A recent study published in the Journal of Clinical Investigation looked at two unrelated families with CMT2 and identified “autosomal dominant mutations of the canonical Notch ligand Jagged1 (or JAG1)” in them — a likely cause for their CMT that was also backed up by experiments in mice.
The CMT News site covers this in greater detail.
There can, of course, be more than one cause (genetic and otherwise) of CMT. CMT1., for example, can be caused by mutations in at least five genes: PMP22, MPZ, GJB1, and MFN2 have been known for a while. Now SEPT9 also appears to be a newcomer to the list.