Genistein induces radioprotection by hematopoietic stem cell quiescence

Purpose: In this study we addressed whether genistein-induced radioprotection in mice is associated with alterations of the cell cycle of hematopoietic stem and progenitor cells.

Materials and methods: C57BL/6J female mice received a single subcutaneous injection of genistein (200 mg/kg) 24 h prior to a lethal dose (7.75 Gy, ⁶⁰Co) of total body irradiation. Proliferation-associated Ki-67 protein/7-aminoactinomycin-D (Ki67/7AAD) cell cycle staining was used to differentiate between G₀, G₁, and S/G₂/M in bone marrow cell populations negative for expression of mature hematopoietic lineage marker cells but positive for expression of stem cell antigen-1 and tyrosine kinase receptor for stem cell factor (Lin^?Sca-1⁺cKit⁺, LSK⁺). Quantitative real-time polymerase chain reaction (qRT-PCR) microarrays were utilized to examine cell cycle specific genes.

Results: At 24 h following radiation exposure, a greater percentage of LSK⁺ in genistein-treated mice accumulated in the G₀ phase of the cell cycle, whereas a large percentage of LSK⁺ bone marrow cells from untreated and vehicle (PEG-400)-treated mice progressed into the G₁ and S/G₂/M phases. Moreover, the absolute number of marrow total LSK⁺, long-term LSK⁺, and short-term LSK⁺ increased 2.8, 12.1, and 4.2-fold, respectively, at 7 days post-irradiation in genistein-treated vs. untreated irradiated mice. Lin^? cells from genistein-treated mice expressed fewer DNA damage responsive and cell cycle checkpoint genes than LSK⁺ from untreated or vehicle-treated mice.

Conclusion: Pretreatment with genistein provides in vivo protection from acute myelotoxicity through extended quiescence followed by reduced senescence of marrow repopulating LSK⁺.     

Genistein induces radioprotection by hematopoietic stem cell quiescence

PURPOSE: In this study we addressed whether genistein-induced radioprotection in mice is associated with alterations of the cell cycle of hematopoietic stem and progenitor cells. MATERIALS AND METHODS: C57BL/6J female mice received a single subcutaneous injection of genistein (200 mg/kg) 24 h prior to a lethal dose (7.75 Gy, (60)Co) of total body irradiation. Proliferation-associated Ki-67 protein/7-aminoactinomycin-D (Ki67/7AAD) cell cycle staining was used to differentiate between G(0), G(1), and S/G(2)/M in bone marrow cell populations negative for expression of mature hematopoietic lineage marker cells but positive for expression of stem cell antigen-1 and tyrosine kinase receptor for stem cell factor (Lin(-)Sca-1(+)cKit(+), LSK(+)). Quantitative real-time polymerase chain reaction (qRT-PCR) microarrays were utilized to examine cell cycle specific genes. RESULTS: At 24 h following radiation exposure, a greater percentage of LSK(+) in genistein-treated mice accumulated in the G(0) phase of the cell cycle, whereas a large percentage of LSK(+) bone marrow cells from untreated and vehicle (PEG-400)-treated mice progressed into the G(1) and S/G(2)/M phases. Moreover, the absolute number of marrow total LSK(+), long-term LSK(+), and short-term LSK(+) increased 2.8, 12.1, and 4.2-fold, respectively, at 7 days post-irradiation in genistein-treated vs. untreated irradiated mice. Lin(-) cells from genistein-treated mice expressed fewer DNA damage responsive and cell cycle checkpoint genes than LSK(+) from untreated or vehicle-treated mice. CONCLUSION: Pretreatment with genistein provides in vivo protection from acute myelotoxicity through extended quiescence followed by reduced senescence of marrow repopulating LSK(+).     

GTF2IRD2 is located in the Williams-Beuren syndrome critical region 7q11.23 and encodes a protein with two TFII-I-like helix-loop-helix repeats

Williams-Beuren syndrome (also known as Williams syndrome) is caused by a deletion of a 1.55- to 1.84-megabase region from chromosome band 7q11.23. GTF2IRD1 and GTF2I, located within this critical region, encode proteins of the TFII-I family with multiple helix-loop-helix domains known as I repeats. In the present work, we characterize a third member, GTF2IRD2, which has sequence and structural similarity to the GTF2I and GTF2IRD1 paralogs. The ORF encodes a protein with several features characteristic of regulatory factors, including two I repeats, two leucine zippers, and a single Cys-2/His-2 zinc finger. The genomic organization of human, baboon, rat, and mouse genes is well conserved. Our exon-by-exon comparison has revealed that GTF2IRD2 is more closely related to GTF2I than to GTF2IRD1 and apparently is derived from the GTF2I sequence. The comparison of GTF2I and GTF2IRD2 genes revealed two distinct regions of homology, indicating that the helix-loop-helix domain structure of the GTF2IRD2 gene has been generated by two independent genomic duplications. We speculate that GTF2I is derived from GTF2IRD1 as a result of local duplication and the further evolution of its structure was associated with its functional specialization. Comparison of genomic sequences surrounding GTF2IRD2 genes in mice and humans allows refinement of the centromeric breakpoint position of the primate-specific inversion within the Williams-Beuren syndrome critical region.