Maintenance Of Myelinated Axons Research Articles

A neutral lipid-enriched diet improves myelination and alleviates peripheral nerve pathology in neuropathic mice

Charcot-Marie-Tooth (CMT) diseases comprise a genetically heterogeneous group of hereditary peripheral neuropathies. Trembler J (TrJ) mice carry a spontaneous mutation in peripheral myelin protein 22 (PMP22) and model early-onset, severe CMT type 1E disease. Recent studies indicate that phospholipid substitution, or cholesterol-enriched diet, benefit myelinated nerves, however such interventions have not been tested in early-onset dysmyelinating neuropathies. Here, we examined the lipid profile of peripheral nerves from 6-month-old TrJ mice with advanced neuropathy and tested the impact of a 6-week-long neutral lipid-enriched high-fat diet (HFD) on neuropathy progression in young, newly-weaned mice. Oil Red O staining showed pronounced neutral lipid accumulation in nerves from 6-month-old TrJ mice, along with elevated levels of key cholesterol and triglyceride transport proteins including apoE, LRP1 and ABCA1, compared with wild type (Wt). In young mice, the short-term HFD intervention increased serum cholesterol levels without impacting triglycerides, or body and liver weights. Tissue samples from neuropathic TrJ mice showed improvements in the maintenance of myelinated axons after the 6-week-long dietary intervention, and this effect was evident both in the sciatic and phrenic nerves. Concomitantly, aberrant Schwann cell proliferation was attenuated, as detected by reduction in mitotic markers and in c-Jun expression. Nerves from HFD-fed TrJ mice contained fewer macrophages, with a normalized count of CD11b + cells. In addition, we detected an increase in neutral lipids in the nerve endoneurium and a trend toward normalization of apoE, LRP1, and ABCA1 expression after the HFD feeding. Together, these results demonstrate the beneficial influence of a short-term neutral lipid-enriched diet on neuropathy progression in young TrJ mice and support further work in investigating the potential benefits of dietary lipids on hereditary neuropathies.

Role of myelin-associated glycoprotein (siglec-4a) in the nervous system.

Myelin-associated glycoprotein (MAG) is a 100 kDa glycoprotein located at the innermost layer of myelin sheets that remains in intimate contact with the axonal membrane. It is selectively expressed by myelinating cells including Schwann cells in the peripheral nervous system (PNS) and oligodendrocytes in the central nervous system (CNS). Due to its selective location and its effects on neurons, it was originally thought to be involved in axon-glia communication. The generation of MAG-deficient mice greatly expanded our knowledge about the physiological role of MAG, which helped to establish its critical roles in the normal formation and maintenance of myelinated axons. Interest in MAG was revived when it was described as the first myelin-derived inhibitor of axon regeneration. Since then numerous publications have provided detailed information about its axonal receptors and their signaling pathways. Recently, the nurture role of MAG on neurons was confirmed. On the other hand, MAG mediates signals coming from the axons that strongly impact on oligodendrocytes and Schwann cells, highlighting the bidirectional nature of axon-glia communication. Overall, MAG is a critical component of axon-glia interactions with multiple functions in the biology of both neurons and glial cells.

Cell adhesion molecules in the CNS

Cell-cell adhesions are important for brain morphology and highly coordinated brain functions such as memory and learning ([Sanes and Yamagata, 1999][1]; [Yamagata et al., 2003][2]; [Washbourne et al., 2004][3]). During early development of the nervous system, neurons elongate their axons towards