Fundación Instituto Leloir

About: Fundación Instituto Leloir is a facility organization based out in Buenos Aires, Argentina. It is known for research contribution in the topics: Dentate gyrus & Neurogenesis. The organization has 702 authors who have published 1052 publications receiving 39299 citations.

Resident Neural Stem Cells

Abstract: In recent decades, emerging evidence has proved that neurogenesis exists in at least two regions in the mammalian adult brain: the subventricular zone around the lateral ventricles and the subgranular layer in the hippocampus. Cells with the properties of neural stem cells have been isolated from these regions and cultivated in vitro. In the presence of trophic factors, these cells proliferate and form neurospheres. When these factors are withdrawn, the neurospheres differentiate into neurons, astrocytes, and oligodendrocytes. In normal brains, the newly generated neurons in the hippocampus contribute to learning and memory formation. The neuroblasts originated in the subventricular zone migrate to the olfactory bulb and differentiate into mature neurons. Neurogenesis in the adult brain may be modulated by physiologic and pathologic situations. After stroke, for instance, neurogenesis increases and the new neurons migrate to the injured area. Therefore, the study of adult neurogenesis is a promising field and brings the possibility of modulating endogenous neural stem cells for therapeutic purposes.

DMT1 iron uptake in the PNS: bridging the gap between injury and regeneration

Abstract: Previous studies by our group demonstrated the key role of iron in Schwann cell maturation through an increase in cAMP, PKA activation and CREB phosphorylation. These studies opened the door to further research on non-transferrin-bound iron uptake, which revealed the presence of DMT1 mRNA all along SC progeny, hinting at a constitutive role of DMT1 in ensuring the provision of iron in the PNS. In light of these previous results, the present work evaluates the participation of DMT1 in the remyelination process following a demyelinating lesion promoted by sciatic nerve crush--a reversible model of Wallerian degeneration. DMT1 was observed to colocalize with a SC marker S100β at all survival times analyzed. In turn, the assessment of DMT1 mRNA expression exhibited an increase 7 days post-injury, while DMT1 protein levels showed an increase 14 days after crush at the lesion site and distal stump; finally, an increase in iron levels became evident as from 14 days post-injury, in parallel with DMT1 values. To sum up, the present work unveils the role of DMT1 in mediating the neuroregenerative action of iron.

Mutational analysis of kinetic partitioning in protein folding and protein-DNA binding

Abstract: Kinetic partitioning between competing routes is present in many biological processes. Here, we propose a methodology to characterize kinetic partitioning through site-directed mutagenesis and apply it to parallel routes for unfolding of the TI I27 protein and for recognition of its target DNA by the human papillomavirus E2 protein. The balance between the two competing reaction routes can be quantified by the partitioning constant K(p). K(p) is easily modulated by point mutations, opening the way for the rational design of kinetic partitioning. Conserved wild-type residues strongly favor one of the two competing reactions, suggesting that in these systems there is an evolutionary pressure to shift partitioning towards a certain route. The mutations with the largest effects on partitioning cluster together in space, defining the protein regions most relevant for the modulation of partitioning. Such regions are neither fully coincident with nor strictly segregated from the regions that are important from each competing reaction. We dissected the mutational effects on partitioning into the contributions from each competing route using a new parameter called pi-value. The results suggest how the design of kinetic partitioning may be approached in each case.

Rapid vesicle replenishment after the immediately releasable pool exocytosis is tightly linked to fast endocytosis, and depends on basal calcium and cortical actin in chromaffin cells

Abstract: The maintenance of the secretory response requires a continuous replenishment of releasable vesicles. It was proposed that the immediately releasable pool (IRP) is important in chromaffin cell secretion during action potentials applied at basal physiological frequencies, because of the proximity of IRP vesicles to voltage dependent Ca2+ channels. However, previous reports showed that IRP replenishment after depletion is too slow to manage such a situation. In this work we used patch-clamp measurements of membrane capacitance, confocal imaging of F-actin distribution and cytosolic Ca2+ measurements with Fura-2 to re-analyze this problem in primary cultures of mouse chromaffin cells. We provide evidence that IRP replenishment has one slow (time constant between 5-10 s) and one rapid component (time constant between 0.5-1.5 s) linked to a dynamin-dependent fast endocytosis. Both, the fast endocytosis and the rapid replenishment component were eliminated when 500 nM Ca2+ was added to the internal solution during patch-clamp experiments, but they became dominant and accelerated when the cytosolic Ca2+ buffer capacity was increased. In addition, both rapid replenishment and fast endocytosis were retarded when cortical F-actin cytoskeleton was disrupted with cytochalasin D. Finally, in permeabilized chromaffin cells stained with rhodamine-phalloidin, the cortical F-actin density was reduced when the Ca2+ concentration was increased in a range of 10-1000 nM. We conclude that low cytosolic Ca2+ concentrations, which favor cortical F-actin stabilization, allow the activation of a fast endocytosis mechanism linked to a rapid replenishment component of IRP.