Maternal effect genes produce mRNA or proteins that accumulate in the egg during oogenesis. We show here that Mater, a mouse oocyte protein dependent on the maternal genome, is essential for embryonic development beyond the two-cell stage. Females lacking the maternal effect gene Mater are sterile. Null males are fertile.

SUMMARY We have identified a subcortical maternal complex (SCMC) that assembles during oocyte growth and is essential for zygotes to progress beyond the first embryonic cell divisions. At least four maternally encoded proteins contribute to this MDa complex: FLOPED, MATER and TLE6 interact with each other while Filia binds independently to MATER. Although the transcripts encoding these proteins are degraded during meiotic maturation and ovulation, the SCMC proteins persist in the early embryo. The SCMC, located in the subcortex of eggs, is excluded from regions of cell-cell contact in the cleavage-stage embryo and segregates to the outer cells of the morulae and blastocyst. Flopedtm/tm and/or Matertm/tm eggs lack the SCMC, but can be fertilized. However, these embryos do not progress beyond cleavage stage development and female mice are sterile. The proteins are conserved in humans and similar maternal effect mutations may result in recurrent embryonic loss.

The hiatus between oocyte and embryonic gene transcription dictates a role for stored maternal factors in early mammalian development. Encoded by maternal-effect genes, these factors accumulate during oogenesis and enable the activation of the embryonic genome, the subsequent cleavage stages of embryogenesis and the initial establishment of embryonic cell lineages. Recent studies in mice have yielded new findings on the role of maternally provided proteins and multi-component complexes in preimplantation development. Nevertheless, significant gaps remain in our mechanistic understanding of the networks that regulate early mammalian embryogenesis, which provide an impetus and opportunities for future investigations.

Objectives Severity of illness measures have long been used in pediatric critical care. The Pediatric Risk of Mortality is a physiologically based score used to quantify physiologic status, and when combined with other independent variables, it can compute expected mortality risk and expected morbidity risk. Although the physiologic ranges for the Pediatric Risk of Mortality variables have not changed, recent Pediatric Risk of Mortality data collection improvements have been made to adapt to new practice patterns, minimize bias, and reduce potential sources of error. These include changing the outcome to hospital survival/death for the first PICU admission only, shortening the data collection period and altering the Pediatric Risk of Mortality data collection period for patients admitted for “optimizing” care before cardiac surgery or interventional catheterization. This analysis incorporates those changes, assesses the potential for Pediatric Risk of Mortality physiologic variable subcategories to improve score performance, and recalibrates the Pediatric Risk of Mortality score, placing the algorithms (Pediatric Risk of Mortality IV) in the public domain. Design Prospective cohort study from December 4, 2011, to April 7, 2013. Measurements and Main Results Among 10,078 admissions, the unadjusted mortality rate was 2.7% (site range, 1.3–5.0%). Data were divided into derivation (75%) and validation (25%) sets. The new Pediatric Risk of Mortality prediction algorithm (Pediatric Risk of Mortality IV) includes the same Pediatric Risk of Mortality physiologic variable ranges with the subcategories of neurologic and nonneurologic Pediatric Risk of Mortality scores, age, admission source, cardiopulmonary arrest within 24 hours before admission, cancer, and low-risk systems of primary dysfunction. The area under the receiver operating characteristic curve for the development and validation sets was 0.88 ± 0.013 and 0.90 ± 0.018, respectively. The Hosmer-Lemeshow goodness of fit statistics indicated adequate model fit for both the development (p = 0.39) and validation (p = 0.50) sets. Conclusions The new Pediatric Risk of Mortality data collection methods include significant improvements that minimize the potential for bias and errors, and the new Pediatric Risk of Mortality IV algorithm for survival and death has excellent prediction performance.

After fertilization, the metalloendoprotease ovastacin is released by cortical granule exocytosis and cleaves the zona pellucida glycoprotein ZP2, an essential step to block sperm binding to an already fertilized egg.

No abstract

The zona pellucida is an extracellular matrix consisting of three glycoproteins that surrounds mammalian eggs and mediates fertilization. The primary structures of mouse ZP1, ZP2, and ZP3 have been deduced from cDNA. Each has a predicted signal peptide and a transmembrane domain from which an ectodomain must be released. All three zona proteins undergo extensive coand post-translational modifications important for secretion and assembly of the zona matrix. In this report, native zonae pellucidae were isolated and structural features of individual zona proteins within the mixture were determined by high resolution electrospray mass spectrometry. Complete coverage of the primary structure of native ZP3, 96% of ZP2, and 56% of ZP1, the least abundant zona protein, was obtained. Partial disulfide bond assignments were made for each zona protein, and the size of the processed, native protein was determined. The N termini of ZP1 and ZP3, but not ZP2, were blocked by cyclization of glutamine to pyroglutamate. The C termini of ZP1, ZP2, and ZP3 lie upstream of a dibasic motif, which is part of, but distinct from, a proprotein convertase cleavage site. The zona proteins are highly glycosylated and 4/4 potential N-linkage sites on ZP1, 6/6 on ZP2, and 5/6 on ZP3 are occupied. Potential O-linked carbohydrate sites are more ubiquitous, but less utilized.The zona pellucida is an extracellular matrix surrounding mammalian eggs that functions in taxon-specific gamete binding, provides a post-fertilization block to polyspermy, and protects the developing pre-implantation embryo (1-3). The mouse zona pellucida (ZP) 1 is composed of three major glycoproteins (ZP1, ZP2, and ZP3) that are synthesized and secreted by oocytes during a 2-3 week growth period (4). The primary structures of ZP1 (623 amino acids), ZP2 (713 amino acids), and ZP3 (424 amino acids) have been deduced from cDNA (5-7). Each glycoprotein has a signal peptide directing it into a secretory pathway, a ϳ260 amino acid zona domain containing 8 conserved cysteine residues, and a transmembrane domain near the C terminus followed by a short cytoplasmic tail (8). The zona domain has been observed in multiple proteins (9) and has been implicated in the polymerization of extracellular matrices (10).During oocyte growth, ZP1, ZP2, and ZP3 traffick through the growing oocyte, and their ectodomains are released from a transmembrane domain at the surface of the cell (11, 12). A conserved hydrophobic patch upstream of the transmembrane domain is required for progression to the cell surface 2 and a consensus cleavage site (RX(K/R)R2) for the proprotein convertase furin is present upstream of the transmembrane domain. Although this site has been implicated in the release of the zona ectodomain (13-15), mutations (RNRR3 ANAA, or RNRR3 ANGE), do not prevent incorporation of reporter-ZP3 proteins into the zona pellucida in growing oocytes (12, 16) or transgenic mice (12) and secretion of recombinant human ZP3 with a similar mutation (RNRR3 ANAA) is not prevented (17).The three zo...

At fertilization, mouse sperm bind to the zona pellucida (which consists of glycoproteins ZP1, ZP2, and ZP3) that surrounds eggs. A ZP2 cleavage model of gamete recognition requires intact ZP2, and a glycan release model postulates that zona glycans are ligands for sperm. These two models were tested by replacing endogenous protein with ZP2 that cannot be cleaved (Zp2Mut) or with ZP3 lacking implicated O glycans (Zp3Mut). Sperm bound to two-cell Zp2Mut embryos despite fertilization and cortical granule exocytosis. Contrary to prediction, sperm fertilized Zp3Mut eggs. Sperm at the surface of the zona pellucida remained acrosome-intact for more than 2 hours and were displaced by additional sperm. These data indicate that sperm-egg recognition depends on the cleavage status of ZP2 and that binding at the surface of the zona is not sufficient to induce sperm acrosome exocytosis.