Biology subjects

Marchena, M.

Publications and source records attributed to Marchena, M..

3 recordsLinked to original sources

bioRxiv2022

Extracellular matrix protein anosmin-1 overexpression regulates dopaminergic phenotype in the CNS and the PNS with no pathogenic consequences in MPTP model of Parkinson disease

The development and survival of dopaminergic neurons are influenced by the fibroblast growth factor (FGF) pathway. Anosmin-1 (A1) is an extracellular matrix protein that acts as a major regulator of this signaling pathway, controlling FGF diffusion, and receptor interaction and shuttling. Furthermore, overexpression of A1 in vivo gives rise to higher number of dopaminergic neurons in the olfactory bulb. Here, using A1 overexpressing mice (A1-mice), we studied the effects of A1 on different populations of catecholaminergic neurons in the central (CNS) and the peripheral nervous systems (PNS). A1 overexpression increases the number of dopaminergic SNpc neurons and alters the striosome/matrix organization of the striatum. Interestingly, these numerical and morphological changes in the nigrostriatal pathway of A1-mice do not confer an altered susceptibility to experimental MPTP-parkinsonism with respect to wild type controls. Moreover, the study of the effects of A1 overexpression was extended to different dopaminergic tissues associated with the PNS, detecting a significant reduction in the number of dopaminergic chemosensitive carotid body glomus cells in A1-mice. Overall, these analyses confirm A1 as a principal regulator of the FGF pathway in the development and survival of dopaminergic neurons in different nuclei of the mammalian nervous system.

neuroscience↗

bioRxiv2020

Insulin receptor activation by proinsulin preserves synapses and vision in retinitis pigmentosa

Synaptic loss, neuronal death, and circuit remodeling are common features of central nervous system neurodegenerative disorders. Retinitis pigmentosa (RP), the leading cause of inherited blindness, is a group of retinal dystrophies characterized by photoreceptor dysfunction and death. The insulin receptor, a key controller of metabolism, also regulates neuronal survival and synaptic formation, maintenance, and activity. Indeed, deficient insulin receptor signaling has been implicated in several brain neurodegenerative pathologies. We present evidence linking impaired insulin receptor signaling with RP. We describe a selective decrease in the levels of the insulin receptor and its downstream effector phospho-S6 in retinal horizontal cell axons in the rd10 mouse model of RP, as well as aberrant synapses between rod photoreceptors and the postsynaptic terminals of horizontal and bipolar cells. A gene therapy strategy to induce sustained proinsulin production restored retinal insulin receptor signaling, by increasing S6 phosphorylation, without peripheral metabolic consequences. Moreover, proinsulin preserved photoreceptor synaptic connectivity and prolonged visual function in electroretinogram and optomotor tests. These findings support the therapeutic potential of proinsulin in RP.

neuroscience↗

bioRxiv2020

Buffering and total calcium levels determine the presence of oscillatory regimes in cardiac cells

Calcium oscillations and waves are often behind instances of extra depolarization in cardiac cells, eventually giving rise to life-threatening arrhythmias. In this work, we study the conditions for the appearance of calcium oscillations in both a detailed subcellular model of calcium dynamics and a minimal model that takes into account just the minimal ingredients of the calcium toolkit. To avoid the effects of homeostatic changes and the interaction with the action potential we consider the somewhat artificial condition of a cell without pacing and with no calcium exchange with the extracellular medium. This permits us to isolate the main reasons responsible for the oscillations by controlling externally the total calcium content of the cell. We find that as the calcium content is increased, the system transitions between two stationary states, corresponding to one with closed ryanodine receptors (RyR) and most calcium in the cell stored in the sarcoplasmic reticulum (SR), and another, with open RyRs and a depleted SR. In between these states, calcium oscillations may appear. This transition depends very sensitively in the amount of buffering in the cell. We find, for instance, that at high values of calsequestrin (CSQ) oscillations disappear, while they are present for a broad range of parameters at low values of CSQ. Using the minimal model, we can relate the stability of the oscillating state to the nullcline structure of the system, and find that its range of existence is bounded by a homoclinic and a Hopf bifurcation. Author summaryIn cardiac cells, calcium plays a very important role. An increase in calcium levels is the trigger used by the cell to initiate contraction. Besides, calcium modulates several transmembrane currents, affecting the cell transmembrane potential. Thus, dysregulations in calcium handling have been associated with the appearance of arrhythmias. Often, this dysregulation results in the appearance of periodic calcium waves or global oscillations, providing a pro-arrhythmic substrate. In this paper, we study the onset of calcium oscillations in cardiac cells using both a detailed subcellular model of calcium dynamics and a minimal model that takes into account just the minimal ingredients of the calcium toolkit. Both reproduce the main experimental results and link this behavior with the presence of different steady-state solutions and bifurcations that depend on the total amount of calcium in the cell and in the level of buffering present. We expect that this work will help to clarify the conditions under which calcium oscillations appear in cardiac myocytes and, therefore, will represent a step further in the understanding of the origin of cardiac arrhythmias.

biophysics↗