Faster Production of Disease Models

By microinjection of TALENs and synthetic oligodesoxynucleotides, the scientists altered the genes in the fertilized egg cells of mice so that all progeny cells were equipped with the same mutation. Because through this method the laborious steps to produce targeted mutants are not required, animal models can be established much faster and using substantially fewer experimental animals.

An efficient method for the rapid production of mouse disease models has been developed  at Helmholtz Zentrum München. Mouse models are used for the genetic analysis of disease mechanisms and are still considered to be indispensable for this purpose. In most cases, models are used which are produced by targeted mutations in embryonic stem cells (ES cells). However, this production process is complex and time-consuming, since among other steps, targeting vectors must be constructed with selection markers, mutated ES cells must be isolated and germline chimeras must be produced. All of these procedures are very laborious and time intensive. Including all steps, the scientists often need one to two years to produce a knockout mouse model using these methods. This poses a hurdle for the analysis of the ever-increasing number of known human disease-associated mutations that are discovered using high-throughput analyses of the human genome.

Scientists of the Institute of Developmental Genetics have succeeded in developing a faster way to produce mouse disease models. By microinjection of so-called TALENs (Transcription Activator-like Effector Nucleases) and synthetic oligodesoxynucleotides directly into the embryos in the one-cell stage, any desired mutation or deletion can be induced within two days and can also be reversed. Since for this purpose neither ES cultures nor targeting vectors are required, this technology enables immediate changes in the germ cells, so that heterozygous mutants are available within 18 weeks. This novel method is thus significantly faster than the previously used methods. Through the intelligent production of mouse models required for drug development, the number of experimental animals needed for this purpose can be drastically reduced.

TALENs – Transcription Activator-like Effector Nuclease are modular enzymes that recognize and cleave specific double-­stranded DNA sequences. It is possible to create different sequence-­specific variants with which virtually all genes in the genome can be cleaved and altered by co-administration of synthetic oligodeoxy­nucleotides. Thus, specific genes can be removed selectively, and genetic defects can be incorporated into the cell or repaired.