Ana Cervero

The role of the leptin in reproduction.

Purpose of review Since its discovery in 1994, leptin has appeared to be a pleiotrophic hormone, governing energy homeostasis and affecting many tissues in the body. Numerous pieces of evidence have accumulated showing that leptin potentially plays an important role in the control of the reproductive function. Recent findings This review presents the major concepts for the role of leptin in the modulation of reproductive function. As a marker of the nutritional status, leptin affects the hypothalamo–pituitary–gonadal axis, regulating gonadotrophin-releasing hormone and luteinising hormone secretion, and appears to be a permissive factor in the onset of the puberty. This protein and its receptor have been found in the reproductive tissues, indicating that this system could be also implicated in several processes such as embryo development, implantation and pregnancy. Moreover, disorders of the leptin system have been related to some reproductive pathologies such as pre-eclampsia and polycystic ovary syndrome. However, controversy surrounds several aspects of the action of leptin in reproduction that require a deeper investigation of this system. Summary Results to date suggest that this system could be implicated in important reproductive processes such as embryonic development and implantation. Moreover, understanding the role of leptin might be useful for new treatments in reproductive pathologies.

Determinants of Endometrial Receptivity

Abstract: Understanding the molecular changes that occur during the window of implantation is fundamental to our knowledge of human reproduction. Lately, the development of microarray technology has allowed this process to be studied from a global molecular perspective. In the last 2 years, researchers have focused their efforts on throwing light on the gene expression profile of the receptive endometrium. The genes hold the key to the development of the endometrium at any stage, and we have focused our work on the window of implantation. The four most recently published works in this field have revealed a long list of genes that are up‐ or downregulated at the time of implantation. Although these studies have been conducted using varying approaches, collectively these studies identify new candidate markers that can be used to accurately diagnose the receptive state of the endometrium. The next step is to perform functional analysis for confirming the importance of these genes. In this article, we gather together these recent findings to provide an overview of the current knowledge regarding the genetic functioning of human endometrial receptivity and related processes.

The impact of next-generation sequencing technology on preimplantation genetic diagnosis and screening

Largely because of efforts required to complete the Human Genome Project, DNA sequencing has undergone a steady transformation with still-ongoing developments of high-throughput sequencing machines for which the cost per reaction is falling drastically. Similarly, the fast-changing landscape of reproductive technologies has been improved by genetic approaches. Preimplantation genetic diagnosis and screening were established more than two decades ago for selecting genetically normal embryos to avoid inherited diseases and to give the highest potential to achieve stable pregnancies. Most recent additions to the IVF practices (blastocyst/trophectoderm biopsy, embryo vitrification) and adoption of new genetics tools such as array comparative genome hybridization have allowed setting up more precise and efficient programs for clinical embryo diagnosis. Nevertheless, there is always room for improvements. Remarkably, a recent explosion in the release of advanced sequencing benchtop platforms, together with a certain maturity of bioinformatics tools, has set the target goal of sequencing individual cells for embryo diagnosis to be a realistically feasible scenario for the near future. Next-generation sequencing technology should provide the opportunity to simultaneously analyze single-gene disorders and perform an extensive comprehensive chromosome screening/diagnosis by concurrently sequencing, counting, and accurately assembling millions of DNA reads.

Human Endometrial CD98 Is Essential for Blastocyst Adhesion

Background Understanding the molecular basis of embryonic implantation is of great clinical and biological relevance. Little is currently known about the adhesion receptors that determine endometrial receptivity for embryonic implantation in humans. Methods and Principal Findings Using two human endometrial cell lines characterized by low and high receptivity, we identified the membrane receptor CD98 as a novel molecule selectively and significantly associated with the receptive phenotype. In human endometrial samples, CD98 was the only molecule studied whose expression was restricted to the implantation window in human endometrial tissue. CD98 expression was restricted to the apical surface and included in tetraspanin-enriched microdomains of primary endometrial epithelial cells, as demonstrated by the biochemical association between CD98 and tetraspanin CD9. CD98 expression was induced in vitro by treatment of primary endometrial epithelial cells with human chorionic gonadotropin, 17-β-estradiol, LIF or EGF. Endometrial overexpression of CD98 or tetraspanin CD9 greatly enhanced mouse blastocyst adhesion, while their siRNA-mediated depletion reduced the blastocyst adhesion rate. Conclusions These results indicate that CD98, a component of tetraspanin-enriched microdomains, appears to be an important determinant of human endometrial receptivity during the implantation window.

Proprotein Convertase 5/6 Is Critical for Embryo Implantation in Women: Regulating Receptivity by Cleaving EBP50, Modulating Ezrin Binding, and Membrane-Cytoskeletal Interactions

Establishment of endometrial receptivity is vital for successful embryo implantation; its failure causes infertility. Epithelial receptivity acquisition involves dramatic structural changes in the plasma membrane and cytoskeleton. Proprotein convertase 5/6 (PC6), a serine protease of the proprotein convertase (PC) family, is up-regulated in the human endometrium specifically at the time of epithelial receptivity and stromal cell decidualization. PC6 is the only PC member tightly regulated in this manner. The current study addressed the importance and mechanisms of PC6 action in regulating receptivity in women. PC6 was dysregulated in the endometrial epithelium during the window of implantation in infertile women of three demographically different cohorts. Its critical role in receptivity was evidenced by a significant reduction in mouse blastocyst attachment of endometrial epithelial cells after PC6 knockdown by small interfering RNA. Using a proteomic approach, we discovered that PC6 cleaved the key scaffolding protein, ezrin-radixin-moesin binding phosphoprotein 50 (EBP50), thereby profoundly affecting its interaction with binding protein ezrin (a key protein bridging actin filaments and plasma membrane), EBP50/ezrin cellular localization, and cytoskeleton-membrane connections. We further validated this novel PC6 regulation of receptivity in human endometrium in vivo in fertile vs. infertile patients. These results strongly indicate that PC6 plays a key role in regulating fundamental cellular remodeling processes, such as plasma membrane transformation and membrane-cytoskeletal interface reorganization. PC6 cleavage of a crucial scaffolding protein EBP50, thereby profoundly regulating membrane-cytoskeletal reorganization, greatly extends the current knowledge of PC biology and provides substantial new mechanistic insight into the fields of reproduction, basic cellular biology, and PC biochemistry.