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Gene Review

Ikzf2  -  IKAROS family zinc finger 2

Mus musculus

Synonyms: A730095J18Rik, Helios, Ikaros family zinc finger protein 2, Zfpn1a2, Zinc finger protein Helios, ...


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Ikzf2, encoding the protein Helios, belongs to the Ikaros family of zinc finger (ZnF) transcription factors. It was discovered by two different groups in 1998, as a gene homologous to Ikaros (encoded by Ikzf1) [Hahm et al., Genes Dev., 1998; Kelley et al., Curr Biol, 1998].




Helios is expressed in the hematopoietic system, in various developmental stages and cell lineages of blood cells. It is expressed in developing T-cells, and it is to date most highly studied in the T-cell lineage.


Disease relevance of Ikzf2

  • These results do not suggest any obvious contribution of Helios or Aiolos to oncogenesis of the mouse thymic lymphomas [1].
  • Although expression of the DNA-binding mutant of Helios did not contribute to developmental abnormalities at early times after transplantation, 60% of animals that expressed the Helios DNA-binding mutant developed an aggressive and transplantable T-cell lymphoma 4 to 10 months after transplantation [2].

High impact information on Ikzf2

  • Unlike the B cell results, however, only a fraction of the Ikaros, presumably the fraction associated with Helios, exhibited centromeric localization in T cells [3].
  • Although Ikaros is present in most hematopoietic cells, Helios was found primarily in T cells [3].
  • Helios, a member of the Ikaros family of DNA-binding proteins, is expressed in multipotential lymphoid progenitors and throughout the T lineage [4].
  • Further evidence that ectopic Helios expression contributes to B cell abnormalities was provided by the observation that Helios transgenic mice developed metastatic lymphoma as they aged [4].
  • To test this possibility, transgenic mice were generated that express Helios under the control of an Ig mu enhancer [4].

Biological context of Ikzf2

  • Analysis using polymorphic markers around the two regions revealed that neither locus exhibited allelic loss in the 78 lymphomas that were induced in p53 wild-type mice, whereas in 102 p53(KO / + ) mouse-derived lymphomas Helios and Aiolos loci showed allelic loss in 8% (8 / 102) and 33% (34 / 102), respectively [1].
  • Helios, a novel dimerization partner of Ikaros expressed in the earliest hematopoietic progenitors [5].
  • The preferential expression of Helios in the earliest stages of hematopoiesis suggests that this gene functions predominantly in early progenitors [5].
  • Analysis of the primary sequences of Helios, Ikaros and Aiolos revealed that the DNA-binding, transcriptional activation and dimerization domains are functionally conserved [5].
  • To evaluate the role of Helios in avian haemato/lymphopoiesis, we have characterized the avian Helios gene [6].

Anatomical context of Ikzf2

  • Expression of Helios was detected in the earliest hematopoietic sites of the embryo, in hematopoietic stem cells in the adult and was subsequently restricted to a subset of cells in the T cell lineage [5].
  • Commitment to the B cell lineage was unaltered in Helios transgenic mice, and numbers of surface IgM(+) B cells were normal in the bone marrow and spleen [4].
  • Additionally, expression in the bursa of Fabricius, germinal centres and B-cell lines suggests a role for Helios also in the B-cell lineage [6].
  • 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 [6].


  1. Genetic mapping and allelic loss analysis in mouse thymic lymphomas of Helios and Aiolos belonging to the Ikaros gene family. Xu, H., Wakabayashi, Y., Okano, H., Saito, Y., Miyazawa, T., Kominami, R. Jpn. J. Cancer Res. (2001) [Pubmed]
  2. Expression of a non-DNA-binding isoform of Helios induces T-cell lymphoma in mice. Zhang, Z., Swindle, C.S., Bates, J.T., Ko, R., Cotta, C.V., Klug, C.A. Blood (2007) [Pubmed]
  3. Helios, a T cell-restricted Ikaros family member that quantitatively associates with Ikaros at centromeric heterochromatin. Hahm, K., Cobb, B.S., McCarty, A.S., Brown, K.E., Klug, C.A., Lee, R., Akashi, K., Weissman, I.L., Fisher, A.G., Smale, S.T. Genes Dev. (1998) [Pubmed]
  4. Transgenic expression of Helios in B lineage cells alters B cell properties and promotes lymphomagenesis. Dovat, S., Montecino-Rodriguez, E., Schuman, V., Teitell, M.A., Dorshkind, K., Smale, S.T. J. Immunol. (2005) [Pubmed]
  5. Helios, a novel dimerization partner of Ikaros expressed in the earliest hematopoietic progenitors. Kelley, C.M., Ikeda, T., Koipally, J., Avitahl, N., Wu, L., Georgopoulos, K., Morgan, B.A. Curr. Biol. (1998) [Pubmed]
  6. Avian Helios and evolution of the Ikaros family. Kohonen, P., Nera, K.P., Lassila, O. Scand. J. Immunol. (2004) [Pubmed]
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