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Open Access Methodology article

Bacillus subtilis genome vector-based complete manipulation and reconstruction of genomic DNA for mouse transgenesis

Tetsuo Iwata1, Shinya Kaneko2, Yuh Shiwa3, Takayuki Enomoto4, Hirofumi Yoshikawa35 and Junji Hirota14*

Author Affiliations

1 Department of Bioengineering, Graduate School of Bioscience and Bioengineering, Tokyo Institute of Technology, Yokohama, 226-8501, Japan

2 Department of Molecular Bioscience, Graduate School of Bioscience and Bioengineering, Tokyo Institute of Technology, Yokohama, 226-8501, Japan

3 Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Tokyo, 156-8502, Japan

4 Center for Biological Resources and Informatics, Tokyo Institute of Technology, 4259-B63 Nagatsuta-cho, Midori-ku, Yokohama, 226-8501, Japan

5 Department of Bioscience, Tokyo University of Agriculture, Tokyo, 156-8502, Japan

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BMC Genomics 2013, 14:300  doi:10.1186/1471-2164-14-300

Published: 3 May 2013

Abstract

Background

The Bacillus subtilis genome (BGM) vector is a novel cloning system for large DNA fragments, in which the entire 4.2 Mb genome of B. subtilis functions as a vector. The BGM vector system has several attractive properties, such as a large cloning capacity of over 3 Mb, stable propagation of cloned DNA and various modification strategies using RecA-mediated homologous recombination. However, genetic modifications using the BGM vector system have not been fully established, and this system has not been applied to transgenesis. In this study, we developed important additions to the genetic modification methods of the BGM vector system. To explore the potential of the BGM vector, we focused on the fish-like odorant receptor (class I OR) gene family, which consists of 158 genes and forms a single gene cluster. Although a cis-acting locus control region is expected to regulate transcription, this has not yet been determined experimentally.

Results

Using two contiguous bacterial artificial chromosome clones containing several class I OR genes, we constructed two transgenes in the BGM vector by inserting a reporter gene cassette into one class I OR gene. Because they were oriented in opposite directions, we performed an inversion modification to align their orientation and then fused them to enlarge the genomic structure. DNA sequencing revealed that no mutations occurred during gene manipulations with the BGM vector. We further demonstrated that the modified, reconstructed genomic DNA fragments could be used to generate transgenic mice. Transgenic mice carrying the enlarged transgene recapitulated the expression and axonal projection patterns of the target class I OR gene in the main olfactory system.

Conclusion

We offer a complete genetic modification method for the BGM vector system, including insertion, deletion, inversion and fusion, to engineer genomic DNA fragments without any trace of modifications. In addition, we demonstrate that this system can be used for mouse transgenesis. Thus, the BGM vector system can be an alternative platform for engineering large DNA fragments in addition to conventional systems such as bacterial and yeast artificial chromosomes. Using this system, we provide the first experimental evidence of a cis-acting element for a class I OR gene.