甲基化N6-腺嘌呤（m6A）是一种众所周知的修饰方式，具有新的表观遗传学功能，并已被报道参与骨质疏松症（OP）的进展，为OP的发病机制提供了新的见解。然而，作为m6A甲基化的关键组分，威廉姆斯瘤1相关蛋白（WTAP）尚未在OP中进行研究。在这里，我们探讨了WTAP在OP和骨髓间充质干细胞（BMMSCs）分化中的生物学作用和潜在机制。我们证明了WTAP在患有OP和去卵巢小鼠的骨标本中表达水平较低。在功能上，WTAP在体内外促进了BMMSCs的成骨分化并抑制了脂肪分化。此外，微RNA-29b-3p（miR-29b-3p）被鉴定为WTAP的下游靶标。WTAP介导的M6A修饰导致miR-29b-3p表达增加。WTAP与microprocessor蛋白DGCR8相互作用并以m6A依赖的方式加速pri-miR-29b-3p的成熟。目标预测和双荧光素酶报告分析确定miR-29b-3p与组蛋白去乙酰化酶4（HDAC4）的直接结合位点。WTAP介导的m6A修饰通过miR-29b-3p/HDAC4轴促进BMMSCs的成骨分化并抑制脂肪分化。此外，WTAP介导的m6A甲基化负向调节成骨细胞的分化。综上，我们的研究首次确定了WTAP介导的m6A甲基化在BMMSC分化中的关键作用，并将WTAP作为OP治疗的潜在治疗靶点。©作者（S）2023年，由牛津大学出版社出版。

N6-methyladenosine (m6A) methylation, a well-known modification with new epigenetic functions, has been reported to participate in the progression of osteoporosis (OP), providing novel insights into the pathogenesis of OP. However, as the key component of m6A methylation, Wilms tumor 1-associated protein (WTAP) has not been studied in OP. Here we explored the biological role and underlying mechanism of WTAP in OP and the differentiation of bone marrow mesenchymal stem cells (BMMSCs). We demonstrated that WTAP was expressed at low levels in bone specimens from patients with OP and OVX mice. Functionally, WTAP promoted osteogenic differentiation and inhibited adipogenic differentiation of BMMSCs in vitro and in vivo. In addition, microRNA-29b-3p (miR-29b-3p) was identified as a downstream target of WTAP. M6A modifications regulated by WTAP led to increased miR-29b-3p expression. WTAP interacted with the microprocessor protein DGCR8 and accelerated the maturation of pri-miR-29b-3p in an m6A-dependent manner. Target prediction and dual-luciferase reporter assays identified the direct binding sites of miR-29b-3p with histone deacetylase 4 (HDAC4). WTAP-mediated m6A modification promoted osteogenic differentiation and inhibited adipogenic differentiation of BMMSCs through the miR-29b-3p/HDAC4 axis. Furthermore, WTAP-mediated m6A methylation negatively regulates osteoclast differentiation. Collectively, our study first identified a critical role of WTAP-mediated m6A methylation in BMMSC differentiation and highlighted WTAP as a potential therapeutic target for OP treatment.© The Author(s) 2023. Published by Oxford University Press.