Water transport in highly water-permeable membranes is conducted by water-selective pores--namely, water channels.
The cloning of water channels revealed the water-selective characteristics of these proteins when expressed in
Xenopus oocytes or reconstituted in liposomes. In adition to the function as water channels, cloning of a member of the water channel that also transports nonionic small
molecules such as urea and glycerol Ishibashi et al. (1994) .
NCBI Summary:
This gene encodes the water channel protein aquaporin 3. Aquaporins are a family of small integral membrane proteins related to the major intrinsic protein, also known as aquaporin 0. Aquaporin 3 is localized at the basal lateral membranes of collecting duct cells in the kidney. In addition to its water channel function, aquaporin 3 has been found to facilitate the transport of nonionic small solutes such as urea and glycerol, but to a smaller degree. It has been suggested that water channels can be functionally heterogeneous and possess water and solute permeation mechanisms. Alternative splicing of this gene results in multiple transcript variants encoding different isoforms. [provided by RefSeq, Dec 2015]
General function
Channel/transport protein
Comment
A Trial to Cryopreserve Immature Medaka (Oryzias latipes) Oocytes after Enhancing Their Permeability by Exogenous Expression of Aquaporin 3. Valdez DM et al. Fish oocytes have not been cryopreserved successfully, probably because it is difficult to prevent intracellular ice from forming. Previously, we have shown in medaka that immature oocytes are more suitable for cryopreservation than mature oocytes or embryos, in terms of permeability. We have also shown in immature medaka oocytes that the exogenous expression of aquaporin 3 (AQP3), a water/cryoprotectant channel, promotes the movement of water and cryoprotectants through the plasma membrane. In the present study, we attempted to cryopreserve immature medaka oocytes expressing AQP3. We first examined effects of hypertonic stress and the chemical toxicity of cryoprotectants on the survival of the AQP3-expressing oocytes. Exposure to hypertonic solutions containing sucrose decreased the survival of oocytes, but the expression of AQP3 did not affect sensitivity to hypertonic stress. Also, AQP3 expression did not markedly increase sensitivity to the toxicity of cryoprotectants. Of the four cryoprotectants tested, propylene glycol was the least toxic. Using a propylene glycol-based solution, therefore, we tried to cryopreserve immature oocytes by vitrification. During cooling with liquid nitrogen, all intact oocytes became opaque, but many AQP3-expressing oocytes remained transparent. This indicates that the expression of AQP3 is effective in preventing intracellular ice from forming during cooling. During warming, however, all the AQP3-expressing oocytes became opaque, indicating that intracellular ice formed. Therefore, the dehydration and permeation by propylene glycol were still insufficient. Further studies are necessary to realize the cryopreservation of fish oocytes.
Cellular localization
Plasma membrane
Comment
Ovarian function
Antrum/Follicular fluid formation, Oogenesis, Oocyte maturation, Early embryo development
Comment
Effect of aquaporin 3 knockdown by RNA interference on antrum formation in sheep secondary follicles cultured in vitro. Paz MP et al. (2018) SummaryThe objectives were to develop an effective protocol for transfection of ovine secondary follicles and to assess the effect of attenuating aquaporin 3 (AQP3) using a small interfering RNA (siRNA-AQP3) on antrum formation and follicular growth in vitro. Various combinations of Lipofectamine® volumes (0.5, 0.75 or 1.0 µl), fluorescent oligonucleotide (BLOCK-iT ™) concentrations (3.18, 27.12 or 36.16 nM) and exposure times (12, 14, 16, 18 or 20 h) were tested. The BLOCK-iT™ was replaced by siRNA-AQP3 in the transfection complex. Ovine secondary follicles were isolated and cultured in vitro for 6 days using standard protocols. Follicles were transfected on day 0 or 3 or on both days (0 and 3) and then cultured for an additional 3 or 6 days. As revealed by the fluorescence signal, the Lipofectamine®/BLOCK-iT™ complex (0.75 µl + 27.12 nM by 12 h of incubation) crossed the basement membrane and granulosa cell and reached the oocytes. In general, the rate of intact follicles was higher and the rate of antrum formation was lower in transfected follicles compared with control follicles. In conclusion, ovine secondary follicles can be successfully transfected during in vitro culture, and siRNA-mediated attenuation of AQP3 gene reduced antrum formation of secondary follicles.//////////////////
Expression of Aquaporins in Human Embryos and Potential Role of AQP3 and AQP7 in Preimplantation Mouse Embryo Development. Xiong Y et al. Background/Aims: Water channels, also named aquaporins (AQPs), play crucial roles in cellular water homeostasis. Methods: RT-PCR indicated the mRNA expression of AQPs 1-5, 7, 9, and 11-12, but not AQPs 0, 6, 8, and 10 in the 2~8-cell stage human embryos. AQP3 and AQP7 were further analyzed for their mRNA expression and protein expression in the oocyte, zygote, 2-cell embryo, 4-cell embryo, 8-cell embryo, morula, and blastocyst from both human and mouse using RT-PCR and immunofluorescence, respectively. Results: AQP3 and AQP7 were detected in all these stages. Knockdown of either AQP3 or AQP7 by targeted siRNA injection into 2-cell mouse embryos significantly inhibited preimplantation embryo development. However, knockdown of AQP3 in JAr spheroid did not affect its attachment to Ishikawa cells. Conclusion: These data demonstrate that multiple aquaporins are expressed in the early stage human embryos and that AQP3 and AQP7 may play a role in preimplantation mouse embryo development.
Effect of maturation on the expression of aquaporin 3 in mouse oocyte. Jo JW et al. SummaryThis study aimed to investigate whether aquaporin 3 (Aqp3) mRNAs are expressed in immature oocytes and altered during in vitro maturation process. Five- to 6-week-old female ICR mice were primed by gonadotropin for 24 and 48 h. Immature oocytes obtained 48 h after priming were also matured in vitro for 17 to 18 h. In vivo matured oocytes were obtained after 48 h priming followed by hCG injection. Total RNAs were extracted from 80 to 150 oocytes in each experimental group, and the levels of Aqp3 mRNA were quantified by real-time reverse transcriptase polymerase chain reaction. The experiments were repeated twice using different oocytes. The Aqp3 mRNA was expressed in immature oocytes, as well as in in vitro and in vivo matured oocytes. The expression level was higher in immature oocytes obtained 48 h after priming (17.2 +/- 8.6, mean +/- SD) than those with no priming (5.7 +/- 0.8) or obtained 24 h after priming (2.5 +/- 0.8). The expression of Aqp3 mRNA decreased after in vitro maturation (1.2 +/- 0.5), which was similar to in vivo matured oocytes (1.0 +/- 0.0). Our work demonstrated that Aqp3 mRNA expression increased during the development of immature oocyte but decreased after completion of in vitro maturation. The results indicate that AQP3 is certainly needed for the acquisition of immature oocytes' full growing potential within antral follicles.
Edashige K, et al 2000 reported the expression of mRNAs of the aquaporin family in mouse oocytes and embryos.
The total RNA of mouse oocytes at metaphase II and
embryos at the 4-cell, morula, and blastocyst stages was isolated,
reverse-transcribed, and subjected to nested PCR amplification. Aquaporins
were expressed in both oocytes and embryos, but the types were different among
the developmental stages: aquaporins 3 and 7 were expressed in oocytes and
embryos at all stages examined, but aquaporins 8 and 9 were expressed only in
blastocysts. On the other hand, aquaporins 1, 2, 4, 5, and 6 were not detected
in any of the stages examined. The present study shows that
aquaporins are expressed in mammalian oocytes and embryos. These aquaporins
may play a role in water transport and conceivably also in cryoprotectant
transport across the plasma membrane in these cells.
Expression regulated by
Comment
Ovarian localization
Oocyte, Granulosa
Comment
Pathway for the Movement of Water and Cryoprotectants in Bovine Oocytes and Embryos. Jin B et al. The permeability of cells is important for cryopreservation. Previously, we showed in mice that the permeability to water and cryoprotectants of oocytes and embryos at early cleavage stages (early embryos) is low because these molecules move across the plasma membrane predominantly by simple diffusion through the lipid bilayer, whereas that of morulae and blastocysts is high because of a water channel, aquaporin 3 (AQP3). In this study, we examined the pathway for the movement of water and cryoprotectants in bovine oocytes/embryos and the role of AQP3 in the movement, by determining permeability, first in intact bovine oocytes/embryos, then in bovine morulae with suppressed AQP3-expression, and finally in mouse oocytes expressing bovine AQP3. The results suggest that water moves through bovine oocytes and early embryos slowly by simple diffusion, as in mice, although channel processes are also involved in the movement. On the other hand, water appears to move through morulae and blastocysts predominantly by facilitated diffusion via channels as in mice. Like water, cryoprotectants appear to move through bovine oocytes/early embryos mostly by simple diffusion, but channel processes would also be involved in the movement of glycerol and ethylene glycol unlike in mice. In bovine morulae, though glycerol and ethylene glycol would move predominantly by facilitated diffusion mostly through AQP3 as in mice, dimethylsulfoxide appears to move predominantly by simple diffusion unlike in mice. These results indicate that permeability-related properties of bovine oocytes/embryos are similar to those of mouse oocytes/embryos but species-specific differences do exist.
Reduced Expression and Function of Aquaporin-3 in Mouse Metaphase-II Oocytes Induced by Controlled Ovarian Hyperstimulation were Associated with Subsequent Low Fertilization Rate. Meng QX et al. Background/Aims: Aquaporin-3 (AQP3), one isoform of water channel family, has been found to be expressed in mouse oocytes. The present study aimed to investigate whether functional AQP3 was expressed in oocytes induced by controlled ovarian hyperstimulation (COH), and whether altered oocyte AQP3 expression was associated with changes in fertilization rate. Methods: Sixty ICR female mice were divided into two groups: COH and control. AQP3 mRNA expression of mouse metaphase II (MII) oocytes was quantified by real-time RT-PCR. The water permeability of oocytes was assessed with cell swelling test. The fertilization profiles of oocytes were generated via in vitro fertilization. Results: AQP3 mRNA was expressed in both natural and COH-induced mouse oocytes. COH significantly reduced AQP3 mRNA expression. The volume of oocytes was significantly increased after exposure to hypotonic medium and pretreatment with HgCl(2) attenuated hypotonic medium-induced increase in oocyte volume and water permeability coefficient (Pf). Furthermore, the expression of AQP3, Pf and the fertilization rate were significantly lower in COH oocytes than those in control. Conclusion: AQP3 might play an important role in controlling oocyte quality and a low in vitro fertilization rate of COH mice might, in part, result from reduced AQP3 expression and water permeability in mouse oocytes. Copyright (c) 2008 S. Karger AG, Basel.
Follicle stages
Antral, Preovulatory
Comment
Steady-state level of messenger RNA and immunolocalization of aquaporins 3, 7, and 9 during in vitro growth of ovine preantral follicles. Sales AD et al. (2015) Aquaporins (AQPs) are a well-conserved family of small (approximately 30 kDa) membrane channel proteins that facilitate rapid movement of fluids and have a unique tissue-specific pattern of expression. These proteins have been found in the female reproductive systems of humans, rats, and mice. However, the expression and cellular localization of AQPs have not extensively been studied in the female reproductive system of sheep. Therefore, this study aimed to evaluate, by real-time polymerase chain reaction and immunohistochemistry respectively, the levels of messenger RNA and the immunolocalization of AQP3, AQP7, and AQP9 in large isolated ovine secondary follicles over a period of IVC. Our analysis revealed that AQP3 and AQP9 were present predominately in follicles that exhibited antrum formation, suggesting a crucial role of these AQPs in the formation of the antrum. Interestingly, AQP7 was only expressed in follicles that had not formed an antrum by Day 12 of culture. In conclusion, the presence of protein channels (AQP3 and AQP9) seems to be essential for the formation of the antrum in isolated ovine secondary follicles cultured in vitro and thus plays an important role during folliculogenesis in this species.//////////////////
Expression and localization of Aquaporin 3 (AQP3) in folliculogenesis of ewes. Sales AD 2014 et al.
The mRNA expression and localization of Aquaporin 3 (AQP3) were investigated in the ovarian follicles of ewes at different stages of development (primordial, primary, secondary, small, and large antral). The gene expression was quantified by qPCR, while the protein identification and localization were determined by Western blot and immunohistochemistry, respectively. Analysis revealed that AQP3 mRNA was detected only in the antral follicles, whereas the protein expression was detected in the oocyte and granulosa cells in all stages of follicular development. The latter observation suggests that the presence of AQP3 in follicles of all categories, especially in the antral follicles, provides novel insights on the mechanisms that regulate the flow of water between cells during the formation of antral follicles in sheep.
/////////////////////////