Avian Ikaros gene is expressed early in embryogenesis

Ikaros transcription factors dictate the key steps in lymphoid lineage determination. To reveal the evolutionary aspects of regulatory molecules involved in early lymphocyte development, we studied the cDNA of the avian Ikaros homolog. We demonstrate here that the Ikaros gene is highly conserved across avian and mammalian species. Importantly, the Ikaros mRNA is already expressed in early chicken embryos, from embryonic day 2 onwards, thus markedly before the traffic of the first precursor cells to the lymphoid primordia, thymus and the bursa of Fabricius. We suggest that the embryonic expression of the Ikaros transcripts represents an early onset of lymphoid differentiation.