The junctional modifications of a T cell receptor gamma chain are determined at the level of thymic precursors.
T precursors from fetal liver and adult bone marrow were compared for their ability to give rise to V gamma 4+ T cell development. Fetal thymic lobes were repopulated with fetal liver or adult bone marrow cells, and the organ-cultured thymocytes were analyzed for their T cell receptor expression by the polymerase chain reaction (PCR). Both day 14 fetal liver and adult bone marrow cells gave rise to thymocytes with V gamma 4-J gamma 1 transcripts. However, the average size of the PCR products derived from adult precursors was slightly larger than that from fetal precursors. DNA sequence analysis of the V gamma 4-J gamma 1 transcripts showed that early fetal liver precursors predominantly gave rise to thymocytes with the V gamma 4-J gamma 1 transcripts without N nucleotide insertion, while late fetal liver and adult marrow precursors predominantly gave rise to thymocytes with modified V gamma 4-J gamma 1 junctions. These results suggest the possibility that the level of the N nucleotide insertion is programmed at the level of thymic precursors. This study also supported the model presented previously that the developmental potential of hematopoietic stem cells may change during ontogeny.
Ikuta
K
K
Howard Hughes Medical Institute, Stanford University School of Medicine, California 94305.
Weissman
I L
IL
D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D005333:Fetus; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009924:Organ Culture Techniques; D016133:Polymerase Chain Reaction; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000032:analysis / Q000235:genetics*; D013950:Thymus Gland / Q000166:cytology*
D016692:Receptors, Antigen, T-Cell, gamma-delta