TFII-I/Gtf2i and Erythro-Megakaryopoiesis

Abstract

TFII-I is a ubiquitously expressed transcription factor that positively or negatively regulates gene expression. TFII-I has been implicated in neuronal and immunologic diseases as well as in thymic epithelial cancer. Williams-Beuren Syndrome (WBS) is caused by a large hemizygous deletion on chromosome 7q11.23 which encompasses 26-28 genes, including GTF2I, the human gene encoding TFII-I. A subset of WBS patients has recently been shown to present with macrocytosis, a mild anemia characterized by enlarged erythrocytes. We conditionally deleted the TFII-I/Gtf2i gene in adult mice by tamoxifen induced Cre-recombination. Bone marrow cells revealed defects in erythro-megakaryopoiesis and an increase in expression of the adult β-globin gene. The data show that TFII-I acts as a repressor of β-globin gene transcription and that it is implicated in the differentiation of erythro-megakaryocytic cells.

Keywords: Gtf2i; TFII-I; erythropoiesis; globin; megakaryopoiesis; transcription factor.

FIGURE 1

Enhanced β-globin gene expression in TFII-I/Gtf2i deficient mice. (A) Relative protein expression levels for TFII-I, β-globin, and TBP during differentiation of erythroid cells. Data were extracted from a proteomic study by Gillespie et al. (2020). MPP, multiple progenitor population; CMP, common myeloid progenitors; MEP, myeloid erythroid progenitors; CFU-E, colony forming unite-erythroid; ProEB, proerythroblast; Baso EB, basophilic erythroblast. (B) Gtf2i floxed mice were mated with mice expressing Cre-recombinase in a tamoxifen inducible manner. PCR bands from three KO and three control mice represent the floxed Gtf2i gene (Floxed, 410 bp), the exon 3 deleted TFII-I gene (Δ, 328 bp), and a non-specific band (NS); lane M shows 500, 400, 300, 200, and 100 bp DNA fragments from top to bottom. Shown below are bone marrow cells and cell pellets from knock-out (KO) or control (Ctrl) mice. (C) RT-qPCR analysis of TFII-I, β-globin, and α-globin expression in bone marrow cells from KO and control mice (C1). Error bars are derived from two experimental replicates and three technical (qPCR) replicates (*p < 0.05).

FIGURE 2

Flow cytometry analysis of TFII-I KO and control bone marrow cells. BM cells isolated from three KO and three control mice (Ctrl) were subjected to flow cytometry analysis using CD71 and Ter119 antibodies (left) or CD41 antibodies (right). The numbers on top of the bars in the middle represent the p-values (error bars derived from three KO and three control mice, n = 3; p-values are shown on top of the graphs in the middle).