Hspa9 is required for pronephros specification and formation inXenopus laevis

Coupling astogenic aging in the colonial tunicate Botryllus schlosseri with the stress protein mortalin

Botryllus schlosseri, a colonial marine invertebrate, exhibits three generations of short-lived astogenic modules that continuously grow and die throughout the colony's entire lifespan, within week-long repeating budding cycles (blastogenesis), each consisting of four stages (A-D). At stage D, aging is followed by the complete absorption of adult modules (zooids) via a massive apoptotic process. Here we studied in Botryllus the protein mortalin (HSP70s member), a molecule largely known for its association with aging and proliferation. In-situ hybridization and qPCR assays reveal that mortalin follows the cyclic pattern of blastogenesis. Colonies at blastogenic stage D display the highest mortalin levels, and young modules exhibit elevated mortalin levels compared to old modules. Manipulations of mortalin with the specific allosteric inhibitor MKT-077 has led to a decrease in the modules' growth rate and the development of abnormal somatic/germinal morphologies (primarily in vasculature and in organs such as the endostyle, the stomach and gonads). We therefore propose that mortalin plays a significant role in the astogeny and aging of colonial modules in B. schlosseri, by direct involvement in the regulation of blastogenesis.

Ca(2+) coding and decoding strategies for the specification of neural and renal precursor cells during development

During embryogenesis, a rise in intracellular Ca(2+) is known to be a widespread trigger for directing stem cells towards a specific tissue fate, but the precise Ca(2+) signalling mechanisms involved in achieving these pleiotropic effects are still poorly understood. In this review, we compare the Ca(2+) signalling events that appear to be one of the first steps in initiating and regulating both neural determination (neural induction) and kidney development (nephrogenesis). We have highlighted the necessary and sufficient role played by Ca(2+) influx and by Ca(2+) transients in the determination and differentiation of pools of neural or renal precursors. We have identified new Ca(2+) target genes involved in neural induction and we showed that the same Ca(2+) early target genes studied are not restricted to neural tissue but are also present in other tissues, principally in the pronephros. In this review, we also described a mechanism whereby the transcriptional control of gene expression during neurogenesis and nephrogenesis might be directly controlled by Ca(2+) signalling. This mechanism involves members of the Kcnip family such that a change in their binding properties to specific DNA sites is a result of Ca(2+) binding to EF-hand motifs. The different functions of Ca(2+) signalling during these two events illustrate the versatility of Ca(2+) as a second messenger.