Targeted modification of the Per2 clock gene alters circadian function in mPer2luciferase (mPer2Luc) mice

Modification of the Per2 clock gene in mPer2Luc reporter mice significantly alters circadian function. Behavioral period in constant dark is lengthened, and dissociates into two distinct components in constant light. Rhythms exhibit increased bimodality, enhanced phase resetting to light pulses, and altered entrainment to scheduled feeding. Mechanistic mathematical modelling predicts that enhanced protein interactions with the modified mPER2 C-terminus, combined with differential clock regulation among SCN subregions, can account for effects on circadian behavior via increased Per2 transcript and protein stability. PER2::LUC produces greater suppression of CLOCK:BMAL1 E-box activity than PER2. mPer2Luc carries a 72 bp deletion in exon 23 of Per2, and retains a neomycin resistance cassette that affects rhythm amplitude but not period. The results show that mPer2Luc acts as a circadian clock mutation illustrating a need for detailed assessment of potential impacts of c-terminal tags in genetically modified animal models.

Nuclear pore protein TPR associates with lamin B1 and affects nuclear lamina organization and nuclear pore distribution

The organization of the nuclear periphery is crucial for many nuclear functions. Nuclear lamins form dense network at the nuclear periphery and play a substantial role in chromatin organization, transcription regulation and in organization of nuclear pore complexes (NPCs). Here, we show that TPR, the protein located preferentially within the nuclear baskets of NPCs, associates with lamin B1. The depletion of TPR affects the organization of lamin B1 but not lamin A/C within the nuclear lamina as shown by stimulated emission depletion microscopy. Finally, reduction of TPR affects the distribution of NPCs within the nuclear envelope and the effect can be reversed by simultaneous knock-down of lamin A/C or the overexpression of lamin B1. Our work suggests a novel role for the TPR at the nuclear periphery: the TPR contributes to the organization of the nuclear lamina and in cooperation with lamins guards the interphase assembly of nuclear pore complexes.

Lead isotopes and heavy minerals analyzed as tools to understand the distribution of lead and other potentially toxic elements in soils contaminated by Cu smelting (Legnica, Poland)

Surroundings of the Legnica Cu smelter (Poland) offer insight into the behavior of Pb and other metal(oid)s in heavily contaminated soils in a relatively simple site, where lithogenic and anthropogenic Pb contributions have uniform Pb isotope composition over the time of smelter activity. Distribution of metal(oid)s decreases asymptotically with depth and below 30 cm reaches concentrations typical or lower than those of upper continental crust. Usually, such distribution is interpreted as the decrease in anthropogenic Pb contribution with depth. However, calculations based on Pb isotopes indicate that anthropogenic Pb is probably distributed both as Pb-rich particles of slags and fly ashes and Pb-poor soil solutions. Generally, anthropogenic Pb constitutes up to 100 % of Pb in the uppermost 10 cm of the soils and comes often from mechanical mixing with slag and fly ash particles as well as their weathering products. On the other hand, lower soil horizon contains anthropogenic Pb in various forms, and at depths below 30 cm, most of anthropogenic Pb comes from soil solutions and can constitute from 1 to 65 % of the Pb budget. This is consistent with secondary electron microscope (SEM) analyses of heavy mineral particles showing that, in upper horizons, Pb, Cu, and Zn are contained in various particles emitted from the smelter, which show different stages of weathering. Currently, large portion of these metals may reside in the secondary Fe-hydro-oxides. On the other hand, in deeper soil horizons, anthropogenic Pb is probably dominated by Pb coming from leaching of slag or fly ash particles. Overall, metal(oid) mobility is a dynamic process and is controlled by the soil type (cultivated versus forest) and the composition and the structure of the metal-rich particles emitted from the smelter. High proportions of anthropogenic Pb at depths below 30 cm in some soil profiles indicate that Pb (and probably other metal(oid)s) can be transported down the soil profile and the present concentration of anthropogenic Pb depends on the availability of binding sites.