title: Distinct expression patterns and biological activities of two isoforms of the mouse orphan receptor TR2.
abstract: An alternatively spliced variant of a testis-specific nuclear orphan receptor TR2-11 was identified and designated as TR2-11-t. As a result of retaining intron 5 of this gene, TR2-11-t mRNA encoded a truncated receptor with the complete ligand-binding domain deleted. Protein expression of both isoforms was confirmed using a prokaryotic expression system. In the mouse, the expression of the two TR2 isoforms was elevated in the testis with distinct profiles beginning at puberty. TR2-11 expression increased at postnatal day 18, peaked between day 20 and day 24 and remained at high levels throughout adulthood, whereas TR2-11-t expression was elevated transiently at postnatal day 24. Among separated primary germ cells and established testicular cell lines, TR2-11 was expressed highly in meiotic and postmeiotic germ cells and weakly in a Leydig cell line and a germ cell line, but not expressed in a Sertoli cell line. In contrast, TR2-11-t was expressed at a much lower level in all the testicular cell types examined. In adult testes blocked at germ cell development by vitamin A depletion or hypophysectomy, TR2-11 expression was dramatically reduced whereas TR2-11-t was highly elevated. Based upon the RNA expression patterns of these isoforms, it was suggested that TR2-11 was specific to meiotic and postmeiotic germ cells whereas TR2-11-t was enriched in early germ cell populations such as premeiotic cells. The biological activities of TR2-11 and TR2-11-t on a direct repeat 5-type retinoic acid (RA) response element (RARE)-containing reporter gene was examined in Cos cells. TR2-11 repressed RA induction of this reporter whereas TR2-11-t enhanced RA induction of the same reporter, and the opposite biological effects of these isoforms were dose-dependent. Gel-shift experiments provided evidence for a direct interaction of TR2-11, but not TR2-11-t, with DNA fragments containing this RARE. Opposite roles of TR2-11 and TR2-11-t on RA induction of promoters containing this particular RARE are suggested.
authors.affiliation: Department of Pharmacology, University of Minnesota, Minneapolis 55455, USA.
authors.forename: C H
authors.initials: CH
authors.lastname: Lee
authors.forename: L
authors.initials: L
authors.lastname: Chang
authors.forename: L N
authors.initials: LN
authors.lastname: Wei
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002455:Cell Division; D015870:Gene Expression; D007536:Isomerism; D007985:Leydig Cells / Q000378:metabolism; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D057107:Nuclear Receptor Subfamily 2, Group C, Member 1; D011987:Receptors, Steroid / Q000235:genetics / Q000378:metabolism*; D011988:Receptors, Thyroid Hormone / Q000235:genetics / Q000378:metabolism*; D012708:Sertoli Cells / Q000378:metabolism; D012741:Sexual Maturation; D013094:Spermatozoa / Q000378:metabolism; D013737:Testis / Q000378:metabolism*
chemical_list: C539823:Nr2c1 protein, mouse; D057107:Nuclear Receptor Subfamily 2, Group C, Member 1; D011987:Receptors, Steroid; D011988:Receptors, Thyroid Hormone