Purification and Properties of Chick Terminal Deoxynucleotidyl Transferase (TdT)
The thymus is made up of two anatomical parts: the stroma, containing the epithelium, and the thymocytes which belong to the lymphoid series of the hematopoietic cells. The embryonic origins of these two populations are different: the thymocytes derive from stem cells which colonize the thymic rudiment (which is initially purely epithelial). This facts were suggested by Moore and Owen (1) and the timing of the lymphoid colonization of the embryonic thymus was established by Le Douarin and Jotereau (2) using a technique based on the production of interspecific chimeras. Such chimeras are obtained by grafting the thymic rudiments of chick embryos in the somatopleure of quail embryos (or vice-versa). Quail cells are easily distinguished from chick cells using the Feulgen-Rossenbeck staining of chromatin: the quail chromatin is condensed in a large mass in the center of the nucleus whereas the chick chromatin is finely dispersed (3). By an appropriate choice of the respective ages of the grafted rudiments and of the host embryos, it could be shown that the epithelial thymus is colonized by stem cells during two receptive periods : from 6 1/2 days to 8 days and from 12 to 13 days.
KeywordsChick Embryo Terminal DEOXYNUCLEOTIDYL Transferase Epithelial Thymus Quail Embryo Receptive Period
Unable to display preview. Download preview PDF.
- 5.L.M.S. Chang, and F.J. Bollum, Deoxyribonucleotide-polymerizing enzymes of calf thymus gland. V. Homogenous terminal deoxynucleotidyl transferase, J. Biol. Chem., 246:909 (1971).Google Scholar
- 10.U.K. Laemmli, Cleavage of structural proteins during the assembly of the head of bacteriophage T4, Nature 241:88 (1970).Google Scholar
- 11.N. Le Douarin, Ontogeny of hematopoietic organs studied in avian embryo interspecific chimeras,: “Differentiation of normal and neoplastic hematopoietic cells” (Clarkson B., Till J. and P. Marks, eds.) pp. 5–31. Cold Spring Harbor Laboratory, New-York (1978).Google Scholar
- 12.F.J. Bollum, Terminal deoxynucleotidyl transferase. J: “The Enzymes” (P.D. Boyer, ed.) Vol. 10 pp. 145–171. Academic Press, New-York (1974).Google Scholar