Pre-selection of integration sites imparts repeatable transgene expression

Area of Science:

• * Molecular Biology
• * Genetics
• * Developmental Biology

Background:

• * Variable transgene expression is a common challenge in transgenic research, often caused by integration site effects and copy number variations.
• * Random DNA integration can lead to unpredictable gene regulation and expression patterns.
• * Consistent and predictable transgene expression is crucial for accurate biological studies.

Purpose of the Study:

• * To develop and validate a method for identifying genomic sites permissive for consistent transgene expression.
• * To demonstrate the efficient introduction of single-copy transgenes using homologous recombination at pre-selected sites.
• * To improve the repeatability and reliability of transgene expression in research models.

Main Methods:

• * Selection of embryonic stem (ES) cell clones expressing a randomly integrated HPRT marker linked to an Oct4/lacZ transgene.
• * In vitro assessment of lacZ expression regulation during differentiation in 794 ES clones.
• * Introduction of developmental promoters (thyroglobulin, Hox2.6, Myf5) into selected integration sites (clones 710 and 91) via homologous recombination.
• * In vivo analysis of lacZ expression patterns in transgenic embryos driven by the introduced promoters.

Main Results:

• * Two ES clones (710 and 91) were identified, exhibiting distinct patterns of lacZ gene regulation.
• * Clone 710 demonstrated appropriate in vitro and in vivo regulation of lacZ expression with developmental promoters.
• * Clone 91 showed ectopic lacZ expression across all tested promoters, indicating site-specific regulatory influence.
• * Homologous recombination facilitated efficient single-copy transgene integration at the targeted sites.

Conclusions:

• * Pre-selecting genomic sites for transgene integration significantly enhances the repeatability of transgene expression.
• * This strategy provides an efficient method for introducing single-copy transgenes through homologous recombination.
• * The findings offer a valuable approach for generating more reliable transgenic models for biological research.