Muscle-selective RUNX3 dependence of sensorimotor circuit development

Area of Science:

• Neuroscience
• Developmental Biology
• Genetics

Background:

• Proprioceptive sensory neurons (PSNs) are crucial for motor control, relaying muscle sensory information to the spinal cord.
• The molecular mechanisms governing the development and maintenance of PSN subtypes and their connections are not fully understood.
• The transcription factor RUNX3 is known to be vital for early PSN differentiation.

Purpose of the Study:

• To investigate the role of RUNX3 in later stages of PSN specification and sensorimotor circuit formation.
• To determine if RUNX3 is required for maintaining PSN identity after peripheral innervation.
• To explore how RUNX3 influences the selectivity of sensorimotor connections.

Main Methods:

• Conditional inactivation of the Runx3 gene in PSNs after peripheral innervation.
• Analysis of PSN cell identity and survival.
• Assessment of sensorimotor connections at the limb level.
• Investigation of factors regulating RUNX3 expression in PSNs.

Main Results:

• Conditional Runx3 inactivation maintains PSN identity in a subgroup of neurons without causing cell death.
• RUNX3 is essential for sensorimotor connections between PSNs and motor neurons, with variable sensitivity across different muscles.
• Muscle-derived signals, including neurotrophin 3, are necessary for maintaining RUNX3 expression in PSNs.

Conclusions:

• RUNX3 acts as a transcriptional regulator essential for specifying generic PSN identity post-neurogenesis.
• Target muscle-derived signals regulate RUNX3 expression, contributing to the specialized aspects of sensorimotor connection selectivity.
• This study reveals a mechanism where RUNX3's role evolves from initial specification to fine-tuning neural circuit specialization based on muscle feedback.