Effects of disruption of the embryonic alkaline phosphatase gene on preimplantation development of the mouse

Study of the regulatory elements of the Ovalbumin gene promoter using CRISPR technology in chicken cells

BACKGROUND

Hormone-dependent promoters are very efficient in transgene expression. Plasmid-based reporter assays have identified regulatory sequences of the Ovalbumin promoter that are involved in response to estrogen and have shown that the deletion of the steroid-dependent regulatory element (SDRE) and negative regulatory element (NRE) leads to a steroid-independent expression of a reporter. However, the functional roles of these regulatory elements within the native genomic context of the Ovalbumin promoter have not been evaluated.

RESULTS

In this study, we show that the negative effects of the NRE element on the Ovalbumin gene can be counteracted by CRISPR interference. We also show that the CRISPR-mediated deletion of SDRE and NRE promoter elements in a non-oviduct cell can lead to the significant expression of the Ovalbumin gene. In addition, the targeted knock-in of a transgene reporter in the Ovalbumin coding region and its expression confirms that the truncated promoter of the Ovalbumin gene can be efficiently used for an estrogen-independent expression of a foreign gene.

CONCLUSIONS

The methodology applied in this paper allowed the study of promoter regulatory sequences in their native nuclear organization.

Tissue-Nonspecific Alkaline Phosphatase, a Possible Mediator of Cell Maturation: Towards a New Paradigm

Alkaline phosphatase (ALP) is a ubiquitous membrane-bound glycoprotein capable of providing inorganic phosphate by catalyzing the hydrolysis of organic phosphate esters, or removing inorganic pyrophosphate that inhibits calcification. In humans, four forms of ALP cDNA have been cloned, among which tissue-nonspecific ALP (TNSALP) (TNSALP) is widely distributed in the liver, bone, and kidney, making it an important marker in clinical and basic research. Interestingly, TNSALP is highly expressed in juvenile cells, such as pluripotent stem cells (i.e., embryonic stem cells and induced pluripotent stem cells (iPSCs)) and somatic stem cells (i.e., neuronal stem cells and bone marrow mesenchymal stem cells). Hypophosphatasia is a genetic disorder causing defects in bone and tooth development as well as neurogenesis. Mutations in the gene coding for TNSALP are thought to be responsible for the abnormalities, suggesting the essential role of TNSALP in these events. Moreover, a reverse-genetics-based study using mice revealed that TNSALP is important in bone and tooth development as well as neurogenesis. However, little is known about the role of TNSALP in the maintenance and differentiation of juvenile cells. Recently, it was reported that cells enriched with TNSALP are more easily reprogrammed into iPSCs than those with less TNSALP. Furthermore, in bone marrow stem cells, ALP could function as a "signal regulator" deciding the fate of these cells. In this review, we summarize the properties of ALP and the background of ALP gene analysis and its manipulation, with a special focus on the potential role of TNSALP in the generation (and possibly maintenance) of juvenile cells.

Regulation of Chromatin Organization in Cell Stemness: The Emerging Role of Long Non-coding RNAs

Chromatin is organized as chromosome territories in the nucleus of an interphase cell. The cell-type- and cell-state-specific organization of chromatin including the location, volume, compaction level, and spatial arrangement of chromosome territories are the major determinants of genome function. In addition, in response to different signaling stimuli and regulatory cues, it is the dynamic adaptation of chromatin structure that establishes and organizes transcriptional programs. It is known that varying levels of stemness are defined by gene regulatory networks. Accordingly, chromatin is the main milieu to host the transcriptional programs and gene regulatory networks responsible for the stemness status of a cell. In this review, our current understanding of the spatial organization of chromatin and the ways by which it defines stemness are discussed. In particular, the role of lncRNAs that regulate and affect chromatin organization and stemness properties are delineated. These roles can be categorized into the topics of specific binding to and epigenetic regulation of the promoter of pluripotency genes, their interaction with transcription factors, coordinating the intra- and inter-chromosomal looping of pluripotency-related genes, and their RNA-independent functions. This review brings together the results of studies that have begun to clarify the emerging roles of lncRNAs in the regulation of chromatin organization adapted for stemness and cancer plasticity.

Polymorphisms of human placental alkaline phosphatase are associated with in vitro fertilization success and recurrent pregnancy loss

Fertility is a quantitative, complex character governed by a considerable number of genes. Despite clinical and scientific advances, several cases of human infertility remain unexplained. In the present study, using a positional cloning approach in a mouse model of interspecific recombinant lines, a candidate gene, ALPP, encoding the placental alkaline phosphatase, was identified as being potentially involved in recurrent spontaneous abortion. We then analyzed patients for detecting putative associations between ALPP polymorphisms, in vitro fertilization failures, and miscarriages. ALPP was sequenced in 100 controls and 100 patients affected by recurrent spontaneous abortion, from the same ethnic background. The frequency of several alleles and allelic combinations were different between recurrent spontaneous abortion and control women. One polymorphism induced a coding substitution (Ile89Leu) that was associated with a decreased risk of abortion and in vitro fertilization failure. Thereafter, the population was increased by the analysis of 92 additional controls and 612 additional patients for the coding polymorphism Ile89Leu. We finally show, by functional analysis, that the 89Leu placental alkaline phosphatase has an enhanced alkaline phosphatase activity. This study suggests that ALPP genotyping could be a strong predictor of implantation success.

Alkaline phosphatases contribute to uterine receptivity, implantation, decidualization, and defense against bacterial endotoxin in hamsters

Alkaline phosphatase (AP) activity has been demonstrated in the uterus of several species, but its importance in the uterus, in general and during pregnancy, is yet to be revealed. In this study, we focused on identifying AP isozyme types and their hormonal regulation, cell type, and event-specific expression and possible functions in the hamster uterus during the cycle and early pregnancy. Our RT-PCR and in situ hybridization studies demonstrated that among the known Akp2, Akp3, Akp5, and Akp6 murine AP isozyme genes, hamster uteri express only Akp2 and Akp6; both genes are co-expressed in luminal epithelial cells. Studies in cyclic and ovariectomized hamsters established that while progesterone (P₄) is the major uterine Akp2 inducer, both P₄ and estrogen are strong Akp6 regulators. Studies in preimplantation uteri showed induction of both genes and the activity of their encoded isozymes in luminal epithelial cells during uterine receptivity. However, at the beginning of implantation, Akp2 showed reduced expression in luminal epithelial cells surrounding the implanted embryo. By contrast, expression of Akp6 and its isozyme was maintained in luminal epithelial cells adjacent to, but not away from, the implanted embryo. Following implantation, stromal transformation to decidua was associated with induced expressions of only Akp2 and its isozyme. We next demonstrated that uterine APs dephosphorylate and detoxify endotoxin lipopolysaccharide at their sites of production and activity. Taken together, our findings suggest that uterine APs contribute to uterine receptivity, implantation, and decidualization in addition to their role in protection of the uterus and pregnancy against bacterial infection.

Purines as potential morphogens during embryonic development

Components of purinergic signalling are expressed in the early embryo raising the possibility that ATP, ADP and adenosine may contribute to the mechanisms of embryonic development. We summarize the available data from four developmental models—mouse, chick, Xenopus and zebrafish. While there are some notable examples where purinergic signalling is indeed important during development, e.g. development of the eye in the frog, it is puzzling that deletion of single components of purinergic signalling often results in rather minor developmental phenotypes. We suggest that a key step in further analysis is to perform combinatorial alterations of expression of purinergic signalling components to uncover their roles in development. We introduce the concept that purinergic signalling could create novel morphogenetic fields to encode spatial location via the concentration of ATP, ADP and adenosine. We show that using minimal assumptions and the known properties of the ectonucleotidases, complex spatial patterns of ATP and adenosine can be set up. These patterns may provide a new way to assess the potential of purinergic signalling in developmental processes.

Involvement of tyrosine kinase signaling in maintaining murine embryonic stem cell functionality

OBJECTIVE

We previously demonstrated that c-kit expression decreases during murine embryonic stem cell (ESC) differentiation induced by leukemia inhibitory factor removal. In this study, we addressed the possibility that c-kit is a marker of undifferentiated murine ESC and, moreover, that it plays a role in maintaining the undifferentiated state of these cells.

MATERIALS AND METHODS

c-kit expression was analyzed under various differentiation conditions by flow cytometry and quantitative reverse transcription polymerase chain reaction. ESC were then sorted on the basis of c-kit expression and functionality was investigated using embryoid body and colony-forming cell assays. Imatinib (Gleevec) and ACK2 were used to block, and stem cell factor was used to stimulate, c-kit activity.

RESULTS

c-kit expression decreased in two murine ESC lines under various differentiation conditions. Sorting of ESC populations on the basis of c-kit expression revealed significant differences in the functional capacities and gene expression profiles of the sorted populations. The inhibition studies revealed an important role for tyrosine kinase activity in maintaining ESC viability and differentiation capacity, at least in part by preventing apoptosis and enhancing cell cycle progression. However, activation of c-kit alone is not sufficient for maintaining undifferentiated ESC.

CONCLUSION

The results suggest that c-kit may represent a useful marker for monitoring ESC functionality. Moreover, tyrosine kinase signaling plays an important role in maintaining undifferentiated ESC. This work provides valuable insights into the complex signaling pathways that synergize to maintain the undifferentiated state of murine ESC.

Subcellular localization of protein kinase C delta and epsilon affects transcriptional and post-transcriptional processes in four-cell mouse embryos

During mouse preimplantation development, two isozymes of protein kinase C (PKC), delta and epsilon, transiently localize to nuclei at the early four-cell stage. In order to study their functions at this stage, we altered the subcellular localization of these isozymes (ratio of nuclear to cytoplasmic concentrations) with peptides that specifically activate or inhibit translocation of each isozyme. The effects of altering nuclear concentration of each isozyme on transcription (5-bromouridine 5'-triphosphate (BrUTP) incorporation), amount and distribution of small nuclear ribonucleoproteins (snRNPs), nucleolar dynamics (immunocytochemistry for Smith antigen (Sm) protein) and the activity of embryonic alkaline phosphatase (EAP; histochemistry) were examined. We found that nuclear concentration of PKC epsilon correlated with total mRNA transcription. Higher nuclear concentrations of both PKC delta and epsilon decreased storage of snRNPs in Cajal bodies and decreased the number of nucleoli, but did not affect the nucleoplasmic concentration of snRNPs. Inhibiting translocation of PKC delta out of the nucleus at the early four-cell stage decreased cytoplasmic EAP activity, whereas inhibiting translocation of PKC epsilon increased EAP activity slightly. These results indicate that translocation of PKC delta and epsilon in and out of nuclei at the early four-cell stage in mice can affect transcription or message processing, and that sequestration of these PKC in nuclei can also affect the activity of a cytoplasmic protein (EAP).

Conserved epitopes in human and mouse tissue-nonspecific alkaline phosphatase. Second report of the ISOBM TD-9 workshop

A panel of 19 monoclonal antibodies (MAbs) against human tissue-nonspecific (liver/bone/kidney) alkaline phosphatase (TNAP) was obtained through the ISOBM TD-9 workshop. In the present study, the reactivity of these MAbs has been characterized against mouse TNAP. A mouse embryonic stem cell line, frozen sections of long bones, alkaline phosphatase extracted from mouse bone, and serum were used as the source of TNAP for individual assays. Each MAb was tested for immunoreactivity to mouse TNAP by Western blot analysis, immunohistochemistry and enzyme immunoassay. Antibodies 314 and 315 reacted strongly with mouse TNAP in Western blots, while all other antibodies were negative. By immunohistochemistry, antibodies 314, 315 and 333 produced strong positive staining using frozen sections, while antibody 334 was moderately positive. Enzyme immunoassays indicated that MAb 333 was also able to bind to serum TNAP. These antibodies represent very useful reagents to study the pathophysiological expression of TNAP in mouse tissues and in mouse serum.

Gene expression and in vitro development of inter-species nuclear transfer embryos

This study examined the chromatin morphology, in vitro development, and expression of selected genes in cloned embryos produced by transfer of mouse embryonic fibroblasts (MEF) into the bovine ooplasm. After 6 hr of activation, inter-species nuclear transfer (NT) embryos (MEF-NT) had one (70%) or two pronuclei (20%), respectively. After 72 hr of culture in vitro, 62.6% of the MEF-NTs were arrested at the 8-cell stage, 31.2% reached the 2- to 4-cell stage, and only 6.2% had more than eight blastomeres, but none of these developed to the blastocyst stage. Whereas, 20% of NT embryos derived from bovine embryonic fibroblast fused with bovine ooplasm (BEF-NT) reached the blastocyst stage. Donor MEF nuclei expressing an Enhanced Green Fluorescent Protein (EGFP) transgene resulted in 1- to 8-cell stage MEF-NT that expressed EGFP. The expression of selected genes was examined in 8-cell MEF-NTs, 8-cell mouse embryos, enucleated bovine oocytes, and MEFs using RT-PCR. The mRNA for heat shock protein 70.1 (Hsp 70.1) gene was detected in MEF-NTs and MEF, but not in mouse embryos. The hydroxy-phosphoribosyl transferase (HPRT) mRNA was found in normal mouse embryos and MEF but not in MEF-NTs. Expression of Oct-4 and embryonic alkaline phospatase (eAP) genes was only detected in normal mouse embryos and not in the inter-species NT embryos. Abnormal gene expression profiles were associated with an arrest in the development at the 8-cell stage, but MEF-NT embryos appeared to have progressed through gross chromatin remodeling, typical of intra-species NT embryos. Therefore, molecular reprogramming rather than chromatin remodeling may be a better indicator of nuclear reprogramming in inter-species NT embryos.

Accelerated fat absorption in intestinal alkaline phosphatase knockout mice

Intestinal alkaline phosphatase (IAP) is the most ancestral of the tissue-specific members of the AP gene family. Several studies have suggested an absorptive function for IAP, but in vivo data to this effect have been lacking. We inactivated the mouse IAP gene in embryo-derived stem cells and generated mice homozygous for the null mutation. The mice were macroscopically and histologically normal and fertile and showed no difference from the wild-type controls under normal laboratory conditions. However, when maintained long-term on a high-fat diet, the IAP-deficient mice showed faster body weight gain than did control animals. Histological examination revealed an accelerated transport of fat droplets through the intestinal epithelium and elevation of serum triglyceride levels in the IAP-deficient mice compared to wild-type mice. Our study suggests that IAP participates in a rate-limiting step regulating fat absorption.

Inhibitor profiles of alkaline phosphatases in bovine preattachment embryos and adult tissues

The alkaline phosphatases are a small family of isozymes. Bovine preattachment embryos transcribe mRNA for two tissue-specific alkaline phosphatases (TSAP2 and TSAP3) beginning at the 4- and 8-cell stages. Whereas no mRNA has been detected in oocytes, there is maternally inherited alkaline phosphatase activity. It is not known which isozyme(s) is responsible for the maternal activity or when TSAP2 and TSAP3 form functional protein. No antibodies are available that recognize the relevant bovine alkaline phosphatases. Therefore, sensitivity to heat and chemical inhibition was used to separate the different isozymes. By screening tissues, it was determined that the bovine tissue-nonspecific alkaline phosphatase (TNAP) is inactivated by low temperatures (65C) and low concentrations of levamisole (<1 mM), whereas bovine tissue-specific isozymes require higher temperatures (90C) and levamisole concentrations (>5 mM). Inhibition by L-homoarginine and L-phenylalanine was less informative. Cumulus cells transcribe two isozymes and the pattern of inhibition suggested heterodimer formation. Inhibition of alkaline phosphatase in bovine embryos before the 8-cell stage indicated the presence of only TNAP. At the 16-cell stage the pattern was consistent with TNAP plus TSAP2 or -3 activity, and in morulae and blastocysts the pattern indicated that the maternal TNAP is fully supplanted by TSAP2 or TSAP3.