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X-chromosome inactivation (XCI) is the epigenetic transcriptional silencing of an X-chromosome during the early stages of embryonic development in female eutherian mammals. XCI assures monoallelic expression in each cell and compensation for dosage-sensitive X-linked genes between females (XX) and males (XY). DNA methylation at the carbon-5 position of the cytosine pyrimidine ring in the context of a CpG dinucleotide sequence (5meCpG) in promoter regions is a key epigenetic marker for transcriptional gene silencing. Using computational analysis, we revealed an extragenic tandem GAAA repeat 230-bp from the landmark CpG island of the human X-linked retinitis pigmentosa 2 RP2 promoter whose 5meCpG status correlates with XCI. We used this RP2 onshore tandem GAAA repeat to develop an allele-specific 5meCpG-based PCR assay that is highly concordant with the human androgen receptor (AR) exonic tandem CAG repeat-based standard HUMARA assay in discriminating active (Xa) from inactive (Xi) X-chromosomes. The RP2 onshore tandem GAAA repeat contains neutral features that are lacking in the AR disease-linked tandem CAG repeat, is highly polymorphic (heterozygosity rates approximately 0.8) and shows minimal variation in the Xa/Xi ratio. The combined informativeness of RP2/AR is approximately 0.97, and this assay excels at determining the 5meCpG status of alleles at the Xp (RP2) and Xq (AR) chromosome arms in a single reaction. These findings are relevant and directly translatable to nonhuman primate models of XCI in which the AR CAG-repeat is monomorphic. We conducted the RP2 onshore tandem GAAA repeat assay in the naturally occurring chimeric New World monkey marmoset (Callitrichidae) and found it to be informative. The RP2 onshore tandem GAAA repeat will facilitate studies on the variable phenotypic expression of dominant and recessive X-linked diseases, epigenetic changes in twins, the physiology of aging hematopoiesis, the pathogenesis of age-related hematopoietic malignancies and the clonality of cancers in human and nonhuman primates.

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Numerous diseases are carried and can be transmitted from the African buffalo (Syncerus caffer) to livestock. Therefore, buffaloes may only be moved with a special transport permit. Disease-free buffaloes are in demand amongst private game farmers. Current disease-free animals derive from a small genetic pool and hence there is a special interest in bringing new genetic material into the disease-free populations. Different breeding programs were developed in the past, which allow producing disease-free offspring from an infected herd. In this study epididymal sperm from 16 mature African buffalo bulls were frozen with Triladyl™ and AndroMed ® (both Minitüb, Germany) with or without the addition of bovine seminal plasma. Post-thaw motility, longevity and acrosomal integrity were compared by means of paired two-tailed t-tests. For both cryodiluents the post-thaw motility was mostly higher when no seminal plasma was added: no differences could be seen for the acrosomal integrity. Triladyl™ was superior to AndroMed ® in regards to total post-thaw motility. This study indicates that the use of bovine seminal plasma in a concentration of 10% is detrimental rather than beneficial in regards to the post-thaw motility. Triladyl™ rather than AndroMed ® should be used to freeze buffalo epididymal sperm, since it is superior in terms of post-thaw motility, even though the former, containing egg yolk, is not a defined medium and therefore lacks quality standards and carries a hygiene risk. Cette étude montre que l'utilisation decplasma séminal bovin à la concentration de 10% est plus nuisible que bénéfique en ce qui concerne la motilité post-congélation. Triladyl TM devrait être préféré à Andromed ® pour congeler le sperme épididymal de bison, puisqu'il est meilleur en ce qui concerne la motilité post-congélation, même s'il contient du jaune d'oeuf et n'est pas un milieu défini ( pas de standards de qualité), ce qui sous-entend un risque hygienique. Zusammenfassung