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Targets of the transcriptional repressor oncoprotein Gfi-1
Zhijun Duan1, Marshall Horwitz
1Division of Medical Genetics, Department of Medicine, University of Washington School of Medicine, 1705 Northeast Pacific Street, HSB-K236B, P.O. Box 357720, Seattle, WA 98195, USA.
Abstract:
Gfi-1 is a zinc finger transcriptional repressor originally recognized for its role in T cell differentiation and lymphomas. Recent experiments reveal that gene-targeted Gfi-1-deficient mice are neutropenic and that Gfi-1 mutations cause human neutropenia. In both cases, myeloid progenitor cells lose the ability to distinctly differentiate granulocytes from monocytes. The molecular mechanism of the hematopoietic abnormalities caused by Gfi-1 deficiency remains undetermined because of a lack of known Gfi-1 target genes. To identify Gfi-1 targets in vivo, we performed large-scale chromatin immunoprecipitation analysis on a set of 34 candidate genes in myeloblast (KG-1 and HL-60), monoblast (U937), and T lymphocyte cell lines (Jurkat), in concert with RT-PCR-based expression profiling. We identified 32 Gfi-1 binding sites in a functionally variable set of 16 genes, including complements of cell-cycle regulators, transcription factors, and granulocyte-specific markers. Cluster analysis of expression patterns and chromatin immunoprecipitation data reveals that Gfi-1 targets a subset of genes differentiating hematopoietic lineages and therefore plays a relatively superior role in the hierarchy of factors governing stem cell differentiation.
Insights
Growth factor independence 1 (Gfi-1) is a transcriptional repressor crucial for hematopoietic stem cell differentiation. Gfi-1 deficiency impairs granulocyte and monocyte development, leading to neutropenia by affecting key lineage differentiation genes.
Area of Science:
- Hematology
- Molecular Biology
- Gene Regulation
Background:
- Growth factor independence 1 (Gfi-1) is a zinc finger transcriptional repressor known for its role in T cell differentiation and lymphomas.
- Recent studies indicate Gfi-1 deficiency in mice and mutations in humans lead to neutropenia, characterized by impaired myeloid progenitor differentiation into granulocytes and monocytes.
- The precise molecular mechanisms underlying these hematopoietic abnormalities due to Gfi-1 deficiency are not fully understood due to a lack of identified Gfi-1 target genes.
Purpose of the Study:
- To identify in vivo Gfi-1 target genes and elucidate the molecular mechanisms of Gfi-1's role in hematopoietic differentiation.
- To investigate the direct targets of Gfi-1 in myeloid and lymphoid cell lines.
Main Methods:
- Large-scale chromatin immunoprecipitation (ChIP) analysis was performed on 34 candidate genes in myeloblast (KG-1, HL-60), monoblast (U937), and T lymphocyte (Jurkat) cell lines.
- RT-PCR-based expression profiling was used in conjunction with ChIP analysis.
- Cluster analysis was applied to expression patterns and ChIP data.
Main Results:
- Thirty-two Gfi-1 binding sites were identified within 16 functionally diverse genes.
- These identified target genes include cell-cycle regulators, transcription factors, and granulocyte-specific markers.
- Gfi-1 was found to target a subset of genes critical for hematopoietic lineage differentiation.
Conclusions:
- Gfi-1 directly regulates a set of genes involved in hematopoietic lineage specification.
- These findings establish Gfi-1 as a key regulator in the hierarchy of factors controlling stem cell differentiation.
- Gfi-1 plays a significant role in maintaining normal granulopoiesis and monopoiesis, and its dysregulation contributes to neutropenia.