mTORC1 Signaling Promotes Limb Bud Cell Growth and Chondrogenesis

Area of Science:

• Developmental Biology
• Cell Signaling
• Skeletal Biology

Background:

• Mammalian target of rapamycin complex 1 (mTORC1) signaling regulates protein synthesis and cell growth.
• While mTORC1 is known to influence chondrocyte growth, its role in early limb mesenchymal cells is unexplored.

Purpose of the Study:

• To investigate the role of mTORC1 signaling in prechondrogenic mesenchymal cells during embryonic limb development.
• To determine the impact of mTORC1 on chondrogenic differentiation in vitro.

Main Methods:

• Genetic deletion of Raptor, an mTORC1 component, in mouse embryonic limb mesenchymal cells.
• Pharmacological and genetic inhibition of mTORC1 signaling in limb bud mesenchymal cells and ATDC5 chondrogenic cells.
• Analysis of limb bud size, cartilage nodule formation, and gene expression (Sox9, Acan, Col2a1).

Main Results:

• Deletion of Raptor in mesenchymal cells reduced limb bud size without altering skeletal patterning.
• Disruption of mTORC1 signaling suppressed cartilage nodule formation and size in vitro.
• Inhibition of mTORC1 decreased Sox9 and cartilage matrix gene expression in chondrogenic cells.

Conclusions:

• mTORC1 signaling is essential for the proliferation of limb mesenchymal cells.
• mTORC1 plays a critical role in promoting chondrogenic differentiation during embryonic skeletal development.