Preparing graduate student teaching assistants in the sciences: An intensive workshop focused on active learning.

In the past ten years, increasing evidence has demonstrated that scientific teaching and active learning improve student retention and learning gains in the sciences. Graduate teaching assistants (GTAs), who play an important role in undergraduate education at many universities, require training in these methods to encourage implementation, long-term adoption, and advocacy. Here, we describe the design and evaluation of a two-day training workshop for first-year GTAs in the life sciences. This workshop combines instruction in current research and theory supporting teaching science through active learning as well as opportunities for participants to practice teaching and receive feedback from peers and mentors. Postworkshop assessments indicated that GTA participants' knowledge of key topics increased during the workshop. In follow-up evaluations, participants reported that the workshop helped them prepare for teaching. This workshop design can easily be adapted to a wide range of science disciplines. Overall, the workshop prepares graduate students to engage, include, and support undergraduates from a variety of backgrounds when teaching in the sciences. © 2018 by The International Union of Biochemistry and Molecular Biology, 46:318-326, 2018.

Pairing of competitive and topologically distinct regulatory modules enhances patterned gene expression.

Biological networks are inherently modular, yet little is known about how modules are assembled to enable coordinated and complex functions. We used RNAi and time series, whole-genome microarray analyses to systematically perturb and characterize components of a Caenorhabditis elegans lineage-specific transcriptional regulatory network. These data are supported by selected reporter gene analyses and comprehensive yeast one-hybrid and promoter sequence analyses. Based on these results, we define and characterize two modules composed of muscle- and epidermal-specifying transcription factors that function together within a single cell lineage to robustly specify multiple cell types. The expression of these two modules, although positively regulated by a common factor, is reliably segregated among daughter cells. Our analyses indicate that these modules repress each other, and we propose that this cross-inhibition coupled with their relative time of induction function to enhance the initial asymmetry in their expression patterns, thus leading to the observed invariant gene expression patterns and cell lineage. The coupling of asynchronous and topologically distinct modules may be a general principle of module assembly that functions to potentiate genetic switches.

Caenorhabditis phylogeny predicts convergence of hermaphroditism and extensive intron loss.

Despite the prominence of Caenorhabditis elegans as a major developmental and genetic model system, its phylogenetic relationship to its closest relatives has not been resolved. Resolution of these relationships is necessary for studying the steps that underlie life history, genomic, and morphological evolution of this important system. By using data from five different nuclear genes from 10 Caenorhabditis species currently in culture, we find a well resolved phylogeny that reveals three striking patterns in the evolution of this animal group: (i) Hermaphroditism has evolved independently in C. elegans and its close relative Caenorhabditis briggsae; (ii) there is a large degree of intron turnover within Caenorhabditis, and intron losses are much more frequent than intron gains; and (iii) despite the lack of marked morphological diversity, more genetic disparity is present within this one genus than has occurred within all vertebrates.