Ribosome biogenesis controls suture mesenchymal stem cell fate via selective regulation ofcomplement pathway in to prevent craniosynostosis [Ribo-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. We performed ribosome profiling in MSCs and its snord118 mutant heterozygote. Experiments were performed in two biological duplicates.