Tool for genomic selection and breeding to evolutionary adaptation: Development of a 100K single nucleotide polymorphism array for the honey bee.

High-throughput high-density genotyping arrays continue to be a fast, accurate, and cost-effective method for genotyping thousands of polymorphisms in high numbers of individuals. Here, we have developed a new high-density SNP genotyping array (103,270 SNPs) for honey bees, one of the most ecologically and economically important pollinators worldwide. SNPs were detected by conducting whole-genome resequencing of 61 honey bee drones (haploid males) from throughout Europe. Selection of SNPs for the chip was done in multiple steps using several criteria. The majority of SNPs were selected based on their location within known candidate regions or genes underlying a range of honey bee traits, including hygienic behavior against pathogens, foraging, and subspecies. Additionally, markers from a GWAS of hygienic behavior against the major honey bee parasite Varroa destructor were brought over. The chip also includes SNPs associated with each of three major breeding objectives-honey yield, gentleness, and Varroa resistance. We validated the chip and make recommendations for its use by determining error rates in repeat genotypings, examining the genotyping performance of different tissues, and by testing how well different sample types represent the queen's genotype. The latter is a key test because it is highly beneficial to be able to determine the queen's genotype by nonlethal means. The array is now publicly available and we suggest it will be a useful tool in genomic selection and honey bee breeding, as well as for GWAS of different traits, and for population genomic, adaptation, and conservation questions.

Cell type-specific modifications of corticotropin-releasing factor (CRF) and its type 1 receptor (CRF1) on startle behavior and sensorimotor gating.

The corticotropin-releasing factor (CRF) family of peptides and receptors coordinates the mammalian endocrine, autonomic, and behavioral responses to stress. Excessive CRF production has been implicated in the etiology of stress-sensitive psychiatric disorders such as posttraumatic stress disorder (PTSD), which is associated with alterations in startle plasticity. The CRF family of peptides and receptors mediate acute startle response changes during stress, and chronic CRF activation can induce startle abnormalities. To determine what neural circuits modulate startle in response to chronic CRF activation, transgenic mice overexpressing CRF throughout the central nervous system (CNS; CRF-COE(CNS)) or restricted to inhibitory GABAergic neurons (CRF-COE(GABA)) were compared across multiple domains of startle plasticity. CRF overexpression throughout the CNS increased startle magnitude and reduced ability to inhibit startle (decreased habituation and decreased prepulse inhibition (PPI)), similar to previous reports of exogenous effects of CRF. Conversely, CRF overexpression confined to inhibitory neurons decreased startle magnitude but had no effect on inhibitory measures. Acute CRF receptor 1 (CRF1) antagonist treatment attenuated only the effects on startle induced by CNS-specific CRF overexpression. Specific deletion of CRF1 receptors from forebrain principal neurons failed to alter the effects of exogenous CRF or stress on startle, suggesting that these CRF1 expressing neurons are not required for CRF-induced changes in startle behaviors. These data indicate that the effects of CRF activation on startle behavior utilize an extensive neural circuit that includes both forebrain and non-forebrain regions. Furthermore, these findings suggest that the neural source of increased CRF release determines the startle phenotype elicited. It is conceivable that this may explain why disorders characterized by increased CRF in cerebrospinal fluid (e.g. PTSD and major depressive disorder) have distinct symptom profiles in terms of startle reactivity.

Assessing behavioural effects of chronic HPA axis activation using conditional CRH-overexpressing mice.

The corticotropin-releasing hormone (CRH) and its cognate receptors have been implicated in the pathophysiology of stress-related disorders. Hypersecretion of central CRH and elevated glucocorticoid levels, as a consequence of impaired feedback control, have been shown to accompany mood and anxiety disorders. However, a clear discrimination of direct effects of centrally hypersecreted CRH from those resulting from HPA axis activation has been difficult. Applying a conditional strategy, we have generated two conditional CRH-overexpressing mouse lines: CRH-COE ( Del ) mice overexpress CRH throughout the body, while CRH-COE ( APit ) mice selectively overexpress CRH in the anterior and intermediate lobe of the pituitary. Both mouse lines show increased basal plasma corticosterone levels and consequently develop signs of Cushing's syndrome. However, while mice ubiquitously overexpressing CRH exhibited increased anxiety-related behaviour, overexpression of CRH in the pituitary did not produce alterations in emotional behaviour. These results suggest that chronic hypercorticosteroidism alone is not sufficient to alter anxiety-related behaviour but rather that central CRH hyperdrive on its own or in combination with elevated glucocorticoids is responsible for the increase in anxiety-related behaviour. In conclusion, the generated mouse lines represent valuable animal models to study the consequences of chronic CRH overproduction and HPA axis activation.