Rac1 drives melanoblast organization during mouse development by orchestrating pseudopod- driven motility and cell-cycle progression

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Highlights? Rac1 and the Scar/WAVE complex drive pseudopod-based motility of melanoblasts ? Rac1-depleted melanoblasts move using unique actin-based stubs and not blebs ? Rac1 controls pseudopod frequency but is dispensable for pseudopod formation ? Loss of Rac1 delays melanoblast cell-cycle progression and cytokinesis     

The Kaposi Sarcoma Herpesvirus Latency-associated Nuclear Antigen DNA Binding Domain Dorsal Positive Electrostatic Patch Facilitates DNA Replication and Episome Persistence

Kaposi sarcoma-associated herpesvirus (KSHV) has a causative role in several human malignancies. KSHV latency-associated nuclear antigen (LANA) mediates persistence of viral episomes in latently infected cells. LANA mediates KSHV DNA replication and segregates episomes to progeny nuclei. The structure of the LANA DNA binding domain was recently solved, revealing a positive electrostatic patch opposite the DNA binding surface, which is the site of BET protein binding. Here we investigate the functional role of the positive patch in LANA-mediated episome persistence. As expected, LANA mutants with alanine or glutamate substitutions in the central, peripheral, or lateral portions of the positive patch maintained the ability to bind DNA by EMSA. However, all of the substitution mutants were deficient for LANA DNA replication and episome maintenance. Mutation of the peripheral region generated the largest deficiencies. Despite these deficiencies, all positive patch mutants concentrated to dots along mitotic chromosomes in cells containing episomes, similar to LANA. The central and peripheral mutants, but not the lateral mutants, were reduced for BET protein interaction as assessed by co-immunoprecipitation. However, defects in BET protein binding were independent of episome maintenance function. Overall, the reductions in episome maintenance closely correlated with DNA replication deficiencies, suggesting that the replication defects account for the reduced episome persistence. Therefore, the electrostatic patch exerts a key role in LANA-mediated DNA replication and episome persistence and may act through a host cell partner(s) other than a BET protein or by inducing specific structures or complexes.     

Epicormic ontogeny in Quercus petraea constrains the highly plausible control of epicormic sprouting by water and carbohydrates

Background and Aims

There is increasing evidence that suppressed bud burst and thus epicormic shoot emergence (sprouting) are controlled by water–carbohydrate supplies to entire trees and buds. This direct evidence is still lacking for oak. In other respects, recent studies focused on sessile oak, Quercus petraea, have confirmed the important constraints of sprouting by epicormic ontogeny. The main objective of this paper was thus to provide provisional confirmation of the water–carbohydrate control and direct evidence of the ontogenic constraints by bringing together results already published in separate studies on water status and distribution of carbohydrates, and on accompanying vegetation and epicormics, which also quantify epicormic ontogeny.

Methods

This paper analyses results gained from a sessile oak experiment in which part of the site was free from fairly tall, dense accompanying vegetation. This experiment was initially focused on stand water status and more recently on the carbohydrate distribution of dominant trees. External observations of the epicormic composition and internal observations with X-ray computer tomography were undertaken on 60 and six trees, respectively.

Key Results

Sprouting was more intense in the part of the stand free from accompanying vegetation and on upper trunk segments. A clear effect of epicormic ontogeny was demonstrated as well: the more epicormics a trunk segment bears, the more chances it had to bear sprouts.

Conclusions

These results indirectly infer water–carbohydrate control and show direct evidence of constraints by epicormic ontogeny. These results have far-reaching consequences related to the quantification of all functions fulfilled by any type of epicormic structure in any part of the tree.     

Application of a novel highly sensitive activity-based probe for detection of cathepsin G

Cathepsins are crucial in antigen processing in the major histocompatibility complex class II (MHC II) pathway. Within the proteolytic machinery, three classes of proteases (i.e., cysteine, aspartic, and serine proteases) are present in the endocytic compartments. The combined action of these proteases generates antigenic peptides from antigens, which are loaded to MHC II molecules for CD4+ T cell presentation. Detection of active serine proteases in primary human antigen-presenting cells (APCs) is restricted because of the small numbers of cells isolated from the peripheral blood. For this purpose, we developed a novel highly sensitive α-aminoalkylphosphonate diphenyl ester (DAP) activity-based probe to detect the serine protease cathepsin G (CatG) in primary APCs and after Epstein-Barr virus (EBV) exposure. Although CatG activity was not altered after short-term exposure of EBV in primary myeloid dendritic cells 1 (mDC1s), the aspartic protease cathepsin D (CatD) was reduced, suggesting that EBV is responsible for mitigating the presentation of a model antigen tetanus toxoid C-fragment (TTCF) by reduction of CatD. In addition, CatG activity was reduced to background levels in B cells during cell culture; however, these findings were independent of EBV transformation. In conclusion, our activity-based probe can be used for both Western blot and 96-well-based high-throughput CatG detection when cell numbers are limited.     

Nutritional correlates of the “lean season”: Effects of seasonality and frugivory on the nutritional ecology of diademed sifakas

Primate field studies often identify “lean seasons,” when preferred foods are scarce, and lower‐quality, abundant foods (fallback foods) are consumed. Here, we quantify the nutritional implications of these terms for two diademed sifaka groups (Propithecus diadema) in Madagascar, using detailed feeding observations and chemical analyses of foods. In particular, we sought to understand 1) how macronutrient and energy intakes vary seasonally, including whether these intakes respond in similar or divergent ways; 2) how the amount of food ingested varies seasonally (including whether changes in amount eaten may compensate for altered food quality); and 3) correlations between these variables and the degree of frugivory. In the lean season, sifakas shifted to non‐fruit foods (leaves and flowers), which tended to be high in protein while low in other macronutrients and energy, but the average composition of the most used foods in each season was similar. They also showed dramatic decreases in feeding time, food ingested, and consequently, daily intake of macronutrients and energy. The degree of frugivory in the daily diet was a strong positive predictor of feeding time, amount ingested and all macronutrient and energy intakes, though season had an independent effect. These results suggest that factors restricting how much food can be eaten (e.g., handling time, availability, or intrinsic characteristics like fiber and plant secondary metabolites) can be more important than the nutritional composition of foods themselves in determining nutritional outcomes—a finding with relevance for understanding seasonal changes in behavior, life history strategies, competitive regimes, and conservation planning. Am J Phys Anthropol 153:78–91, 2014. © 2013 Wiley Periodicals, Inc.     

Fagus sylvatica trunk epicormics in relation to primary and secondary growth

Background and Aims

European beech epicormics have received far less attention than epicormics of other species, especially sessile oak. However, previous work on beech has demonstrated that there is a negative effect of radial growth on trunk sprouting, while more recent investigations on sessile oak proved a strong positive influence of the presence of epicormics. The aims of this study were, first, to make a general quantification of the epicormics present along beech stems and, secondly, to test the effects of both radial growth and epicormic frequency on sprouting.

Methods

In order to test the effect of radial growth, ten forked individuals were sampled, with a dominant and a dominated fork of almost equal length for every individual. To test the effects of primary growth and epicormic frequency, on the last 17 annual shoots of each fork arm, the number of axillary buds, shoot length, ring width profiles, epicormic shoots and other epicormics were carefully recorded.

Key Results

The distribution of annual shoot length, radial growth profiles and parallel frequencies of all epicormics are presented. The latter frequencies were parallel to the annual shoot lengths, nearly equivalent for both arms of each tree, and radial growth profiles included very narrow rings in the lowest annual shoots and even missing rings in the dominated arms alone. The location of the latent buds and the epicormics was mainly at branch base, while epicormic shoots, bud clusters and spheroblasts were present mainly in the lowest annual shoots investigated. Using a zero-inflated mixed model, sprouting was shown to depend positively on epicormic frequency and negatively on radial growth.

Conclusions

Support for a trade-off between cambial activity and sprouting is put forward. Sprouting mainly depends on the frequency of epicormics. Between- and within-tree variability of the epicormic composition in a given species may thus have fundamental and applied implications.     

Antibody to beta-amyloid protein increases acetylcholine in the hippocampus of 12 month SAMP8 male mice

Amyloid beta protein (Abeta) is the primary constituent of plaque seen in Alzheimer's disease. Abeta is proposed to play an etiological role in Alzheimer's disease and to be a cause of the decrease in the level of acetylcholine in the hippocampus. The SAMP8 strain of mouse develops age-related increases in Abeta and deficits in learning and memory by 12 months of age. We examined in 12 month old SAMP8 mice the effects of giving antibody to Abeta by septal or intracerebroventricular (ICV) injection on acetylcholine levels in the hippocampus. Antibody to Abeta increased acetylcholine in the hippocampus over 100% after ICV injection and over 200% after septal injection. Injection of rabbit serum, antibody directed towards mouse IgG, or a blocking antibody directed towards human interleukin-1beta were without effect. These results suggest that antagonism of Abeta increases acetylcholine concentrations in the hippocampus, an area important for learning and memory.