Development of the craniofacial structures requires the precise differentiation of cranial neural crest cells into osteoblasts or chondrocytes. Here, we explore the epigenetic and non-epigenetic mechanisms that are required for the development of craniofacial chondrocytes. We previously demonstrated that the acetyltransferase activity of the highly conserved acetyltransferase GCN5, or KAT2A, is required for murine craniofacial development. We show that Gcn5 is required cell autonomously in the cranial neural crest. Moreover, GCN5 is required for chondrocyte development following the arrival of the cranial neural crest within the pharyngeal arches. Using a combination of in vivo and in vitro inhibition of GCN5 acetyltransferase activity, we demonstrate that GCN5 is a potent activator of chondrocyte maturation, acting to control chondrocyte maturation and size increase during pre-hypertrophic maturation to hypertrophic chondrocytes. Rather than acting as an epigenetic regulator of histone H3K9 acetylation, our findings suggest GCN5 primarily acts as a non-histone acetyltransferase to regulate chondrocyte development. Here, we investigate the contribution of GCN5 acetylation to the activity of the mTORC1 pathway. Our findings indicate that GCN5 acetylation is required for activation of this pathway, either via direct activation of mTORC1 or through indirect mechanisms. We also investigate one possibility of how mTORC1 activity is regulated through RAPTOR acetylation, which is hypothesized to enhance mTORC1 downstream phosphorylation. This study contributes to our understanding of the specificity of acetyltransferases, and the cell type specific roles in which these enzymes function.

颅面结构的发育需要颅神经嵴细胞精确分化为成骨细胞或软骨细胞。在这里，我们探讨了颅面软骨细胞发育所需的表观遗传和非表观遗传机制。我们之前证明了高度保守的乙酰转移酶 GCN5 或 KAT2A 的乙酰转移酶活性是小鼠颅面发育所必需的。我们表明Gcn5是颅神经嵴中自主需要的细胞。此外，在颅神经嵴到达咽弓内后，软骨细胞发育需要 GCN5。使用体内和体外的组合通过抑制 GCN5 乙酰转移酶活性，我们证明 GCN5 是软骨细胞成熟的有效激活剂，可在肥大前成熟到肥大软骨细胞期间控制软骨细胞成熟和大小增加。我们的研究结果表明，GCN5 不是作为组蛋白 H3K9 乙酰化的表观遗传调节剂，而是主要作为一种非组蛋白乙酰转移酶来调节软骨细胞的发育。在这里，我们研究了 GCN5 乙酰化对 mTORC1 通路活性的贡献。我们的研究结果表明，通过直接激活 mTORC1 或通过间接机制，该途径的激活需要 GCN5 乙酰化。我们还研究了如何通过 RAPTOR 乙酰化调节 mTORC1 活性的一种可能性，假设这会增强 mTORC1 下游磷酸化。