Phage-based E. coli homologous recombination systems have been extensively developed in recent years, and these recombination-mediated genetic engineering (“recombineering”) methods are now the preferred technique for carrying out genetic modifications in chromosomes and plasmids. Recombineering is efficient and precise and circumvents many of the problems of traditional genetic engineering methods, primarily the need to locate specific restriction enzyme sites. Construction of Gene-Targeting Vectors by Recombineering, from Pentao Liu and colleagues at the Wellcome Trust Sanger Institute gives detailed instructions for using recombineering to construct targeting vectors for the generation of conditional knockout mice. As one of September’s Featured Articles in Cold Spring Harbor Protocols, the method is freely available to subscribers and non-subscribers alike.

Although many feel that RSS is dead, I still find it to be a highly useful tool for finding new interesting reading material. As such, we’re happy to announce some new functionality in Cold Spring Harbor Protocols involving our RSS feeds that send out alerts when new articles are published. Previously you could only sign up for RSS feeds for article types–protocols, emerging model organisms, etc. Now you can sign up for notice of new material by subject area. This will let you see when new protocols are available in your specific subject area, whether it’s Genome Analysis, Imaging Development or Plant Cell Culture. For those more reliant on e-mail than RSS feeds, remember you can sign up for a wide variety of alerts by table of contents, subject, citation, keyword or author.

Our long-running series of articles highlighting emerging model organisms continues in September with three entries, The Starlet Sea Anemone (Nematostella vectensis), Cephalochordates (Amphioxus or Lancelets) and The Western Clawed Frog (Xenopus tropicalis).

The slow rate of sequence evolution, the presumed high degree of preservation of ancestral traits, the ease of culturing, and the availability and experimental tractability of the early embryos have made Nematostella a prime cnidarian model for a number of biological studies. It serves not only as a model system for cnidarians, but also as an important representative of its phylum in comparisons with other lower Metazoa or Bilateria. Ulrich Technau and colleagues provide an overview of Nematostella, and protocols for spawning, in situ hybridization, antibody and phalloidin staining and BrdU labeling.

Cephalochordates, commonly called amphioxus or lancelets, are marine invertebrate chordates. Studies on cephalochordates have answered some long-standing questions concerning the evolution of vertebrates from their invertebrate ancestors and have also generated interesting avenues for further investigation of the evolutionary origin of developmental mechanisms that led to the emergence of the vertebrate body plan. Linda Holland and colleagues provide background on Cephalochordates, along with detailed methods for Amphioxus embryo collection, in situ hybridization, DNA extraction, and RNA extraction and extracting RNA from small amounts of tissue for RT-PCR.

Xenopus tropicalis is a small, wholly aquatic frog that is a diploid relative of Xenopus laevis. It shares many of the advantages of X. laevis as a model organism for studying aspects of vertebrate biology, particularly the genetic, biochemical, and environmental factors that influence vertebrate development from embryonic stages through adulthood. X. tropicalis is also finding uses as an important test species for assessing the impact of environmental toxins and disease on amphibians, which are in decline in many areas of the world due to water-borne pollutants and infectious agents such as the chytrid fungus. Frank Conlon and colleagues have contributed an overview of X. tropicalis, along with protocols for natural mating, in vitro fertilization, and tissue sampling and genomic DNA preparation.

Chromatin Immunoprecipitation (ChIP) is an invaluable method for studying the interactions between proteins and DNA on a genome-wide scale. ChIP can be used to determine whether a transcription factor interacts with a candidate target gene, and is used to monitor the presence of histones with posttranslational modifications at specific genomic locations. The results are often extremely useful for investigating the functions of specific transcription factors or histone modifications. In the September issue of Cold Spring Harbor Protocols, Michael Carey, Craig Peterson and Stephen Smale present Chromatin Immunoprecipitation (ChIP), an optimized protocol for use in mammalian cells. This is one of September’s featured articles, and like all our featured articles, it is freely available to subscribers and non-subscribers alike.