title: Avian Helios and evolution of the Ikaros family.
abstract: Abstract Helios (Znfn1a2) is an Ikaros-related lymphoid regulatory protein with possible involvement in T-cell development and function as well as in the early events of haematopoietic stem cell differentiation. To evaluate the role of Helios in avian haemato/lymphopoiesis, we have characterized the avian Helios gene. In contrast to studies in mouse and human, we have found that the highly conserved avian Helios encodes a novel exon and three isoforms. Furthermore, the avian Helios expression precedes Ikaros in the ontogeny, being present already on the first day of embryonic development. Additionally, expression in the bursa of Fabricius, germinal centres and B-cell lines suggests a role for Helios also in the B-cell lineage. Phylogenetic studies of the Ikaros family along with data on paralogous chromosome segments in the human genome connect the expansion of the Ikaros family and thus possibly the emergence of the adaptive immune system with the putative second round of genome duplications and indicate that the Ikaros gene family is linked with the Hox gene clusters.
authors.affiliation: Department of Medical Microbiology, Turku Graduate School of Biomedical Sciences, University of Turku, Kiinamyllynkatu 13, FIN-20520 Turku, Finland. pekka.kohonen@utu.fi
authors.forename: P
authors.initials: P
authors.lastname: Kohonen
authors.forename: K-P
authors.initials: KP
authors.lastname: Nera
authors.forename: O
authors.initials: O
authors.lastname: Lassila
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002642:Chick Embryo; D002645:Chickens / Q000235:genetics / Q000276:immunology; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000235:genetics*; D019143:Evolution, Molecular; D051740:Ikaros Transcription Factor; D008969:Molecular Sequence Data; D010802:Phylogeny; D012313:RNA / Q000737:chemistry / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; D014157:Transcription Factors; C491746:Zfpn1a2 protein, mouse; D051740:Ikaros Transcription Factor; D012313:RNA