Papers by Daniel A Priego Espinosa
PLOS Computational Biology, 2020
Intracellular calcium ([Ca 2+ ] i) is a basic and ubiquitous cellular signal controlling a wide v... more Intracellular calcium ([Ca 2+ ] i) is a basic and ubiquitous cellular signal controlling a wide variety of biological processes. A remarkable example is the steering of sea urchin spermatozoa towards the conspecific egg by a spatially and temporally orchestrated series of [Ca 2+ ] i spikes. Although this process has been an experimental paradigm for reproduction and sperm chemotaxis studies, the composition and regulation of the signalling network underlying the cytosolic calcium fluctuations are hitherto not fully understood. Here, we used a differential equations model of the signalling network to assess which set of channels can explain the characteristic envelope and temporal organisation of the [Ca 2+ ] i-spike trains. The signalling network comprises an initial membrane hyperpolarisation produced by an Upstream module triggered by the egg-released chemoattractant peptide, via receptor activation, cGMP synthesis and decay. Followed by downstream modules leading to intraflagellar pH (pH i), voltage and [Ca 2+ ] i fluctuations. The Upstream module outputs were fitted to kinetic data on cGMP activity and early membrane potential changes measured in bulk cell populations. Two candidate modules featuring voltage-dependent Ca 2+-channels link these outputs to the downstream dynamics and can independently explain the typical decaying envelope and the progressive spacing of the spikes. In the first module, [Ca 2+ ] i-spike trains require the concerted action of a classical Ca V-like channel and a potassium channel, BK (Slo1), whereas the second module relies on pH i-dependent CatSper dynamics articulated with voltage-dependent neutral sodium-proton exchanger (NHE). We analysed the dynamics of these two modules alone and in mixed scenarios. We show that the [Ca 2+ ] i dynamics observed experimentally after sustained alkalinisation can be reproduced by a model featuring the Cat-Sper and NHE module but not by those including the pH-independent Ca V and BK module or proportionate mixed scenarios. We conclude in favour of the module containing CatSper and NHE and highlight experimentally testable predictions that would corroborate this conclusion.
INTER DISCIPLINA, 2020
En este trabajo se describen los niveles de complejidad en el proceso de fecundación, haciendo én... more En este trabajo se describen los niveles de complejidad en el proceso de fecundación, haciendo énfasis en el aspecto de criticalidad. Asimismo, se utilizan redes lógicas para describir el funcionamiento de el proceso de fertilización en el erizo de mar.
PLOS ONE, 2021
Capacitation is a complex maturation process mammalian sperm must undergo in the female genital t... more Capacitation is a complex maturation process mammalian sperm must undergo in the female genital tract to be able to fertilize an egg. This process involves, amongst others, physiological changes in flagellar beating pattern, membrane potential, intracellular ion concentrations and protein phosphorylation. Typically, in a capacitation medium, only a fraction of sperm achieve this state. The cause for this heterogeneous response is still not well understood and remains an open question. Here, one of our principal results is to develop a discrete regulatory network, with mostly deterministic dynamics in conjunction with some stochastic elements, for the main biochemical and biophysical processes involved in the early events of capacitation. The model criterion for capacitation requires the convergence of specific levels of a select set of nodes. Besides reproducing several experimental results and providing some insight on the network interrelations, the main contribution of the model ...
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Papers by Daniel A Priego Espinosa