ABSTRACT
Sperm dysfunction is the single most common defined cause of infertility. One in 15 men is sub-fertile and the condition is increasing in frequency. However, the diagnosis is poor and, excluding assisted conception, there is no treatment. The reason for this is our limited understanding of the biochemical, molecular and genetic functions of the spermatozoon. The underlying premise of our research programme is to establish a rudimentary understanding of the processes necessary for successful fertilisation. In this manuscript, we detail advances in our understanding of calcium signalling in the cell and outline genetic and proteomic technologies that are being used to improve the diagnosis of the condition.
Subject(s)
Calcium Signaling/physiology , Infertility, Male/diagnosis , Spermatozoa/physiology , Calcium/metabolism , Humans , Infertility, Male/pathology , Infertility, Male/therapy , Male , Proteomics , Sodium-Calcium Exchanger/metabolismABSTRACT
A functional zona pellucida is critical for both fertilization and the early stages of embryo development. Recent data from genomic and proteomic studies have questioned our simplistic view of the zona as being composed of three proteins whose functions are clearly defined. In the human, for example, the zona pellucida is composed of four proteins, not three. The increased complexity of the zona pellucida in humans and other species across the evolutionary tree now demands that we reconsider our reliance on the mouse model for understanding early fertilization events. Additionally, we are now well placed to examine, for the first time, potential defects in zona genes and their proteins associated with defined pathology.
Subject(s)
Egg Proteins/genetics , Membrane Glycoproteins/genetics , Receptors, Cell Surface/genetics , Zona Pellucida/physiology , Animals , Egg Proteins/classification , Egg Proteins/metabolism , Female , Fertilization , Gene Expression Regulation, Developmental , Genome, Human , Humans , Infertility, Female/genetics , Male , Membrane Glycoproteins/classification , Membrane Glycoproteins/metabolism , Mice , Receptors, Cell Surface/classification , Receptors, Cell Surface/metabolism , Species Specificity , Terminology as Topic , Zona Pellucida/chemistry , Zona Pellucida GlycoproteinsABSTRACT
BACKGROUND: The zona pellucida (ZP) is an extracellular glycoprotein matrix which surrounds all mammalian oocytes. Recent data have shown the presence of four human zona genes (ZP1, ZP2, ZP3 and ZPB). The aim of the study was to determine if all four ZP proteins are expressed and present in the human. METHODS: cDNA derived from human oocytes were used to amplify by PCR the four ZP genes. In addition, isolated native human ZP were heat-solubilized, trypsin-digested and subjected to tandem mass spectrometry (MS/MS). RESULTS: All four genes were expressed and the respective proteins present in the human ZP. Moreover, a bioinformatics approach showed that the mouse ZPB gene, although present, is likely to encode a non-functional protein. CONCLUSIONS: Four ZP genes are expressed in human oocytes (ZP1, ZP2, ZP3 and ZPB) and preliminary data show that the four corresponding ZP proteins are present in the human ZP. Therefore, this is a fundamental difference with the mouse model
Subject(s)
Egg Proteins/metabolism , Membrane Glycoproteins/metabolism , Oocytes/metabolism , Receptors, Cell Surface/metabolism , Zona Pellucida/metabolism , Amino Acid Sequence , Animals , Base Sequence , Computational Biology/methods , Egg Proteins/genetics , Female , Gene Expression , Humans , Membrane Glycoproteins/genetics , Mice/genetics , Mice/metabolism , Molecular Sequence Data , Proteomics , Receptors, Cell Surface/genetics , Zona Pellucida GlycoproteinsABSTRACT
The vertebrate egg envelope is composed of a family of related proteins, the zona pellucida (ZP) proteins, which are characterized by the presence of a conserved zona pellucida domain. Analysis of teleost fish ZP gene sequences has demonstrated that there are no direct orthologues of the mammalian ZPB and ZP1 genes, but that teleost fish contain multiple copies of two classes of genes (ZPXa and ZPXb) that are equally related to ZPB and ZP1. The two classes of genes are further distinguished by expression in liver or ovary, respectively, indicating there was probably an initial duplication event, followed by a switch to hepatic expression of one of the paralogues. This switch was followed in some species by additional amplification of one of the paralogues with the subsequent loss of the other. It is proposed that the expansion of the number of ZPXa and ZPXb genes and the acquisition of dual sites of synthesis are the result of an ancient polyploidization event, followed by additional species-specific gene amplifications.
