miRNA deep sequencing of the human brain. RNA isolated from the superior and middle temporal gyrus was analyzed using deep sequencing (see text for more details), resulting in slightly over 1,000,000 reads of annotated miRNAs. Note the Y axis uses a logarithmic scale to describe the number of a particular miRNA species; each blue diamond is a particular annotated miRNA. Fewer than 900 total annotated miRNAs were detected, of which fewer than 200 were detected with more than 100 reads in this sample. More than one-third (358,073) of the total miRNAs were represented in the top four high copy number miRNAs. These data underscore the point that relatively few miRNAs are highly expressed in brain.