Progressive axonopathy when oligodendrocytes lack the myelin protein CMTM5

Chemokine-like factor-like MARVEL-transmembrane domain containing protein 5 (CMTM5) is a tetraspan-transmembrane protein highly enriched in oligodendrocytes and central nervous system (CNS) myelin. We analyzed the proteome of myelin biochemically purified from mouse brains upon genetic disruption of the Cmtm5-gene specifically in myelinating cells. An ion mobility-enhanced version of data-independent acquisition (DIA) workflow with alternating low and elevated energy (referred to as UDMSE) was used to compare protein abundance in Cmtm5 cKO and CTRL samples by label-free quantification. Specifically, dynamic range enhancement (DRE)-UDMSE was applied as a dedicated data acquisition mode recently introduced for routine differential myelin proteome profiling. We found that Cmtm5 cKO mice displayed a largely similar myelin proteome composition as control mice and, together with other data such as electron micrographs, concluded that CMTM5 is not essential for myelin biogenesis and composition. However, oligodendroglial Cmtm5-deficiency causes an early-onset progressive axonopathy, presumably following a Wallerian-like pathomechanism. These results indicate that CMTM5 is involved in the function of oligodendrocytes to maintain axonal integrity rather than myelin biogenesis.