Germline Specification: Small Things Have a Big Role

The role of embryonic stem cells, transcription and growth factors in mammals: A review

Mammals represent a relevant species in worldwide cultures with significant commercial value. These animals are considered an attractive large animal model for biomedical and biotechnology research. The development of large animal experimental models may open alternative strategies for investigating stem cells (SCs) physiology and potential application in the veterinary field. The embryonic stem cells (ESCs) are known to possess natural pluripotency that confers the ability to differentiate into various tissues in vivo and in vitro. These notable characteristics can be useful for research and innovative applications, including biomedicine, agriculture and industry. Transcription factors play a crucial role in preserving stem cell self-renewal, whereas growth factors are involved in both growth and differentiation. However, to date, many questions concerning pluripotency, cellular differentiation regulator genes, and other molecules such as growth factors and their interactions in many mammalian species remain unresolved. The purpose of this review is to provide an overall review regarding the study of ESCs in mammals and briefly discuss the role of transcription and growth factors.

Dynamics of gene expression patterns during early development of the European seabass (Dicentrarchus labrax)

Larval and embryonic stages are the most critical period in the life cycle of marine fish. Key developmental events occur early in development and are influenced by external parameters like stress, temperature, salinity, and photoperiodism. Any failure may cause malformations, developmental delays, poor growth, and massive mortalities. Advanced understanding of molecular processes underlying marine larval development may lead to superior larval rearing conditions. Today, the new sequencing and bioinformatic methods allow transcriptome screens comprising messenger (mRNA) and microRNA (miRNA) with the scope of detecting differential expression for any species of interest. In the present study, we applied Illumina technology to investigate the transcriptome of early developmental stages of the European seabass ( Dicentrarchus labrax). The European seabass, in its natural environment, is a euryhaline species and has shown high adaptation processes in early life phases. During its embryonic and larval phases the European seabass lives in a marine environment and as a juvenile it migrates to coastal zones, estuaries, and lagoons. Investigating the dynamics of gene expression in its early development may shed light on factors promoting phenotypic plasticity and may also contribute to the improvement and advancement of rearing methods of the European seabass, a species of high economic importance in European and Mediterranean aquaculture. We present the identification, characterization, and expression of mRNA and miRNA, comprising paralogous genes and differentially spliced transcripts from early developmental stages of the European seabass. We further investigated the detection of possible interactions of miRNA with mRNA.

Chromatin modifications regulate germ cell development and transgenerational information relay

Germ cells transmit genetic, cytoplasmic and epigenetic information to the next generation. Recent reports describe the importance of chromatin modifiers and small RNAs for germ cells development in Drosophila. We also review exciting progress in our understanding of piRNAs functions, which demonstrate that this class of small RNAs is both an adaptive and inheritable epigenetic memory.

Comparative genomic analysis of Drosophila melanogaster and vector mosquito developmental genes

Genome sequencing projects have presented the opportunity for analysis of developmental genes in three vector mosquito species: Aedes aegypti, Culex quinquefasciatus, and Anopheles gambiae. A comparative genomic analysis of developmental genes in Drosophila melanogaster and these three important vectors of human disease was performed in this investigation. While the study was comprehensive, special emphasis centered on genes that 1) are components of developmental signaling pathways, 2) regulate fundamental developmental processes, 3) are critical for the development of tissues of vector importance, 4) function in developmental processes known to have diverged within insects, and 5) encode microRNAs (miRNAs) that regulate developmental transcripts in Drosophila. While most fruit fly developmental genes are conserved in the three vector mosquito species, several genes known to be critical for Drosophila development were not identified in one or more mosquito genomes. In other cases, mosquito lineage-specific gene gains with respect to D. melanogaster were noted. Sequence analyses also revealed that numerous repetitive sequences are a common structural feature of Drosophila and mosquito developmental genes. Finally, analysis of predicted miRNA binding sites in fruit fly and mosquito developmental genes suggests that the repertoire of developmental genes targeted by miRNAs is species-specific. The results of this study provide insight into the evolution of developmental genes and processes in dipterans and other arthropods, serve as a resource for those pursuing analysis of mosquito development, and will promote the design and refinement of functional analysis experiments.

Sequential SDF1a and b-induced mobility guides Medaka PGC migration

Assembly and formation of the gonad primordium are the first steps toward gonad differentiation and subsequent sex differentiation. Primordial germ cells (PGCs) give rise to the gametes that are responsible for the development of a new organism in the next generation. In many organisms, following their specification the germ cells migrate toward the location of the prospective gonadal primordium. To accomplish this, the PGCs obtain directional cues from cells positioned along their migration path. One such cue, the chemokine SDF1 (stromal cell-derived factor 1) and its receptor CXCR4 have recently been found to be critical for proper PGC migration in zebrafish, chick and mouse. We have studied the mechanisms responsible for PGC migration in Medaka. In contrast to the situation observed in zebrafish, where proper PGC positioning is the result of active migration in the direction of the source of SDF1a, Medaka PGC movements are shown to be the consequence of a combination of active SDF1a and SDF1b-guided migration. In this process both SDF1 co-orthologues show only partly overlapping expression pattern and cooperate in the correct positioning of the PGCs.

Stem cells and their niche: an inseparable relationship

A recent Keystone symposium on 'Stem Cell Interactions with their Microenvironmental Niche' was organized by David T. Scadden and Allan C. Spradling. The meeting was held in conjunction with another Keystone symposium, 'Stem Cells and Cancer', at Keystone, Colorado. Among the work that was presented at this meeting, scientists presented data that advances our understanding of the contribution that the niche makes to stem cell maintenance. Novel types of stem cells and niches were also reported and new findings that clarify our understanding of the molecular mechanisms that regulate and maintain stem cells were presented.