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SUMOylation is a dynamic post-translational protein modification that primarily takes place in cell nuclei, where it plays a key role in multiple DNA-related processes. In neurons, the SUMOylation-dependent control of a subset of neuronal transcription factors is known to regulate various aspects of nerve cell differentiation, development, and function. In an unbiased screen for endogenous SUMOylation targets in the developing mouse brain, based on a His6 -HA-SUMO1 knock-in mouse line, we previously identified the transcription factor Zinc finger and BTB domain-containing 20 (Zbtb20) as a new SUMO1-conjugate. We show here that the three key SUMO paralogues SUMO1, SUMO2, and SUMO3 can all be conjugated to Zbtb20 in vitro in HEK293FT cells, and we confirm the SUMOylation of Zbtb20 in vivo in mouse brain. Using primary hippocampal neurons from wild-type and Zbtb20 knock-out (KO) mice as a model system, we then demonstrate that the expression of Zbtb20 is required for proper nerve cell development and neurite growth and branching. Furthermore, we show that the SUMOylation of Zbtb20 is essential for its function in this context, and provide evidence indicating that SUMOylation affects the Zbtb20-dependent transcriptional profile of neurons. Our data highlight the role of SUMOylation in the regulation of neuronal transcription factors that determine nerve cell development, and they demonstrate that key functions of the transcription factor Zbtb20 in neuronal development and neurite growth are under obligatory SUMOylation control.

Summary A proper equilibrium of post‐translational protein modifications is essential for normal cell physiology, and alteration in these processes is key in neurodegenerative disorders such as Alzheimer's disease. Recently, for instance, alteration in protein SUMOylation has been linked to amyloid pathology. In this work, we aimed to elucidate the role of protein SUMOylation during aging and increased amyloid burden in vivo using a His6‐HA‐SUMO1 knock‐in mouse in the 5XFAD model of Alzheimer's disease. Interestingly, we did not observe any alteration in the levels of SUMO1‐conjugation related to Alzheimer's disease. SUMO1 conjugates remained localized to neuronal nuclei upon increased amyloid burden and during aging and were not detected in amyloid plaques. Surprisingly however, we observed age‐related alterations in global levels of SUMO1 conjugation and at the level of individual substrates using quantitative proteomic analysis. The identified SUMO1 candidate substrates are dominantly nuclear proteins, mainly involved in RNA processing. Our findings open novel directions of research for studying a functional link between SUMOylation and its role in guarding nuclear functions during aging.

The objectives of this study were to identify potential alterations in gene expression of melanocortin-4 receptor (MC4-R), proopiomelanocortin (POMC), and Agouti-related protein (AgRP) in mouse hypothalamus under a chronic peripheral infusion of leptin or at early (8 weeks) and advanced (16 weeks) phases of diet-induced obesity. Control or diet-induced obesity mice (8 or 16 weeks of high-fat diet) were either treated or not treated with leptin. Metabolic features were analyzed and expression of the genes of interest was measured by quantitative reverse transcriptase-PCR (RT-qPCR) and western blot. We reported that in control mice, but not in obese mice, leptin infusion induced an increase in POMC mRNA level as well as in MC4-R mRNA level suggesting that leptin could act directly and/or through alpha-melanocyte-stimulating hormone (alpha-MSH). This hypothesis was reinforced after in vitro studies, using the mouse hypothalamic GT1-7 cell line, since both leptin and Norleucine(4), D-Phenylalanine(7)-alpha-MSH (NDP-alpha-MSH) treatments increased MC4-R expression. After 8 weeks of high-fat diet, nondiabetic obese mice became resistant to the central action of leptin and their hypothalamic content of POMC and AgRP mRNA were decreased without modification of MC4-R mRNA level. After 16 weeks of high-fat diet, mice exhibited more severe metabolic disorders with type 2 diabetes. Moreover, hypothalamic expression of MC4-R was highly increased. In conclusion, several alterations of the melanocortin system were found in obese mice that are probably consecutive to their central resistance to leptin. Moreover, when the metabolic status is highly degraded (with all characteristics of a type 2 diabetes), other regulatory mechanisms (independent of leptin) can also take place.

Because immune defences are costly, life-history theories predict a modulation of immune investment according to its potential benefits. Social insects provide interesting models since infection risk may vary among individuals within a colony. In particular, the foraging workers, that have to leave the nest, suffer a higher infection risk and can contaminate their nest, which may favour high immune investments. However, evolutionary theories of aging predict that foragers should reduce their immune investment when they suffer high extrinsic mortality. To test these two predictions, we investigated the levels of phenoloxidase (PO) and prophenoloxidase, two important enzymes of the insect immune system, in workers of the ant Cataglyphis velox. We found a higher PO activity in foragers than in intra-nidal workers. This could result from an adaptive upregulation of the harmful PO (an enzyme potentially leading to autoimmune reactions) only when the risk of infection and wounding is high.

In many species of social Hymenoptera, totipotency of workers induces potential conflicts over reproduction. However, actual conflicts remain rare despite the existence of a high reproductive skew. One of the current hypotheses assumes that conflicts are costly and thus selected against. We studied the costs of conflicts in 20 colonies of the queenless ant Diacamma sp. "nilgiri" by testing the effects of conflicts on labor and worker immunocompetence, two parameters closely linked to the indirect fitness of workers. In this species, the dominant female is the only mated worker (gamergate) and monopolizes reproduction. We experimentally induced conflicts by splitting each colony into two groups, a control group containing the gamergate and an orphaned group displaying aggressions until a new dominant worker arises. Immunocompetence was assessed by the clearance of Escherichia coli bacteria that we injected into the ants. Time budget analysis revealed a lower rate of labor and especially brood care in orphaned groups, supporting the existence of a cost of conflicts on labor. Fifteen days after splitting, a lower immunocompetence was also found in orphaned groups, which concerned workers involved and not involved in conflicts. We propose that this immunosuppression induced by conflicts could stem from stress and not directly from aggression.

11 pages; International audience; UNCORRECTED PROOF Maternal effects such as androgen in avian eggs can mediate evolutionary responses to selection, allowing manipulation of offspring phenotype and promoting trans-generational adaptive effects. We tested the predictions of two adaptive hypotheses that have been proposed to explain female variation in yolk androgen allocation in birds, using the barn swallow Hirundo rustica as a model. We found no support for the first hypothesis proposing that yolk androgen varies as a function of breeding density in order to prepare offspring for different breeding densities. However, we found experimental support for the hypothesis that female yolk androgen allocation depends on mate attractiveness and that it constitutes an example of differential allocation. Females increased the concentration of androgens in their eggs when mated to males with experimentally elongated tails. Female phenotypic quality in terms of arrival date and clutch size was positively related to egg androgen concentration, consistent with the hypothesis that this is a costly investment, constrained by female condition. We found correlative evidence of a direct relationship between egg androgen concentration and performance of offspring as measured by mass increase.

Due to the close association between parasites and their hosts, many ‘generalist’ parasites have a high potential to become specialized on different host species. We investigated this hypothesis for a common ectoparasite of seabirds, the tick Ixodes uriae that is often found in mixed host sites. We examined patterns of neutral genetic variation between ticks collected from Black-legged kittiwakes (Rissa tridactyla) and Atlantic puffins (Fratercula arctica) in sympatry. To control for a potential distance effect, values were compared to differences among ticks from the same host in nearby monospecific sites. As predicted, there was higher genetic differentiation between ticks from different sympatric host species than between ticks from nearby allopatric populations of the same host species. Patterns suggesting isolation by distance were found among tick populations of each host group, but no such patterns existed between tick populations of different hosts. Overall, results suggest that host-related selection pressures have led to the specialization of I. uriae and that host race formation may be an important diversifying mechanism in parasites.

Fos-related antigens (Fra) were detected in the nuclei of neurones in young adult Acheta domesticus female crickets by immunohistochemical analysis, using an antibody that recognizes the amino-acid sequence 127-152 of c-Fos protein. Specificity of Fra immunoreactivity was confirmed by Western blot analysis of nuclear extracts from neural tissues. A major immunoreactive doublet with an apparent molecular mass of 52,000/54,000 Da was detected in nuclear extracts. Immunostaining of the 52,000/54,000 Da doublet showed variations in intensity during the first 5 days following the imaginal molt. Staining was more intense between day 2 and day 4 when ecdysteroid titers were high. Expression of Fra was low in allatectomized (i.e., deprived of juvenile hormone and ecdysteroids) and ovariectomized (i.e., deprived of ecdysteroids) females as compared to control females. These results show the involvement of hormone-regulated process in expression of Fra. The effect of nociceptive stimulation on Fra expression was tested. Twenty minutes after removal of the ovipositor, a supplementary band with an apparent molecular mass of 70,000 Da appeared in the nuclear extracts, then decreased and disappeared totally after 45 min. Several other Fos-related antigens with different temporal patterns of expression were also detected.

This study documented casein kinase II (CK II) activity in Acheta domesticus brain using specific antibodies and its regulation by polyamines. In control animals a transient decrease in CK II activity at day 3 after imaginal moult was observed in the brain but not in the fat body. If deprived of ecdysone by ovariectomy a different pattern was observed, with CK II activity being significantly higher on days 3 and 4 after emergence. After ecdysone injection in ovariectomized females, CK II activity decreased to levels similar to those in controls. The implications of ecdysone regulation of brain CK II activity are discussed.

The activities of ornithine decarboxylase and S-adenosylmethionine decarboxylase, two key enzymes in polyamine metabolism, were determined during the first 10 days of imaginal life in the nervous tissue and the fat body of the adult cricket Acheta domesticus. The kinetic constants of the two enzymes were also determined in both tissues. Both decarboxylases presented a higher activity in fat body than in nervous tissue. In nervous tissue, the activity of the two enzymes peaked at 16 h postemergence, then slowly decreased up to day 3–4. By contrast, the enzymatic activities in fat body, low at emergence, strongly increased on day 2. Thereafter, whereas ornithine decarboxylase activity remained rather high. S-adenosyl-methionine decarboxylase activity dropped back to emergence levels by day 10. These results, examined in light of the temporal alterations of polyamine levels observed in the two tissues, demonstrate synchronous variations between polyamine contents and the enzymes involved in their biosynthesis. © 1993 Wiley-Liss, Inc.

The three major polyamines—putrescine, spermidine, and spermine—were studied and changes of their levels were examined in extracts of cerebral ganglia and fat body from adult Acheta domesticus. In nervous tissue, only spermidine and spermine were present and spermine was two- to three-fold more abundant than spermidine. The polyamine levels were high up to day 3, decreased on day 4, and then remained relatively unchanged up to day 10. The spermidine/spermine ratios decreased during the imaginal life. Higher spermidine titres were observed in the neural tissue of egg-laying females compared to virgin females. In the fat body, putrescine was detected together with spermidine and spermine. Spermidine and spermine levels were two-fold higher than putrescine. Fat body of virgin females contained two times more polyamines than male fat body. Low at emergence, spermidine and spermine concentrations peaked on days 2–3 only in females, and egg-laying was characterized by an increase of putrescine and spermidine titres. Starvation did not change polyamine contents, implying homeostatic regulation of the intracellular polyamine metabolism. These data showing tissue specific changes in polyamine levels during the imaginal life of Acheta domesticus point to the physiological importance of polyamines as possible intracellular regulators during adult insect development. © 1993 Wiley-Liss, Inc.

A low cost scalable spacer technology is required for the commercial development of medium and high voltage FED products. Various techniques can be used to shape glass into high aspect ratio spacers. In this paper, we will describe and interpret the short term effects associated with charging under electron bombardment, as well as the long term reliability effects such as flashover and image degradation, under 5 V / micron anode fields.