Upregulation of large myelin protein zero leads to Charcot-Marie-Tooth disease-like neuropathy in mice

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Charcot-Marie-Tooth (CMT) disease is a group of inherited neuropathies often linked to mutations in genes encoding peripheral myelin proteins.
• Myelin protein zero (P0) is a key component of peripheral myelin, and its isoform, large myelin protein zero (L-MPZ), is produced via translational readthrough.
• The specific function of L-MPZ and the impact of its ratio with P0 on myelin integrity and nerve function remain largely unknown.

Purpose of the Study:

• To investigate the physiological role of L-MPZ and the consequences of an altered L-MPZ/P0 ratio in peripheral myelin.
• To elucidate the role of translational readthrough in myelin protein expression and its contribution to peripheral neuropathy.

Main Methods:

• Generation of a novel mouse line (L-MPZ mice) using genome editing, engineered to exclusively produce L-MPZ instead of P0.
• Comprehensive analysis including motor function tests, electrophysiology, immunohistology, and electron microscopy to assess neurological and myelin phenotypes.

Main Results:

• Homozygous L-MPZ mice displayed Charcot-Marie-Tooth (CMT)-like phenotypes, characterized by thin and/or loose myelin sheaths, an increased proportion of small-caliber axons, and disrupted axo-glial interactions.
• Heterozygous L-MPZ mice exhibited a milder neuropathy, suggesting a dose-dependent effect.
• The study demonstrated that aberrant readthrough of myelin protein genes can directly lead to neuropathy.

Conclusions:

• An appropriate ratio between L-MPZ and P0 is crucial for maintaining peripheral myelin integrity and function.
• Aberrant translational readthrough of myelin proteins, leading to an altered L-MPZ/P0 ratio, is a causative factor in peripheral neuropathies like CMT.
• This research provides new insights into the molecular mechanisms underlying myelin disorders and identifies translational control as a potential therapeutic target.