Sex selection in mammals: A review

Stage-dependent expression of extra-embryonic tissue-spermatogenesis-homeobox gene 1 (ESX1) protein, a candidate marker for X chromosome-bearing sperm

Extra-embryonic tissue-spermatogenesis-homeobox gene 1 (Esx1) encodes an X-linked homeobox protein. Despite the fact that the temporal and spatial mRNA expression pattern of the protein has been studied extensively in the testis, specific localisation of ESX1 in the testis remains to be determined. In the present study, we generated ESX1 antiserum to investigate the stage- and tissue-specific expression of ESX1 in the mouse. Western blotting and immunofluorescent analyses revealed that general localisations of ESX1 were consistent with its RNA expression patterns; that is, it was restricted mainly to the placenta and testis. Immunofluorescent studies demonstrated that ESX1 existed in the testes after 3 weeks of age, coincident with the appearance of round spermatids in the seminiferous tubules. Moreover, ESX1 expression became more abundant in the luminal regions of the seminiferous tubules as the development of round spermatids progressed into spermatozoa. In contrast, reduced expression of ESX1 was observed in experimentally induced cryptorchid testes. The later expression of ESX1 suggests a role in post-meiotic germ cell development. To further understand ESX1 expression in sperm with respect to X chromosome-bearing sperm, we used ESX1 antiserum to immunostain sperm by confocal laser microscopy. Approximately half the sperm population was recognised by the ESX1 antiserum. On the basis of results of the present study, we suggest that ESX1 could be used as a protein marker for X chromosome-bearing sperm.

Use of the polymerase chain reaction to sex the bovine fetus using cells recovered by ultrasound-guided fetal fluid aspiration

The aim of this study was to carry out first trimester fetal sex diagnosis using the polymerase chain reaction (PCR) to amplify DNA from bovine fetal cells recovered by transvaginal ultrasound-guided uterine puncture and fetal fluid aspiration. For sex determination, a nested, allele-specific, PCR amplification of the bovine zfx and zfy gene fragments was utilised. The PCR assay was validated using fetal fluids recovered from uteri post mortem. Cells were harvested from the fetal fluids, genomic DNA extracted and the PCR assay applied. A technique which was developed for transvaginal ultrasound-guided follicle aspiration was modified to recover fetal fluid from live animals. Small volumes of fetal fluid (0.5-5 ml) were recovered between days 61-97 of gestation and the PCR assay applied. The gender determined by PCR of fetal fluid cells was in all cases confirmed by visual inspection (n = 15 abattoir specimens) or ultrasound scanning (n = 7 live animals). Fetal death, attributed to the introduction of intrauterine infection, occurred in 4/4 cows in the first series of aspirations but in only 1/3 heifers in the second series of aspirations.