Transsexual cells instead of spermatozoa
Researchers from the Shanghai Institute of Biological Sciences, working under the leadership of Jinsong Li, have developed a new method for creating genetically modified animals for research purposes. The secret of the method is to fertilize immature eggs using haploid embryonic stem cells (GAESCS) instead of spermatozoa. Just like spermatozoa, such stem cells carry only one (paternal) copy of each of the chromosomes.
Currently, genetically modified mice are obtained from embryonic stem cells that have two copies (maternal and paternal) of each gene. Diploid embryonic cells with modified genes are injected into blastocysts in the early stages of development to produce chimeras – animals whose tissues consist of cells, each of which has one of two possible genomes. Since the modified genome randomly enters the cells that give rise to eggs and spermatozoa, the necessary genetic modifications are transmitted to a certain number of descendants. However, the process of raising such animals is very slow and does not provide stable results.
Haploid embryonic stem cells, proposed by the authors to replace spermatozoa, are created by removing nuclei from immature eggs (oocytes), followed by the introduction of spermatozoa into them. The "male" chemical modifications preserved by such transsexual cells are sufficient to start the process of fertilization of a real egg.
Using the described technique, scientists managed to grow adult mice capable of producing offspring and carrying genetic traits encoded in the genome of haploid embryonic stem cells.
The developed approach will not only facilitate the work on the creation of genetically modified mice, but will also make it possible to endow the studied traits with other animals whose genomes cannot be modified using existing methods, for example, monkeys. Theoretically, it can also be used during assisted reproductive procedures for patients with genetic diseases.
In the near future, the researchers plan to devote their work to the improvement of haploid embryonic stem cells, the purpose of which is to maximize the approximation of the characteristics to the characteristics of spermatozoa.
Article by Hui Yang et al. Generation of Genetically Modified Mice by Oocyte Injection of Androgenetic Haploid Embryonic Stem Cells is published in the journal Cell.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of ScienceDaily:
From Embryonic Stem Cells, a Sperm Replacement and Easier Path to Genetic Modification.
27.04.2012