Gene expression profiling of early intervertebral disc degeneration reveals a down-regulation of canonical Wnt signaling and caveolin-1 expression: implications for development of regenerative strategies

Introduction

Early degeneration of the intervertebral disc (IVD) involves a change in cellular differentiation from notochordal cells (NCs) in the nucleus pulposus (NP) to chondrocyte-like cells (CLCs). The purpose of this study was to investigate the gene expression profiles involved in this process using NP tissue from non-chondrodystrophic and chondrodystrophic dogs, a species with naturally occurring IVD degeneration.

Methods

Dual channel DNA microarrays were used to compare 1) healthy NP tissue containing only NCs (NC-rich), 2) NP tissue with a mixed population of NCs and CLCs (Mixed), and 3) NP tissue containing solely CLCs (CLC-rich) in both non-chondrodystrophic and chondrodystrophic dogs. Based on previous reports and the findings of the microarray analyses, canonical Wnt signaling was further evaluated using qPCR of relevant Wnt target genes. We hypothesized that caveolin-1, a regulator of Wnt signaling that showed significant changes in gene expression in the microarray analyses, played a significant role in early IVD degeneration. Caveolin-1 expression was investigated in IVD tissue sections and in cultured NCs. To investigate the significance of Caveolin-1 in IVD health and degeneration, the NP of 3-month-old Caveolin-1 knock-out mice was histopathologically evaluated and compared with the NP of wild-type mice of the same age.

Results

Early IVD degeneration involved significant changes in numerous pathways, including Wnt/β-catenin signaling. With regard to Wnt/β-catenin signaling, axin2 gene expression was significantly higher in chondrodystrophic dogs compared with non-chondrodystrophic dogs. IVD degeneration involved significant down-regulation of axin2 gene expression. IVD degeneration involved significant down-regulation in Caveolin-1 gene and protein expression. NCs showed abundant caveolin-1 expression in vivo and in vitro, whereas CLCs did not. The NP of wild-type mice was rich in viable NCs, whereas the NP of Caveolin-1 knock-out mice contained chondroid-like matrix with mainly apoptotic, small, rounded cells.

Conclusions

Early IVD degeneration involves down-regulation of canonical Wnt signaling and Caveolin-1 expression, which appears to be essential to the physiology and preservation of NCs. Therefore, Caveolin-1 may be regarded an exciting target for developing strategies for IVD regeneration.     

Colonization,stability, and adaptation in a transplant experiment of the polymorphic land snail Cepaea nemoralis (Gastropoda: Pulmonata) at the edge of its geographical range

At the eastern margins of the geographical distribution in Europe, populations of Cepaea nemoralis are sparse and limited to urban environments to which they are possibly confined by relatively warmer climates. In 1999 we introduced 1101 C. nemoralis individuals originating from nine urban populations to a rural location in the area. The snails established a viable population, which suggests that confinement to urban settings is dispersal‐ rather than climate‐limited. The snails filled available habitats at a rate of approximately 400–600 m² year^?1. On the whole, morph frequencies remained remarkably stable; changes that occurred are attributable to segregation of alleles or chromosomes. However, snails responded to habitat heterogeneity: consistent and predictable divergence occurred between habitat types, such that light‐shelled snails were repeatedly more frequent in the open than in adjoining shaded habitats. This suggests the operation of climatic and/or visual selection. As the whole area encompassing seven distinct habitat patches was only 0.3 ha, and the maximum duration of population divergence was only 11 years (fewer than four snail generations), these results indicate extremely small temporal and spatial scales of adaptation during initial phases of population establishment and spread. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 462–470.     

Dynamic horizontal cultural transmission of humpback whale song at the ocean basin scale

Cultural transmission, the social learning of information or behaviors from conspecifics, is believed to occur in a number of groups of animals, including primates, cetaceans, and birds. Cultural traits can be passed vertically (from parents to offspring), obliquely (from the previous generation via a nonparent model to younger individuals), or horizontally (between unrelated individuals from similar age classes or within generations). Male humpback whales (Megaptera novaeangliae) have a highly stereotyped, repetitive, and progressively evolving vocal sexual display or "song" that functions in sexual selection (through mate attraction and/or male social sorting). All males within a population conform to the current version of the display (song type), and similarities may exist among the songs of populations within an ocean basin. Here we present a striking pattern of horizontal transmission: multiple song types spread rapidly and repeatedly in a unidirectional manner, like cultural ripples, eastward through the populations in the western and central South Pacific over an 11-year period. This is the first documentation of a repeated, dynamic cultural change occurring across multiple populations at such a large geographic scale.     

Short-Term Behavioural Responses of Impalas in Simulated Antipredator and Social Contexts

Prey animals often have to trade off foraging against vigilance. However, vigilance is costly and individuals are expected to adjust their vigilance and its cost in relation to social cues and their predation risk. To test this, we conducted playback experiments in the field to study how lions’ (Panthera leo) roars and male impalas’ (Aepyceros melampus) territorial vocalizations affected the vigilance and foraging behaviours as well as movements of female impalas. Our results show that impalas adjusted their activities in different ways depending on the vocalizations broadcast. After lions’ roars were played, female impalas increased their vigilance activity (in particular increasing their high-cost vigilance – vigilance without chewing), decreased their bite rates and increased their movements, whereas male impalas’ vocalizations caused females to decrease their vigilance (decreasing their low-cost vigilance – vigilance while chewing) and increase their movements without affecting their bite rates. Therefore, it appears that predators’ vocalizations stimulate anti-predator behaviours such as vigilance and movement at the expense of foraging, whereas males’ vocalizations increase individuals’ displacements at the expense of vigilance. Overall, this study shows that both predator and social cues have direct effects on the behaviour of gregarious prey and need to be considered in future studies.     

Advances in the timing of spring cleaning by the honeybee Apis mellifera in Poland

1. The honeybee Apis mellifera is of huge worldwide economic importance in the pollination of crops for human consumption. In recent years, honeybee populations have declined under pressure from diseases and pests. Climate change is increasingly being viewed as an additional threat to honeybees and yet only limited research has been carried out in this area. 2. This paper reports the advance of the first cleansing flight (‘spring cleaning’) of the honeybee in Poznań, Poland, i.e. flights to excrete faeces, over a month in the period 1985–2009. The timing of this flight is advanced not only by higher late winter/spring temperatures but also by higher temperatures in the previous summer and autumn. 3. This earlier activity gives hope that the reported earlier flowering of many native and cultivated species will not cause a pollination synchrony crisis.     

Three divergent lineages within an Australian marsupial (Petrogale penicillata) suggest multiple major refugia for mesic taxa in southeast Australia

Mesic southeastern Australia represents the continent's ancestral biome and is highly biodiverse, yet its phylogeographic history remains poorly understood. Here, we examine mitochondrial DNA (mtDNA) control region and microsatellite diversity in the brush‐tailed rock‐wallaby (Petrogale penicillata; n = 279 from 31 sites), to assess historic evolutionary and biogeographic processes in southeastern Australia. Our results (mtDNA, microsatellites) confirmed three geographically discrete and genetically divergent lineages within brush‐tailed rock‐wallabies, whose divergence appears to date to the mid‐Pleistocene. These three lineages had been hypothesized previously but data were limited. While the Northern and Central lineages were separated by a known biogeographic barrier (Hunter Valley), the boundary between the Central and Southern lineages was not. We propose that during particularly cool glacial cycles, the high peaks of the Great Dividing Range and the narrow adjacent coastal plain resulted in a more significant north–south barrier for mesic taxa in southeastern Australia than has been previously appreciated. Similarly, located phylogeographic breaks in codistributed species highlight the importance of these regions in shaping the distribution of biodiversity in southeastern Australia and suggest the existence of three major refuge areas during the Pleistocene. Substructuring within the northern lineage also suggests the occurrence of multiple local refugia during some glacial cycles. Within the three major lineages, most brush‐tailed rock‐wallaby populations were locally highly structured, indicating limited dispersal by both sexes. The three identified lineages represent evolutionarily significant units and should be managed to maximize the retention of genetic diversity within this threatened species.     

Anatomy of the coracoid and diversity of the Procellariiformes (Aves) in the Oligocene of Europe

Abstract: Two European species of the Diomedeoididae, an extinct family of procellariiform (tube‐nose) birds, have hitherto been distinguished primarily by size of their limb bones. Here, we describe an Early Oligocene (Rupelian) procellariifom coracoid that in all probability represents the larger species, Diomedeoides lipsiensis, and compare it to the coracoids of smaller diomedeoidids and extant procellariiforms. Using multivariate (Principal Component Analysis) and univariate analyses, we demonstrate that nearly all measurements are heavily size dependent, which makes the proportions and some other shape characters of little use as phylogenetic markers. Among eight measurements, the coracoid corpus width shows the highest correlation (higher than corpus depth) with body mass, permitting a precise calculation of over twofold difference in body mass between D. lipsiensis and smaller species. Among 16 qualitative characters analysed, the majority proved too variable to be used as markers of interfamily relationships and only 2–3, the ventral intermuscular line, sternocoracoid articulation (divided vs. undivided), and, with reservations, epimarginal crest vary consistently between the families. By far the most variable is the acrocoracoid process that tends to be deeper (more elongate dorsoventrally) in larger petrels but not in the albatrosses. However, the detailed shapes of the acrocoracoid heads are highly genus specific and suggest a genus‐level diversity among the Diomedeoididae from the Oligocene of Europe. The common features of the diomedeoidid coracoids are best interpreted as plesiomorphies, which accounts for some similarities to the Oceanitinae (that are probably basal among the crown‐group procellariiforms). The evidence from the coracoid is consistent with a stem‐group position of the Diomedeoididae as previously proposed by others. We emphasize the need of a group‐specific character analysis, primarily of allometries and levels of character variation, prior to a phylogenetic reconstruction.     

Investigating Differences in Vigilance Tactic Use within and between the Sexes in Eastern Grey Kangaroos

Aggregation is thought to enhance an animal’s security through effective predator detection and the dilution of risk. A decline in individual vigilance as group size increases is commonly reported in the literature and called the group size effect. However, to date, most of the research has only been directed toward examining whether this effect occurs at the population level. Few studies have explored the specific contributions of predator detection and risk dilution and the basis of individual differences in the use of vigilance tactics. We tested whether male and female (non-reproductive or with young) eastern grey kangaroos (Macropus giganteus) adopted different vigilance tactics when in mixed-sex groups and varied in their reliance on predator detection and/or risk dilution as group size changed. This species exhibits pronounced sexual dimorphism with females being much smaller than males, making them differentially vulnerable toward predators. We combined field observations with vigilance models describing the effects of detection and dilution on scanning rates as group size increased. We found that females with and without juveniles relied on predator detection and risk dilution, but the latter adjusted their vigilance to the proportion of females with juveniles within their group. Two models appeared to equally support the data for males suggesting that males, similarly to females, relied on predator detection and risk dilution but may also have adjusted their vigilance according to the proportion of mothers within their group. Differential vulnerability may cause sex differences in vigilance tactic use in this species. The presence of males within a group that do not, or only partially, contribute to predator detection and are less at risk may cause additional security costs to females. Our results call for reexamination of the classical view of the safety advantages of grouping to provide a more detailed functional interpretation of gregariousness.