The chicken has played an important role in biological discoveries since the 17th century (Stern, 2005). Many investigations into vertebrate development have utilized the chicken due to the accessibility of the chick embryo and its ease of manipulation (Brown et al., 2003). However, the lack of genetic resources has often handicapped these studies and so the chick is frequently overlooked as a model organism for the analysis of vertebrate gene function in favor of mice or zebrafish. In the past six years this situation has altered dramatically with the generation of over half a million expressed sequence tags and >20,000 fully sequenced chicken cDNAs (Boardman et al. 2002; Caldwell et al., 2005; Hubbard et a... More
The chicken has played an important role in biological discoveries since the 17th century (Stern, 2005). Many investigations into vertebrate development have utilized the chicken due to the accessibility of the chick embryo and its ease of manipulation (Brown et al., 2003). However, the lack of genetic resources has often handicapped these studies and so the chick is frequently overlooked as a model organism for the analysis of vertebrate gene function in favor of mice or zebrafish. In the past six years this situation has altered dramatically with the generation of over half a million expressed sequence tags and >20,000 fully sequenced chicken cDNAs (Boardman et al. 2002; Caldwell et al., 2005; Hubbard et al., 2005) together with a 6X coverage genome sequence (Hillier et al., 2004). These resources have created a comprehensive catalogue of chicken genes with readily accessible cDNA and EST resources available via ARK-GENOMICS (www.ark-genomics.org) for the functional analysis of vertebrate gene function.
The chicken embryo is conveniently packaged in an egg shell and it is a relatively straightforward process to create a window in this shell. This allows access to the embryo at any stage of development and facilitates manipulation of the embryo. After this procedure, the window can be resealed and the egg incubated for a suitable time period prior to analyzing the results of the manipulation. Such manipulations traditionally involved "cut and paste" experiments in which tissue is excised and transplanted to ectopic locations in the embryo or from quail embryos, which are readily distinguished histologically, to chick embryos to generate chimeras. Whilst these studies have led to many important discoveries (Brown et al., 2003), there has recently been an increase in direct genetic manipulation approaches that can be applied to the chick embryo.
