Expression of laminin chain-specific gene transcripts in mouse uterine tissues during peri-implantation period

Suppression of Nek2A in mouse early embryos confirms its requirement for chromosome segregation

Nek2, a mammalian structural homologue of Aspergillus protein kinase NIMA, is predominantly known as a centrosomal kinase that controls centriole-centriole linkage during the cell cycle. However, its dynamic subcellular localization during mitosis suggested that Nek2 might be involved in diverse cell cycle events in addition to the centrosomal cycle. In order to determine the importance of Nek2 during mammalian development, we investigated the expression and function of Nek2 in mouse early embryos. Our results show that both Nek2A and Nek2B were expressed throughout early embryogenesis. Unlike cultured human cells, however, embryonic Nek2A appeared not to be destroyed upon entry into mitosis, suggesting that the Nek2A protein level is controlled in a unique manner during mouse early embryogenesis. Suppression of Nek2 expression by RNAi resulted in developmental defects at the second mitosis. Many of the blastomeres in Nek2-suppressed embryos showed abnormality in nuclear morphology, including dumbbell-like nuclei, nuclear bridges and micronuclei. These results indicate the importance of Nek2 for proper chromosome segregation in embryonic mitoses.

Global gene expression analysis to identify molecular markers of uterine receptivity and embryo implantation

Infertility and spontaneous pregnancy losses are an enduring problem to women's health. The establishment of pregnancy depends on successful implantation, where a complex series of interactions occurs between the heterogeneous cell types of the uterus and blastocyst. Although a number of genes are implicated in embryo-uterine interactions during implantation, genetic evidence suggests that only a small number of them are critical to this process. To obtain a global view and identify novel pathways of implantation, we used a dual screening strategy to analyze the expression of nearly 10,000 mouse genes by microarray analysis. Comparison of implantation and interimplantation sites by a conservative statistical approach revealed 36 up-regulated genes and 27 down-regulated genes at the implantation site. We also compared the uterine gene expression profile of progesterone-treated, delayed implanting mice to that of mice in which delayed implantation was terminated by estrogen. The results show up-regulation of 128 genes and down-regulation of 101 genes after termination of the delayed implantation. A combined analysis of these experiments showed specific up-regulation of 27 genes both at the implantation site and during uterine activation, representing a broad diversity of molecular functions. In contrast, the majority of genes that were decreased in the combined analysis were related to host immunity or the immune response, suggesting the importance of these genes in regulating the uterine environment for the implanting blastocyst. Collectively, we identified genes with recognized roles in implantation, genes with potential roles in this process, and genes whose functions have yet to be defined in this event. The identification of unique genetic markers for the onset of implantation signifies that genome-wide analysis coupled with functional assays is a promising approach to resolve the molecular pathways required for successful implantation.

Definitive evidence for the existence of morphological plasticity in the external zone of the median eminence during the rat estrous cycle: implication of neuro-glio-endothelial interactions in gonadotropin-releasing hormone release

Despite intense investigation, the demonstration of morphological plasticity in the external zone of the median eminence concerning the gonadotropin-releasing hormone system has never been reported. In this study, we investigate whether dynamic transformations of the gonadotropin-releasing hormone nerve terminals and/or tanycytes in the external zone of the median eminence of the hypothalamus occurred during the rat estrous cycle, by following individual gonadotropin-releasing hormone-immunoreactive nerve terminals on serial ultrathin sections observed by electron microscopy. Female rats were killed at 16.00 diestrus II (n = 3), i.e. when estrogen levels are basal and gonadotropin-releasing hormone release is low, and at 16.00 proestrus (n = 4), i.e. when estrogen levels peak and the preovulatory gonadotropin-releasing hormone surge occurs. Our results show that, in the median eminence obtained from proestrus rats, 12+/-2% of the gonadotropin-releasing hormone nerve terminals were observed to make physical contact with the parenchymatous basal lamina, i.e. the pericapillary space. In the median eminence obtained from diestrus II rats, no contacts were observed. On proestrus, numerous physical contacts between gonadotropin-releasing hormone nerve terminals and the basal lamina occurred by evagination of the basal lamina and/or by emerging processes from gonadotropin-releasing hormone nerve terminals. The quantification of the evagination of the basal lamina revealed that the basal lamina was at least twofold more tortuous in appearance during proestrus. These results demonstrate for the first time the existence of dynamic plastic changes in the external zone of the median eminence, allowing gonadotropin-releasing hormone nerve terminals to contact the pericapillary space on the day of proestrus, thus facilitating the release of the neurohormone into the pituitary portal blood.