Search

Gfi-1B is a transcriptional repressor that is crucial for erythroid differentiation: inactivation of the GFI1B gene in mice leads to embryonic death due to failure to produce differentiated red cells. Accordingly, GFI1B expression is tightly regulated during erythropoiesis, but the mechanisms involved in such regulation remain partially understood. We here identify HMGB2, a high-mobility group HMG protein, as a key regulator of GFI1B transcription. HMGB2 binds to the GFI1B promoter in vivo and up-regulates its trans-activation most likely by enhancing the binding of Oct-1 and, to a lesser extent, of GATA-1 and NF-Y to the GFI1B promoter. HMGB2 expression increases during erythroid differentiation concomitantly to the increase of GfI1B transcription. Importantly, knockdown of HMGB2 in immature hematopoietic progenitor cells leads to decreased Gfi-1B expression and impairs their erythroid differentiation. We propose that HMGB2 potentiates GATA-1-dependent transcription of GFI1B by Oct-1 and thereby controls erythroid differentiation.

Gene transduction into immature hematopoietic cells collected at birth from the umbilical cord could be useful for the treatment of genetic or acquired disorders of the hematopoietic system diagnosed during pregnancy. The SCID-hu mouse is a convenient model to investigate T-cell lineage gene therapy, since it allows replication of human intrathymic T-cell development. CD34+ cells isolated from cord blood were cocultured with CRIP MFG-murine CD2 (mCD2) cells that produce recombinant retroviruses encoding the mCD2 antigen, a cell surface marker easily detectable by flow cytometry. After 3 and 4 days in coculture, a mean of 19% and 39% human hematopoietic cells, respectively, expressed the mCD2 antigen. CD34+ cells cocultured for 4 days were used to reconstitute human fetal thymus implanted in SCID mice. Five to 10 weeks later, the mCD2 antigen was detected on approximately 10% of human thymocytes repopulating the thymic grafts in four of nine SCID mouse chimeras. Vector genomes were detected in graft cell DNA by Southern blot. Analysis of vector integration indicated that positive cells were of polyclonal origin in three animals and predominantly monoclonal in the other one. Our data show that foreign genes can be transduced into CD34+ cord blood cells endowed with T-cell differentiation potential, and suggest strategies for T-cell lineage gene therapy in the neonate.

Mice homozygous for the gusmps allele lack beta-glucuronidase activity and provide a useful model for human Mucopolysaccharidosis type VII (MPS VII), also known as Sly syndrome. Bone marrow (BM) transplantation was shown to correct the metabolic defect and to increase the life span of diseased animals. We have used this murine model in a preclinical study aimed at evaluating whether the techniques currently available for gene transfer into large mammalian and human BM cells will provide efficient enzyme replacement therapy in MPS patients. Autologous BM was transplanted into deficient mice after retrovirus-mediated transfer of the human beta-glucuronidase cDNA. Conditioning of recipients was performed by a single sublethal irradiation of 4.5 Gy, giving rise to low donor engraftment. In recipient mice analyzed until 145 days after gene transfer, the percentage of genetically modified hematopoietic cells was less than 5%. Nevertheless, beta-glucuronidase enzyme activity was detectable in various organs, including the brain, and disappearance of lysosomal storage was obvious in the liver and spleen. These results show that the autologous transplantation of genetically engineered BM cells could be beneficial in MPS patients.