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Point mutations and deletions in the Znfn1a1/Ikaros gene in chemically induced murine lymphomas
Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
2002 (English)In: Cancer Research, ISSN 0008-5472, Vol. 62, no 9, 2650-2653 p.Article in journal (Refereed) Published
Abstract [en]

The Znfn1a1 gene encodes a zinc finger protein called Ikaros, which is criticalfor T-cell development and differentiation. The execution of normalfunction of Ikaros requires sequence-specific DNA binding, transactivation, and dimerization domains. In this study, exons 3–5 and exon 7 of the Znfn1a1 gene that encode the functional domains of Ikaros were analyzed for point mutations and deletions in murine lymphomas induced by 1,3-butadiene, 2',3'-dideoxycytidine, or phenolphthalein. Missense and frameshift mutations were identified in 11% (11 of 104) of the tumors. Interestingly, 8 of the mutations were identified in the NH2-terminal zinc finger motifs, which are crucial for the DNA-binding function of Ikaros. The other 3 samples carried frameshift mutations in exon 7 that resulted in truncations and abrogation of both transactivation and dimerization domains. One tumor with a missense mutation in the DNA-binding domain also displayed a 45-bp deletion in the dimerization domain. Southern analysis disclosed interstitial homozygous deletions in the functional domains of Ikaros in 4% (3 of 68) of the lymphomas examined. Allelic losses on markers surrounding the Znfn1a1 gene were detected in 27% (12 of 45) of the tumors analyzed. However, only 2 tumors with allelic losses also showed mutations in the Znfn1a1 gene, indicating that other tumor suppressor genes located on this region might be involved as well. Our results suggest inactivation of Ikaros in a subset of chemically induced lymphomas and additionally support the contention of tumor-suppressor activity for Ikaros.

Place, publisher, year, edition, pages
2002. Vol. 62, no 9, 2650-2653 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-12923OAI: oai:DiVA.org:liu-12923DiVA: diva2:17400
Available from: 2008-01-30 Created: 2008-01-30 Last updated: 2009-05-22
In thesis
1. Genetic Alterations in Lymphoma: with Focus on the Ikaros, NOTCH1 and BCL11B Genes
Open this publication in new window or tab >>Genetic Alterations in Lymphoma: with Focus on the Ikaros, NOTCH1 and BCL11B Genes
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cell proliferation is a process that is strictly regulated by a large number of proteins. An alteration in one of the encoding genes inserts an error into the regulative protein, which may result in uncontrolled cell growth and eventually tumor formation. Lymphoma is a cancer type originating in the lymphocytes, which are part of the body’s immune defence. In the present thesis, Znfn1a1, Notch1 and Bcl11b were studied; all involved in the differentiation of T lymphocytes. The three genes are located in chromosomal regions that have previously shown frequent loss of heterozygosity in tumor DNA.

Ikaros is a protein involved in the early differentiation of T lymphocytes. In this thesis, mutation analysis of the Znfn1a1 gene in chemically induced murine lymphomas revealed point mutations and homozygous deletions in 13 % of the tumors. All of the detected deletions lead to amino acid substitutions or abrogation of the functional domains in the Ikaros protein. Our results support the role of Ikaros as a potential tumor suppressor in a subset of tumors.

Notch1 is a protein involved in many differentiation processes in the body. In lymphocytes, Notch1 drives the differentiation towards a T-cell fate and activating alterations in the Notch1 gene have been suggested to be involved in T-cell lymphoma. We identified activating mutations in Notch1 in 39 % of the chemically induced murine lymphomas, supporting the involvement of activating Notch1 mutations in the development of T-cell lymphoma.

Bcl11b has been suggested to be involved in the early T-cell specification, and mutations in the Bcl11b gene has been identified in T-cell lymphoma. In this thesis, point mutations and deletions were detected in the DNA-binding zinc finger regions of Bcl11b in 15 % of the chemically induced lymphomas in C57Bl/6×C3H/HeJ F1 mice. A mutational hotspot was identified, where four of the tumors carried the same mutation. Three of the identified alterations, including the hotspot mutation in Bcl11b, increased cell proliferation when introduced in a cell without endogenous Bcl11b, whereas cell proliferation was suppressed by wild-type Bcl11b in the same cell line. Mutations in Bcl11b may therefore be an important contributing factor to lymphomagenesis in a subset of tumors.

A germ line point mutation was identified in BCL11B in one of 33 human B-cell lymphoma patients. Expression of BCL11B in infiltrating T cells was significantly lower in aggressive compared to indolent lymphomas, suggesting that the infiltrating T cells may affect the B-cell lymphomas.

Place, publisher, year, edition, pages
Linköping University Electronic Press, 2008. 60 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1040
Keyword
Cell proliferation, Lymphoma, Znfn1a1, Notch1, Bcl11b, chromosomal regions, Ikaros, B-cell lymphomas
National Category
Cancer and Oncology
Identifiers
urn:nbn:se:liu:diva-10694 (URN)978-91-7393-985-0 (ISBN)
Public defence
2008-02-15, Berzeliussalen, Campus US, Linköpings universitet, Linköping, 09:00 (English)
Opponent
Supervisors
Available from: 2008-01-30 Created: 2008-01-30 Last updated: 2015-11-19

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Karlsson, AnneliSöderkvist, PeterZhuang, Shi-Mei

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