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Primary structure and ontogeny of an avian CD3 transcript.
1Institut d'Embryologie Cellulaire et Moléculaire du Centre National de la Recherche Scientifique et du Collège de France, Nogent sur Marne.
Summary
Researchers identified a chicken CD3 chain, T11.15, crucial for T-cell development. This finding suggests an ancestral CD3 protein may have served roles now performed by separate gamma and delta chains in mammals.
Area of Science:
- Immunology
- Molecular Biology
- Avian Biology
Background:
- The CD3 complex is essential for T-cell receptor (TCR) function in vertebrates.
- Understanding avian CD3 structure provides insights into immune system evolution.
Purpose of the Study:
- To determine the structure and expression of a chicken CD3 chain.
- To compare avian CD3 sequences with mammalian counterparts.
- To elucidate the evolutionary origins of CD3 subunits.
Main Methods:
- Isolation of a chicken cDNA clone (T11.15) encoding a CD3 protein.
- Northern blot analysis to detect transcript expression in embryonic thymus.
- Amino acid sequence comparison with mammalian CD3 gamma and delta chains.
Main Results:
- A 175-amino-acid chicken CD3 protein (T11.15) was identified, including a signal peptide.
- T11.15 transcript expression was detected in the thymus at embryonic day 10.
- Sequence similarity to mammalian CD3 gamma (36-39%) and delta (39-40%) was observed, with conserved functional domains.
Conclusions:
- The chicken CD3 T11.15 polypeptide may represent an ancestral form of mammalian CD3 gamma and delta chains.
- A single avian CD3 chain might perform functions of both mammalian gamma and delta subunits.
- This suggests independent gene duplication events in avian and mammalian CD3 evolution.