D. Dunon et al., ONTOGENY OF TCR V-BETA-1 EXPRESSION REVEALED NOVEL INVARIANT ALTERNATIVE TRANSCRIPTS, The Journal of immunology, 154(3), 1995, pp. 1256-1264
Analysis of TCR-beta gene recombination and expression was performed b
y quantitative PCR amplification technique throughout chicken embryoge
nesis and development. Our data demonstrated that TCR V beta 1 promote
rs were turned on by day 10 of embryogenesis, 2 days before detection
of TCR-beta gene recombination. The V to D recombination step was firs
t detected by day 11 of embryogenesis whereas DJ and V(D)J rearranged
genes were detected 1 day later, on day 12 of embryogenesis. Thus, tra
nscription of unrearranged TCR-beta genes in chickens precedes the exp
ression of V(D)J recombinase activity as in mammals. In contrast, alth
ough TCR-beta rearrangement starts with the D to J recombination step
in mammals, it can start either by the VD or the DJ step in chickens.
Furthermore, reverse transcriptase-PCR amplification of TCR-beta trans
cripts revealed the presence of two kinds of alternative transcripts.
These novel alternatively spliced products appeared in thymocytes from
embryonic thymus during colonization periods and were absent in trans
formed T cell lines. Splicing sites are located in the middle of V bet
a 1 segments and lead to Delta V beta 1-C beta and Delta V beta 1-D be
ta-J beta-C beta transcripts. Delta V beta 1-C beta transcripts might
lead to synthesis of invariant truncated TCR beta-chains containing th
e aminoterminal portion of the V beta 1 region followed by the C beta
region. Because this type of splicing can be generated by using all kn
own V beta 1 members, these invariant forms could play a role in thymo
cyte development.