types of cancers, bone pathologies, retinal degeneration and hypophosphatemic diseases, indicating that their activity is fundamental for tissue homeostasis. Here we review some of the debated aspects of SFRP-Wnt interactions and discuss the new and emerging roles of SFRPs. Journal of Cell Science 738 were isolated either through sequence homology with Fz receptors (Rattner et al., 1997) or, independently of Wnt activity, through their involvement in apoptosis (Melkonyan et al., 1997), or their co-purification with the heparin-binding factor hepatocyte growth factor/scattered factor (Finch et al., 1997).Since their discovery, interest in this family of molecules has grown progressively, particularly because recent observations have offered a new perspective on their functions and mechanisms of action in both development and disease. These studies indicate that SFRPs are not merely Wnt-binding proteins but can also antagonise one another's activity (Yoshino et al., 2001), bind to Fz receptors (Bafico et al., 1999;Rodriguez et al., 2005) and provide axon-guidance information (Rodriguez et al., 2005). Moreover, they can interact with other receptors or matrix molecules (Chuman et al., 2004;Hausler et al., 2004; and interfere with BMP signalling (Lee, H. et al., 2006;Muraoka et al., 2006;Yabe et al., 2003) by acting as proteinase inhibitors (Lee, H. et al., 2006). Furthermore, their expression is altered in different types of cancers (Rubin et al., 2006), in bone pathologies , retinal degeneration (Jones et al., 2000) and hypophosphatemic diseases (Berndt and Kumar, 2007), which indicates that their activity is fundamental for tissue homeostasis. Reviews that centre on Wnt antagonism by SFRPs have recently been published elsewhere (Cadigan and Liu, 2006;Jones and Jomary, 2002;Kawano and Kypta, 2003); here, we discuss new aspects of SFRP activity, and review SFRP structure, expression and interactions with Wnt proteins. The family of SFRPsThe SFRP family comprises five members in humans, SFRP1 to SFRP5, in which SFRP3 is the orthologue of the founding member Frzb. Sequence comparison and phylogenetic analysis show that SFRP1, SFRP2 and SFRP5 are closely related, and cluster together in a subgroup that diverges from the one formed by the related SFRP3 and SFRP4 (Fig. 1). This clustering also reflects a different genomic organisation. SFRP1, SFRP2 and SFRP5 are encoded by three exons on chromosome 8p12-p11.1, 4q31.3 and 10q24.1, respectively (Garcia-Hoyos et al., 2004), whereas SFRP3 and SFRP4 are both encoded by six exons -on chromosome 2q31-q33 and 7p14-p13, respectively. Orthologues of the five human genes have been found in all vertebrate species analysed so far ( Fig. 1). Notably, a third subgroup, apparently not present in mammals, has been identified in Xenopus, zebrafish and chick. The components of this subgroup, named Sizzled, Crescent and Tlc, share sequence similarities with the SFRP1-SFRP2-SFRP5 subgroup (Fig. 1), and are characterised by a very restricted and anterior expression in gastrulating embryos (B...

Mediterranean areas of both southern Europe and North Africa are subject to dramatic changes that will affect the sustainability, quantity, quality, and management of water resources. Most climate models forecast an increase in temperature and a decrease in precipitation at the end of the 21st century. This will enhance stress on natural forests and shrubs, and will result in more water consumption, evapotranspiration, and probably interception, which will affect the surface water balance and the partitioning of precipitation between evapotranspiration, runoff, and groundwater flow. As a consequence, soil water content will decline, saturation conditions will be increasingly rare and restricted to periods in winter and spring, and snow accumulation and melting will change, especially in the mid-mountain areas. Future land management will be characterized by forest and shrub expansion in most Mediterranean mountain areas, as a consequence of farmland and grazing abandonment, with increasing human pressure localized only in some places (ski resorts, urbanized of valley floors). In the lowlands, particularly in the coastal fringe, increasing water demand will occur as a consequence of expansion of irrigated lands, as well as the growth of urban and industrial areas, and tourist resorts. Future scenarios for water resources in the Mediterranean region suggest (i) a progressive decline in the average streamflow (already observed in many rivers since the 1980s), including a decline in the frequency and magnitude of the most frequent floods due to the expansion of forests; (ii) changes in important river regime characteristics, including an earlier decline in high flows from snowmelt in spring, an intensification of low flows in summer, and more irregular discharges in winter; (iii) changes in reservoir inputs and management, including lower available discharges from dams to meet the water demand from irrigated and urban areas. Most reservoirs in mountain areas will be subject to increasing water resource uncertainty, because of the reduced influence of snow accumulation and snowmelt processes. Besides, reservoir capacity is naturally reduced due to increasing sedimentation and, in some cases, is also decreased to improve the safety control of 2 floods, leading to a reduction in efficiency for agriculture. And (iv) hydrological and population changes in coastal areas, particularly in the delta zones, affected by water depletion, groundwater reduction and saline water intrusion. These scenarios enhance the necessity of improving water management, water prizing and water recycling policies, in order to ensure water supply and to reduce tensions among regions and countries. Key words: climate change, meteorological and hydrological drought, land use changes, land cover changes, snow accumulation, snowmelt, river regime, stream flow decline, reservoir management, Mediterranean region common dependence on water availability to meet the needs of increasing populations and living standards, development of irrigated agriculture...