Schematic of the mouse OPRM1 gene structure, alternative splicing and predicted protein structures.

A, Genomic structure of the mouse OPRM1gene. Exons and introns are showed by boxes and horizontal lines, respectively. Intron size is indicated below the introns as kilobases (kb). Promoters are showed by arrows. Exons are numbered based upon the published data. B, Alternative splicing of C-terminal splice variants with 7-TM domains. Translational start and termination sites are indicated by downward and upward lines on exon boxes, respectively. The lines between exons are introns that are spliced out during splicing. Predicted receptor structures are inserted at the right with colored bars indicating different coding exons. C, Alternative splicing of truncated variants with 6-TM domains. D, Alternative splicing of truncated variants with 1-TM domain.