A bovine protocol for training professionals in preimplantation genetic diagnosis using polymerase chain reaction

Molecular morphology and function of bull spermatozoa linked to histones and associated with fertility

Sub-par fertility in bulls is influenced by alterations in sperm chromatin, and it might not be solved with increased sperm concentration in artificial insemination. Appropriate histone retention during sperm chromatin condensation plays critical roles in male fertility. The objective of this study was to determine failures of sperm chromatin condensation associated with abnormal persistence or accessibility of histones by aniline blue (ANBL) test, expression levels, and cellular localizations of one variant and two core histones (H3.3, H2B, and H4 respectively) in the spermatozoa of low-fertility (LF) vs high-fertility (HF) bulls. The expression levels and cellular localizations of histones in spermatozoa were studied using immunoblotting, immunocytochemistry, and staining methods. The bioinformatics focused on the sequence identity and evolutionary distance of these proteins among three mammalian species: bovine, mouse, and human. We demonstrated that ANBL staining was different within the LF (1.73 (0.55, 0.19)) and HF (0.67 (0.17, 0.06)) groups (P<0.0001), which was also negatively correlated within vivobull fertility (r=−0.90,P<0.0001). Although these histones were consistently detectable and specifically localized in bull sperm cells, they were not different between the two groups. Except H2B variants, H3.3 and H4 showed 100% identity and were evolutionarily conserved in bulls, mice and humans. The H2B variants were more conserved between bulls and humans, than in mice. In conclusion, we showed that H2B, H3.3, and H4 were detectable in bull spermatozoa and that sperm chromatin condensation status, changed by histone retention, is related to bull fertility.

Post-biopsy bovine embryo viability and whole genome amplification in preimplantation genetic diagnosis

OBJECTIVE

To evaluate the effect of the biopsy of 8-cell to 16-cell bovine embryos on their subsequent development and the effect of whole genome amplification (WGA) on removed blastomeres.

DESIGN

Randomized study.

SETTING

Molecular genetics and animal reproduction laboratories.

PATIENT(S)

Cow ovaries obtained from slaughterhouses.

INTERVENTION(S)

The ovaries were punctured, and the oocytes were matured and fertilized in vitro. On the fourth day after fertilization, 8-cell to 16-cell bovine embryos were biopsied, one quarter of each embryo being removed. The blastomeres were submitted to WGA followed by polymerase chain reaction (PCR). The embryos were returned to culture for evaluation of their development.

MAIN OUTCOME MEASURE(S)

Subsequent rate of blastocyst development, embryo cell number, WGA efficiency, and sex determination.

RESULT(S)

A total of 92 embryos were submitted to biopsy. The blastocyst production was 53.3%, with 44.9% of hatching rate. These results were similar to those of the control group (66.0% and 42.6%) of 103 embryos. Overall, no impact was detected on embryo quality in blastocyst cell number between the two groups. Removed blastomeres were submitted to WGA, resulting in 98.2% of efficiency. However, only 59% of the samples were sexed by PCR.

CONCLUSION(S)

Biopsy of 8-cell to 16-cell bovine embryos did not affect their subsequent development. WGA was successful in removed blastomeres.

Use of a Combined Duplex PCR/Dot Blot Assay for more sensitive genetic characterization

A reliable and sensitive method of genetic analysis is necessary to detect multiple specific nucleic acid sequences from samples containing limited template. The most widely utilized method of specific gene detection, polymerase chain reaction (PCR), imparts inconsistent results when assessing samples with restricted template, especially in a multiplex reaction when copies of target genes are unequal. This study aimed to compare two methods of PCR product analysis, fluorescent detection following agarose gel electrophoresis or dot blot hybridization with chemiluminescent evaluation, in the detection of a single copy gene (SRY) and a multicopy gene (β-actin). Bovine embryo sex determination was employed to exploit the limited DNA template available and the target genes of unequal copies. Primers were used either independently or together in a duplex reaction with purified bovine genomic DNA or DNA isolated from embryos. When used independently, SRY and β-actin products were detected on a gel at the equivalent of 4-cell or 1-cell of DNA, respectively; however, the duplex reaction produced visible SRY bands at the 256 cell DNA equivalent and β-actin products at the 64 cell DNA equivalent. Upon blotting and hybridization of the duplex PCR reaction, product was visible at the 1–4 cell DNA equivalent. Duplex PCR was also conducted on 186 bovine embryos and product was subjected to gel electrophoresis or dot-blot hybridization in duplicate. Using PCR alone, sex determination was not possible for 22.6% of the samples. Using PCR combined with dot blot hybridization, 100.0% of the samples exhibited either both the male specific and β-actin products or the β-actin signal alone, indicating that the reaction worked in all samples. This study demonstrated that PCR amplification followed by dot blot hybridization provided more conclusive results in the evaluation of samples with low DNA concentrations and target genes of unequal copies.

Use of pig oocytes for training new professionals in human assisted reproduction laboratories

OBJECTIVE

To evaluate whether swine oocytes are useful for training new technicians in a human reproduction laboratory.

DESIGN

Prospective study.

SETTING

Graduate school in assisted reproductive techniques (ART) in Brazil.

PATIENT(S)

Students in a human reproduction laboratory.

INTERVENTION(S)

Medium-sized follicles were aspirated from prepubertal gilts' ovaries and collected at a slaughterhouse. Oocytes were retrieved from the follicular fluid. Twenty-one students trained during four periods of 20 hours each were evaluated as to their ability to perform micromanipulation and were compared with a group of well-trained professionals (control group).

MAIN OUTCOME MEASURE(S)

Students' ability in oocyte retrieval, oocyte manipulation, and intracytoplasmic sperm injection during and after the 80 hours of training.

RESULT(S)

Students were able to retrieve, on average, 23.8 oocytes per ovary. Their micromanipulation skills substantially increased, reaching an oocyte retrieval rate of 77.2%, compared with 84.9% in the control group after the training period. Although the oocyte damage rate gradually decreased, from 52.0% after 20 hours of training to 5.4% after 80 hours, these figures were still above the control group oocyte damage rate by 0.3%, which was a statistically significant level. Regarding intracytoplasmic sperm injection, within 40 hours, no students were able to perform a single injection; and by the end of 80 hours, they achieved an average of 4.0 oocytes per hour, whereas the control group injected 20.6 oocytes per hour, a statistically significant difference.

CONCLUSION(S)

Swine ovaries may be a useful tool in the spectrum of training techniques for unskilled assisted reproductive techniques laboratory professionals.