Artificial Light at Night Increases Recruitment of New Neurons and Differentially Affects Various Brain Regions in Female Zebra Finches

Despite growing evidence that demonstrate adverse effects of artificial light at night (ALAN) on many species, relatively little is known regarding its effects on brain plasticity in birds. We recently showed that although ALAN increases cell proliferation in brains of birds, neuronal densities in two brain regions decreased, indicating neuronal death, which might be due to mortality of newly produced neurons or of existing ones. Therefore, in the present study we studied the effect of long-term ALAN on the recruitment of newborn neurons into their target regions in the brain. Accordingly, we exposed zebra finches (Taeniopygia guttata) to 5 lux ALAN, and analysed new neuronal recruitment and total neuronal densities in several brain regions. We found that ALAN increased neuronal recruitment, possibly as a compensatory response to ALAN-induced neuronal death, and/or due to increased nocturnal locomotor activity caused by sleep disruption. Moreover, ALAN also had a differential temporal effect on neuronal densities, because hippocampus was more sensitive to ALAN and its neuronal densities were more affected than in other brain regions. Nocturnal melatonin levels under ALAN were significantly lower compared to controls, indicating that very low ALAN intensities suppress melatonin not only in nocturnal, but also in diurnal species.

Questioning Seasonality of Neuronal Plasticity in the Adult Avian Brain

To date, studies that reported seasonal patterns of adult neurogenesis and neuronal recruitment have correlated them to seasonal behaviors as the cause or as a consequence of neuronal changes. The aim of our study was to test this correlation, and to investigate whether there is a seasonal pattern of new neuronal recruitment that is not correlated to behavior. To do this, we used adult female zebra finches (songbirds that are not seasonal breeders), kept them under constant social, behavioral, and spatial environments, and compared neuronal recruitment in their brains during two seasons, under natural and laboratory conditions. Under natural conditions, no significant differences were found in the pattern of new neuronal recruitment across seasons. However, under artificial indoor conditions that imitated the natural conditions, higher neuronal recruitment occurred in late summer (August) compared to early spring (February). Moreover, our data indicate that "mixing" temperature and day length significantly reduces new neuronal recruitment, demonstrating the importance of the natural combination of temperature and day length. Taken together, our findings show, for the first time, that neuroplasticity changes under natural vs. artificial conditions, and demonstrate the importance of both laboratory and field experiments when looking at complex biological systems.

Active immunization against vasoactive intestinal polypeptide decreases neuronal recruitment and inhibits reproduction in zebra finches

Neurogenesis and neuronal recruitment occur in adult brains of many vertebrates, and the hypothesis is that these phenomena contribute to the brain plasticity that enables organisms to adjust to environmental changes. In mammals, vasoactive intestinal polypeptide (VIP) is known to have many neuroprotective properties, but in the avian brain, although widely distributed, its role in neuronal recruitment is not yet understood. In the present study we actively immunized adult zebra finches against VIP conjugated to KLH and compared neuronal recruitment in their brains, with brains of control birds, which were immunized against KLH. We looked at two forebrain regions: the nidopallium caudale (NC), which plays a role in vocal communication, and the hippocampus (HC), which is involved in the processing of spatial information. Our data demonstrate that active immunization against VIP reduces neuronal recruitment, inhibits reproduction, and induces molting, with no change in plasma prolactin levels. Thus, our observations suggest that VIP has a direct positive role in neuronal recruitment and reproduction in birds. J. Comp. Neurol. 524:2516-2528, 2016. © 2016 Wiley Periodicals, Inc.

Anthropometric and bone-related biochemical factors are associated with different haplotypes of ANKH locus

BACKGROUND

The human homologue of the mouse progressive ankylosis (ANKH) gene is one of the key genetic factors involved in bone mineralization. Previous studies have shown that plasma levels of osteoprotegerin (OPG) and parathyroid hormone (PTH) are associated with the distal region of the ANKH gene, whereas skeletal size measurements are associated with the promoter region.

AIM

The present study examines the possible phenotype-haplotype specificity of the associations in these two gene regions.

SUBJECTS AND METHODS

The total sample consists of 1249 healthy individuals (mean age = 47.7, SD = 16.8) from 404 nuclear families. Fifteen interrelated anthropometric measurements were transformed into two principal components, reflecting body size and mass. Those, plus circulating levels of PTH and OPG, were subjected to association analysis, using transmission disequilibrium tests (TDTs) with ANKH gene. From 805 to 1150 individuals per SNP were genotyped.

RESULTS

In the proximal region (rs3006069-rs835154-rs835141), associations were found between the A-A-C haplotype and the first principal component reflecting body size (p < or = 0.048), whereas another haplotype, G-G-C, was associated with the first principal component, reflecting the body mass (p < or = 0.008). In the distal region of ANKH (rs39968-rs696294-rs875525), the A-A-C haplotype was found to be associated with OPG plasma levels (p < or = 0.001), whereas the G-A-C haplotype was associated with PTH circulating concentrations (p < or = 0.025).

CONCLUSION

Taken together, the results show discrimination between the corresponding regions and haplotypes, suggesting trait-specific gene variants that influenced bone-related phenotypic variation in the studied population.

Contribution of the putative genetic factors and ANKH gene polymorphisms to variation of circulating calciotropic molecules, PTH and BGP

It is well known that regulation of calcium homeostasis in bone remodeling is one of the most crucial factors for maintaining healthy bones. Parathyroid hormone (PTH) is probably the most important hormone that participates in the bone remodeling process. Another important biochemical factor governing bone metabolism is osteocalcin (BGP). Although the physiological functions of both of these factors are well known, there is still very little known regarding their specific genetic determination and in particular, the specific genes that may regulate the circulating concentrations of these substances. In the present study, we examined whether nine single nucleotide polymorphisms (SNPs) in the human homologue of the mouse progressive ankylosis gene (ANKH)-one of the key genetic factors involved in bone mineralization-can be associated with PTH and BGP levels in apparently healthy human populations. The study sample comprised 244 nuclear families (840 individuals). After adjustment of BGP and PTH for the significant covariates (sex, age and BMI), the contribution of the putative genetic effects was statistically significant (P < 0.001) for both biochemical factors: 45.27 +/- 10.8% for PTH and 30.19 +/- 12.6% for BGP. Application of transmission disequilibrium tests (TDTs) revealed a significant association (P < 0.05) between PTH and two SNPs: rs39968 and rs875525. However, the association became particularly significant for four TDTs (P-values ranging from 0.0025 to 0.0008) when the association with the haplotypes generated from the above SNP was tested. This association remained significant even after correction for multiple testing with a false discovery rate of 0.05.

Genetic and environmental determinants of variation of soluble adhesion molecules

In our research we examined the contribution of putative genetic sources on interindividual variation and cross-sectional correlations of several adhesion molecules, including intracellular (ICAM-1) and vascular cell adhesion molecules (VCAM-1) and E-selectin, in a population-based sample of ethnically homogeneous families of European origin. The plasma levels of these molecules were measured in 947 apparently healthy individuals from 217 nuclear families. Quantitative statistical-genetic analysis implementing the model fitting technique revealed significant parent/offspring and sibling correlations (p < 0.01) for all three molecules. The putative genetic effects explained 55.2 +/- 7.2% (VCAM-1), 63.3 +/- 7.5% (ICAM) and 63.8 +/- 8.1% (E-selectin) of the variation. Common family environmental factors also significantly influenced the variation of E-selectin (13%) and VCAM-1 (28.6%). The main results of our bivariate analysis showed that the observed phenotypic correlations between ICAM-1 and VCAM-1, and between ICAM-1 and E-selectin, were mostly attributable to shared environmental factors (r(E)= 0.896 and 0.737, respectively; p < 0.01). However, the correlation between VCAM-1 and E-selectin was likely caused by common genetic effects (r(G)= 0.334, p < 0.05). Our results show that familial clustering of adhesion molecules is likely due to strong genetic effects, supplemented with shared environmental factors.

Osteoprotegerin plasma levels are strongly associated with polymorphisms in human homologue of the mouse progressive ankylosis (ANKH) gene

Osteoprotegerin inhibits osteoclastogenesis and plays an important role in the control of bone resorption. However, the genetic mechanisms underlying regulation of OPG levels are currently not fully elucidated. The aim of the present study was to determine whether the ANKH gene, which plays a central role in bone mineralization, contributes to the genetic regulation of OPG levels. A family-based association study used a sample of 159 ethnically homogeneous nuclear families, comprising 556 apparently healthy individuals. Statistical analyses included family aggregation analysis of OPG variation and four types of transmission disequilibrium tests. Each individual was genotyped for 11 SNPs in the ANKH gene. Four TDTs consistently showed a highly significant association between OPG levels and the intronic SNP rs875525 located between exons 6 and 7. The combined p-value for four tests to reject the null hypothesis of no association was 0.0003. Furthermore, haplotypes generated between rs875525 and two additional neighbouring SNPs (rs2291943 and rs2288474) also revealed a significant association with OPG plasma levels (p < 10(-4)-10(-3)). ANKH genetic polymorphisms in the area between SNP rs2291943 and rs2288474 are strongly associated with OPG plasma levels. The molecular mechanism underlying this association is not obvious, and therefore these results should be regarded cautiously until they are confirmed in independent studies.