Hadron Polarizabilities and Form Factors

This is the summary of the working group on Hadron Polarizabilities and Form Factors of the Chiral Dynamics Workshop in Mainz, September 1-5, 1997.Comment: 21 pages LaTeX2e, uses epsf, 9 fig

Human Vav1 Expression in Hematopoietic and Cancer Cell Lines Is Regulated by c-Myb and by CpG Methylation

Vav1 is a signal transducer protein that functions as a guanine nucleotide exchange factor for the Rho/Rac GTPases in the hematopoietic system where it is exclusively expressed. Recently, Vav1 was shown to be involved in several human malignancies including neuroblastoma, lung cancer, and pancreatic ductal adenocarcinoma (PDA). Although some factors that affect vav1 expression are known, neither the physiological nor pathological regulation of vav1 expression is completely understood. We demonstrate herein that mutations in putative transcription factor binding sites at the vav1 promoter affect its transcription in cells of different histological origin. Among these sites is a consensus site for c-Myb, a hematopoietic-specific transcription factor that is also found in Vav1-expressing lung cancer cell lines. Depletion of c-Myb using siRNA led to a dramatic reduction in vav1 expression in these cells. Consistent with this, co-transfection of c-Myb activated transcription of a vav1 promoter-luciferase reporter gene construct in lung cancer cells devoid of Vav1 expression. Together, these results indicate that c-Myb is involved in vav1 expression in lung cancer cells. We also explored the methylation status of the vav1 promoter. Bisulfite sequencing revealed that the vav1 promoter was completely unmethylated in human lymphocytes, but methylated to various degrees in tissues that do not normally express vav1. The vav1 promoter does not contain CpG islands in proximity to the transcription start site; however, we demonstrated that methylation of a CpG dinucleotide at a consensus Sp1 binding site in the vav1 promoter interferes with protein binding in vitro. Our data identify two regulatory mechanisms for vav1 expression: binding of c-Myb and CpG methylation of 5′ regulatory sequences. Mutation of other putative transcription factor binding sites suggests that additional factors regulate vav1 expression as well

Application of MesoCASiMiR: assessment of Baetis rhodani habitat suitability

Abstract: The assessment of the ecological status of running waters at a mesohabitat scale is commonly based on fish. Nevertheless, due to their strong dependence on a good physical and chemical habitat, macroinvertebrate species can also be used for this assessment. A new approach is presented by applying the MesoCASiMiR module of the CASiMiR modeling system. In this way, the habitat suitability for the mayfly Baetis rhodani was modeled at a mesohabitat scale in the river Zwalm (Flanders, Belgium). The model inference system was based on fuzzy logic. Fuzzy variable sets and rules were derived from expert knowledge and from a database of biological samples. The suitability of the different mesohabitats for Baetis rhodani in the river Zwalm could be reliably described by three hydromorphological variables (depth, velocity and dominating substrate) and by the oxygen concentration. As a result, the habitat suitability was calculated and a habitat map of the studied reach was generated. Validation of this map was performed by biological samples at different sites along the reach, indicating that predicted habitat suitability was closely correlated to the observed abundances in most of the sampling sites. Due to the universality of the MesoCASiMiR module, the presented approach is applicable on other rivers and can be used for quick assessment of the ecological river status. This allows identification of the bottlenecks in the river basin and definition of restoration options. By adjusting the input parameters, the model can predict the impact of these restoration actions at a mesohabitat scale. Due to its transparent design and graphical user interface, the model has proved to be a useful tool for river management