High dynamics of rDNA cluster location in kissing bug holocentric chromosomes (Triatominae, Heteroptera).

In this paper, we determine by fluorescent in situ hybridization the variability in the chromosomal location of 45S rDNA clusters in 38 species belonging to 7 genera of the Triatominae subfamily, using a triatomine-specific 18S rDNA probe. Our results show a striking variability at the inter- and intraspecific level, never reported so far in holocentric chromosomes, revealing the extraordinary genomic dynamics that occurred during the evolution in this group of insects. Our results also demonstrate that the chromosomal position of rDNA clusters is an important marker to disclose chromosomal differentiation in species karyotypically homogenous in their chromosome number.

Effect of low-dose IL-2 immunotherapy on frequency and phenotype of regulatory T cells and NK cells in HIV/HCV-coinfected patients.

We evaluated the effect of low-dose IL-2 therapy (daily 1.2 MIU/m(2), subcutaneously) on the number and phenotype of regulatory T cells (T(regs)) and natural killer (NK) cells in HIV/HCV-coinfected patients taking antiretroviral therapy. The frequency and phenotype of circulating T(regs) (defined as CD3(+) CD4(+) CD25(high) or CD3(+) CD4(+) FOXP3(+)) and NK cells (CD3(-) CD16(+)/CD56(+)) were evaluated at baseline and after 12 weeks of treatment. The expression of CD25, CTLA-4, and granzymes A and B by CD4(+) FOXP3(+) cells, as well as the expression of KIR receptors (NKB1, CD158a, and NKAT2) on NK cells, was evaluated. Low doses of IL-2 resulted in the augmented frequency and absolute number of T(regs) in coinfected individuals. FOXP3 levels per cell as well as augmented CD25 and CTLA-4 expression by T(regs) suggested that IL-2 may lead to both expansion and activation of T(regs), although changes in the proportion of CD4(+) FOXP3(+) cells were not associated with changes in HCV viral load and CD4(+) cells between baseline and week 12. NK cell frequency also increased after IL-2 therapy. Interestingly, the pattern of expression of KIR receptors was changed by IL-2 treatment, since the frequency of NK cells expressing NKB1 augmented whereas the frequency of NK expressing CD158a and NKAT2 decreased.

Fibroblast growth factor 2 up regulates telomerase activity in neural precursor cells.

During brain development, neuronal and glial cells are generated from neural precursors on a precise schedule involving steps of proliferation, fate commitment and differentiation. We report that telomerase activity is highly expressed during embryonic murine cortical neurogenesis and early steps of gliogenesis and progressively decreases thereafter during cortex maturation to be undetectable in the normal adult brain. We evidenced neural precursor cells (NPC) as the principal telomerase-expressing cells in primary cultures from E15 mouse embryo cortices. Their differentiation either in neurons or in glial cells lead to a down regulation of telomerase activity that was directly correlated to the decrease of telomerase core protein (mTERT) mRNA synthesis. Furthermore, we show that FGF2 (fibroblast growth factor 2), one of the main regulators of CNS development, induces a dose-dependant increase of both the proliferation of NPC and telomerase activity in primary cortical cultures without affecting the mTERT mRNA synthesis compared to that of glyceraldehyde-3-phosphate dehydrogenase (mGAPDH). Finally, we evidenced that AZT (3'-azido-2', 3'-dideoxythymidine), known to inhibit telomerase activity, blocks in a dose dependant manner the FGF2-induced proliferation of NPC. Altogether, our results are in favor of an important role of telomerase activity during brain organogenesis. Oncogene (2000).