Characterizing a first occurrence of bison deposits in southeastern Nevada

Late Holocene bison bones eroding from the badlands topography of Cathedral Gorge State Park in southeastern Nevada have been identified as the remains of Bison and date between approximately 400 and 850 years old. The bones were originally thought to be turn-of-the-century cattle and then early bison, so park personnel had need to solve this interpretive problem. A multidisciplinary team sought information on archaeology, geomorphology, paleontology, and paleoenvironment to document the 1st established occurrence of bison in this part of Nevada and to develop a hypothesis explaining their demise.     

A meiotic gene conversion gradient opposite to the direction of transcription.

Genetic recombination involves classical crossing-over and gene conversion (aberrant segregation). In fungi that produce an ascus containing four spores, a gene conversion event is manifested as 3:1 or 1:3 (or more rarely 4:0 or 0:4) segregations, in contrast to the normal mendelian 2:2 segregation. Polarity is one of the properties of gene conversion; in almost all cases the frequency of conversion exhibits a gradient across the gene monitored. The frequency of conversion is usually independent of the specific allele used as a marker, but dependent on its location. An interpretation of conversion polarity is that it is caused by the existence of specific initiation sites for meiotic recombination, located at the high end of the polarity gradient. Here we show that the polarity gradient for the HIS2 gene of Saccharomyces cerevisiae is high at the 3' end of the gene, implying that the promoter of HIS2 is not the initiation site.     

Transforming growth factor-beta induces development of the T(H)17 lineage

A new lineage of effector CD4+ T cells characterized by production of interleukin (IL)-17, the T-helper-17 (T(H)17) lineage, was recently described based on developmental and functional features distinct from those of classical T(H)1 and T(H)2 lineages. Like T(H)1 and T(H)2, T(H)17 cells almost certainly evolved to provide adaptive immunity tailored to specific classes of pathogens, such as extracellular bacteria. Aberrant T(H)17 responses have been implicated in a growing list of autoimmune disorders. T(H)17 development has been linked to IL-23, an IL-12 cytokine family member that shares with IL-12 a common subunit, IL-12p40 (ref. 8). The IL-23 and IL-12 receptors also share a subunit, IL-12Rbeta1, that pairs with unique, inducible components, IL-23R and IL-12Rbeta2, to confer receptor responsiveness. Here we identify transforming growth factor-beta (TGF-beta) as a cytokine critical for commitment to T(H)17 development. TGF-beta acts to upregulate IL-23R expression, thereby conferring responsiveness to IL-23. Although dispensable for the development of IL-17-producing T cells in vitro and in vivo, IL-23 is required for host protection against a bacterial pathogen, Citrobacter rodentium. The action of TGF-beta on naive T cells is antagonized by interferon-gamma and IL-4, thus providing a mechanism for divergence of the T(H)1, T(H)2 and T(H)17 lineages.