A cDNA clone encoding for a Prothymosin α (Prot-α) has been isolated and characterized from the testis of the frog Rana esculenta. Frog Prothymosin α (fProt-α) predicted a 109 amino acid protein with a high homology to the mammalian Prot-α. fProt-α contains 28 aspartic and 25 glutamic acid residues and presents the typical basic KKQK amino acid sequence in the close carboxyl terminal region. Northern blot analysis revealed that fProt-α is highly expressed in the testis. A different expression of fProt-α transcript was found during the frog reproductive cycle with a peak in September/October in concomitance with germ cell maturation, strongly suggesting a role for this protein in the testicular activity. In situ hybridization evidenced that the only germ cells expressing fProt-α are the primary and secondary spermatocytes; in addition, the hybridization signal was stronger in the October testis. Taken together, our findings indicate that fProt-α might contribute to the efficiency of frog spermatogenesis with a role during the meiosis. This study is the first report on the isolation and characterization of a Prot-α in a non-mammalian vertebrate. In addition, our results indicate that the testis of the frog R. esculenta may be a useful model to increase the knowledge concerning the physiological role of Prot-α in vertebrates.
All Authors contributed equally in the preparation of the manuscript. This work was supported by the Italian Ministry of University and Scientific Research MURST (ex 40% ‘Geremia’) and the Second University of Naples (ex 60%) grants.