Transcriptome profiling of sheep granulosa cells and oocytes during early follicular development obtained by Laser Capture Microdissection

<p>Abstract</p> <p>Background</p> <p>Successful achievement of early folliculogenesis is crucial for female reproductive function. The process is finely regulated by cell-cell interactions and by the coordinated expression of genes in both the oocyte and in granulosa cells. Despite many studies, little is known about the cell-specific gene expression driving early folliculogenesis. The very small size of these follicles and the mixture of types of follicles within the developing ovary make the experimental study of isolated follicular components very difficult.</p> <p>The recently developed laser capture microdissection (LCM) technique coupled with microarray experiments is a promising way to address the molecular profile of pure cell populations. However, one main challenge was to preserve the RNA quality during the isolation of single cells or groups of cells and also to obtain sufficient amounts of RNA.</p> <p>Using a new LCM method, we describe here the separate expression profiles of oocytes and follicular cells during the first stages of sheep folliculogenesis.</p> <p>Results</p> <p>We developed a new tissue fixation protocol ensuring efficient single cell capture and RNA integrity during the microdissection procedure. Enrichment in specific cell types was controlled by qRT-PCR analysis of known genes: six oocyte-specific genes (<it>SOHLH2</it>, <it>MAEL</it>, <it>MATER</it>, <it>VASA</it>, <it>GDF9</it>, <it>BMP15</it>) and three granulosa cell-specific genes (<it>KL</it>, <it>GATA4</it>, <it>AMH</it>).</p> <p>A global gene expression profile for each follicular compartment during early developmental stages was identified here for the first time, using a bovine Affymetrix chip. Most notably, the granulosa cell dataset is unique to date. The comparison of oocyte vs. follicular cell transcriptomes revealed 1050 transcripts specific to the granulosa cell and 759 specific to the oocyte.</p> <p>Functional analyses allowed the characterization of the three main cellular events involved in early folliculogenesis and confirmed the relevance and potential of LCM-derived RNA.</p> <p>Conclusions</p> <p>The ovary is a complex mixture of different cell types. Distinct cell populations need therefore to be analyzed for a better understanding of their potential interactions. LCM and microarray analysis allowed us to identify novel gene expression patterns in follicular cells at different stages and in oocyte populations.</p

Ocean acidification alters fish populations indirectly through habitat modification

Ocean ecosystems are predicted to lose biodiversity and productivity from increasing ocean acidification1. Although laboratory experiments reveal negative effects of acidification on the behaviour and performance of species2, 3, more comprehensive predictions have been hampered by a lack of in situ studies that incorporate the complexity of interactions between species and their environment. We studied CO2 vents from both Northern and Southern hemispheres, using such natural laboratories4 to investigate the effect of ocean acidification on plant–animal associations embedded within all their natural complexity. Although we substantiate simple direct effects of reduced predator-avoidance behaviour by fishes, as observed in laboratory experiments, we here show that this negative effect is naturally dampened when fish reside in shelter-rich habitats. Importantly, elevated CO2 drove strong increases in the abundance of some fish species through major habitat shifts, associated increases in resources such as habitat and prey availability, and reduced predator abundances. The indirect effects of acidification via resource and predator alterations may have far-reaching consequences for population abundances, and its study provides a framework for a more comprehensive understanding of increasing CO2 emissions as a driver of ecological change

The Hygiene Hypothesis and Its Inconvenient Truths about Helminth Infections

Current iterations of the hygiene hypothesis suggest an adaptive role for helminth parasites in shaping the proper maturation of the immune system. However, aspects of this hypothesis are based on assumptions that may not fully account for realities about human helminth infections. Such realities include evidence of causal associations between helminth infections and asthma or inflammatory bowel disease as well as the fact that helminth infections remain widespread in the United States, especially among populations at greatest risk for inflammatory and autoimmune diseases

High recruitment associated with increased sea temperatures towards the southern range edge of a Western Australian endemic reef fish Choerodon rubescens (family Labridae)

Choerodon rubescens is a subtropical wrasse endemic to Western Australia which has recently recruited in high abundance into lagoonal habitats at the southern end of its distribution. Abundance, size structure and habitat associations of juvenile C. rubescens were assessed during summer and autumn 2013 (January–May) via underwater visual census across available shallow water habitats towards the southern range edge of their distribution (32°S, 115°E). High abundances of juveniles (up to 14 fish/40 m2) were found in areas where they were previously absent or in low abundance. Lagoonal habitats presented abundances three to eight times higher than seagrass beds or rocky reef, indicating preference of C. rubescens for mixed lagoonal habitatsas settlement grounds. Such habitats contain open sandy areas with small rocks and rubble that are important feeding grounds for juveniles. Based on the size structure of populations encountered, recruitment was estimated to occur during summer 2011–12 and 2012–13.This coincides with water temperatures 1 to 2 °C higher than long-term averages in the region, making conditions more favourable for recruits to survive in greater numbers. We conclude that the high abundance of C. rubescens recruits towards the southern end of their distribution together with trends of increasing water temperature and the availability of suitable settlement habitat to the south of their present range, indicate a capacity for the species to shift its distribution southwards.Monitoring of future recruitment events will be crucial to determining range expansion capacity andguiding management efforts for this endemic and important fisheries species

Suspended sediment alters predator–prey interactions between two coral reef fishes

Sediment derived from agriculture and development increases water turbidity and threatens the health of inshore coral reefs. In this study, we examined whether suspended sediment could change predation patterns through a reduction in visual cues. We measured survivorship of newly settled Chromis atripectoralis exposed to Pseudochromis fuscus, a common predator of juvenile damselfishes, in aquaria with one of four turbidity levels. Increased turbidity led to a nonlinear response in predation patterns. Predator-induced mortality was ~50 % in the control and low turbidity level, but exhibited a substantial increase in the medium level. In the highest turbidity level, predation rates declined to the level seen in the control. These results suggest an imbalance in how the predator and prey cope with turbidity. A turbidity-induced change to the outcome of predator–prey interactions represents a major change to the fundamental processes that regulate fish assemblages