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Differences in the Kinetic of the First Meiotic Division and in Active Mitochondrial Distribution between Prepubertal and Adult Oocytes Mirror Differences in their Developmental Competence in a Sheep Model.

Leoni GG, Palmerini MG, Satta V, Succu S, Pasciu V, Zinellu A, Carru C, Macchiarelli G, Nottola SA, Naitana S, Berlinguer F - PLoS ONE (2015)

Bottom Line: Maturation and fertilization rates did not differ between prepubertal and adult oocytes (95.1% vs 96.7% and 66.73% vs 70.62% respectively for prepubertal and adult oocytes).In prepubertal oocytes ATP rise is delayed and did not reach levels comparable to adult ones.Taken together our data suggest that oocytes with low developmental competence have a slowed down energetic metabolism which delays later development.

View Article: PubMed Central - PubMed

Affiliation: Department of Veterinary Medicine, Sassari University, Sassari, Italy; Sardinian Animal Biodiversity Center (Centro di Competenza per la Biodiversità Animale-CCBA), Sassari, Italy.

ABSTRACT
Our aim is to verify if oocyte developmental potential is related to the timing of meiotic progression and to mitochondrial distribution and activity using prepubertal and adult oocytes as models of low and high developmental capacity respectively. Prepubertal and adult oocytes were incorporated in an in vitro maturation system to determine meiotic and developmental competence and to assess at different time points kinetic of meiotic maturation, 2D protein electrophoresis patterns, ATP content and mitochondria distribution. Maturation and fertilization rates did not differ between prepubertal and adult oocytes (95.1% vs 96.7% and 66.73% vs 70.62% respectively for prepubertal and adult oocytes). Compared to adults, prepubertal oocytes showed higher parthenogenesis (17.38% vs 2.08% respectively in prepubertals and adults; P<0.01) and polispermy (14.30% vs 2.21% respectively in prepubertals and adults; P<0.01), lower cleavage rates (60.00% vs 67.08% respectively in prepubertals and adults; P<0.05) and blastocyst output (11.94% vs 34.% respectively in prepubertals and adults; P<0.01). Prepubertal oocytes reached MI stage 1 hr later than adults and this delay grows as the first meiotic division proceeds. Simultaneously, the protein pattern was altered since in prepubertal oocytes it fluctuates, dropping and rising to levels similar to adults only at 24 hrs. In prepubertal oocytes ATP rise is delayed and did not reach levels comparable to adult ones. CLSM observations revealed that at MII, in the majority of prepubertal oocytes, the active mitochondria are homogenously distributed, while in adults they are aggregated in big clusters. Our work demonstrates that mitochondria and their functional aggregation during maturation play an active role to provide energy in terms of ATP. The oocyte ATP content determines the timing of the meiotic cycle and the acquisition of developmental competence. Taken together our data suggest that oocytes with low developmental competence have a slowed down energetic metabolism which delays later development.

No MeSH data available.


Related in: MedlinePlus

Morphology of adult ovine oocytes (control group).(a) Clusters of mitochondria (m) in close proximity to tubular element of the smooth endoplasmic reticulum (SER) and clear vacuoles (V). TEM, bar: 1 μm. (b) Groups of round-to-ovoid mitochondria (m) near to tubular elements of SER and a Golgi apparatus (G). TEM, bar: 1 μm. (c). N: nucleus, NE: nuclear envelope; V: vacuoles; m: mitochondria. Arrows: hooded mitochondria; asterisks: mitochondria containing a clear vesicle.
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pone.0124911.g006: Morphology of adult ovine oocytes (control group).(a) Clusters of mitochondria (m) in close proximity to tubular element of the smooth endoplasmic reticulum (SER) and clear vacuoles (V). TEM, bar: 1 μm. (b) Groups of round-to-ovoid mitochondria (m) near to tubular elements of SER and a Golgi apparatus (G). TEM, bar: 1 μm. (c). N: nucleus, NE: nuclear envelope; V: vacuoles; m: mitochondria. Arrows: hooded mitochondria; asterisks: mitochondria containing a clear vesicle.

Mentions: By LM and TEM at low magnification, all the oocytes evidenced a round shape, with a thin perivitelline space surrounded by a continuous zona pellucida. The ooplasm appeared rich of clear vacuoles and strongly electron-dense lipid droplets (Fig 5a). A rosette-type arrangement of round-to-ovoid mitochondria, interspersed among single mitochondria, vacuoles, lipid droplets and SER, was evidenced in prepubertal and adult oocytes by TEM (Figs 5 and 6). Mitochondrial clusters were often bigger in the cortical area than in the perinuclear cytoplasm. At high magnification, numerous mitochondria presented a clear vesicle inside or showed a typical hooded configuration (Figs 5b, 5c and 6). Mitochondrial cristae were easily discernible (Fig 5c). Well developed smooth endoplasmic reticulum (SER) and Golgi membranes were observed in adult oocytes (Fig 6).


Differences in the Kinetic of the First Meiotic Division and in Active Mitochondrial Distribution between Prepubertal and Adult Oocytes Mirror Differences in their Developmental Competence in a Sheep Model.

Leoni GG, Palmerini MG, Satta V, Succu S, Pasciu V, Zinellu A, Carru C, Macchiarelli G, Nottola SA, Naitana S, Berlinguer F - PLoS ONE (2015)

Morphology of adult ovine oocytes (control group).(a) Clusters of mitochondria (m) in close proximity to tubular element of the smooth endoplasmic reticulum (SER) and clear vacuoles (V). TEM, bar: 1 μm. (b) Groups of round-to-ovoid mitochondria (m) near to tubular elements of SER and a Golgi apparatus (G). TEM, bar: 1 μm. (c). N: nucleus, NE: nuclear envelope; V: vacuoles; m: mitochondria. Arrows: hooded mitochondria; asterisks: mitochondria containing a clear vesicle.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4403920&req=5

pone.0124911.g006: Morphology of adult ovine oocytes (control group).(a) Clusters of mitochondria (m) in close proximity to tubular element of the smooth endoplasmic reticulum (SER) and clear vacuoles (V). TEM, bar: 1 μm. (b) Groups of round-to-ovoid mitochondria (m) near to tubular elements of SER and a Golgi apparatus (G). TEM, bar: 1 μm. (c). N: nucleus, NE: nuclear envelope; V: vacuoles; m: mitochondria. Arrows: hooded mitochondria; asterisks: mitochondria containing a clear vesicle.
Mentions: By LM and TEM at low magnification, all the oocytes evidenced a round shape, with a thin perivitelline space surrounded by a continuous zona pellucida. The ooplasm appeared rich of clear vacuoles and strongly electron-dense lipid droplets (Fig 5a). A rosette-type arrangement of round-to-ovoid mitochondria, interspersed among single mitochondria, vacuoles, lipid droplets and SER, was evidenced in prepubertal and adult oocytes by TEM (Figs 5 and 6). Mitochondrial clusters were often bigger in the cortical area than in the perinuclear cytoplasm. At high magnification, numerous mitochondria presented a clear vesicle inside or showed a typical hooded configuration (Figs 5b, 5c and 6). Mitochondrial cristae were easily discernible (Fig 5c). Well developed smooth endoplasmic reticulum (SER) and Golgi membranes were observed in adult oocytes (Fig 6).

Bottom Line: Maturation and fertilization rates did not differ between prepubertal and adult oocytes (95.1% vs 96.7% and 66.73% vs 70.62% respectively for prepubertal and adult oocytes).In prepubertal oocytes ATP rise is delayed and did not reach levels comparable to adult ones.Taken together our data suggest that oocytes with low developmental competence have a slowed down energetic metabolism which delays later development.

View Article: PubMed Central - PubMed

Affiliation: Department of Veterinary Medicine, Sassari University, Sassari, Italy; Sardinian Animal Biodiversity Center (Centro di Competenza per la Biodiversità Animale-CCBA), Sassari, Italy.

ABSTRACT
Our aim is to verify if oocyte developmental potential is related to the timing of meiotic progression and to mitochondrial distribution and activity using prepubertal and adult oocytes as models of low and high developmental capacity respectively. Prepubertal and adult oocytes were incorporated in an in vitro maturation system to determine meiotic and developmental competence and to assess at different time points kinetic of meiotic maturation, 2D protein electrophoresis patterns, ATP content and mitochondria distribution. Maturation and fertilization rates did not differ between prepubertal and adult oocytes (95.1% vs 96.7% and 66.73% vs 70.62% respectively for prepubertal and adult oocytes). Compared to adults, prepubertal oocytes showed higher parthenogenesis (17.38% vs 2.08% respectively in prepubertals and adults; P<0.01) and polispermy (14.30% vs 2.21% respectively in prepubertals and adults; P<0.01), lower cleavage rates (60.00% vs 67.08% respectively in prepubertals and adults; P<0.05) and blastocyst output (11.94% vs 34.% respectively in prepubertals and adults; P<0.01). Prepubertal oocytes reached MI stage 1 hr later than adults and this delay grows as the first meiotic division proceeds. Simultaneously, the protein pattern was altered since in prepubertal oocytes it fluctuates, dropping and rising to levels similar to adults only at 24 hrs. In prepubertal oocytes ATP rise is delayed and did not reach levels comparable to adult ones. CLSM observations revealed that at MII, in the majority of prepubertal oocytes, the active mitochondria are homogenously distributed, while in adults they are aggregated in big clusters. Our work demonstrates that mitochondria and their functional aggregation during maturation play an active role to provide energy in terms of ATP. The oocyte ATP content determines the timing of the meiotic cycle and the acquisition of developmental competence. Taken together our data suggest that oocytes with low developmental competence have a slowed down energetic metabolism which delays later development.

No MeSH data available.


Related in: MedlinePlus