Ribosome biogenesis controls suture mesenchymal stem cell fate via selective regulation of complement pathway in to prevent craniosynostosis [RNA-seq]

Suture mesenchymal stem cell (MSC) drives calvarial suture development, homeostasis, and regeneration. Its loss leads to craniosynostosis, a prevailing craniofacial disorder characterized by premature suture closure. Ribosome biogenesis, historically thought to be a static house-keeping process, is now known to have tissue-specific roles. However, the functional specificity of ribosome biogenesis in suture MSCs remains largely unexplored, hampering development of therapeutic strategies for craniofacial tissue regeneration. We genetically perturb ribosome biogenesis using Snord118, a small nucleolar RNA (snoRNA) required for ribosomal RNA (rRNA) maturation. MSC specific conditional knockout (cKO) of Snord118 in mice leads to p53 activation, cell death, mesenchymal and MSC loss, impaired osteogenic and osteoclastic activity, resulting in suture growth and craniosynostosis defects. Using our newly established human induced pluripotent stem cell (iPSC)-derived MSCs combined with ribosome profiling, we found that SNORD118deficiency in MSCs causes global translation dysregulations and downregulation of complement pathway, a part of innate immune system with selective but poorly characterized physiological functions in craniofacial tissue homeostasis. Overall, ribosome biogenesis controls suture MSC fate via selective regulation of complement pathway. Overall design: Comparative gene expression profiling analysis of RNA-seq data for MSCs and its snord118 mutant heterozygote. Experiments were performed in two biological duplicates.

缝线间充质干细胞（suture mesenchymal stem cell, MSC）调控颅骨缝的发育、稳态维持与再生过程。该细胞的缺失会引发颅缝早闭症——一种以缝线过早闭合为典型特征的高发颅面部疾病。核糖体生物发生（ribosome biogenesis）曾被视作静态的持家过程，如今已被证实具备组织特异性功能。然而，缝线间充质干细胞中核糖体生物发生的功能特异性仍未得到充分探索，这一现状阻碍了颅面部组织再生治疗策略的研发。我们利用Snord118——一种参与核糖体RNA（ribosomal RNA, rRNA）成熟过程的小核仁RNA（small nucleolar RNA, snoRNA）——对核糖体生物发生进行遗传扰动。在小鼠体内对缝线间充质干细胞特异性条件性敲除（conditional knockout, cKO）Snord118，会引发p53通路激活、细胞死亡、间充质细胞与间充质干细胞丢失，以及成骨与破骨活性受损，最终导致缝线生长异常与颅缝早闭表型缺陷。借助我们新建立的人诱导多能干细胞（induced pluripotent stem cell, iPSC）分化获得的间充质干细胞，结合核糖体谱分析（ribosome profiling）技术，我们发现SNORD118缺失的间充质干细胞会出现整体翻译失调，以及补体通路（complement pathway）表达下调。补体通路作为先天免疫系统的组成部分，其在颅面部组织稳态中的生理功能具有选择性，但目前相关机制尚待明确。综上，核糖体生物发生通过选择性调控补体通路来决定缝线间充质干细胞的命运。整体实验设计：对间充质干细胞及其snord118突变杂合子的RNA测序（RNA-seq）数据开展比较基因表达谱分析，实验设置两个生物学重复。