Identification and expression of Helios, a member of the Ikaros family, in the Mexican axolotl: implications for the embryonic origin of lymphocyte progenitors.
Transcription factors of the Ikaros gene family are critical for the differentiation of T and B lymphocytes from pluripotent hematopoietic stem cells. To study the first steps of lymphopoiesis in the Mexican axolotl, we have cloned the Helios ortholog in this urodele amphibian species. We demonstrated that the axolotl Helios contains a 144-bp deletion at the 5' end of the activation domain. Helios is expressed in both the thymus and spleen but not in the liver of the pre-adult axolotl. During ontogeny, Helios transcripts are detected from neurula stage, before the apparition of the first Ikaros transcripts and the colonization of lymphoid tissues. Interestingly, Helios and Ikaros mRNA are found predominantly in the ventral blood islands of late tail-bud embryos. These results suggest that in contrast to the Xenopus and amniote embryos where two sites of hematopoiesis have been characterized, the ventral blood islands could be the major site of hematopoiesis in the axolotl.
Durand
Charles
C
Comparative Immunology Group, National Centre for Scientific Research, Pierre and Marie Curie University, Paris, France.
Kerfourn
Fabienne
F
Charlemagne
Jacques
J
Fellah
Julien S
JS
D000558:Ambystoma mexicanum / Q000196:embryology*; D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics*; D005260:Female; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000502:physiology; D008214:Lymphocytes / Q000502:physiology*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000032:analysis; D016415:Sequence Alignment; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics*
D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D014157:Transcription Factors