Boosting neuregulin 1 type-III expression hastens SMA motor axon maturation

Area of Science:

• Neuroscience
• Developmental Biology
• Genetics

Background:

• Intercellular communication between axons and Schwann cells is vital for axon maturation.
• Spinal muscular atrophy (SMA) is characterized by underdeveloped, dysfunctional motor axons.
• Current SMA therapeutics have limited efficacy due to these developmental deficits.

Purpose of the Study:

• To investigate if accelerating motor axon maturation can improve function and reduce disease features in SMA.
• To examine the role of neuregulin 1 type III (NRG1-III) in SMA motor axon development.
• To determine the impact of neuronal NRG1-III overexpression on SMA motor axon maturation.

Main Methods:

• Assessed NRG1 mRNA and protein expression in human and mouse SMA tissues.
• Utilized NRG1-III overexpressing mice bred with SMA∆7 mice.
• Analyzed ventral root size, axon segregation, diameter, myelination, and conduction velocities.

Main Results:

• Reduced NRG1 expression observed in SMA spinal cord and ventral root axons.
• Neonatal NRG1-III overexpression improved SMA ventral root size, axon development, and myelination.
• Improved motor axon conduction velocities were observed in treated SMA mice.
• NRG1-III did not prevent distal degeneration or improve long-term outcomes in older mice.

Conclusions:

• Early motor axon developmental impairments in SMA can be ameliorated by NRG1-III.
• This molecular strategy is independent of SMN replacement.
• Findings suggest potential for combinatorial therapeutic approaches for SMA.