Temporal and spatial localization of prothymosin α transcript in the Harderian gland of the frog, Rana esculenta

• Published in: The Journal of experimental zoology Vol. 292; no. 7; pp. 633 - 639
• Main Authors: de Rienzo, Gianluca, di Sena, Rona, Ferrara, Diana, Palmiero, Carmela, Baccari, Gabriella Chieffi, Minucci, Sergio
• Format: Journal Article
• Language: English
• Published: New York Wiley Subscription Services, Inc., A Wiley Company 01-06-2002
• Subjects: Animals; Gene Expression Regulation; Harderian Gland - cytology; Harderian Gland - metabolism; In Situ Hybridization; Organ Specificity; Protein Precursors - genetics; Rana esculenta; Rana esculenta - genetics; RNA, Messenger - genetics; RNA, Messenger - metabolism; Seasons; Thymosin - analogs & derivatives; Thymosin - genetics
• ISSN: 0022-104X; 1097-010X
• DOI: 10.1002/jez.10097

The Harderian gland (hg) is the only orbital gland of the frog Rana esculenta, and it has the essential function of lubricating the eyes. The hg secretory activity is seasonal, showing the highest value in summer. There is, at present, no data on gene expression of the frog hg. This study reports, for the first time, on the temporal and spatial expression of a cDNA clone encoding for the prothymosin α (Prot‐α), a highly acidic nuclear protein present in virtually all mammalian cells. Northern blot analysis revealed a single 1.7 kb transcript detected in the frog hg throughout the year, with a lowest expression in September in concomitance with the minimum secretory activity. In situ hybridization indicated that hg secretory cells express Prot‐α transcript, and the hybridization signal was less intense in the September gland. The constant expression of the frog Prot‐α mRNA during the whole year suggests a constitutive role for this molecule in the hg. In addition, taking into account that, in mammals, many immunomodulatory functions have been attributed to this protein, it is suggested that frog Prot‐α might contribute to the hg immunity processes, probably acting as a protective agent against infections of the eyeball. Interestingly, although the presence of Prot‐α gene in animals other than mammals has been considered to be highly unlikely, the present paper confirms the presence of Prot‐α transcript in a nonmammalian vertebrate, the frog R. esculenta. J. Exp. Zool. 292:633–639, 2002. © 2002 Wiley‐Liss, Inc.