A murine model of the human CREBRFR457Q obesity-risk variant does not influence energy or glucose homeostasis in response to nutritional stress

Obesity and diabetes have strong heritable components, yet the genetic contributions to these diseases remain largely unexplained. In humans, a missense variant in Creb3 regulatory factor (CREBRF) [rs373863828 (p.Arg457Gln); CREBRFR457Q] is strongly associated with increased odds of obesity but decreased odds of diabetes. Although virtually nothing is known about CREBRF's mechanism of action, emerging evidence implicates it in the adaptive transcriptional response to nutritional stress downstream of TORC1. The objectives of this study were to generate a murine model with knockin of the orthologous variant in mice (CREBRFR458Q) and to test the hypothesis that this CREBRF variant promotes obesity and protects against diabetes by regulating energy and glucose homeostasis downstream of TORC1. To test this hypothesis, we performed extensive phenotypic analysis of CREBRFR458Q knockin mice at baseline and in response to acute (fasting/refeeding), chronic (low- and high-fat diet feeding), and extreme (prolonged fasting) nutritional stress as well as with pharmacological TORC1 inhibition, and aging to 52 weeks. The results demonstrate that the murine CREBRFR458Q model of the human CREBRFR457Q variant does not influence energy/glucose homeostasis in response to these interventions, with the exception of possible greater loss of fat relative to lean mass with age. Alternative preclinical models and/or studies in humans will be required to decipher the mechanisms linking this variant to human health and disease.

New roles for dopamine in motor skill acquisition: lessons from primates, rodents, and songbirds

Motor learning is a core aspect of human life and appears to be ubiquitous throughout the animal kingdom. Dopamine, a neuromodulator with a multifaceted role in synaptic plasticity, may be a key signaling molecule for motor skill learning. Though typically studied in the context of reward-based associative learning, dopamine appears to be necessary for some types of motor learning. Mesencephalic dopamine structures are highly conserved among vertebrates, as are some of their primary targets within the basal ganglia, a subcortical circuit important for motor learning and motor control. With a focus on the benefits of cross-species comparisons, this review examines how "model-free" and "model-based" computational frameworks for understanding dopamine's role in associative learning may be applied to motor learning. The hypotheses that dopamine could drive motor learning either by functioning as a reward prediction error, through passive facilitating of normal basal ganglia activity, or through other mechanisms are examined in light of new studies using humans, rodents, and songbirds. Additionally, new paradigms that could enhance our understanding of dopamine's role in motor learning by bridging the gap between the theoretical literature on motor learning in humans and other species are discussed.

Loss of CREBRF Reduces Anxiety-like Behaviors and Circulating Glucocorticoids in Male and Female Mice

Glucocorticoid signaling controls many key biological functions ranging from stress responses to affective states. The putative transcriptional coregulator CREB3 regulatory factor (CREBRF) reduces glucocorticoid receptor levels in vitro, suggesting that CREBRF may impact behavioral and physiological outputs. In the present study, we examined adult male and female mice with global loss of CREBRF (CrebrfKO) for anxiety-like behaviors and circulating glucocorticoids in response to various acute stress conditions. Results demonstrate that both male and female CrebrfKO mice have preserved locomotor activity but reduced anxiety-like behaviors during the light-dark box and elevated plus maze. These behavioral phenotypes were associated with lower plasma corticosterone after restraint stress. Further studies using unhandled female mice also demonstrated a loss of the diurnal circulating corticosterone rhythm in CrebrfKO mice. These results suggest that CREBRF impacts anxiety-like behavior and circulating glucocorticoids in response to acute stressors and serves as a basis for future mechanistic studies to define the impact of CREBRF in glucocorticoid-associated behavioral and physiological responses.

Purification and partial characterization of a novel thermophilic carboxylesterase with high mesophilic specific activity

An esterase activity obtained from a strain of Bacillus stearothermophilus was purified 5,133-fold to electrophoretic homogeneity with 26% recovery. The purified esterase had a specific activity of 2,032 mumol min-1 mg-1 based on the hydrolysis of p-nitrophenyl caproate at pH 7.0 and 30 degrees C. The apparent molecular mass was 50,000 +/- 2,000 daltons from sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 45,000 +/- 3,000 daltons from gel filtration. Native polyacrylamide gels stained for esterase activity showed three bands. The isoelectric points were estimated to be 5.7, 5.8, and 6.0. Forty amino acid residues were sequenced at the N-terminus. The sequence showed no degeneracy, suggesting that the three esterases are functionally identical carboxylesterases differing by a limited number of amino acids. The enzyme showed maximum activity at pH 7.0 and was very stable at pH 6.0-8.9 with optimum stability at pH 6.0. At this pH and 60 degrees C the half-life was 170 h. Esterase activity was totally inhibited by phenylmethanesulfonyl fluoride, parahydroxymercuribenzoate, eserine, and tosyl-L-phenylalanine, but not by ethylendiaminetetra acetic acid. The esterase obeyed Michaelis-Menten kinetics in the hydrolysis of p-nitrophenyl esters, but both Vmax and KM were protein concentration-dependent. The esterase was able to hydrolyse a number of p-nitrophenyl derivatives (amino acid derivatives and aliphatic acids with different chain lengths).