January’s issue of Cold Spring Harbor Protocols wraps up the second volume of our ongoing Emerging Model Organisms series. The idea behind the series is that technical advances have allowed for great expansion in the range of organisms used for research. Each set of articles is meant to introduce the reader to a new organism, to explain why it’s useful for laboratory research and to provide information on husbandry, genetics and genomics, and a set of basic laboratory protocols. The first set of 23 emerging model systems was collected in a laboratory manual, and the current set of 18 will soon be as well. January’s organisms are:

The Rabbit (Oryctolagus cuniculus): The rabbit is a valuable animal model for a variety of biomedical research areas including in vitro fertilization, early embryology and organogenesis, neurophysiology, ophthalmology, and cardiovascular research. The rabbit is also used as a model for toxicology studies and analyses of drug effects on embryo and fetal development, as well as for research involving the immune system, not to mention its common use in antibody production. Christoph Viebahn and colleagues from the University of Göttingen provide an overview of the rabbit as an experimental system, and protocols for mating and embryo isolation, dissection and fixation of embryos, embryo culture, staining and imaging, immunofluorescence, in situ hybridization, mounting, embedding and sectioning, embryo transfer, artificial insemination and cryopreservation of embryos.

Paramecium tetraurelia: Paramecium makes an interesting unicellular model, as the authors note:

Paramecium tetraurelia is a widely distributed, free-living unicellular organism that feeds on bacteria and can easily be cultured in the laboratory. Its position within the phylum Ciliophora, remote from the most commonly used models, offers an interesting perspective on the basic cellular and molecular processes of eukaryotic life. Its large size and complex cellular organization facilitate morphogenetic studies of conserved structures, such as cilia and basal bodies, as well as electrophysiological studies of swimming behavior. Like all ciliates, P. tetraurelia contains two distinct types of nuclei, the germline micronucleus (MIC) and the somatic macronucleus (MAC), which differentiate from copies of the zygotic nucleus after fertilization. The sexual cycle can be managed by controlling food uptake, allowing the study of a developmentally regulated differentiation program in synchronous cultures. Spectacular genome rearrangements occur during the development of the somatic macronucleus. Their epigenetic control by RNA-mediated homology-dependent mechanisms, which might underlie long-known cases of non-Mendelian inheritance, provides evolutionary insight into the diversity of small RNA pathways involved in genome regulation. Being endowed with two alternative modes of sexual reproduction (conjugation and autogamy), P. tetraurelia is ideally suited for genetic analyses, and the recent sequencing of its macronuclear genome revealed one of the largest numbers of genes in any eukaryote. Together with the development of new molecular techniques, including complementation cloning and an easily implemented technique for reverse genetics based on RNA interference (RNAi), these features make P. tetraurelia a very attractive unicellular model.

Eric Meyer and colleagues from the CNRS have written an overview of P tetraurelia as a model system, and protocols for maintaining cell lines, mass culture, gene silencing, DNA microinjection, immunocytochemistry, and fluorescence in situ hybridization.

We have some new organisms in the works for Volume 3, but would welcome your suggestions.