Studies of male and female meiosis in inv(4)(p1.4;q2.3) pig carriers.
Inversions are well-known structural chromosomal rearrangements in humans and pigs. Such rearrangements generally have no effect on the carrier's phenotype. However, the presence of an inversion may impair spermatogenesis and lead to the production of recombinant gametes, responsible for early miscarriages, stillbirth, or congenital abnormalities. This is the first report on meiotic segregation and pairing behavior of the inv(4)(p1.4;q2.3) pericentric inversion in pigs. Despite the very large size of the inverted fragment (76% of the chromosome), SpermFISH results showed that only 4.08% of the gametes produced by male heterozygotes were unbalanced. This low proportion could be explained by the particular behavior of normal and inverted SSC4 chromosomes during the initial stages of meiosis. Indeed, immunohistochemistry analyses revealed that heterosynapsis occurred in 92% of the cells, whereas synaptic adjustment was detected in a few spermatocytes only. Unexpectedly, the proportion of unbalanced gametes produced by female heterozygotes, estimated by FISH on metaphase II oocytes, was also very low (3.69%) and comparable to that in males. According to previous results for male and female meiotic processes, different proportions of recombinant gametes in the two genders would have been expected. Complementary studies should be carried out to further document the meiotic behavior of inversions in pigs.
Ecole Nationale Vétérinaire de Toulouse, UMR 444 INRA-ENVT Génétique Cellulaire, 23 chemin des Capelles, BP 87614, 31076 Toulouse Cedex 3, France.
Katia
K
Massip
Martine
M
Yerle
Yvon
Y
Billon
Stéphane
S
Ferchaud
Nathalie
N
Bonnet
Anne
A
Calgaro
Nicolas
N
Mary
Anne-Marie
AM
Dudez
Céline
C
Sentenac
Christophe
C
Plard
Alain
A
Ducos
Alain
A
Pinton
D000818:Animals; D007446:Chromosome Inversion / Q000235:genetics*; D023902:Chromosome Pairing / Q000235:genetics; D020090:Chromosome Segregation / Q000235:genetics; D005260:Female; D006579:Heterozygote; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008540:Meiosis / Q000235:genetics*; D009865:Oocytes; D013091:Spermatogenesis / Q000235:genetics; D013094:Spermatozoa; D013552:Swine