Prethymic progenitors from the avian para-aortic mesoderm express GATA-3 and distinct chTcf isoforms but still lack T-cell receptor-gamma rearrangements.
Haematopoietic precursors first colonizing the avian embryonic thymus are derived from the intraembryonic sites located around the dorsal aortae. These intraembryonic precursors have previously been demonstrated to include cells that harbour T-cell progenitor capacity and express the Ikaros transcription factor, known to be a prerequisite for lymphocyte development. In this study, we further evaluated the properties of these prethymic cells. We show that early intraembryonic cells and prethymic progenitors already express the GATA-3 transcription factor. The chicken homologue of T-cell factor-1, chTcf, is also detected in cells isolated from the avian para-aortic region. However, these intraembryonic cells retain their T-cell receptor gamma loci in germline configuration. Interestingly, chTcf was found to express different alternatively spliced isoforms during early ontogeny and thymic T-cell development, which indicates developmentally regulated expression of chTcf variants. Taken together, these results demonstrate that, although the avian prethymic progenitor cells express T-lineage-associated transcription factors, they have not yet undergone TCR rearrangements. It is therefore suggested that activation of lineage-associated genes is an early event in the generation of haematopoietic progenitor cells during ontogeny.
Liippo
J
J
Turku Graduate School of Biomedical Sciences and Department of Medical Microbiology, University of Turku, Finland. jussi.liippo@utu.fi
Koskela
K
K
Lassila
O
O
D000595:Amino Acid Sequence; D000818:Animals; D001011:Aorta / Q000196:embryology; D019070:Cell Lineage; D002642:Chick Embryo; D004268:DNA-Binding Proteins / Q000032:analysis* / Q000737:chemistry*; D050990:GATA3 Transcription Factor; D015334:Gene Rearrangement, gamma-Chain T-Cell Antigen Receptor; D006412:Hematopoietic Stem Cells / Q000276:immunology*; D051821:Lymphoid Enhancer-Binding Factor 1; D008648:Mesoderm / Q000166:cytology; D008969:Molecular Sequence Data; D020033:Protein Isoforms; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000235:genetics; D051822:T Cell Transcription Factor 1; D013950:Thymus Gland / Q000196:embryology* / Q000276:immunology; D015534:Trans-Activators / Q000032:analysis*; D014157:Transcription Factors / Q000737:chemistry*
D004268:DNA-Binding Proteins; D050990:GATA3 Transcription Factor; D051821:Lymphoid Enhancer-Binding Factor 1; D020033:Protein Isoforms; D016692:Receptors, Antigen, T-Cell, gamma-delta; D051822:T Cell Transcription Factor 1; D015534:Trans-Activators; D014157:Transcription Factors