No abstract

Anticipated future temperature changes in the mountainous U.S. Pacific Northwest will cause reduced spring snow pack, earlier melt, earlier spring peak flow and lower summer flow in transient rain-snow and snowmelt dominant river basins. In the context of managed flood control, these systematic changes are likely to disrupt the balance between flood control and reservoir refill in existing reservoir systems. To adapt to these hydrologic changes, refill timing and evacuation requirements for flood control need to be modified. This work poses a significant systems engineering problem, especially for large, multiobjective water systems. An existing optimization/ simulation procedure is refined for rebalancing flood control and refill objectives for the Columbia River Basin for anticipated global warming. To calibrate the optimization model for the 20th century flow, the objective function is tuned to reproduce the current reliability of reservoir refill, while providing comparable levels of flood control to those produced by current flood control practices. After the optimization model is calibrated using the 20th century flow the same objective function is used to develop flood control curves for a global warming scenario which assumes an approximately 2°C increase in air temperature. Robust decreases in system storage deficits are simulated for the climate change scenario when optimized flood rule curves replace the current flood control curves, without increasing monthly flood risks.

The leucine zipper motif has been identified as an important and specific interaction motif used by various sperm tail proteins that localize to the outer dense fibers. We had found that rat Odf1, a major integral ODF protein, utilizes its leucine zipper to associate with Odf2, another major ODF protein, Spag4 which localizes to the interface between ODF and axonemal microtubule doublets, and Spag5. The rat Spag5 sequence indicated a close relationship with human Astrin, a microtubule-binding spindle protein suggesting that Spag5, like Spag4, may associate with the sperm tail axoneme. RT PCR assays indicated expression of Spag5 in various tissues and in somatic cells Spag5 localizes to endoplasmic reticulum and microtubules, as expected for an Astrin orthologue. MT binding was confirmed both in vivo and in in vitro MT-binding assays: somatic cells contain a 58 kDa MT-associated Spag5 protein. Western blotting assays of rat somatic cells and male germ cells at different stages of development using anti-Spag5 antibodies demonstrated that the protein expression pattern changes during spermatogenesis and that sperm tails contain a 58 kDa Spag5 protein. Use of affinity-purified anti-Spag5 antibodies in immuno electron microscopy shows that in rat elongated spermatids and epididymal sperm the Spag5 protein associates with ODF, but not with the axonemal MTs. This observation is in contrast to that for the other Odf1-binding, MT-binding protein Spag4, which is present between ODF and axoneme. Our data demonstrate that Spag5 has different localization in somatic versus male germ cells suggesting the possibility of different function.

Post-transcriptional mechanisms including differential splicing expand the protein repertoire beyond that provided by the one gene-one protein model. Trans-splicing has been observed in mammalian systems but is low level (sometimes referred to as noise), and a contribution to hybrid protein expression is unclear. In the study of rat sperm tail proteins a cDNA, called 1038, was isolated representing a hybrid mRNA derived in part from the ornithine decarboxylase antizyme 3 (Oaz3) gene located on rat chromosome 2 fused to sequences encoded by a novel gene on chromosome 4. Cytoplasmic Oaz3 mRNA is completely testis specific. However, in several tissues Oaz3 is transcribed and contributes to hybrid 1038 mRNA synthesis, without concurrent Oaz3 mRNA synthesis. 1038 mRNA directs synthesis of a hybrid 14-kDa protein, part chromosome 2-and part chromosome 4-derived as shown in vitro and in transfected cells. Antisera that recognize a chromosome 4-encoded C-terminal peptide confirm the hybrid character of endogenous 14-kDa protein and its presence in sperm tail structures and 1038-positive tissue. Our data suggest that the testis-specific OAZ3 gene may be an example of a mammalian gene that in several tissues is transcribed to contribute to a hybrid mRNA and protein. This finding expands the repertoire of known mechanisms available to cells to generate proteome diversity.The mammalian sperm tail contains unique structures not present in cilia, viz. the outer dense fibers (ODF) 2 and the fibrous sheath (FS). In the midpiece region of spermatozoa ODF are each associated with one microtubule doublet of the axoneme. In the sperm tail principal piece, two ODF are replaced by the longitudinal columns of the FS that are connected throughout the principal piece by ribs (1-3). ODF are thought to provide elastic recoil for tail movement (4), and FS acts as scaffold for components involved in signaling pathways (5). Several major ODF proteins, including Odf1, Odf2, and Spag4, have been cloned by us (6 -8) and others (9 -11), and we proposed that many of them specifically interact through dimerization motifs (7). For example, we showed that Spag4 precedes synthesis of other ODF proteins, binds to the forming axoneme, and likely acts as starting point for ODF development by attracting Odf1, followed by several other ODF proteins (12). ODF in turn bind ODF-associated proteins, including Spag5, which plays multiple roles both in germ cells and in somatic cells (13,14), and KLC3, a kinesin light chain motor protein (15, 16). Analysis of major ODF proteins indicated that several appear related and are encoded by differentially spliced mRNAs. For example, differentially spliced mRNAs encoding Spag5 (14) and Odf2 (17) variants were detected. Clearly, differential splicing expands the protein repertoire available to spermatids and can result in production of functionally different but related proteins. Indeed, it has been estimated that 40 -60% of human genes are alternatively spliced (18).Few reports have been published demonstrating mammali...