Fetal brain mTOR signaling activation in tuberous sclerosis complex

Area of Science:

• Neuroscience
• Developmental Biology
• Molecular Biology

Background:

• Tuberous sclerosis complex (TSC) is a genetic disorder causing benign tumors in multiple organs.
• Brain malformations in TSC are linked to enhanced mammalian target of rapamycin (mTOR) signaling.
• Prior research lacked data on mTORC1 and mTORC2 activation in fetal TSC tubers and neural progenitor cells lacking Tsc2.

Purpose of the Study:

• To investigate mTORC1 and mTORC2 activation in fetal TSC tubers.
• To examine the effects of Tsc2 deficiency on mTOR signaling and neural progenitor cell development in vitro and in vivo.
• To explore the therapeutic potential of mTOR inhibition in TSC-related brain development.

Main Methods:

• Immunohistochemical analysis of mTORC1 and mTORC2 substrates in fetal TSC tubers.
• Tsc2 shRNA knockdown in mouse neural progenitor cells (mNPCs) in vitro.
• In utero electroporation of Tsc2 shRNA in fetal mouse brains.
• Treatment with rapamycin, an mTORC1 inhibitor.

Main Results:

• mTORC1 and mTORC2 signaling pathways were activated in fetal TSC tubers.
• Tsc2 knockdown in mNPCs led to increased mTORC1/mTORC2 signaling and cell enlargement, which was reversed by rapamycin.
• In vivo Tsc2 knockdown caused disorganized cortical lamination and increased cell volume, prevented by rapamycin.

Conclusions:

• This study provides the first evidence of mTORC1 and mTORC2 activation in fetal TSC tubers and Tsc2-deficient neural progenitor cells.
• mTOR pathway dysregulation contributes to abnormal brain development in TSC.
• Inhibiting the mTOR pathway during embryogenesis may offer a strategy to prevent TSC-related brain malformations.