Short sequence-paper Cloning, structural organization and tissue-speci¢c expression of the rabbit transferrin gene

AbstractWe cloned the rabbit transferrin (rTf) cDNA and gene, and quantified the expression of the rTf gene at the RNA level invarious organs. The tissue-specific pattern of expression of rTf gene is different to those in other species, with a highexpression in mammary gland and kidney. The exon/intron structure of the rTf gene (17 exons/16 introns) is similar to thoseof transferrins from other species. The sequence of the rTf cDNA already published is corrected and lengthened in the5P region, and a likely polymorphism is documented. s 1998 Elsevier Science B.V. All rights reserved. Keywords: Mammary gland; Kidney; Liver; Iron responsive element; Polymorphism Transferrin (Tf) is the major iron-binding glyco-protein found in the serum of all vertebrates, andis mainly secreted by the liver. In mammals, anotheriron-binding glycoprotein related to Tf lactoferrin(Lf) is also produced. The exon/intron structure ofboth genes is the same (17 exons and 16 introns) [1^6]. Consequently, the Lf gene is thought to havearisen from a Tf gene duplication during evolution[7]. Despite its name, Lf is not only found in milk butalso in a variety of other exocrine secretions [8^10]and in granules of neutrophils [11]. Moreover, organsexpressing the Lf gene are not the same in all species,and in some like rabbit, rat and dog the milk isdevoid of Lf [8]. In the same manner, tissue-speci¢ctransferrin expression diiers between species, andonly mice, rats and rabbits have been shown to ex-press the Tf gene in their mammary glands. Thismammary-speci¢c Tf expression is at least as highas the liver-speci¢c expression in the mouse [12], two-fold higher in the rat [13] and threefold higher in therabbit [14]. The rabbit thus appears to display someunique features in the tissue speci¢city of the Tf geneexpression. In order to de¢ne the precise pattern ofthe rabbit Tf gene expression, we ¢rst cloned the rTfcDNA and quanti¢ed the expression of the rTf geneat the RNA level in various organs. We then clonedthe entire rTf gene, determined its structure and com-pared it with those of other Tf and Lf genes.Rabbit Tf cDNA was cloned by RTPCR followingstandard procedures and using two oligonucleotidesTf1.1 (5P-CCACCACCCCTGAGCTACAA-3P) and