Biomedical subjects

Cécile Tonnelle

Publications and source records attributed to Cécile Tonnelle.

3 recordsLinked to original sources

PubMed2004

Restriction of transgene expression to the B-lymphoid progeny of human lentivirally transduced CD34+ cells.

Development of gene transfer strategies will necessitate improved efficiency and control of transduction and transgene expression. We here provide evidence that targeting expression of the GFP reporter gene to the B-lymphoid progeny of genetically modified human hematopoietic progenitor cells can be achieved through the insertion of regulatory sequences from the human CD19 gene promoter into a lentiviral vector. Based on a bioinformatics approach, three human CD19-derived sequences were designed and inserted into a self-inactivated lentiviral vector backbone upstream of the GFP gene: S.CD19 (230 bp), M.CD19 (464 bp), and L.CD19 (1274 bp). These new lentiviral vectors efficiently transduced cord blood CD34(+) cells. The M.CD19 and especially L.CD19 sequences preferentially targeted GFP expression to in vitro and in vivo differentiated CD19(+) progeny; moreover, transgene expression was detected from the CD34(+) pro/pre-B cell to the mature peripheral IgM(+) B cell stage. In contrast, GFP expression was weak or absent in primary T-lymphoid and uncommitted progenitor cells or in erythroid, natural killer, or myeloid differentiated cells. Such B-lineage-specific lentiviral vectors may be useful for correcting inherited disorders that affect B-lymphoid cells or for deciphering the transcriptional program that controls B cell commitment and differentiation.

Animals↗

PubMed2003

Overexpression of dominant-negative Ikaros 6 protein is restricted to a subset of B common adult acute lymphoblastic leukemias that express high levels of the CD34 antigen.

Ikaros is a critical regulator of hematopoiesis. Its effects result in part from the balance between the isoforms that are produced by differential splicing of the pre-mRNA. Short isoforms that lack the DNA-binding domain act as dominant negatives by binding long isoforms through the C-terminal zinc-finger domain, which allows for the homo- or heterodimerization of the proteins. There are a number of evidences that different subsets of murine hematopoietic progenitors - as defined by phenotype - have different patterns of Ikaros expression. Forced expression of short isoforms (Ik5, Ik6 or Ik7) in murine or human hematopoietic progenitors alters the differentiation capacities of these cells. Human leukemias provide additional information: because of the blockade in differentiation, leukemias represent an equivalent of a particular stage of human hematopoietic hierarchy. We and others have shown that human acute leukemias are heterogeneous for the pattern of Ikaros isoform expression. The present study focused on adult de novo B ALLs and the Ikaros 6 isoform. ProB (BI, n=3), common B (BII, n=15) and preB (BIII, n=3) ALL were identified by their phenotype. RT-PCR and Western blot analyses of blast cell protein lysates suggest that approximately 50% of BII leukemias overexpress Ikaros 6 RNA and protein. Comparison of BII cells with high or normal levels of Ik6 shows a higher level of expression for the membrane stem cell antigen CD34 in the former, as detected with flow cytometry and confirmed with DNA arrays.

Adolescent↗

PubMed2002

Ikaros gene expression and leukemia.

The Ikaros (Ik) protein, or LyF1, was initially described as a protein binding to regulatory sequences of a number of genes expressed in murine lymphoid cells. Ikaros is a critical regulator of normal hematopoietic stem cell differentiation, as evidenced by dramatic defects in the lymphoid compartments, in homozygous animals with gene inactivation. Because differential splicing produces multiple isoforms with potentially different functions, Ikaros provides a unique model to study how post-transcriptional mechanisms may be involved in neoplastic processes. Indeed, several groups including ours have underlined evidences that expression of different Ikaros isoforms vary among different types of leukemias. The predominance of short isoforms in certain subsets is intriguing. Here, additional observations reinforced the hypothesis that Ikaros expression may be deregulated in human leukemias. Whether this is a cause or a consequence of the leukemic process remains speculative. Other human diseases however, provide examples of abnormal post-transcriptional regulations that have been further characterized.

Alternative Splicing↗