Institute Cytology and Genetics

Laboratory of Developmental Genetics

Head O.L.Serov, Dr.Biol.Sci., Prof.

Radiation induced map of the p-arm of pig chromosome 2 (in cR)

The results on testing of pluripotency in intraspecific hybrid cells obtained by a fusion of ES cells (strain HM-1, derived from a 129/Ola mouse, right) with splenocytes from an adult DD female. After introduction of the hybrid cells into the blastocoele (recipient strain C57BL/J, left), 5 chimeric mice were produced, one is shown in the center. Yellow spots appeared as a result of hybrid cell participation in the formation of variegated color of a chimera. The results of biochemical analysis (Gpi-1 marker coding for glucose-6-phosphate isomerase) of chimeras showed that the hybrid cells, indeed, have participated in the formation of most organs and tissues

Cytogenetic analysis of a hybrid cell clone using an X-chromosome specific probe (a). Just one X giving a positive signal on this chromosome is distinctive in the karyotype. PCR analysis showed that the markers characteristic of the DD/c X chromosome are present in hybrid clones only (b). These results show that the X chromosome of HM-1 cells (129/Ola mice) were substituted by the X chromosome of splenocytes from an adult DD female

Genetic map of American mink. It consists of 85 genes, 82 of which were mapped by the group; the order for 8 genes were determined in mink chromosome 5 and linkage for 7 genes in chromosomes 7 and 17. This a new chromosome nomenclature, the previous is in parentheses. ZooFISH data (1997) next to the ideograms of mink chromosomes. Large chromosome regions identified using chromosome-specific probes are clearly seen in the mink genome. These data are supported by the presence of mink genes homeologous to the human in these regions of the mink genes, i.e., these data idicate that the gene composition of the conserved regions to the human and mink genomes are similar

Genetic map of common shrew consist of 45 genes marking 8 chromosomes of 10 of Sorex araneus karyotipe. ZOOFISH data obtained in collaboration with Hameister's Laboratory (Germany, University of Elm) , are given next to the ideograms of the shrew chromosomes. The large conserved regions are seenin the shrew genome, as in the case of the mink genome.

Gene mapping is an intensively developing area of modern genetics that is highly relevant to studies of the organization of the human and animal genomes. Its narrow scope is building of genetic maps providing a basis for medical and animal genetics. Its broader scope is to open up new possibilities to a better understanding of the anatomy of the genome, its organization principles. Comparative gene mapping has offered new prospects for the research of the patterns produced by evolving linkage groups, chromosomes and single gene associations that brought closer to examination of a fundamental biological problem: "Do genes combine randomly or not into linkage groups, and for the research of may be the role of natural selection in their combination?"

The genes of three species are being mapped at the laboratory: pig (Sus scrofa, Artiodactyla), American mink (Mustela vison, Carnivora), and common shrew (Sorex araneus, Insectivora). The approaches used to build genetic maps include: interspecific cell hybridization, radiation hybridization, in situ hybridization, linkage analysis, and gene transfer using metaphase chromosomes. Based on these methods, chromosomal and regional assignments of genes were made, and genes were ordered on physical and genetic maps.

To date, the genetic map for American mink contains 85 genes marking all the chromosomes, except the Y; the genetic map of common shrew contains 45 genes; detailed maps were built for porcine chromosomes 2 and 12. Comparison of genetic maps with those for human and other mammalian species indicates that large gene associations that possibly are the remains of the mammalian ancestral genome were conserved during evolution. These conserved regions determined on the basis of comparative gene mapping and ZooFISH are shown on Fig. The obtained results are widely used and cited in numerous reviews and reports. The most recent report "Comparative Genomics, Mammalian Radiation X" was published in Science.

Another research line at the laboratory is study of pluripotency of the embryonic genome and reprogramming mechanisms of the differentiated cell genome. Murine intraspecific cell hybrids obtained by fusion of pluripotent embryonic stem (ES) cells with somatic differentiated cells (splenocytes) were used. These hybrid cells showed high pluripotent capacity because after injection in the blastocoele, they contributed to different organs and tissues of chimaeras. The obtained results demonstrated that, despite the contact between pluripotent and differentiated genomes in the forming hybrid cell and presence of the "somatic" X chromosome in the hybrid cell karyotype, pluripotency behaves as a dominant character.

Detailed analysis of segregation of the parental chromosomes in intraspecific hybrid cells showed that segregation was biparental. Taking advantage of this unusual phenomenon, we succeeded in generating pluripotent hybrid cells whose own "pluripotent" X chromosome was substituted by the "somatic" counterpart. Analysis of chimeric mice produced by introduction of hybrid cells into the blastocoele showed that the splenocyte derived X chromosome can be reprogrammed since expressed its marker gene in many tissues of chimeras.

It should be noted that this is first study on transfer of a whole intact chromosome derived from differentiated cells of an adult (DD mouse) into the genome of another animal (129/Ola mouse). This offers promise that new ways and means would be developed for modifying the genome through transfer of individual chromosomes using highly pluripotent hybrid cells as a vector.