Borna disease virus is the causative agent of Borna disease, a persistent non-cytolytic infection of the central nervous system in most warm-blooded animals. Atypically, only a low number of mature virus particles can be observed within infected animals. The negative-stranded non-segmented RNA-genome encodes for only six proteins including the Borna disease virus matrix protein (BDVM). BDVM is associated with membrane binding and thereby with viral assembly and budding. Furthermore, BDVM is able to bind and protect single-stranded RNA. BDVM variants, designed for the investigation of RNA-binding abilities and the oligomerization state of BDVM, indicate that RNA-binding influences the oligomerization state and that a monomeric, RNA-binding form of BDVM is important for cell-to-cell spread of the Borna disease virus.