 Due to alternative splicing within the coding regions, supplemental diversity is observed referred to as variable regions 1, 2, and 3  Firstly, variable region 1 (vr1) consists of a short exon containing three amino acids.In mice, the transcripts including this exon are primarily restricted to the brain but are present in the brain, heart, and skeletal muscle in humans.Secondly, variable region 2 (vr2) consists of exons 17A and 17B which encodes the unique C-terminal tail of α-dystrobrevin 2.