экспрессии мкРНК2861 блокирует эпиге-нетический регулятор HDAC5, который посредством де-ацетилирования гистонов ингибирует остеобластогенез.…”