At the end of the Miocene, water exchange between the Mediterranean Sea and the world ocean was severely reduced, leading to deposition of huge volumes of evaporites during the Messinian salinity crisis (MSC). The onset of this event has been precisely dated at 5.971 Ma by means of magneto-, bio-and cyclostratigraphic tools, but clear paleobiological proxies for its recognition are so far missing, especially in those basins in which evaporite deposition is delayed. The disappearence of calcareous microfossils was the only paleobiological signal used to approximate the beginning of the crisis, but recently calcareous plankton has been recorded above the onset in several sections. Calcareous nannofossil and planktonic foraminifer data from the Piedmont Basin indicate that the cycle recording the beginning of the crisis is characterized by a peculiar succession of bioevents. These bioevents are (i) a calcareous nannofossil Sphenolithus abies abundance peak, followed or accompanied by minor peaks of Helicosphaera carteri, Umbilicosphara rotula and Rhabdosphaera procera, and (ii) the planktonic foraminifer Globorotalia scitula and G. suterae influx. The same sequence of bioevents has been recorded in sections from the Eastern and Central Mediterranean (Pissouri and Tokhni sections in Cyprus; Fanantello section in the Apennines) within the same age range. We thus propose that the S. abies and U. rotula peaks (often accompanied by minor peaks of H. carteri and R. procera) provide a reliable tool for the identification of the onset of the MSC independently from the occurrence of evaporites. This is particularly useful when studying successions deposited in intermediate-and deep-water basins, where evaporites are absent or their deposition is delayed. Our findings can potentially provide a reliable proxy for the identification of the MSC onset in deep-sea cores.

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Prep1 is a developmentally essential TALE class homeodomain transcription factor. In zebrafish and mouse, Prep1 is already ubiquitously expressed at the earliest stages of development, with important tissue-specific peculiarities. The Prep1 gene in mouse is developmentally essential and has haploinsufficient tumor suppressor activity [1]. We have determined the human Prep1 transcription start site (TSS) by primer extension analysis and identified, within 20 bp, the transcription start region (TSR) of the zebrafish Prep1.1 promoter. The functions of the zebrafish 59 upstream sequences were analyzed both by transient transfections in Hela Cells and by injection in zebrafish embryos. This analysis revealed a complex promoter with regulatory sequences extending up to 21.8, possibly 25.0 Kb, responsible for tissue specific expression. Moreover, the first intron contains a conserved tissue-specific enhancer both in zebrafish and in human cells. Finally, a two nucleotides mutation of an EGR-1 site, conserved in all species including human and zebrafish and located at a short distance from the TSS, destroyed the promoter activity of the 25.0 Kb promoter. A transgenic fish expressing GFP under the 21.8 Kb zebrafish promoter/enhancer co-expressed GFP and endogenous Prep1.1 during embryonic development. In the adult fish, GFP was expressed in hematopoietic regions like the kidney, in agreement with the essential function of Prep1 in mouse hematopoiesis. Sequence comparison showed conservation from man to fish of the sequences around the TSS, within the first intron enhancer. Moreover, about 40% of the sequences spread throughout the 5 Kbof the zebrafish promoter are concentrated in the 23 to 25 Kb of the human upstream region.