sept8a and sept8b mRNA expression in the developing and adult zebrafish

Genome Wide Analysis for Growth at Two Growth Stages in A New Fast-Growing Common Carp Strain (Cyprinus carpio L.)

In order to identify candidate genes or loci associated with growth performance of the newly established common carp strain, Xinlong, we conducted a genome-wide association analysis using 2b-RAD technology on 123 individuals. We constructed two sets of libraries associated with growth-related parameters (weight, length, width and depth) measured at two different grow-out stages. Among the 413,059 SNPs identified using SOAP SNP calling, 147,131 were tested for GWAS after quality filtering. Finally, 39 overlapping SNPs, assigned to four genomic locations, were associated with growth traits in two stages. These loci were assigned to functional classes related to immune response, response to stress, neurogenesis, cholesterol metabolism and development, and proliferation and differentiation of cells. By overlapping results of Plink and EMMAX analyses, we identified three genes: TOX, PLK2 and CD163 (both methods P < 0.05). Our study results could be used for marker-assisted selection to further improve the growth of the Xinlong strain, and illustrate that largely different sets of genes drive the growth of carp in the early and late grow-out stages.

Three-sectioning method: A procedure for studying hard tissues and large pieces under light and electron microscopy

The histological study of hard pieces such as tendons and calcified lesions and tissues is a field that has been gaining increased attention owing to the rapid development of implantable prostheses, among other factors. In these studies, serial sectioning is utilized to detect areas of interest throughout the entire piece, as it enables the application of the appropriate light and electron microscopy techniques in these areas. We propose the "three-sectioning method" that subjects the pieces to three consecutive cycles of embedding and sectioning to localize and study the areas of interest, as an efficient technique for these histological studies. The pieces were first embedded in epoxy resin and then cut into thick sections (approximately 300 μm) for the first cycle. Next, areas of interest selected on these thick sections were re-embedded in epoxy resin to be sectioned again (second sectioning) to obtain a series of semithin sections (1-3 μm). These semithin sections are usually studied using the most relevant techniques for light microscopy. Smaller areas of interest are selected to be cut into ultrathin sections (60-90 nm) for transmission electron microscopy. If necessary, the selected areas of the semithin sections can be embedded again, and then cut into new ultrathin sections. The different kinds of sections we have described here may also be studied using scanning electron microscopy. This systematic method facilitates correlative microscopy from lower to higher magnifications along with the usage of a broad variety of histological techniques including electron microscopy.

Analysis of the Role of the Mc4r System in Development, Growth, and Puberty of Medaka

In mammals the melanocortin 4 receptor (Mc4r) signaling system has been mainly associated with the regulation of appetite and energy homeostasis. In fish of the genus Xiphophorus (platyfish and swordtails) puberty onset is genetically determined by a single locus, which encodes the mc4r. Wild populations of Xiphophorus are polymorphic for early and late-maturing individuals. Copy number variation of different mc4r alleles is responsible for the difference in puberty onset. To answer whether this is a special adaptation of the Mc4r signaling system in the lineage of Xiphophorus or a more widely conserved mechanism in teleosts, we studied the role of Mc4r in reproductive biology of medaka (Oryzias latipes), a close relative to Xiphophorus and a well-established model to study gonadal development. To understand the potential role of Mc4r in medaka, we characterized the major features of the Mc4r signaling system (mc4r, mrap2, pomc, agrp1). In medaka, all these genes are expressed before hatching. In adults, they are mainly expressed in the brain. The transcript of the receptor accessory protein mrap2 co-localizes with mc4r in the hypothalamus in adult brains indicating a conserved function of modulating Mc4r signaling. Comparing growth and puberty between wild-type and mc4r knockout medaka revealed that absence of Mc4r does not change puberty timing but significantly delays hatching. Embryonic development of knockout animals is retarded compared to wild-types. In conclusion, the Mc4r system in medaka is involved in regulation of growth rather than puberty.