Js. Marchant et I. Parker, Xenopus tropicalis oocytes as an advantageous model system for the study of intracellular Ca2+ signalling, BR J PHARM, 132(7), 2001, pp. 1396-1410
1 The purpose of this study was to compare oocytes from the pipid frogs Xen
opus tropicalis and Xenopus laevis, with respect to their utility for study
ing Ca2+ signalling mechanisms and for expression of heterologous proteins.
2 We show that X. tropicalis oocytes possess an intracellular Ca2+ store th
at is mobilized by inositol (1,4,5) trisphosphate (IP3) Ca2+ signalling is
activated by endogenous lysophosphatidic acid receptors and cytosolic Ca2activates a plasma membrane chloride conductance. The spatiotemporal organi
zation of cytosolic Ca2+ signals, from the microscopic architecture of elem
entary Ca2+ 'puffs' to the macroscopic patterns of Ca2+ spiking are closely
similar to the local and global patterns of Ca2+ release previously charac
terized in oocytes from X, laevis.
3 By injecting X. tropicalis oocytes with cDNA encoding an ER-targeted fluo
rescent protein construct, we demonstrate the capacity of the X. tropicalis
oocyte to readily express heterologous proteins. The organization of ER is
polarized across the oocyte, with the IP3-releaseable store targeted withi
n an similar to8 mum wide band that circumscribes the cell.
4 We conclude that the X. tropicalis oocyte shares many of the characterist
ics that have made oocytes of X. laevis a favoured system for studying Ca2 signalling mechanisms. Moreover, X. tropicalis oocytes display further pra
ctical advantages in terms of imaging depth, Ca2+ signal magnitude and elec
trical properties. These further enhance the appeal of X, tropicalis as an
experimental system, in addition to its greater amenability to transgenic a
pproaches.