Experimental embryonic-somatic chimaerism in the sheep confirmed by random amplified polymorphic DNA assay.

Developmental potencies of sheep somatic cells (foetal fibroblasts, FFs) in chimaeric animals were analysed. FFs from pigmented Polish Heatherhead (wrzosowka) breed were microsurgically injected into morulae or blastocysts of white Polish Merino breed (5 cells to each embryo). In one experiment the cells were stained with vital fluorescent dye PKH26, and chimaeric blastocysts were cultured in vitro to confirm the presence of fluorescent cells. In the majority of experiments the blastocysts were transferred to synchronized recipient ewes for development until term. Cultured embryonic cells (CEC), earlier known to produce chimaeras, were injected into blastocysts in control experiments. Seven young were born from FF-injected embryos and three were born from CEC-injected ones. All of them were white, but all three control lambs and three experimental lambs showed small areas of skin pigmentation, which indicated Heatherhead CEC or FF contribution. Tissue samples originating from three germ layers were taken from two FFs-originating presumably chimaeric lambs (male and female) at the age of one month for DNA analysis. The random amplified polymorphic DNA-PCR method supplied two markers of chimaerism, which were amplification products of 643 bp and 615 bp long DNA fragments, found in tissues of experimental lambs as well as in FFs, but not in the blood of parents of blastocysts. The 643 bp marker was found in the majority of tissues of both lambs. The 615 bp amplicon was detected in the skin and lungs of the female lamb and in the hooves of the male lamb. Our data show that foetal fibroblasts introduced to sheep blastocysts can participate in development and can contribute to all tissue lineages up to at least one month of age.