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Expression and localization of aquaporin 1b during oocyte development in the Japanese eel (Anguilla japonica).

Kagawa H, Kishi T, Gen K, Kazeto Y, Tosaka R, Matsubara H, Matsubara T, Sawaguchi S - Reprod. Biol. Endocrinol. (2011)

Bottom Line: Light microscopic immunocytochemical analysis of ovary revealed that the Japanese eel AQP1b was expressed in the cytoplasm around the yolk globules which were located in the peripheral region of oocytes during the primary yolk globule stage; thereafter, the immunoreactivity was observed throughout the cytoplasm of oocyte as vitellogenesis progressed.The immunoreactivity became localized around the large membrane-limited yolk masses which were formed by the fusion of yolk globules during the oocyte maturation phase.These results together indicate that AQP1b, which is synthesized in the oocyte during the process of oocyte growth, is essential for mediating water uptake into eel oocytes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Faculty of Agriculture, University of Miyazaki, Miyazaki 889-2192, Japan. kagawa@cc.miyazaki-u.ac.jp

ABSTRACT
To elucidate the molecular mechanisms underling hydration during oocyte maturation, we characterized the structure of Japanese eel (Anguilla japonica) novel-water selective aquaporin 1 (AQP1b) that thought to be involved in oocyte hydration. The aqp1b cDNA encodes a 263 amino acid protein that includes the six potential transmembrane domains and two Asn-Pro-Ala motifs. Reverse transcription-polymerase chain reaction showed transcription of Japanese eel aqp1b in ovary and testis but not in the other tissues. In situ hybridization studies with the eel aqp1b cRNA probe revealed intense eel aqp1b signal in the oocytes at the perinucleolus stage and the signals became faint during the process of oocyte development. Light microscopic immunocytochemical analysis of ovary revealed that the Japanese eel AQP1b was expressed in the cytoplasm around the yolk globules which were located in the peripheral region of oocytes during the primary yolk globule stage; thereafter, the immunoreactivity was observed throughout the cytoplasm of oocyte as vitellogenesis progressed. The immunoreactivity became localized around the large membrane-limited yolk masses which were formed by the fusion of yolk globules during the oocyte maturation phase. These results together indicate that AQP1b, which is synthesized in the oocyte during the process of oocyte growth, is essential for mediating water uptake into eel oocytes.

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Immunohistochemical localization of AQP1b in Japanese eel primary yolk globule oocytes. Two successive sections of the Japanese eel oocytes at the primary yolk globule stage stained with hematoxylin and eosin (A, B) and immunocytochemically stained with anti-eel AQP1b (C, D). Intense AQP1b immunoreaction was detected around yolk granules located in the peripheral region of oocyte (B, D).
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Figure 7: Immunohistochemical localization of AQP1b in Japanese eel primary yolk globule oocytes. Two successive sections of the Japanese eel oocytes at the primary yolk globule stage stained with hematoxylin and eosin (A, B) and immunocytochemically stained with anti-eel AQP1b (C, D). Intense AQP1b immunoreaction was detected around yolk granules located in the peripheral region of oocyte (B, D).

Mentions: Immunoblotting analysis using the eel AQP1b antisera on the extracts from ovarian fragments showed a single protein band with a molecular mass of approximately 28 kDa, thus corresponding to the calculated molecular mass of Japanese eel AQP1b (Figure 5). Immunocytochemical observation for eel AQP1b was performed in ovarian fragments containing oocytes at various developmental stages. Previtellogenic ovarian follicles at the perinucleolus and oil droplet stages were devoid of eel AQP1b positive reaction (Figure 6). Intense immunoreaction was first observed in oocytes at the primary yolk globule stage, exclusively in the vesicles (which are surmise yolk globules) located at the peripheral ooplasm (Figure 7). Full-grown oocytes at the tertiary yolk globule stage showed the germinal vesicle in a central position and small yolk globules distributed in the cytoplasm. Intense immunoreactions were located around yolk globules occupied in oocyte cytoplasm (Figure 8A, D). During oocyte maturation phase, yolk globules fused together and increased in size in oocytes at the migratory nucleus stage (Figure 8B) and yolk globules became larger yolk masses but they did not fuse into a single yolk mass in oocytes at the mature stage (Figure 8C). Immunoreactions were observed around the membrane bound yolk masses in oocytes at the migratory nucleus stage (Figure 8E) and at the mature stage (Figure 8F).


Expression and localization of aquaporin 1b during oocyte development in the Japanese eel (Anguilla japonica).

Kagawa H, Kishi T, Gen K, Kazeto Y, Tosaka R, Matsubara H, Matsubara T, Sawaguchi S - Reprod. Biol. Endocrinol. (2011)

Immunohistochemical localization of AQP1b in Japanese eel primary yolk globule oocytes. Two successive sections of the Japanese eel oocytes at the primary yolk globule stage stained with hematoxylin and eosin (A, B) and immunocytochemically stained with anti-eel AQP1b (C, D). Intense AQP1b immunoreaction was detected around yolk granules located in the peripheral region of oocyte (B, D).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3117773&req=5

Figure 7: Immunohistochemical localization of AQP1b in Japanese eel primary yolk globule oocytes. Two successive sections of the Japanese eel oocytes at the primary yolk globule stage stained with hematoxylin and eosin (A, B) and immunocytochemically stained with anti-eel AQP1b (C, D). Intense AQP1b immunoreaction was detected around yolk granules located in the peripheral region of oocyte (B, D).
Mentions: Immunoblotting analysis using the eel AQP1b antisera on the extracts from ovarian fragments showed a single protein band with a molecular mass of approximately 28 kDa, thus corresponding to the calculated molecular mass of Japanese eel AQP1b (Figure 5). Immunocytochemical observation for eel AQP1b was performed in ovarian fragments containing oocytes at various developmental stages. Previtellogenic ovarian follicles at the perinucleolus and oil droplet stages were devoid of eel AQP1b positive reaction (Figure 6). Intense immunoreaction was first observed in oocytes at the primary yolk globule stage, exclusively in the vesicles (which are surmise yolk globules) located at the peripheral ooplasm (Figure 7). Full-grown oocytes at the tertiary yolk globule stage showed the germinal vesicle in a central position and small yolk globules distributed in the cytoplasm. Intense immunoreactions were located around yolk globules occupied in oocyte cytoplasm (Figure 8A, D). During oocyte maturation phase, yolk globules fused together and increased in size in oocytes at the migratory nucleus stage (Figure 8B) and yolk globules became larger yolk masses but they did not fuse into a single yolk mass in oocytes at the mature stage (Figure 8C). Immunoreactions were observed around the membrane bound yolk masses in oocytes at the migratory nucleus stage (Figure 8E) and at the mature stage (Figure 8F).

Bottom Line: Light microscopic immunocytochemical analysis of ovary revealed that the Japanese eel AQP1b was expressed in the cytoplasm around the yolk globules which were located in the peripheral region of oocytes during the primary yolk globule stage; thereafter, the immunoreactivity was observed throughout the cytoplasm of oocyte as vitellogenesis progressed.The immunoreactivity became localized around the large membrane-limited yolk masses which were formed by the fusion of yolk globules during the oocyte maturation phase.These results together indicate that AQP1b, which is synthesized in the oocyte during the process of oocyte growth, is essential for mediating water uptake into eel oocytes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Faculty of Agriculture, University of Miyazaki, Miyazaki 889-2192, Japan. kagawa@cc.miyazaki-u.ac.jp

ABSTRACT
To elucidate the molecular mechanisms underling hydration during oocyte maturation, we characterized the structure of Japanese eel (Anguilla japonica) novel-water selective aquaporin 1 (AQP1b) that thought to be involved in oocyte hydration. The aqp1b cDNA encodes a 263 amino acid protein that includes the six potential transmembrane domains and two Asn-Pro-Ala motifs. Reverse transcription-polymerase chain reaction showed transcription of Japanese eel aqp1b in ovary and testis but not in the other tissues. In situ hybridization studies with the eel aqp1b cRNA probe revealed intense eel aqp1b signal in the oocytes at the perinucleolus stage and the signals became faint during the process of oocyte development. Light microscopic immunocytochemical analysis of ovary revealed that the Japanese eel AQP1b was expressed in the cytoplasm around the yolk globules which were located in the peripheral region of oocytes during the primary yolk globule stage; thereafter, the immunoreactivity was observed throughout the cytoplasm of oocyte as vitellogenesis progressed. The immunoreactivity became localized around the large membrane-limited yolk masses which were formed by the fusion of yolk globules during the oocyte maturation phase. These results together indicate that AQP1b, which is synthesized in the oocyte during the process of oocyte growth, is essential for mediating water uptake into eel oocytes.

Show MeSH
Related in: MedlinePlus