The microenvironment of ovarian follicles in fertile dairy cows is associated with high oocyte quality

We hypothesised that heifers and cows with positive genetic merit for fertility would have a follicular microenvironment that resulted in better quality oocytes. To test this, we compared cumulus cell-oocyte complexes (COC) and follicular fluid from preovulatory follicles of 36 Holstein-Friesian nulliparous heifers and 50 primiparous lactating cows with either positive (POS, +5%) or negative (NEG, -5%) fertility breeding values (FertBV). Established gene markers of oocyte quality were measured in individual cumulus cell masses and oocytes, and concentrations of amino acids, steroids, and metabolites were quantified in corresponding follicular fluid and plasma. The timing of visually detectable oestrus in NEG FertBV heifers was inconsistent with their stage of COC maturation. Retrospective analyses of oestrous activity data indicated that NEG FertBV heifers were sampled earlier. Their recovered COC were morphologically less mature and exhibited differential expression of genes that are associated with follicular maturation (lower levels of BMPR2) and protein processing (higher levels of HSP90B1). Despite consistent sampling times being achieved in the lactating cows, lower concentrations of serine, proline, methionine, isoleucine, and non-esterified fatty acids were present in follicular fluid from POS FertBV cows. This was associated with higher expression of gene biomarkers of good oocyte quality (VCAN, PDE8A) in COC recovered from POS FertBV cows. This study supports our hypothesis that the follicular microenvironment in lactating dairy cows with high genetic merit leads to COC with higher metabolic rates and oocytes of superior quality. Moreover, an additional stressor such as lactation is required for this difference to be pronounced.

Prenatal diagnosis of trisomy 21, 18 and 13 by quantitative pyrosequencing of segmental duplications

Chromosomal aberration mostly occurs in chromosomes 21, 18 and 13, with an incidence approximately 1 out of 160 live births in humans, therefore making prenatal diagnosis necessary in clinics. Current methods have drawbacks such as time consuming, high cost, complicated operations and low sensitivity. In this paper, a novel method for rapid and accurate prenatal diagnosis of aneuploidy is proposed based on pyrosequencing, which quantitatively detects the peak height ratio (PHR) of different bases of segmental duplication. A direct polymerase chain reaction (PCR) approach was undertaken, where a small volume of amniotic fluid was used as the starting material without DNA extraction. Single-stranded DNA was prepared from PCR products and subsequently analyzed using pyrosequencing. The PHR between target and reference chromosome of 2.2 for euploid and 3:2 for a trisomy fetus were used as reference. The reference intervals and z scores were calculated for discrimination of aneuploidy. A total of 132 samples were collected, within trisomy 21 (n = 11), trisomy 18 (n = 3), trisomy 13 (n = 2), and unaffected controls (n = 116). A set of six segmental duplications were chosen for analysis. This method had consistent results with karyotyping analysis, a correct diagnosis with 100% sensitivity and 99.9% specificity.

Normal reproductive and macrophage function in Pem homeobox gene-deficient mice

Interaction between germ cells and the supporting somatic cells guides many of the differentiative processes of gametogenesis. The expression pattern of the Pem homeobox gene suggests that it may mediate specific inductive events in murine reproductive tissues. During gestation, Pem is expressed in migrating and early postmigratory primordial germ cells, as well as in all embryo-derived extraembryonic membranes. Pem expression ceases in the germline after Embryonic Day 14 in both sexes and then reappears postnatally in the supporting cells of the gonad. In mature mice, Pem is produced by testicular Sertoli cells during stages VI-VIII of spermatogenesis and transiently by ovarian granulosa cells lining periovulatory follicles. Despite this tightly regulated reproductive expression pattern, mice with a targeted mutation in Pem have normal fecundity, with no detectable alteration in extraembryonic testicular or ovarian development or function. We also show that Pem is expressed throughout embryonic and adult development in a subset of a tissue-specific class of macrophages, Kupffer cells, as well as in a localized fraction of cells in macrophage cell lines. Although the number of Pem-positive Kupffer cells increases in mice treated with lipopolysaccharide, loss of Pem does not detectably interfere with the cells' ability to induce iNOS expression, demonstrating this Kupffer cell function does not require Pem. No differences were observed between Pem-knockout mice in 129, C57BL6/J, or mixed genetic backgrounds. Together, these data show that Pem is dispensable for embryonic and postnatal development, gonadal function, and Kupffer cell activation, perhaps due to compensatory expression of a similar homeobox gene.

The Pem homeobox gene is X-linked and exclusively expressed in extraembryonic tissues during early murine development

We previously reported the isolation of a cDNA clone for a homeobox-containing gene designated Pem, shown by Northern analysis of Day 7 through Day 16 mouse embryos to be expressed in extraembryonic tissues. In this study, Pem gene expression was further examined using in situ hybridization and immunocytochemistry to determine the spatial distribution of Pem transcripts and protein in peri-implantation embryos and in embryoid bodies (EBs). Low amounts of Pem mRNA were detected in undifferentiated EBs. When EBs were induced to differentiate, the outer cell layer of visceral or parietal endoderm expressed both Pem mRNA and protein. In developing embryos, no Pem protein was detectable in the uncompacted morula; 12% of the nuclei in compacted morulae were Pem positive, while 25% of the blastocyst trophectoderm and 15% of inner cell mass cells expressed Pem protein. Shortly after implantation, in 5.5 and 6.5 d.p.c. embryos, Pem expression was limited to extraembryonic tissues and was present in distal and proximal visceral endoderm, parietal endoderm, and ectoplacental cone. By 7.5-8.5 d.p.c. neither Pem RNA nor protein was found in the distal squamous visceral endoderm, which surrounds the embryonic region of the egg cylinder, nor in the parietal endoderm. Expression was retained in the proximal columnar epithelium of the visceral endoderm. Prominent Pem expression was observed in the chorion, in trophoblast-derived cells of the ectoplacental cone, and in secondary giant cells, localized in the nuclear compartment. Pem was localized to the X chromosome and found to be expressed in cell lineages where only the maternal X chromosome is active. The data indicate a possible role for Pem in regulating genes involved in the differentiation of extraembryonic tissues.