Meiotic Chromosome Asynapsis in a Boar with a Reciprocal Translocation and Acquired Testicular Degeneration

Abstract

During a period of performance testing, a boar used for artificial insemination purposes was found responsible for reduced litter size and slightly increased incidence of repeat breeding. The qualitative and quantitative semen characteristics, however, were within normal limits. Later, evaluation of the semen during a period of 3 months revealed a decreased sperm concentration, but sperm cell morphology and mobility were normal. At castration, the boar, which had suffered from scrotal inflammation, was found to have hypoplastic gonads, the right testis being smaller than the left one. Histologically there was spermatogenic arrest at the primary spermatocyte level in almost all tubules of the right testis. In the left testis, histology was more heterogeneous, with some tubules containing all developmental stages, while others had an almost complete spermatogenic arrest. Cytogenetically the boar was carrying a translocation, rcp(2;14)(p14;q23). Synaptonemal complex analysis revealed complete quadrivalent pairing in 21 out of 43 cells analysed. The remaining cells demonstrated quadrivalents with axes moderately or extensively unpaired. There was a distinct difference between cells from the right vs. the left testis. The latter cells showed more completely paired translocation configurations. Moreover, in 14 and 7 cells analysed from the right and left testis, respectively, the translocation configuration could not be identified. This was due to chromosome asynapsis and frequent occurrence of gaps in the chromosomes, including others than those of the translocation, plus an abundant cellular deposit which formed a dense cell background. Association or pairing of the quadrivalent with the sex bivalent was seen in one cell only. At diakinesis‐MI, most cells had a ring‐shaped quadrivalent. It is believed that the asynapsis of chromosomes during the prophase of meiosis was to a large extent due to the degeneration caused by the inflammation processes. Copyright © 1993, Wiley Blackwell. All rights reserved