Unique trophoblast chromatin environment mediated by the PcG protein SFMBT2.

Stem/progenitor cells are maintained by a chromatin environment, mediated in part by Polycomb group (PcG) proteins, which depress differentiation. The trophoblast-specific PcG protein SFMBT2 is known to be required for maintenance of trophoblast progenitors. Rather than binding to trophoblast-specific genes repressed in TSC, SFMBT2 is concentrated at chromocentres and regions rich in repetitive elements, specifically LINE sequences and major satellites, suggesting that it is involved in higher-order organization of the trophoblast genome.

What does genetics tell us about imprinting and the placenta connection?

Genomic imprinting is an epigenetic gene silencing phenomenon that is specific to eutherians in the vertebrate lineage. The acquisition of both placentation and genomic imprinting has spurred interest in the possible evolutionary link for many years. In this review we examine the genetic evidence and find that while many imprinted domains are anchored by genes required for proper placenta development in a parent of origin fashion, an equal number of imprinted genes have no apparent function that depends on imprinting.

Positive regulation of TRAF6-dependent innate immune responses by protein phosphatase PP1-γ.

Innate immune sensors such as Toll-like receptors (TLRs) differentially utilize adaptor proteins and additional molecular mediators to ensure robust and precise immune responses to pathogen challenge. Through a gain-of-function genetic screen, we identified the gamma catalytic subunit of protein phosphatase 1 (PP1-γ) as a positive regulator of MyD88-dependent proinflammatory innate immune activation. PP1-γ physically interacts with the E3 ubiquitin ligase TRAF6, and enhances the activity of TRAF6 towards itself and substrates such as IKKγ, whereas enzymatically inactive PP1-γ represses these events.

IFPA Meeting 2013 Workshop Report III: maternal placental immunological interactions, novel determinants of trophoblast cell fate, dual ex vivo perfusion of the human placenta.

Workshops are an important part of the IFPA annual meeting as they allow for discussion of specialised topics. At IFPA meeting 2013 there were twelve themed workshops, three of which are summarized in this report. These workshops related to various aspects of placental biology but collectively covered areas of placental function, cell turnover and immunology: 1) immunology; 2) novel determinants of placental cell fate; 3) dual perfusion of human placental tissue.

The imprinted polycomb group gene Sfmbt2 is required for trophoblast maintenance and placenta development.

Imprinted genes play important roles in placenta development and function. Parthenogenetic embryos, deficient in paternally expressed imprinted genes, lack extra-embryonic tissues of the trophoblast lineage. Parthenogenetic trophoblast stem cells (TSCs) are extremely difficult to derive, suggesting that an imprinted gene(s) is necessary for TSC establishment or maintenance.

PPP1CC2 can form a kinase/phosphatase complex with the testis-specific proteins TSSK1 and TSKS in the mouse testis.

The mouse protein phosphatase gene Ppp1cc is essential for male fertility, with mutants displaying a failure in spermatogenesis including a widespread loss of post-meiotic germ cells and abnormalities in the mitochondrial sheath. This phenotype is hypothesized to be responsible for the loss of the testis-specific isoform PPP1CC2. To identify PPP1CC2-interacting proteins with a function in spermatogenesis, we carried out GST pull-down assays in mouse testis lysates.

The application of proteomic approaches to the study of mammalian spermatogenesis and sperm function.

Spermatogenesis is the process by which terminally differentiated sperm are produced from male germline stem cells. This complex developmental process requires the coordination of both somatic and germ cells through phases of proliferation, meiosis, and morphological differentiation, to produce the cell responsible for the delivery of the paternal genome. With infertility affecting ~ 15% of all couples, furthering our understanding of spermatogenesis and sperm function is vital for improving the diagnosis and treatment of male factor infertility.

Tandem affinity purification in transgenic mouse embryonic stem cells identifies DDOST as a novel PPP1CC2 interacting protein.

Members of the PP1 family of protein phosphatases achieve functional diversity through numerous and varied protein-protein interactions. In mammals, there are four PP1 isoforms, the ubiquitously expressed PPP1CA, PPP1CB, and PPP1CC1, and the testis specific splice isoform PPP1CC2. When the mouse Ppp1cc gene is deleted, the only phenotypic consequence is a failure of spermatogenesis in homozygous males.

New candidate targets of protein phosphatase-1c-gamma-2 in mouse testis revealed by a differential phosphoproteome analysis.

Reversible phosphorylation has been implicated in many developmental processes. Dephosphorylation is mediated by several families of phosphatases, including type 1 serine/threonine phosphatases (protein phosphatase-1 or PP1). The loss of the murine Ppp1cc gene causes male infertility as a result of impaired spermatogenesis.

Metakaryotic stem cell lineages in organogenesis of humans and other metazoans.

A non-eukaryotic, metakaryotic cell with large, open mouthed, bell shaped nuclei represents an important stem cell lineage in fetal/juvenile organogenesis in humans and rodents. each human bell shaped nucleus contains the diploid human DNA genome as tested by quantitative Feulgen DNA cytometry and fluorescent in situ hybridization with human pan-telomeric, pan-centromeric and chromosome specific probes. From weeks approximately 5-12 of human gestation the bell shaped nuclei are found in organ anlagen enclosed in sarcomeric tubular syncytia.

Loss of protein phosphatase 1c{gamma} (PPP1CC) leads to impaired spermatogenesis associated with defects in chromatin condensation and acrosome development: an ultrastructural analysis.

Human male infertility affects approximately 5% of men, with one-third suffering from testicular failure, likely the result of an underlying genetic abnormality that disrupts spermatogenesis during development. Mouse models of male infertility such as the Ppp1cc knockout mouse display very similar phenotypes to humans with testicular failure. Male Ppp1cc mutant mice are sterile due to disruptions in spermatogenesis that begin during prepubertal testicular development, and continue into adulthood, often resulting in loss of germ cells to the point of Sertoli cell-only syndrome.

Developmental consequences of alternative Bcl-x splicing during preimplantation embryo development.

Elevated cell death in human preimplantation embryos is one of the cellular events compromising pregnancy rates after assisted reproductive technology treatments. We therefore explored the molecular pathways regulating cell death at the blastocyst stage in human embryos cultured in vitro. Owing to limited availability of human embryos, these pathways were further characterized in mouse blastocysts.

Imprinting and extraembryonic tissues-mom takes control.

Genomic imprinting is an epigenetic mechanism that silences one parental allele of a small subset of genes. Many imprinted genes exhibit this property only in extraembryonic tissues-placenta and yolk sac. This has led to the idea that imprinting in mammals coevolved with some aspect of placentation.

Identification of potentially damaging amino acid substitutions leading to human male infertility.

There are a number of known genetic alterations found in men with nonobstructive azoospermia, or testicular failure, such as Y microdeletions and cytogenetic abnormalities. However, the etiology of nonobstructive azoospermia is unknown in the majority of men. The aim of this study was to investigate the possibility that unexplained cases of nonobstructive azoospermia are caused by nonsynonymous single-nucleotide polymorphisms (SNPs) in the coding regions of autosomal genes associated with sperm production and fertility.

The PcG gene Sfmbt2 is paternally expressed in extraembryonic tissues.

Genomic imprinting has dramatic effects on placental development, as has been clearly observed in interspecific hybrid, somatic cell nuclear transfer, and uniparental embryos. In fact, the earliest defects in uniparental embryos are evident first in the extraembryonic trophoblast. We performed a microarray comparison of gynogenetic and androgenetic mouse blastocysts, which are predisposed to placental pathologies, to identify imprinted genes.

A testis specific isoform of endophilin B1, endophilin B1t, interacts specifically with protein phosphatase-1c gamma2 in mouse testis and is abnormally expressed in PP1c gamma null mice.

Male mice homozygous for a null mutation in the protein phosphatase-1c gamma (PP1c gamma) gene are infertile, displaying a severe impairment in spermatogenesis that is not compensated by the presence of PP1c alpha and PP1c beta in mutant testes. A lack of the PP1c gamma2 splice variant seems the most likely cause of the mutant phenotype, as it is the most heavily expressed PP1c gamma isoform in wild type testes. Yeast two-hybrid screening using PP1c gamma2 has identified several new binding partners, including endophilin B1t, a testis enriched isoform of endophilin B1a which differs from the somatic form by virtue of a carboxy terminal deletion spanning the last 10 amino acids.

Identification of the spermatogenic zip protein Spz1 as a putative protein phosphatase-1 (PP1) regulatory protein that specifically binds the PP1cgamma2 splice variant in mouse testis.

The spermatogenic zip protein (Spz1) was originally isolated from a mouse testis library and identified as a novel member of the basic helix-loop-helix family of transcription factors. Here we identify Spz1 as a specific binding partner of the gamma2 catalytic subunit of protein phosphatase-1. Male mice homozygous for a null mutation in the protein phosphatase-1cgamma (PP1cgamma) gene are infertile and display a distinct impairment in spermiogenesis despite the continued presence of closely related PP1c isoforms.

Epigenetics and the renaissance of heresy.

Classic neo-Darwinian theory is predicated on the notion that all heritable phenotypic change is mediated by alterations of the DNA sequence in genomes. However, evidence is accumulating that stably heritable phenotypes can also have an epigenetic basis, lending support to the long-discarded notion of inheritance of acquired traits. As many of the examples of epigenetic inheritance are mediated by position effects, the possibility exists that chromosome rearrangements may be one of the driving forces behind evolutionary change by exerting position effect alterations in gene activity, an idea articulated by Richard Goldschmidt.

Protein phosphatase 1cgamma is required in germ cells in murine testis.

The protein phosphatase 1cgamma (PP1cgamma) gene is required for spermatogenesis. Males homozygous for a null mutation are sterile, and display both germ cell and Sertoli cell defects. As these two cell types are physically and functionally intimately connected in the testis, the question arises as to whether the primary site of PP1cgamma action is in Sertoli cells, germ cells, or both.

Expression of apoptosis-related genes during human preimplantation embryo development: potential roles for the Harakiri gene product and Caspase-3 in blastomere fragmentation.

In order to resolve the mechanisms and reasons of cellular fragmentation it is crucial to understand what genes may be responsible for regulation of this process. We report herein that human oocytes and preimplantation embryos possess abundant levels of transcripts encoding cell death suppressors, Mcl-1, Bcl-x and Bag-1, and the cell death inducer genes, Bax and Caspase-2. Lower but detectable levels of mRNA expression for the Bfl-1/a1, Bcl-w, Harakiri (Hrk) and Caspase-3 genes were also detected during all developmental stages.

Development to blastocyst is impaired when intracytoplasmic sperm injection is performed with abnormal sperm from infertile mice harboring a mutation in the protein phosphatase 1cgamma gene.

Idiopathic azoospermia, characterized by abnormal spermatogenesis, is commonly treated by performing intracytoplasmic sperm injection (ICSI) with sperm retrieved from testicular biopsies. However, no controlled experiments have been performed using an animal model to assess the efficacy or safety of the procedure. We have performed ICSI with testicular sperm obtained in a similar manner from testes of male mice homozygous for a null mutation in the protein phosphatase 1cgamma gene (PP1cgamma) or those of their wild-type littermates.

Increased recombination frequency showing evidence of loss of interference is associated with abnormal testicular histopathology.

Nondisjunction leading to aneuploid gametes has been linked genetically to both increases and decreases in recombination frequency on the aneuploid chromosome. In the present study, we present physical evidence of increased frequency of recombination nodules as measured by Mut-S-like homologue-1 (MLH1) foci on pachytene chromosomes from sterile male mice homozygous for a mutation in the protein phosphatase 1cgamma (PP1cgamma) gene. The pattern of elevated recombination frequency in PP1cgamma mutant spermatocytes is consistent with a loss of interference.

The rate of aneuploidy is altered in spermatids from infertile mice.

Background: It is now possible for infertile males to father their own genetic children through the technique of ICSI. This prospect has consequently prompted several investigations into the quality of sperm being retrieved from infertile males. One potential risk is the use of aneuploid sperm or spermatids, which might then be transferred to the fertilized oocyte.

Xenopus adenine nucleotide translocase mRNA exhibits specific and dynamic patterns of expression during development.

We report the isolation and characterization of the Xenopus homolog to human T1 ANT (adenine nucleotide translocase). The 1290-nucleotide sequence contains initiation and termination signals, and encodes a conceptual protein of 298 amino acids. The sequence shares high amino acid identity with the mammalian adenine translocases.