Opposite phenotypes of muscle strength and locomotor function in mouse models of partial trisomy and monosomy 21 for the proximal Hspa13-App region.

The trisomy of human chromosome 21 (Hsa21), which causes Down syndrome (DS), is the most common viable human aneuploidy. In contrast to trisomy, the complete monosomy (M21) of Hsa21 is lethal, and only partial monosomy or mosaic monosomy of Hsa21 is seen. Both conditions lead to variable physiological abnormalities with constant intellectual disability, locomotor deficits, and altered muscle tone. To search for dosage-sensitive genes involved in DS and M21 phenotypes, we created two new mouse models: the Ts3Yah carrying a tandem duplication and the Ms3Yah carrying a deletion of the Hspa13-App interval syntenic with 21q11.2-q21.3. Here we report that the trisomy and the monosomy of this region alter locomotion, muscle strength, mass, and energetic balance. The expression profiling of skeletal muscles revealed global changes in the regulation of genes implicated in energetic metabolism, mitochondrial activity, and biogenesis. These genes are downregulated in Ts3Yah mice and upregulated in Ms3Yah mice. The shift in skeletal muscle metabolism correlates with a change in mitochondrial proliferation without an alteration in the respiratory function. However, the reactive oxygen species (ROS) production from mitochondrial complex I decreased in Ms3Yah mice, while the membrane permeability of Ts3Yah mitochondria slightly increased. Thus, we demonstrated how the Hspa13-App interval controls metabolic and mitochondrial phenotypes in muscles certainly as a consequence of change in dose of Gabpa, Nrip1, and Atp5j. Our results indicate that the copy number variation in the Hspa13-App region has a peripheral impact on locomotor activity by altering muscle function.

Gut microbiota limits heavy metals burden caused by chronic oral exposure.

Environmental exposure to pollutants such as heavy metal(s) is responsible for various altered physiological functions which are detrimental for health. The gut microbiota is critical for intestinal homeostasis but its role on xenobiotic handling is not fully understood, especially when continuous sub-chronic exposure is addressed. We first confirmed the essential role of the intestinal microbiome to limit heavy metal body burden by using germ-free mice following 6-weeks oral exposure. Significant increases of cadmium and lead absorption and dissemination in blood and target organs were measured in germ-free mice when compared with conventional specific pathogen free (SPF) mice. Besides the "barrier" function of the luminal microbiota, this may involve specific host-genes such as metallothioneins, which are differentially expressed in the gastrointestinal tract of each group of mice. Considering genes relevant for divalent metal transporters and oxidative pathways, significant differences in basal gene expression were measured between control and germ-free mice. Moreover, the magnitude of induction of these genes upon stimulation by heavy metals varied greatly depending on the dose and type of metal as well as the microbial status of the animal. Collectively, these data illustrate the complex host-microbes interplay occurring with environmental pollutants inside the gut.

The telomeric part of the human chromosome 21 from Cstb to Prmt2 is not necessary for the locomotor and short-term memory deficits observed in the Tc1 mouse model of Down syndrome.

Trisomy 21 or Down syndrome (DS) is the most common form of human aneuploid disorder. Increase in the copy number of human chromosome 21 genes leads to several alterations including mental retardation, heart and skeletal dysmorphologies with additional physiological defects. To better understand the genotype and phenotype relationships, several mouse models have been developed, including the transchromosomic Tc1 mouse, which carries an almost complete human chromosome 21, that displays several locomotor and cognitive alterations related to DS. In this report we explore the contribution of the genetic dosage of 47 mouse genes located in the most telomeric part of Hsa21, using a novel model, named Ms4Yah, carrying a deletion of the 2.2Mb Ctsb-Prmt2 genetic interval. We combine this deletion with the Tc1 Hsa21 in a rescue experiment. We could recapitulate most of the Tc1 phenotypes but we found no phenotypes induced by the Ms4Yah and no contribution to the Tc1-induced phenotypes even if we described new alteration in social preference but not in olfaction. Thus we conclude that the genes conserved between mouse and human, found in the most telomeric part of Hsa21, and trisomic in Tc1, are not contributing to the major Tc1 phenotypes, suggesting that the Cstb-Prmt2 region is not playing a major role in locomotor and cognitive deficits found in DS.

Methylphenidate reduces impulsive behaviour in juvenile Wistar rats, but not in adult Wistar, SHR and WKY rats.

RATIONALE: Impulsivity is a core symptom of attention deficit/hyperactivity disorder (ADHD). The spontaneously hypertensive rats (SHR) is a strain commonly used as an animal model of ADHD. However, there is no clear evidence that psychostimulants, which are used for treatment of ADHD, reduce impulsivity in SHR. Because ADHD mainly affects children, it may be relevant to study psychostimulants on juvenile animals. OBJECTIVES: Using tolerance to delay of reward as index of impulsivity, the effects of methylphenidate were assessed in adult SHR, Wistar Kyoto (WKY) and Wistar rats and in juvenile Wistar rats. MATERIALS AND METHODS: Animals were trained in a T-maze to choose between a small-but-immediate and a large-but-delayed reward. Adult SHR, WKY and Wistar rats were compared for their ability to tolerate a 15-s delay. The effect of methylphenidate on the tolerance to a 30-s delay was studied in adult rats of the three strains and in juvenile (4.5 to 6.5-week-old) Wistar rats. RESULTS: In adult rats, the waiting ability was lower in SHR than in control strains. Waiting ability was improved by methylphenidate (3 and 5 mg/kg) in juveniles, but not by methylphenidate (3 mg/kg) in adults. CONCLUSIONS: These data support the idea that SHR are more impulsive than control strains. However, at the dose studied, methylphenidate fails to improve tolerance to delay in adult rats whatever the strain used. The reduction of impulsivity induced by methylphenidate in juvenile Wistar rats indicates that juvenile animals may be suitable for testing the therapeutic potential of drugs intended to the treatment of ADHD in children.

NF-kappaB regulates spatial memory formation and synaptic plasticity through protein kinase A/CREB signaling.

Synaptic activity-dependent de novo gene transcription is crucial for long-lasting neuronal plasticity and long-term memory. In a forebrain neuronal conditional NF-kappaB-deficient mouse model, we demonstrate here that the transcription factor NF-kappaB regulates spatial memory formation, synaptic transmission, and plasticity. Gene profiling experiments and analysis of regulatory regions identified the alpha catalytic subunit of protein kinase A (PKA), an essential memory regulator, as a new NF-kappaB target gene. Consequently, NF-kappaB inhibition led to a decrease in forskolin-induced CREB phosphorylation. Collectively, these results disclose a novel hierarchical transcriptional network involving NF-kappaB, PKA, and CREB that leads to concerted nuclear transduction of synaptic signals in neurons, accounting for the critical function of NF-kappaB in learning and memory.

Chronic treatment with sulbutiamine improves memory in an object recognition task and reduces some amnesic effects of dizocilpine in a spatial delayed-non-match-to-sample task.

The effect of a sulbutiamine chronic treatment on memory was studied in rats with a spatial delayed-non-match-to-sample (DNMTS) task in a radial maze and a two trial object recognition task. After completion of training in the DNMTS task, animals were subjected for 9 weeks to daily injections of either saline or sulbutiamine (12.5 or 25 mg/kg). Sulbutiamine did not modify memory in the DNMTS task but improved it in the object recognition task. Dizocilpine, impaired both acquisition and retention of the DNMTS task in the saline-treated group, but not in the two sulbutiamine-treated groups, suggesting that sulbutiamine may counteract the amnesia induced by a blockade of the N-methyl-D-aspartate glutamate receptors. Taken together, these results are in favor of a beneficial effect of sulbutiamine on working and episodic memory.

Strain differences in sucrose preference and in the consequences of unpredictable chronic mild stress.

Effects of unpredictable chronic mild stress (UCMS) on anhedonic-like behaviour, physical state, body weight, learning and memory were investigated in three strains of mice. These strains were chosen among 11 strains that were tested in a first experiment for their sucrose consumption and preference for sucrose solutions of different concentrations. In the second experiment, groups of mice of the CBA/H, C57BL/6 and DBA/2 strains were submitted to 7 weeks of UCMS. Measures of the sucrose consumption, the evaluation of the physical state and the measurement of body weight were weekly assessed. Following 4-week period of UCMS, sub-groups of stressed and non-stressed mice were submitted to the spontaneous alternation test in the Y-maze, and then to the water-maze test for spatial learning and memory. UCMS induced a significant decrease of the sucrose consumption in CBA/H and in C57BL/6 but not in DBA/2 mice. The UCMS effect on sucrose intake in CBA/H mice was associated with a body weight loss and a physical state degradation. Spatial learning in a water maze was not disturbed by UCMS, however, a long-term memory impairment was observed in CBA/H stressed mice during a probe test. In the Y-maze, UCMS did not modify spontaneous alternation. These results show both an anhedonic-like and an amnesic effect of UCMS in CBA/H mice. They also reveal a difference of sensitivity to UCMS according to the strain of mice.