Microglia
Research has discovered dystrophic (defective development) human microglia. "These cells are characterized by abnormalities in their cytoplasmic structure, such as deramified, atrophic, fragmented or unusually tortuous processes, frequently bearing spheroidal or bulbous swellings." The incidence of dystrophic microglia increases with aging. Microglial degeneration and death have been reported in research on Prion disease, Schizophrenia and Alzheimer's disease, indicating that microglial deterioration might be involved in neurodegenerative diseases. A complication of this theory is the fact that it is difficult to distinguish between "activated" and "dystrophic" microglia in the human brain.
Small nucleolar RNA-derived microRNA
Small nucleolar RNA derived microRNA was first described in 2008. The protozoal intestinal parasite "Giardia lamblia" lacks the Drosha protein involved in pre-miRNA cleavage from pri-miRNA. However the miRNA processing protein dicer is found in "Giardia". A 26 nucleotide RNA, miR2, is processed from the "Giardia lamblia" snoRNA GlsR17 by dicer. MiR2 is a microRNA which may regulate the expression of variant surface proteins.