Electrophysiological evidence for the presence of cystic fibrosis transmembrane conductance regulator (CFTR) in mouse sperm.

Mammalian sperm must undergo a maturational process, named capacitation, in the female reproductive tract to fertilize the egg. Sperm capacitation is regulated by a cAMP/protein kinase A (PKA) pathway and involves increases in intracellular Ca(2+), pH, Cl(-), protein tyrosine phosphorylation, and in mouse and some other mammals a membrane potential hyperpolarization. The cystic fibrosis transmembrane conductance regulator (CFTR), a Cl(-) channel modulated by cAMP/PKA and ATP, was detected in mammalian sperm and proposed to modulate capacitation. Our whole-cell patch-clamp recordings from testicular mouse sperm now reveal a Cl(-) selective component to membrane current that is ATP-dependent, stimulated by cAMP, cGMP, and genistein (a CFTR agonist, at low concentrations), and inhibited by DPC and CFTR(inh) -172, two well-known CFTR antagonists. Furthermore, the Cl(-) current component activated by cAMP and inhibited by CFTR(inh) -172 is absent in recordings on testicular sperm from mice possessing the CFTR ΔF508 loss-of-function mutation, indicating that CFTR is responsible for this component. A Cl(-) selective like current component displaying CFTR characteristics was also found in wild type epididymal sperm bearing the cytoplasmatic droplet. Capacitated sperm treated with CFTR(inh) -172 undergo a shape change, suggesting that CFTR is involved in cell volume regulation. These findings indicate that functional CFTR channels are present in mouse sperm and their biophysical properties are consistent with their proposed participation in capacitation.

T-type Ca2+ channels in sperm function.

Intracellular Ca2+ regulates many fundamental physiological processes in excitable and non-excitable cells. Certainly this is the case of sperm where the local concentration of intracellular Ca2+ ([Ca2+]i) is significantly influenced by Ca2+ permeable channels present in the cell plasma membrane. Amongst these channels, the voltage dependent Ca2+ channels (CaV) of the T-type (CaV3) appear to have an eminent role in the acrosome reaction (AR) of some sperm species, though they may participate in other important functions like motility and capacitation. The AR is an exocytotic event where the acrosome vesicle in the posterior region of the head fuses with the plasma membrane. This reaction allows sperm to fuse and fertilize the egg. Here we summarize our present knowledge regarding CaV3 channels in sperm, show the first direct electrophysiological evidence for their presence in maturing mouse sperm and discuss some of the relevant unanswered questions.

KATP channels in mouse spermatogenic cells and sperm, and their role in capacitation.

Mammalian sperm must undergo a series of physiological changes after leaving the testis to become competent for fertilization. These changes, collectively known as capacitation, occur in the female reproductive tract where the sperm plasma membrane is modified in terms of its components and ionic permeability. Among other events, mouse sperm capacitation leads to an increase in the intracellular Ca(2+) and pH as well as to a hyperpolarization of the membrane potential. It is well known that ion channels play a crucial role in these events, though the molecular identity of the particular channels involved in capacitation is poorly defined. In the present work, we report the identification and potential functional role of K(ATP) channels in mouse spermatogenic cells and sperm. By using whole-cell patch clamp recordings in mouse spermatogenic cells, we found K(+) inwardly rectifying (K(ir)) currents that are sensitive to Ba(2+), glucose and the sulfonylureas (tolbutamide and glibenclamide) that block K(ATP) channels. The presence of these channels was confirmed using inhibitors of the ATP synthesis and K(ATP) channel activators. Furthermore, RT-PCR assays allowed us to detect transcripts for the K(ATP) subunits SUR1, SUR2, K(ir)6.1 and K(ir)6.2 in total RNA from elongated spermatids. In addition, immunoconfocal microscopy revealed the presence of these K(ATP) subunits in mouse spermatogenic cells and sperm. Notably, incubation of sperm with tolbutamide during capacitation abolished hyperpolarization and significantly decreased the percentage of AR in a dose-dependent fashion. Together, our results provide evidence for the presence of K(ATP) channels in mouse spermatogenic cells and sperm and disclose the contribution of these channels to the capacitation-associated hyperpolarization.

Manifestaciones oculares del síndrome de Marfán / Ocular manifestations of Marfan syndrome

El síndrome de Marfán (SM) es una patología que afecta múltiples órganos y cuando no se maneja de manera adecuada es muy discapacitante con alto costo social para los sistemas de salud. Dentro de los órganos afectados se encuentra el visual, con manifestaciones que no exhiben un patrón de tipicidad debido a la falta de estudios que incluyan el examen oftalmológico completo como parte integral de la valoración y el tratamiento. La presencia de alteraciones oftalmológicas y la identificación de ciertas características al examen físico pueden anteceder las manifestaciones de los otros sistemas que comprenden el complejo diagnóstico de este síndrome, lo que da lugar a un abordaje precoz con manejo temprano y eficaz de alteraciones visuales. El objetivo del presente trabajo es analizar los hallazgos oftalmológicos de los pacientes con SM y describir las alteraciones más comunes en esta población.