IVM media, oocyte diameter and donor genotype at RYR1 locus in relation to the incidence of porcine diploid oocytes after maturation in vitro.
In the present study three factors were investigated that may affect the process of the first polar body extrusion in pig oocytes matured in vitro: IVM medium, oocyte diameter and donor genotype at the ryanodine receptor (RYR1) locus. In the first experiment, COCs were collected by the aspiration of slaughterhouse ovaries. Oocytes were matured in vitro at 39 degrees C, in humidified 5% CO(2) atmosphere for 44 h using the following media: (1) TCM199+hCG+eCG+follicular fluid (FF), (2) TCM199+hCG+17beta-estradiol and (3) NCSU23+hCG+eCG+FF. According to cytogenetic analysis, 98.1% of cells reached the second metaphase stage (MII). No significant differences were observed among IVM groups in terms of diploidy level. In the second experiment, oocytes collected by the aspiration or slicing of individual ovaries were matured in vitro in groups reflecting their origin. One ovary was considered a donor. IVM was carried out under conditions described in experiment I, with the use of TCM199+hCG+17beta-estradiol. A total of 68 ovaries/donors were included in this study. Granulosa cells collected from each ovary were used as DNA source in molecular (RFLP) analysis. Genotype frequencies at the RYR1 locus were as follows: CC, 0.46; CT, 0.48 and TT, 0.06. After maturation the diameter of each denuded oocyte was determined with the use of a computer aided system. Five size categories were distinguished: <90, 90-100, 100.1-110, 110.1-120 and >120 microm. The average diameter of haploid oocytes at MII stage was 111.7 microm, whereas that of diploid cells was 110.4 microm. According to statistical analysis, diploidy was not related to the oocyte diameter. That trait, however, was influenced by the donor genotype at the RYR1 locus. The TT genotype was associated with a higher rate of diploidy.
Lechniak
Dorota
D
Department of Genetics and Animal Breeding, August Cieszkowski Agricultural University of Poznan, Wolynska 33, 60-637 Poznan, Poland. lechniak@jay.au.poznan.pl
Szczepankiewicz
Dawid
D
Kauss
Dominika
D
Szulc
Joanna
J
Szydłowski
Maciej
M
D000818:Animals; D048429:Cell Size; D002478:Cells, Cultured; D003470:Culture Media; D020732:Cytogenetic Analysis; D004171:Diploidy; D005260:Female; D005838:Genotype; D008540:Meiosis; D018587:Oocyte Donation / Q000662:veterinary; D009865:Oocytes / Q000166:cytology*; D012150:Polymorphism, Restriction Fragment Length; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics*; D013552:Swine
D003470:Culture Media; D019837:Ryanodine Receptor Calcium Release Channel