Graded expression patterns of ephrin-As in the superior colliculus after lesion of the adult mouse optic nerve.

The idea has been put forward that molecules and mechanisms acting during development are re-used during regeneration in the adult, for example in response to traumatic injury in order to re-establish the functional integrity of neuronal circuits. Members of the Eph family of receptor tyrosine kinases and their 'ligands', the ephrins, play a prominent role during development of the retinocollicular projection in rodents, where EphA receptors and ephrin-As are expressed in gradients in both the retina and the superior colliculi (SC). We were interested in investigating whether EphA family members are also expressed or re-expressed in the adult after optic nerve lesion, since the presence of axon guidance information is an important prerequisite for a topographically appropriate re-connection by retinal ganglion cell (RGC) axons. This analysis was encouraged by results showing that RGC axons do not exert guidance preferences in response to membranes from adult unlesioned SC, but in response to membranes from the adult deafferented SC. We found a graded expression pattern of ephrin-As in the SC both before and after deafferentation, which was remarkably similar to those found during development. EphA receptor levels were reduced in the SC after deafferentation and the expression patterns of the EphB family were not changed. In particular, the presence of a graded ephrin-A expression in the deafferented SC suggests that - if robust regeneration of RGC axons can be achieved - topographic guidance information as a likely requirement for a functionally successful re-establishment of the retinocollicular projection is available.

IL-10 induces DNA binding activity of three STAT proteins (Stat1, Stat3, and Stat5) and their distinct combinatorial assembly in the promoters of selected genes.

Interaction of IL-10 with its receptor leads to the activation of STAT transcription factors. Herein we report the IL-10 dependent simultaneous activation of three STAT transcription factors: Stat1, Stat3, and Stat5. Upon IL-10 treatment multiple Stat proteins become simultaneously activated, and bind to different promoters with equal kinetics but form distinct homo- and heterodimeric transcriptionally active complexes depending on the STAT-consensus elements of a selected gene promoter. Upon IL-10 treatment Stat1, 3, and 5 bind to the GRR of the FcgammaRI gene, activated Stat1 and 3 bind to the SIE sequence of the c-fos promoter and transcriptionally active Stat5 assembles at the PRL-STAT consensus sequence of the beta-casein gene. Thus, functionally relevant STAT dimerization is influenced by the activated cytokine receptor as well as the specific STAT consensus sequence present in a specific gene promoter.

Interleukin-10 increases Bcl-2 expression and survival in primary human CD34+ hematopoietic progenitor cells.

Bcl-2 expression has been shown in hematopoietic progenitor cells. Through the use of Bcl-2 specific antisense oligonucleotides we herein report the biologic importance of Bcl-2 expression in primary human CD34+ hematopoietic progenitor cells committed to the myeloid lineage. In bone marrow or peripheral blood derived CD34+ cells Bcl-2 specific antisense decreased cell survival and inhibited the outgrowth of mixed myeloid colonies. A short-term overnight pretreatment of CD34+ cells with 25 mumol/L of Bcl-2 antisense in liquid culture completely ablated the growth of granulocyte-macrophage colony-forming cells (GM-CFC) in a subsequent 14 days methylcellulose colony assay. Control experiments using corresponding Bcl-2 sense or nonsense oligonucleotides did not significantly impair cell survival or growth of GM-colony-forming unit. Western blot analyses revealed the Bcl-2 antisense dependent inhibition of expression of the Bcl-2 protein in CD34+ progenitor cells. Furthermore, regulation of Bcl-2 expression by various cytokines including interleukin-10 (IL-10) was studied. IL-10's effects on the formation of mixed myeloid colonies were examined in the absence or presence of Bcl-2 specific antisense. In the absence of Bcl-2 antisense IL-10 significantly extended the colony forming potential of mixed myeloid colonies to 14 days. In the presence of Bcl-2 antisense rhIL-10 completely restored GM-CSF driven colony growth. Fluorescent microscopy, Western blot analysis, and reverse transcriptase-polymerase chain reaction revealed the IL-10 dependent increase in cellular expression of Bcl-2 protein and Bcl-2 mRNA transcripts in CD34+ cells. Thus these results show that Bcl-2 expression is necessary for the formation of GM-CSF-dependent colony growth in vitro and that rhIL-10 increases Bcl-2 expression and survival in primary human CD34+ hematopoietic progenitor cells that are committed to the myeloid lineage.

Constitutive activation of STAT proteins in primary lymphoid and myeloid leukemia cells and in Epstein-Barr virus (EBV)-related lymphoma cell lines.

Although various molecular mechanisms of STAT protein (signal transducers and activators of transcription) activation have been identified, little is known about the functional role of STAT-dependent transcriptional activation. Herein we report the constitutive nuclear localization, phosphorylation, and DNA-binding activity of STAT proteins in leukemia cells and lymphoma cell lines. With the use of oligonucleotide probes derived from the Fc gamma RI promoter, the beta-casein promoter and a STAT-binding element in the promoter of the Bci-2 gene constitutive activation of STAT proteins was detected in untreated acute T- and C/B-leukemia cells (3 of 5 and 12 of 19 patients, respectively). Supershift analyses using Stats 1-6 specific antisera showed the constitutive DNA binding activity of Stat5 in these cells. Confocal microscopy revealed the nuclear localization of Stat5 and Western blot analyses showed tyrosine phosphorylation of Stat5 in nuclear extracts of acute leukemia cells. In contrast, peripheral blood mononuclear cells did not display constitutive STAT-DNA interaction. Further studies were performed on freshly isolated acute myeloid leukemia cells as well as on cell line derived K562, lymphoblastoid cells (LCL), and Burkitt's lymphoma cells (BL). Fluorescence microscopy, gelshift, and supershift experiments showed the nuclear localization and constitutive DNA-binding activity of Stat5 in K562 cells. Stat1 and Stat3 were constitutively activated in freshly isolated AML cells (10 of 14 patients) and in Epstein Barr virus-positive or interleukin-10 expressing permanent LCL and BL cells. Thus, these data indicate a differential pattern of STAT protein activation in lymphoid or myeloid leukemia and in lymphoma cells.