title: Identification of five mouse mu-opioid receptor (MOR) gene (Oprm1) splice variants containing a newly identified alternatively spliced exon.
abstract: The mouse mu-opioid receptor gene, Oprm1, currently contains 18 recognized alternatively spliced exons [Doyle, G.A., Sheng, X.R., Lin, S.S.J., Press, D.M., Grice, D.E., Buono, R.J., Ferraro, T.N., Berrettini, W.H., 2007. Identification of three mouse mu-opioid receptor (MOR) gene (Oprm1) splice variants containing a newly identified alternatively spliced exon. Gene 388 (1-2) 135-147, in press (doi:10.1016/j.gene.2006.10.017). Electronic publication 2006 November 1] that generate 27 splice variants encoding at least 11 morphine-binding isoforms of the receptor. Here, we identify five MOR variants that contain an as yet undescribed exon (exon 19) of the gene, and we provide evidence that these MOR splice variants are expressed in the C57BL/6 and DBA/2 mouse strains. Three splice variants, MOR-1Eii, MOR-1Eiii and MOR-1Eiv, encode the MOR-1E isoform and contain the newly identified exon 19 in their 3' untranslated regions. The fourth splice variant encodes a novel mu-opioid receptor isoform, MOR-1U, and contains exon 19 in its coding region. The cytoplasmic tail of the putative MOR-1U isoform contains a putative nuclear localization signal encoded by the sequence of exon 19. Exon 19 appears to be conserved in the rat, but not in humans. In mouse and rat Oprm1, exon 19 is located between described exons 7 and 8. We also report the cloning of the "full-length" MOR-1T splice variant [Kvam, T.-M., Baar, C., Rakvag, T.T., Kaasa, S., Krokan, H.E., Skorpen, F., 2004. Genetic analysis of the murine mu-opioid receptor: increased complexity of Oprm1 gene splicing, J. Mol. Med. 82 (4) 250-255] that encodes MOR-1 and contains the newly identified exon in its 3' UTR. RT-PCR analysis suggests that splice variants MOR-1Eii, MOR-1Eiii, MOR-1Eiv, MOR-1T and MOR-1U are expressed in all brain regions analyzed (cortex, cerebellum, hypothalamus, thalamus and striatum). These exon 19-containing splice variants add to the growing complexity of the mouse Oprm1 gene.
authors.affiliation: The Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States. e_gad@verizon.net
authors.forename: Glenn A
authors.initials: GA
authors.lastname: Doyle
authors.forename: X Rebecca
authors.initials: XR
authors.lastname: Sheng
authors.forename: Sharon S J
authors.initials: SS
authors.lastname: Lin
authors.forename: Danielle M
authors.initials: DM
authors.lastname: Press
authors.forename: Dorothy E
authors.initials: DE
authors.lastname: Grice
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Buono
authors.forename: Thomas N
authors.initials: TN
authors.lastname: Ferraro
authors.forename: Wade H
authors.initials: WH
authors.lastname: Berrettini
mesh_terms: D020413:3' Untranslated Regions; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D005091:Exons; D014644:Genetic Variation; D007438:Introns; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017450:Receptors, Opioid, mu / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
chemical_list: D020413:3' Untranslated Regions; D017931:DNA Primers; D018076:DNA, Complementary; C404943:Oprm protein, mouse; D012333:RNA, Messenger; D017450:Receptors, Opioid, mu