BackgroundVertebrate skin appendages are constructed of keratins produced by multigene families. Alpha (α) keratins are found in all vertebrates, while beta (β) keratins are found exclusively in reptiles and birds. We have studied the molecular evolution of these gene families in the genomes of 48 phylogenetically diverse birds and their expression in the scales and feathers of the chicken.ResultsWe found that the total number of α-keratins is lower in birds than mammals and non-avian reptiles, yet two α-keratin genes (KRT42 and KRT75) have expanded in birds. The β-keratins, however, demonstrate a dynamic evolution associated with avian lifestyle. The avian specific feather β-keratins comprise a large majority of the total number of β-keratins, but independently derived lineages of aquatic and predatory birds have smaller proportions of feather β-keratin genes and larger proportions of keratinocyte β-keratin genes. Additionally, birds of prey have a larger proportion of claw β-keratins. Analysis of α- and β-keratin expression during development of chicken scales and feathers demonstrates that while α-keratins are expressed in these tissues, the number and magnitude of expressed β-keratin genes far exceeds that of α-keratins.ConclusionsThese results support the view that the number of α- and β-keratin genes expressed, the proportion of the β-keratin subfamily genes expressed and the diversification of the β-keratin genes have been important for the evolution of the feather and the adaptation of birds into multiple ecological niches.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-014-0249-1) contains supplementary material, which is available to authorized users.

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the post-transcriptional level. Previous studies have shown that miRNA regulation contributes to a diverse set of processes including cellular differentiation and morphogenesis which leads to the creation of different cell types in multicellular organisms and is thus key to animal development. Feathers are one of the most distinctive features of extant birds and are important for multiple functions including flight, thermal regulation, and sexual selection. However, the role of miRNAs in feather development has been woefully understudied despite the identification of cell signaling pathways, cell adhesion molecules and structural genes involved in feather development. In this study, we performed a microarray experiment comparing the expression of miRNAs and mRNAs among three embryonic stages of development and two tissues (scutate scale and feather) of the chicken. We combined this expression data with miRNA target prediction tools and a curated list of feather related genes to produce a set of 19 miRNA-mRNA duplexes. These targeted mRNAs have been previously identified as important cell signaling and cell adhesion genes as well as structural genes involved in feather and scale morphogenesis. Interestingly, the miRNA target site of the cell signaling pathway gene, Aldehyde Dehydrogenase 1 Family, Member A3 (ALDH1A3), is unique to birds indicating a novel role in Aves. The identified miRNA target site of the cell adhesion gene, Tenascin C (TNC), is only found in specific chicken TNC splice variants that are differentially expressed in developing scutate scale and feather tissue indicating an important role of miRNA regulation in epidermal differentiation. Additionally, we found that β-keratins, a major structural component of avian and reptilian epidermal appendages, are targeted by multiple miRNA genes. In conclusion, our work provides quantitative expression data on miRNAs and mRNAs during feather and scale development and has produced a highly diverse, but manageable list of miRNA-mRNA duplexes for future validation experiments.

Gene co-expression network analysis has been a research method widely used in systematically exploring gene function and interaction. Using the Weighted Gene Co-expression Network Analysis (WGCNA) approach to construct a gene co-expression network using data from a customized 44K microarray transcriptome of chicken epidermal embryogenesis, we have identified two distinct modules that are highly correlated with scale or feather development traits. Signaling pathways related to feather development were enriched in the traditional KEGG pathway analysis and functional terms relating specifically to embryonic epidermal development were also enriched in the Gene Ontology analysis. Significant enrichment annotations were discovered from customized enrichment tools such as Modular Single-Set Enrichment Test (MSET) and Medical Subject Headings (MeSH). Hub genes in both trait-correlated modules showed strong specific functional enrichment toward epidermal development. Also, regulatory elements, such as transcription factors and miRNAs, were targeted in the significant enrichment result. This work highlights the advantage of this methodology for functional prediction of genes not previously associated with scale- and feather trait-related modules.

Prior to Spring Semester 2011, the University of South Carolina Biological Sciences curriculum offered only a face‐to‐face histology course where students were required to attend lectures and labs utilizing the microscope. Laboratory space and equipment limited enrollment in the face‐to‐face class which never exceeded 50 consisting mainly of pre‐medical and pre‐dental students. In Spring, 2011, for the first time, we offered a fully online histology course in which all lectures, labs, quizzes and exams were online with no face‐to‐face meetings. Enrollment jumped to 121 in that first semester to include students from more than ten curricular programs across the institution such as anthropology, biochemistry, biomedical sciences and experimental psychology. We now have eight semesters of experience with the course that includes nearly 800 undergraduate, graduate and special certificate program students having completed the course successfully. Lectures have evolved to include SCORM grading of quizzes at the end of each lecture permitting the assignment of viewing lectures as course activity. For the virtual labs, a web based virtual microscopy program is used that contains a collection of over 100 annotated specimens, including two forms of self‐assessment. Recently, we have implemented Biolucida Cloud (MBFbioscience.com) allowing the inclusion of virtual slides in practical exams as unknowns and delivered in random order integrated with Blackboard. Exams have evolved from two attempts with feedback to one attempt with no feedback except the score. Included will be the impact of midterm and final exam construction and administration changes on final grade distribution. The online histology course is now offered year around and remains very popular. Grant Funding Source: Supported by NSF Grant‐1317771