Limits...
Bioelectric patterning during oogenesis: stage-specific distribution of membrane potentials, intracellular pH and ion-transport mechanisms in Drosophila ovarian follicles.

Krüger J, Bohrmann J - BMC Dev. Biol. (2015)

Bottom Line: Bioelectric phenomena have been found to exert influence on various developmental and regenerative processes.Striking similarities between Vmem-patterns and activity patterns of voltage-dependent Ca(2+)-channels were found, suggesting a mechanism for transducing bioelectric signals into cellular responses.Our data suggest that spatial patterning of Vmem, pHi and specific membrane-channel proteins results in bioelectric signals that are supposed to play important roles during oogenesis, e. g. by influencing spatial coordinates, regulating migration processes or modifying the cytoskeletal organization.

View Article: PubMed Central - PubMed

Affiliation: RWTH Aachen University, Institut für Biologie II, Abt. Zoologie und Humanbiologie, Worringerweg 3, 52056, Aachen, Germany. Julia-Krueger@gmx.net.

ABSTRACT

Background: Bioelectric phenomena have been found to exert influence on various developmental and regenerative processes. Little is known about their possible functions and the cellular mechanisms by which they might act during Drosophila oogenesis. In developing follicles, characteristic extracellular current patterns and membrane-potential changes in oocyte and nurse cells have been observed that partly depend on the exchange of protons, potassium ions and sodium ions. These bioelectric properties have been supposed to be related to various processes during oogenesis, e. g. pH-regulation, osmoregulation, cell communication, cell migration, cell proliferation, cell death, vitellogenesis and follicle growth. Analysing in detail the spatial distribution and activity of the relevant ion-transport mechanisms is expected to elucidate the roles that bioelectric phenomena play during oogenesis.

Results: To obtain an overview of bioelectric patterning along the longitudinal and transversal axes of the developing follicle, the spatial distributions of membrane potentials (Vmem), intracellular pH (pHi) and various membrane-channel proteins were studied systematically using fluorescent indicators, fluorescent inhibitors and antisera. During mid-vitellogenic stages 9 to 10B, characteristic, stage-specific Vmem-patterns in the follicle-cell epithelium as well as anteroposterior pHi-gradients in follicle cells and nurse cells were observed. Corresponding distribution patterns of proton pumps (V-ATPases), voltage-dependent L-type Ca(2+)-channels, amiloride-sensitive Na(+)-channels and Na(+),H(+)-exchangers (NHE) and gap-junction proteins (innexin 3) were detected. In particular, six morphologically distinguishable follicle-cell types are characterized on the bioelectric level by differences concerning Vmem and pHi as well as specific compositions of ion channels and carriers. Striking similarities between Vmem-patterns and activity patterns of voltage-dependent Ca(2+)-channels were found, suggesting a mechanism for transducing bioelectric signals into cellular responses. Moreover, gradients of electrical potential and pH were observed within single cells.

Conclusions: Our data suggest that spatial patterning of Vmem, pHi and specific membrane-channel proteins results in bioelectric signals that are supposed to play important roles during oogenesis, e. g. by influencing spatial coordinates, regulating migration processes or modifying the cytoskeletal organization. Characteristic stage-specific changes of bioelectric activity in specialized cell types are correlated with various developmental processes.

No MeSH data available.


Characteristic distribution patterns of voltage-dependent L-type Ca2+-channels. Verapamil-FL staining, SIM, S9 to S10B, A, B, C: representative grey-scale images, A´, B´, C´: corresponding pseudocolour images. In S9 (A, A´) and S10A (B, B´) the concentration of labeled Ca2+-channels is considerably higher in tFC, cFC and sFC than in mFC (see scale bar). BC and PC show the highest concentrations of labeled Ca2+-channels in S9. In S10B (C, C´) the ventral side of the FC epithelium exhibits a considerably higher concentration of labeled, i. e. activated, or open, (and inactivated) channels than the dorsal side, where resting, or closed, channels predominate. In D the characteristic distribution patterns are summarized schematically; high concentrations of activated (and inactivated) Ca2+-channels are shown in green (staining in NC is not considered). For abbreviations, see Figure 1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4302609&req=5

Fig5: Characteristic distribution patterns of voltage-dependent L-type Ca2+-channels. Verapamil-FL staining, SIM, S9 to S10B, A, B, C: representative grey-scale images, A´, B´, C´: corresponding pseudocolour images. In S9 (A, A´) and S10A (B, B´) the concentration of labeled Ca2+-channels is considerably higher in tFC, cFC and sFC than in mFC (see scale bar). BC and PC show the highest concentrations of labeled Ca2+-channels in S9. In S10B (C, C´) the ventral side of the FC epithelium exhibits a considerably higher concentration of labeled, i. e. activated, or open, (and inactivated) channels than the dorsal side, where resting, or closed, channels predominate. In D the characteristic distribution patterns are summarized schematically; high concentrations of activated (and inactivated) Ca2+-channels are shown in green (staining in NC is not considered). For abbreviations, see Figure 1.

Mentions: Using the fluorescent inihibitor verapamil-FL, we analysed the distribution of L-type Ca2+-channels. Since binding of the inhibitor depends on the channel’s conformational state, we used immunohistochemistry as a control to discriminate between distribution and activity patterns. While Anti-Cavα1 revealed uniform distributions of L-type Ca2+-channels along the longitudinal and transversal follicle axes during mid-vitellogenic stages (data not shown), verapamil-FL showed asymmetric staining patterns (Figure 5), that are supposed to represent differences in the conformational state of these voltage-dependent channels. Verapamil binds with higher affinity to channels being exposed to depolarized Vmem, which means that they are activated, or open (and inactivated). The distribution patterns of verapamil-FL-labeled channels were very similar to the Vmem-patterns described above (Figure 2). Regions having more depolarized Vmem contained higher concentrations of supposed activated (and inactivated) channels. In S9 and S10A, these regions are the tFC, cFC and sFC as well as the BC and PC, while in the mFC the concentration of supposed resting, or closed, channels was higher.Figure 5


Bioelectric patterning during oogenesis: stage-specific distribution of membrane potentials, intracellular pH and ion-transport mechanisms in Drosophila ovarian follicles.

Krüger J, Bohrmann J - BMC Dev. Biol. (2015)

Characteristic distribution patterns of voltage-dependent L-type Ca2+-channels. Verapamil-FL staining, SIM, S9 to S10B, A, B, C: representative grey-scale images, A´, B´, C´: corresponding pseudocolour images. In S9 (A, A´) and S10A (B, B´) the concentration of labeled Ca2+-channels is considerably higher in tFC, cFC and sFC than in mFC (see scale bar). BC and PC show the highest concentrations of labeled Ca2+-channels in S9. In S10B (C, C´) the ventral side of the FC epithelium exhibits a considerably higher concentration of labeled, i. e. activated, or open, (and inactivated) channels than the dorsal side, where resting, or closed, channels predominate. In D the characteristic distribution patterns are summarized schematically; high concentrations of activated (and inactivated) Ca2+-channels are shown in green (staining in NC is not considered). For abbreviations, see Figure 1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4302609&req=5

Fig5: Characteristic distribution patterns of voltage-dependent L-type Ca2+-channels. Verapamil-FL staining, SIM, S9 to S10B, A, B, C: representative grey-scale images, A´, B´, C´: corresponding pseudocolour images. In S9 (A, A´) and S10A (B, B´) the concentration of labeled Ca2+-channels is considerably higher in tFC, cFC and sFC than in mFC (see scale bar). BC and PC show the highest concentrations of labeled Ca2+-channels in S9. In S10B (C, C´) the ventral side of the FC epithelium exhibits a considerably higher concentration of labeled, i. e. activated, or open, (and inactivated) channels than the dorsal side, where resting, or closed, channels predominate. In D the characteristic distribution patterns are summarized schematically; high concentrations of activated (and inactivated) Ca2+-channels are shown in green (staining in NC is not considered). For abbreviations, see Figure 1.
Mentions: Using the fluorescent inihibitor verapamil-FL, we analysed the distribution of L-type Ca2+-channels. Since binding of the inhibitor depends on the channel’s conformational state, we used immunohistochemistry as a control to discriminate between distribution and activity patterns. While Anti-Cavα1 revealed uniform distributions of L-type Ca2+-channels along the longitudinal and transversal follicle axes during mid-vitellogenic stages (data not shown), verapamil-FL showed asymmetric staining patterns (Figure 5), that are supposed to represent differences in the conformational state of these voltage-dependent channels. Verapamil binds with higher affinity to channels being exposed to depolarized Vmem, which means that they are activated, or open (and inactivated). The distribution patterns of verapamil-FL-labeled channels were very similar to the Vmem-patterns described above (Figure 2). Regions having more depolarized Vmem contained higher concentrations of supposed activated (and inactivated) channels. In S9 and S10A, these regions are the tFC, cFC and sFC as well as the BC and PC, while in the mFC the concentration of supposed resting, or closed, channels was higher.Figure 5

Bottom Line: Bioelectric phenomena have been found to exert influence on various developmental and regenerative processes.Striking similarities between Vmem-patterns and activity patterns of voltage-dependent Ca(2+)-channels were found, suggesting a mechanism for transducing bioelectric signals into cellular responses.Our data suggest that spatial patterning of Vmem, pHi and specific membrane-channel proteins results in bioelectric signals that are supposed to play important roles during oogenesis, e. g. by influencing spatial coordinates, regulating migration processes or modifying the cytoskeletal organization.

View Article: PubMed Central - PubMed

Affiliation: RWTH Aachen University, Institut für Biologie II, Abt. Zoologie und Humanbiologie, Worringerweg 3, 52056, Aachen, Germany. Julia-Krueger@gmx.net.

ABSTRACT

Background: Bioelectric phenomena have been found to exert influence on various developmental and regenerative processes. Little is known about their possible functions and the cellular mechanisms by which they might act during Drosophila oogenesis. In developing follicles, characteristic extracellular current patterns and membrane-potential changes in oocyte and nurse cells have been observed that partly depend on the exchange of protons, potassium ions and sodium ions. These bioelectric properties have been supposed to be related to various processes during oogenesis, e. g. pH-regulation, osmoregulation, cell communication, cell migration, cell proliferation, cell death, vitellogenesis and follicle growth. Analysing in detail the spatial distribution and activity of the relevant ion-transport mechanisms is expected to elucidate the roles that bioelectric phenomena play during oogenesis.

Results: To obtain an overview of bioelectric patterning along the longitudinal and transversal axes of the developing follicle, the spatial distributions of membrane potentials (Vmem), intracellular pH (pHi) and various membrane-channel proteins were studied systematically using fluorescent indicators, fluorescent inhibitors and antisera. During mid-vitellogenic stages 9 to 10B, characteristic, stage-specific Vmem-patterns in the follicle-cell epithelium as well as anteroposterior pHi-gradients in follicle cells and nurse cells were observed. Corresponding distribution patterns of proton pumps (V-ATPases), voltage-dependent L-type Ca(2+)-channels, amiloride-sensitive Na(+)-channels and Na(+),H(+)-exchangers (NHE) and gap-junction proteins (innexin 3) were detected. In particular, six morphologically distinguishable follicle-cell types are characterized on the bioelectric level by differences concerning Vmem and pHi as well as specific compositions of ion channels and carriers. Striking similarities between Vmem-patterns and activity patterns of voltage-dependent Ca(2+)-channels were found, suggesting a mechanism for transducing bioelectric signals into cellular responses. Moreover, gradients of electrical potential and pH were observed within single cells.

Conclusions: Our data suggest that spatial patterning of Vmem, pHi and specific membrane-channel proteins results in bioelectric signals that are supposed to play important roles during oogenesis, e. g. by influencing spatial coordinates, regulating migration processes or modifying the cytoskeletal organization. Characteristic stage-specific changes of bioelectric activity in specialized cell types are correlated with various developmental processes.

No MeSH data available.