Study reveals molecular differences in human myelin sheaths linked to primate evolution
Researchers have found that a lipid-binding protein called FABP8/PMP2 is present in the myelin sheaths of humans and old-world monkeys but absent in other mammals, including mice. This protein preferentially coats the myelin around large-diameter axons and appears to have evolved specifically in the primate lineage through a process called neofunctionalization. The finding challenges the long-held view that myelin is a uniform structure and suggests human brain wiring has molecular complexity not captured by standard animal models.
A new study published on bioRxiv demonstrates that fatty acid binding protein-8 (FABP8/PMP2) is a primate-specific component of central nervous system (CNS) myelin, present in humans and old-world monkeys but absent in rodents and other non-primate mammals. Within the human CNS, the protein does not coat all myelin sheaths equally — it preferentially marks sheaths surrounding large-diameter axons, revealing previously unrecognized sheath-to-sheath molecular heterogeneity. Epigenetic analysis showed that the PMP2 gene locus is accessible in human oligodendrocytes but not in mouse oligodendrocytes, and when human oligodendrocytes were transplanted into mouse brains, they continued to express FABP8/PMP2, confirming the difference is intrinsic to the cells rather than driven by environmental signals. Transgenic mice engineered to express FABP8/PMP2 in their oligodendrocytes developed myelin that was transiently thicker during development and had elevated cholesterol content, consistent with the protein's known ability to bind cholesterol. The authors propose that the evolutionary emergence of FABP8/PMP2 in primates contributed to the higher cholesterol enrichment observed in human myelin compared to other species. These results reframe myelin as a modular, evolvable structure and raise questions about how well rodent models capture human-specific aspects of myelination and neurological disease.
What's missing
As a preprint, this study has not yet undergone formal peer review, so its findings should be treated as preliminary. The study does not address whether FABP8/PMP2 expression levels or distribution change across human lifespan, during demyelinating diseases such as multiple sclerosis, or in response to injury — questions with direct clinical relevance. It also remains unclear whether the transient myelin thickening observed in transgenic mice has any functional consequence for nerve conduction velocity or neurological behavior.
What different sources said
- bioRxivCenter
Fatty acid binding protein-8 (FABP8/PMP2) reveals molecular heterogeneity of myelin sheaths in the human CNS
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