Aneuploidy rates in in vitro matured MII oocytes with corresponding first polar body in the Podolian and Maremmana cattle breeds by using dual color fluorescent in situ hybridization (FISH)

This study provides preliminary data for establishinga 'baseline-level' of aneuploidy in the female germcells of two Italian autochthonous cattle (Bos taurus)breeds, the Podolian and Maremmana, by FISHapplied on MII metaphase oocytes with thecorresponding first polar body (PB). Painting probesfor chromosomes Xcen and 5 were obtained bymicrodissection and DOP-PCR. COCs from 15Podolian and 11 Maremmana cows were matured invitro in TCM199 with 20% FCS, 0.5 ?g/ml FSH and5 ?g/ml LH. After denudation, the oocytes wereindividually fixed on slides with 1:1 Carnoy fixative.Totally, out of 396 COCs selected for IVM, 305reached the MII stage (77.0%); of these, 31 (10.2%)were unreduced. Out of 274 MII reduced oocytes, 200(73.0%) had visible PB, therefore were FISH analyzed.Aneuploid oocytes were 4 out of 200 (2.0%), 3were nullisomic and 1 disomic, all for chromosome 5.Premature separation of sister chromatids (PSSC) wasfound only in two oocytes (1%), one for each breed.At breed level, out of 100 oocytes examined in thePodolian, two were found to be nullisomic and onedisomic, all for chromosome 5; out of 100 oocytesexamined in the Maremmana, only one oocyte wasfound to be nullisomic for chromosome 5. Interestingly,chromosome X was never involved in aneuploidy.Totally, the two breeds showed differentaneuploidy rates: 3% (Podolian) vs 1% (Maremmana).These preliminary results, together withprevious results obtained on the Friesian and Brownbreeds, suggest that 'interbreed' differences can befound among the various domestic breeds. This aspectis worth to be further investigated.