A novel murine tryptase involved in blastocyst hatching and outgrowth

Using extended growth of cattle embryos in culture to gain insights into bovine developmental events on embryonic days 8 to 10

We have previously described an extended embryo culture system, based on uterine composition, growth factors and the cell culture additive B27, for growing cattle embryos in vitro beyond embryonic day 7. Here, extended in vitro embryos are compared to embryos developed in the uterus and are used to establish a developmental staging framework useful for understanding developmental events occurring until Day 10. Immunofluorescence or mRNA expression of the ICM/epiblast markers OCT4, SOX2 and NANOG, hypoblast markers GATA6, SOX17 and GATA4 and trophoblast genes CDX2, GATA3, ASCL2 and IFNT revealed the presence of four stages during this period that can be molecularly distinguished. These are expanded blastocyst, hatched blastocyst, hypoblast layering and early hypoblast migration. Interestingly NANOG and SOX17 show reciprocal expression at the expanded blastocyst stage, well before SOX2 and GATA6 expression refines to a similar so-called "salt and pepper" mutually exclusive expression in the ICM at the hatched blastocyst stage. GATA4 expression is only seen from stages when the hypoblast starts migrating around the blastocyst cavity. Intriguingly, trophoblast still expresses GATA6 and OCT4 in all cells during the expanded blastocyst phase, while SOX2 and SOX17 are seen in only some trophoblast cells. By the hypoblast-epiblast layering stage no trophoblast expression remains except for that of OCT4 protein, which starts waning in trophoblast once the hypoblast begins migrating. Lastly, it is shown that cultured embryos exhibit increased expression of the stress marker TP53 in the epiblast and hypoblast at late stages in comparison to embryos produced in the uterine environment.

Spontaneously hatching human blastocyst is associated with high development potential and live birth rate in vitrified-warmed single blastocyst transfer: A retrospective cohort study

OBJECTIVE

To investigate the effect of hatching status on predicting pregnancy outcomes in single vitrified-warmed blastocyst transfer (SVBT) by objectively subdividing pre-implantation blastocysts according to hatching status.

METHODS

This retrospective study included 817 SVBT cycles performed between January 2016 and December 2017. Transferred embryos were categorized according to their hatching status as follows: group I (n = 147), non-hatching blastocysts; group II (n = 484), hatching blastocysts; and group III (n = 186), completely hatched blastocysts. Hatching blastocysts (group II) were then classified based on the ratio of the blastocystic diameter outside and inside the zona pellucida into early (n = 185), mid- (n = 103), and late (n = 196) hatching stages. Implantation rate (IR), clinical pregnancy rate (CPR), live birth rate (LBR), multiple pregnancy rate (MPR), miscarriage rate, and neonatal outcomes were evaluated.

RESULTS

For groups I, II, and III, respectively, the results were as follows: IR (28.6%, 43.6%, and 53.8%; P < 0.001), CPR (27.9%, 42.8%, and 53.2%; P < 0.001), and LBR (23.1%, 32.0%, and 42.5%; P < 0.001). Group III had better IR, CPR, and LBR. Among hatching blastocysts, late-hatching blastocysts had the highest IR (33.5%, 46.6%, and 51.5% for early, mid-, and late hatching, respectively; P = 0.002) and CPR (33.0%, 45.6%, and 50.5%; P = 0.002), with a tendency for a higher rate of LBR. Neonatal outcomes were not influenced by the hatching status.

CONCLUSION

Advanced hatching status is positively associated with a higher rate of clinical pregnancy and live birth with no negative effects on neonatal outcomes. Additionally, the quantitative classification of hatching status was found to be predictive of pregnancy outcomes.

Prss29 Cre recombinase mice are useful to study adult uterine gland function

All mammalian uteri contain glands in their endometrium that develop only or primarily after birth. In mice, those endometrial glands govern post implantation pregnancy establishment via regulation of blastocyst implantation, stromal cell decidualization, and placental development. Here, we describe a new uterine glandular epithelium (GE) specific Cre recombinase mouse line that is useful for the study of uterine gland function during pregnancy. Utilizing CRISPR-Cas9 genome editing, Cre recombinase was inserted into the endogenous serine protease 29 precursor (Prss29) gene. Both Prss29 mRNA and Cre recombinase activity was specific to the GE of the mouse uterus following implantation, but was absent from other areas of the female reproductive tract. Next, Prss29-Cre mice were crossed with floxed forkhead box A2 (Foxa2) mice to conditionally delete Foxa2 specifically in the endometrial glands. Foxa2 was absent in the glands of the post-implantation uterus, and Foxa2 deleted mice exhibited complete infertility after their first pregnancy. These results establish that Prss29-Cre mice are a valuable resource to elucidate and explore the functions of glands in the adult uterus.

Site specificity of blastocyst hatching significantly influences pregnancy outcomes in mice

Blastocysts hatch from the zona pellucida (ZP) to enable implantation into the uterine endometrial epithelium, but little is known regarding the effect of hatching sites on pregnancy outcomes. Murine hatching embryos were categorized into five groups based on initial trophectoderm projection (TEP)/ZP position corresponding to the inner cell mass center. In blastocysts (3.5 dpc) post-12 hours in vitro culture, TEP rates of A-site (44.4%) and B-site (38.6%) embryos were higher than those of C-site (12.5%) and D-site (3.1%) embryos, while the O-site (1.4%) was the lowest (P < .05). Post-ET A-site (55.6%) and B-site (65.6%) birth rates were higher than those of C-site embryos (21.3%) and controls (P < .05). Furthermore, live birth rate of B-site embryos remained higher than C-site embryos (68.8% vs 31.3%; P < .05) when both were transferred into the same recipients. Different TEP site blastocysts exhibited different implantation competences: the implantation rate of C-site embryos was lower than that of both A- and B-site groups (67.7% vs 84.3% and 83.2%, respectively; P < .05) at 2 days post-ET. C-site embryos also had a distinctly higher ratio of developmental defects (47.5%) than A- and B-site embryos (22.5% and 14.6%, respectively), with implantation failure mainly associated with poor birth rate, a finding corroborated by differential gene expression analysis such as LIF, LIFR, and S100a9. Surprisingly, acidified Tyrode's solution (AAH)-treated B-site blastocysts had a significantly increased birth rate (77.1%) than C-site (55.3%) and controls (43.4%). Site specificity and differential gene expression during embryo hatching can be applied in ART screening. More importantly, assisted hatching by AAH is effective and feasible for improving pregnancy and term development, particularly at the B-site, for humans and in animal husbandry.

Generation and analysis of Prss28 and Prss29 deficient mice using CRISPR-Cas9 genome-editing

Glands of the uterus are essential for the establishment of pregnancy in mice and their products regulate embryo implantation and stromal cell decidualization critical for pregnancy establishment. Forkhead box A2 (FOXA2) is expressed specifically in the glands and a critical regulator of their differentiation, development and function. Progesterone and FOXA2 regulate members of a serine proteinase gene family (Prss28 and Prss29). Here, CRISPR-Cas9 genome-editing was used to create mice with a heterozygous or homozygous deletion of Prss28 or/and Prss29 to determine their biological roles in uterine function. Female mice lacking Prss28 and Prss29 or both developed normally and were fertile without alterations in uterine histoarchitecture, uterine gland number, or and gene expression. Thus, Prss28 and Prss29 are dispensable for female fertility and do not impact endometrial gland development or uterine function mice.

Expression and function of interleukin-1β is required for hamster blastocyst hatching: Involvement of hatching-associated cathepsin proteases

In mammals, the phenomenon of blastocyst hatching is an essential prerequisite for successful implantation. Blastocyst hatching is regulated by various molecules. Of them, cytokines, expressed by preimplantation embryos, are thought to be functionally important in blastocyst development and hatching, but their mechanistic roles are not clearly understood. Here, we examined the involvement of two cytokines, namely, interleukin-1β (IL-1β) and its natural antagonist, IL-1ra, in blastocyst hatching in the golden hamster. Blastocysts expressed both cytokines and their receptor, IL-1rt1. Supplementation of IL-1β to cultured eight-cell embryos improved blastocyst hatching (84.1% ± 4.2% vs. 66.6% ± 6.8%; treated vs. control). This improvement was diminished by IL-1ra treatment (23.6% ± 12.9% vs. 76.4% ± 12.9%; treated vs. control). Interestingly, IL-1β-treated embryos showed increased messenger RNA expression of zonalytic proteases, that is, cathepsin-L and -B by 1.9 ± 0.5- and 3.5 ± 0.1-folds, respectively. This was accompanied by their increased enzyme activities; cathepsin-L by 2.8 ± 0.7 fold and -B by 2.3 ± 0.7-fold. Strikingly, proteases and IL-1β were intensely colocalized to trophectodermal projections of hatching blastocysts. This is the first report to show the involvement of embryonic IL-1β in regulating hatching-associated proteases required for blastocyst hatching.

Parental genetic material and oxygen concentration affect hatch dynamics of mouse embryo in vitro

BACKGROUND

Hatching is crucial for mammalian embryo implantation, since difficulties during this process can lead to implantation failure, ectopic pregnancy and consequent infertility. Despite years of intensive researches, how internal and external factors affecting embryo hatch are still largely unclear.

METHODS

The effects of parental genetic material and oxygen concentration on hatch process were examined. Fertilized and parthenogenetic mouse preimplantation embryos were cultured in vitro under 5 and 20% oxygen for 120 h. Zona pellucida drilling by Peizo micromanipulation were performed to resemble the breach by sperm penetration.

RESULTS

Firstly, parthenogenetic embryos had similarly high blastocyst developmental efficiency as fertilized embryos, but significantly higher hatch ratio than fertilized embryos in both O₂ concentrations. 5% O₂ reduced the hatch rate of fertilized embryos from 58.2 to 23.8%, but increased that of parthenogenetic embryos from 81.2 to 90.8% significantly. Analogously, 5% O₂ decreased the ratio of Oct4-positive cells in fertilized blastocysts, whereas increased that in parthenogenetic blastocysts. Additionally, 5% O₂ increased the total embryonic cell number in both fertilized and parthegenetic embryos, when compared to 20% O₂, and the total cell number of fertilized embryos was also higher than that of parthegenetic embryos, despite O₂ concentration. Real-time PCR revealed that the expression of key genes involving in MAPK pathway and superoxide dismutase family might contribute to preimplantation development and consequent blastocyst hatch in vitro. Finally, we showed that fertilized and parthenogenetic embryos have diverse hatch dynamics in vitro, although the zona pellucida integrity is not the main reason for their mechanistic differences.

CONCLUSION

Both parental genetic material and O₂ concentration, as the representative of intrinsic and extrinsic factors respectively, have significant impacts on mouse preimplantation development and subsequent hatch dynamics, probably by regulating the gene expression involving in MAPK pathway and superoxide dismutase family to control embryonic cell proliferation and allocation of ICM cells.

Thyroid hormone regulates protease expression and activation of Notch signaling in implantation and embryo development

A clinical association between thyroid dysfunction and pregnancy complications has been extensively reported; however, the molecular mechanisms through which TH might regulate key events of pregnancy have not been elucidated yet. In this respect, we performed in vivo studies in MMI-induced hypothyroid pregnant mice, evaluating the effect of hypothyroidism on the number of implantation sites, developing embryos/resorptions and pups per litter, at 4.5, 10.5, 18.5 days post-coitum (dpc) and at birth. We also studied the expression of major molecules involved in implantation and placentation, such as the proteases ISPs, MMPs, TIMPs and Notch pathway-related genes. Our results demonstrate that hypothyroidism may have a dual effect on pregnancy, by initially influencing implantation and by regulating placental development at later stages of gestation. To further elucidate the role of TH in implantation, we performed in vitro studies by culturing 3.5 dpc blastocysts in the presence of TH, with or without endometrial cells used as the feeder layer, and studied their ability to undergo hatching and outgrowth. We observed that, in the presence of endometrial feeder cells, TH is able to anticipate blastocyst hatching by upregulating the expression of blastocyst-produced ISPs, and to enhance blastocyst outgrowth by upregulating endometrial ISPs and MMPs. These results clearly indicate that TH is involved in the bidirectional crosstalk between the competent blastocyst and the receptive endometrium at the time of implantation.

Cathepsin B inhibitor improves developmental competency and cryo-tolerance of in vitro ovine embryos

Background

Cathepsin B is a lysosomal cysteine protease involved in apoptosis and oocytes which have lower developmental competence show higher expression of Cathepsin B. Furthermore, expression of Cathepsin B show a decreasing trend from oocyte toward blastocyst stage.

Results

Present study assessed the effect of cathepsin B inhibitor, E-64, on developmental competency and cryo-survival of pre-implantation ovine IVF derived embryos. Cathepsin B inhibitor was added during day 3 to 8 of development. One μM E-64 was defined as the optimal concentration required for improving blastocyst rate. This concentration also reduced DNA fragmentation and BAX as apoptotic markers while increasing total cell number per blastocyst and improving anti-apoptotic marker, the BCL2. We further showed that addition of 1.0 μM of E-64 during day 3 to 8 of development improved re-expansion and hatching rates of blastocysts post vitrification. E-64 also reduced rate of DNA fragmentation and BAX expression and increased total cell number per blastocyst and BCL2 expression post vitrification. However, addition of E-64 post vitrification reduced the hatching rate.

Conclusion

Therefore, it can be concluded that inhibition of cathepsin B in IVC, not only improves quality and quantity of blastocysts but also improves the cryo-survival of in vitro derived blastocysts.

The bovine embryo hatches from the zona pellucida through either the embryonic or abembryonic pole

PURPOSE

Implantation of the mammalian embryo in the uterus is preceded by escape from the zona pellucida. In some species, hatching from the zona occurs preferentially from one or the other poles of the embryo. The situation for the bovine embryo, in which hatching precedes attachment to the uterus by more than a week, is unclear. The purpose was to describe whether hatching of the bovine embryo from the zona pellucida occurs preferentially from the embryonic or abembryonic pole.

METHODS

Bovine blastocysts undergoing hatching were examined by light microscopy (n = 84) and epifluorescence imaging using antibodies for markers of epiblast, hypoblast, and trophectoderm (TE) (n = 26). The location of hatching was classified as being at the embryonic pole, if hatching occurred ipsilateral to the inner cell mass (ICM), or abembryonic, if hatching occurred contralateral to the ICM.

RESULTS

A total of 55% of blastocysts exited the zona pellucida through an opening at the embryonic pole. In these cases, 68% of the cells emerging through the zona pellucida were derived from the ICM. The remainder of blastocysts hatched from an opening either contralateral or to the side of the ICM. In these cases, 87% of hatched cells were TE.

CONCLUSION

For the bovine embryo, there is nearly equal probability of hatching from the embryonic or abembryonic poles. Given that the surface area of the zona pellucida in contact with the TE overlying the ICM is less than for the remainder of the blastocyst, there is some preference for hatching through the embryonic pole. Thus, the bovine embryo is distinct from the mouse and human, where hatching occurs preferentially at the abembryonic pole.

Combined effects of individual culture and atmospheric oxygen on preimplantation mouse embryos in vitro

Embryos are routinely cultured individually, although this can reduce blastocyst development. Culture in atmospheric (20%) oxygen is also common, despite multiple detrimental effects on embryos. Although frequently occurring together, the consequences of this combination are unknown. Mouse embryos were cultured individually or grouped, under physiological (5%) or atmospheric (20%) oxygen. Embryos were assessed by time-lapse and blastocyst cell allocation. Compared with the control group (5% oxygen group culture), 5-cell cleavage (t5) was delayed in 5% oxygen individual culture and 20% oxygen group culture (59.91 ± 0.23, 60.70 ± 0.29, 63.06 ± 0.32 h post-HCG respectively, P < 0.05). Embryos in 20% oxygen individual culture were delayed earlier (3-cell cleavage), and at t5 cleaved later than embryos in other treatments (66.01 ± 0.40 h, P < 0.001), this delay persisting to blastocyst hatching. Compared with controls, hatching rate and cells per blastocyst were reduced in 5% oxygen single culture and 20% oxygen group culture (134.1 ± 3.4, 104.5 ± 3.2, 73.4 ± 2.2 cells, P < 0.001), and were further reduced in 20% oxygen individual culture (57.0 ± 2.8 cells, P < 0.001), as was percentage inner cell mass. These data indicate combining individual culture and 20% oxygen is detrimental to embryo development.

Cytokines and Blastocyst Hatching

Blastocyst implantation into the uterine endometrium establishes early pregnancy. This event is regulated by blastocyst- and/or endometrium-derived molecular factors which include hormones, growth factors, cell adhesion molecules, cytokines and proteases. Their coordinated expression and function are critical for a viable pregnancy. A rate-limiting event that immediately precedes implantation is the hatching of blastocyst. Ironically, blastocyst hatching is tacitly linked to peri-implantation events, although it is a distinct developmental phenomenon. The exact molecular network regulating hatching is still unclear. A number of implantation-associated molecular factors are expressed in the pre-implanting blastocyst. Among others, cytokines, expressed by peri-implantation blastocysts, are thought to be important for hatching, making blastocysts implantation competent. Pro-inflammatory (IL-6, LIF, GM-CSF) and anti-inflammatory (IL-11, CSF-1) cytokines improve hatching rates; they modulate proteases (MMPs, tPAs, cathepsins and ISP1). However, functional involvement of cytokines and their specific mediation of hatching-associated proteases are unclear. There is a need to understand mechanistic roles of cytokines and proteases in blastocyst hatching. This review will assess the available knowledge on blastocyst-derived pro-inflammatory and anti-inflammatory cytokines and their role in potentially regulating blastocyst hatching. They have implications in our understanding of early embryonic loss and infertility in mammals, including humans.

Is the zona pellucida thickness of human embryos influenced by women's age and hormonal levels?

OBJECTIVE

To evaluate whether zona pellucida thickness (ZPT) of human embryos is correlated with maternal age, patient's hormonal status, embryo quality, and IVF outcomes.

DESIGN

Prospective study.

SETTING

University-affiliated IVF clinic.

PATIENT(S)

Couples undergoing IVF-ET cycles.

INTERVENTION(S)

Zona measurements, clinical data collection.

MAIN OUTCOME MEASURE(S)

Correlation between the ZPT and maternal age, basal FSH and E(2) levels, stimulation protocols, cause of infertility, embryo quality, and implantation/pregnancy rates.

RESULT(S)

The measurements of ZPT were collected from 5,184 day 3 human embryos originated from 744 IVF patients. The overall mean ZPT was 16.18 ± 2.00 μm. No significant correlation was observed between the ZPT and the patient's age, E(2) values on the day of hCG administration, basal concentration of serum FSH, stimulation protocol, infertility diagnosis, and implantation/pregnancy rates. The ZPT was strongly influenced only by the embryo quality: Embryos with good morphology exhibited considerably thinner ZP compared with those of less favorable morphology (mean 15.87 ± 2.48 μm vs. 16.36 ± 2.57 μm, respectively). The ZPT had no significant impact on the implantation and pregnancy rates.

CONCLUSION(S)

The thickness of the human ZP of day 3 embryos is not influenced by women's age and hormonal levels. The strong correlation between ZPT and embryo quality suggests that thickness of ZP depends on inherent embryo properties. The overall ZPT is not a good predictive indicator for IVF clinical outcomes.

Small-conductance calcium-activated K(+) channels 3 (SK3) regulate blastocyst hatching by control of intracellular calcium concentration

BACKGROUND

The present study was designed to investigate the expression of small-conductance calcium-activated K(+) channels 3 (SK3) in preimplantation embryos and to explore their role in the underlying mechanism of blastocyst hatching.

METHODS

Human preimplantation embryos were donated by patients who achieved successful pregnancy with in vitro fertilization. Mouse preimplantation embryos in different stages were collected and cultured with or without siRNA cell injection. The expression of SK3 was examined by RT-PCR, quantitative real-time PCR, western blot and immunofluorescence. Functional expression of SK3 was investigated using the patch-clamp technique. [Ca(2+)]i was measured by fluorescent imaging. Embryos were cultured in vitro to investigate the effect of SK3 knockdown or apamin, an SK3 inhibitor, on blastocyst hatching and F-actin formation.

RESULTS

In human blastocysts, the level of SK3 expression was significantly lower in blastocysts that failed to hatch than in blastocysts that hatched successfully. In mouse embryos, SK3 mRNA and protein were not found in zygotes, but were detected from the 2-cell stage onward, with the highest levels observed in blastocysts. SK3 was predominately located in the trophectoderm cell membrane of expanded blastocysts. SK3 knockdown in trophectoderm cells not only suppressed the SK3 current, but also reduced [Ca(2+)]i elevation and membrane potential hyperpolarization induced by thapsigargin. Although the formation of expanded blastocysts was not affected, blastocyst hatching and F-actin formation were significantly inhibited after SK3 knockdown in trophectoderm cells.

CONCLUSIONS

SK3-mediated [Ca(2+)]i elevation and membrane potential hyperpolarization in trophectoderm cells are important for blastocyst hatching, and defects in SK3 expression may contribute to infertility.

Implantation serine proteinase 1 exhibits mixed substrate specificity that silences signaling via proteinase-activated receptors

Implantation S1 family serine proteinases (ISPs) are tryptases involved in embryo hatching and uterine implantation in the mouse. The two different ISP proteins (ISP1 and ISP2) have been detected in both pre- and post-implantation embryo tissue. To date, native ISP obtained from uterus and blastocyst tissues has been isolated only as an active hetero-dimer that exhibits trypsin-like substrate specificity. We hypothesised that in isolation, ISP1 might have a unique substrate specificity that could relate to its role when expressed alone in individual tissues. Thus, we isolated recombinant ISP1 expressed in Pichia pastoris and evaluated its substrate specificity. Using several chromogenic substrates and serine proteinase inhibitors, we demonstrate that ISP1 exhibits trypsin-like substrate specificity, having a preference for lysine over arginine at the P1 position. Phage display peptide mimetics revealed an expanded but mixed substrate specificity of ISP1, including chymotryptic and elastase activity. Based upon targets observed using phage display, we hypothesised that ISP1 might signal to cells by cleaving and activating proteinase-activated receptors (PARs) and therefore assessed PARs 1, 2 and 4 as potential ISP1 targets. We observed that ISP1 silenced enzyme-triggered PAR signaling by receptor-disarming. This PAR-disarming action of ISP1 may be important for embryo development and implantation.

Initiation of trophectoderm lineage specification in mouse embryos is independent of Cdx2

The separation of the first two lineages - trophectoderm (TE) and inner cell mass (ICM) - is a crucial event in the development of the early embryo. The ICM, which constitutes the pluripotent founder cell population, develops into the embryo proper, whereas the TE, which comprises the surrounding outer layer, supports the development of the ICM before and after implantation. Cdx2, the first transcription factor expressed specifically in the developing TE, is crucial for the differentiation of cells into the TE, as lack of zygotic Cdx2 expression leads to a failure of embryos to hatch and implant into the uterus. However, speculation exists as to whether maternal Cdx2 is required for initiation of TE lineage separation. Here, we show that effective elimination of both maternal and zygotic Cdx2 transcripts by an RNA interference approach resulted in failure of embryo hatching and implantation, but the developing blastocysts exhibited normal gross morphology, indicating that TE differentiation had been initiated. Expression of keratin 8, a marker for differentiated TE, further confirmed the identity of the TE lineage in Cdx2-deficient embryos. However, these embryos exhibited low mitochondrial activity and abnormal ultrastructure, indicating that Cdx2 plays a key role in the regulation of TE function. Furthermore, we found that embryonic compaction does not act as a 'switch' regulator to turn on Cdx2 expression. Our results clearly demonstrate that neither maternal nor zygotic Cdx2 transcripts direct the initiation of ICM/TE lineage separation.

High degree of conservation of the multigene tryptase locus over the past 150-200 million years of mammalian evolution

Activated mast cells release a number of potent inflammatory mediators including histamine, proteoglycans, cytokines, and serine proteases. The proteases constitute the majority of the mast cell granule proteins, and they belong to either the chymase or the tryptase family. In mammals, these enzymes are encoded by two different loci, the mast cell chymase and the multigene tryptase loci. In mice and humans, a relatively large number of tryptic enzymes are encoded from the latter locus. These enzymes can be grouped into two subfamilies, the group 1 tryptases, with primarily membrane-anchored enzymes, and the group 2 tryptases, consisting of the soluble mast cell tryptases. In order to study the appearance of these enzymes during vertebrate evolution, we have analyzed the dog, cattle, opossum, and platypus genomes and sought orthologues in the genomes of several bird, frog, and fish species as well. Our results show that the overall structure and the number of genes within this locus have been well conserved from marsupial to placental mammals. In addition, two relatively distantly related group 2 tryptase genes and several direct homologues of some of the group 1 genes are present in the genome of the platypus, a monotreme. However, no direct homologues of the individual genes of either group 1 or 2 enzymes were identified in bird, amphibian, or fish genomes. Our results indicate that the individual genes within the multigene tryptase locus, in their present form, are essentially mammal-specific.

Growth-differentiation factor-8 (GDF-8) in the uterus: its identification and functional significance in the golden hamster

Transforming growth factor-beta superfamily regulates many aspects of reproduction in the female. We identified a novel member of this family, growth-differentiation factor 8 (GDF-8) in the 72 h post coital uterine fluid of the golden hamster by proteomic techniques. Uterine GDF-8 mRNA decreased as pregnancy progressed while its active protein peaked at 72 h post coitus (hpc) and thereafter stayed at a lower level. At 72 hpc, the GDF-8 transcript was localized to the endometrial epithelium while its protein accumulated in the stroma. Exogenous GDF-8 slowed down proliferation of primary cultures of uterine smooth muscle cells (SMC) and endometrial epithelial cells (EEC). In addition, GDF-8 attenuated the release of LIF (leukaemia inhibiting factor) by EEC. As for the embryo in culture, GDF-8 promoted proliferation of the trophotoderm (TM) and hatching but discouraged attachment. Our study suggests that GDF-8 could regulate the behavior of preimplantation embryos and fine-tune the physiology of uterine environment during pregnancy.

Acid peptidase activity released from in vitro produced porcine embryos: a candidate marker to predict developmental competence

The ability to efficiently create high quality embryos, competent to produce normal viable offspring in vitro, facilitates diverse technological advancements in animal agriculture and assisted reproduction. Current methods for evaluation of embryos are predominantly based on morphological characteristics which are prone to potential bias of the scorer. Metabolic and genetic markers have also been explored for quality assessment, but they are cost prohibitive or require longer periods of time for evaluation. We hypothesized that secreted enzymes could provide another means of embryo quality assessment. In this report, we provide evidence that medium conditioned by porcine embryos often has proteolytic activity that operates in acidic conditions (acid peptidase activity or APA). The APA could be inhibited by pepstatin A, suggesting that the activity is derived from one or more aspartic peptidases. We also provide evidence that single embryos, incubated for as few as 24 hr, released enough APA that it was possible to measure it accurately at day 5 of culture. We also observed that such activity on day 6 could be positively correlated with advanced developmental stage and embryo quality. In addition, those embryos that were graded identically by morphological evaluations often differed in the amount of APA--with some being significantly higher than the experimental threshold value. Therefore, the APA of embryos might serve as an additional marker for evaluation of embryos.

Expression of rat uterine serine proteinases homologous to mouse implantation serine proteinase 2

Implantation serine protease (ISP) was first identified in the uteri of pregnant mice. It is thought that ISP may have an important role in the initiation of implantation. However, the expression status and detailed functions of ISP remain unclear. In this study, the expression of ISP was investigated in the rat uterus. The analysis of two rat genes registered in GenBank, accession nos. XM_220240 and XM_577076, exhibited high identities to the mouse ISP2 genes, respectively at an mRNA level. We labeled the former as rISP2a and the latter as rISP2b. Using RT-PCR, we found that both genes were expressed in the uterus. Specifically, rISP2a mRNA was detected in the uterus throughout pregnancy, whereas rISP2b mRNA was only expressed in the uterus from day 5 of pregnancy until the end of gestation. Expression of both genes was observed specifically within the endometrial gland epithelium. Furthermore, rISP2a was also observed to be expressed in the fetus and placenta, whereas rISP2b expression was observed in the fetus but not in the placenta. An expressional signal of the rISP2a gene was observed in the spongiotrophoblasts, giant cells and decidual endometrium in the placenta. In the embryo, the ventral specific region was positive in rISP2a and rISP2b gene expression. These findings indicate the possibility that the presently examined genes with high identity to mouse ISP2 may play some role not only during the implantation phase, but also in the development of the placenta and embryo.

Characterization of secretory leukocyte protease inhibitor as an inhibitor of implantation serine proteinases

We have recently identified and characterized two implantation serine proteinase genes, ISP1 and ISP2, which give rise to a dimeric proteinase, ISP that facilitates embryo invasion during peri-implantation period. As many proteinases have cognate serpins that regulate their proteolytic activity, we have been investigating anti-tryptases, expressed during this window of implantation. Here, we report the differential expression of secretory leukocyte protease inhibitor (SLPI) in uterine endometrium around the implantation period. The co-localization of SLPI and ISP suggests the possibility that SLPI is an ISP serpin and that expression of SLPI may lead to a reduction in ISP activity. The expression of SLPI is down regulated during the window of embryo-uterine receptivity. Our results are consistent with a model suggesting that the drop in SLPI expression may help to refine the opening of the window of implantation, by allowing the proteolytic activity of embryo invasive serine proteinases such as the ISPs.

Substrate specificity determination of mouse implantation serine proteinase and human kallikrein-related peptidase 6 by phage display

We constructed a random library of hexapeptides displayed on the surface of bacteriophage T7 to determine the substrate specificity of proteinases. The phage-displayed library was subjected to repeated rounds of biopanning with native implantation serine proteinase and recombinant human kallikrein-related peptidase 6 (KLK6) followed by selection and identification of putative substrates. For both enzymes, the results obtained demonstrate a preference for arginine and lysine at multiple positions in the recognition cleavage motif, confirming their previously reported trypsin-like substrate specificity. In the case of KLK6, there is also a pronounced presence of tryptophan within the cleaved peptide sequences, indicating its potential dual substrate specificity, acting as both a trypsin and chymotrypsin-like enzyme.

Protease-proteoglycan complexes of mouse and human mast cells and importance of their beta-tryptase-heparin complexes in inflammation and innate immunity

Approximately 50% of the weight of a mature mast cell (MC) consists of varied neutral proteases stored in the cell's secretory granules ionically bound to serglycin proteoglycans that contain heparin and/or chondroitin sulfate E/diB chains. Mouse MCs express the exopeptidase carboxypeptidase A3 and at least 15 serine proteases [designated as mouse MC protease (mMCP) 1-11, transmembrane tryptase/tryptase gamma/protease serine member S (Prss) 31, cathepsin G, granzyme B, and neuropsin/Prss19]. mMCP-6, mMCP-7, mMCP-11/Prss34, and Prss31 are the four members of the chromosome 17A3.3 family of tryptases that are preferentially expressed in MCs. One of the challenges ahead is to understand why MCs express so many different protease-proteoglycan macromolecular complexes. MC-like cells that contain tryptase-heparin complexes in their secretory granules have been identified in the Ciona intestinalis and Styela plicata urochordates that appeared approximately 500 million years ago. Because sea squirts lack B cells and T cells, it is likely that MCs and their tryptase-proteoglycan granule mediators initially appeared in lower organisms as part of their innate immune system. The conservation of MCs throughout evolution suggests that some of these protease-proteoglycan complexes are essential to our survival. In support of this conclusion, no human has been identified that lacks MCs. Moreover, transgenic mice lacking the beta-tryptase mMCP-6 are unable to combat a Klebsiella pneumoniae infection effectively. Here we summarize the nature and function of some of the tryptase-serglycin proteoglycan complexes found in mouse and human MCs.

A single intrauterine injection of the serine protease inhibitor 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride reversibly inhibits embryo implantation in mice

BACKGROUND

The study was conducted to investigate the inhibitory effect of 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride (AEBSF) on embryo implantation in mice with a view to identifying whether it might be a suitable agent for postcoital contraception.

STUDY DESIGN

The anti-implantation efficacy of AEBSF was determined by counting the number of visible implanted embryos on Day 8 of pregnancy following a single intrauterine injection of AEBSF at doses of 30, 300 and 3000 microg per mouse uterine horn on Day 3 of pregnancy. The reversibility of the inhibitory effect of AEBSF on implantation was further evaluated by observing the outcome of a subsequent pregnancy without AEBSF treatment.

RESULTS

A dose-dependent inhibitory effect of AEBSF on embryo implantation in vivo was observed. Morphological analysis revealed no significant cytotoxicity of AEBSF on the mouse uterine epithelia. Furthermore, the anti-implantation effect of AEBSF was reversible.

CONCLUSION

Intrauterine administration of AEBSF at an appropriate dose might provide a basis for the development of novel contraception.

Implantation Serine Proteinases heterodimerize and are critical in hatching and implantation

Background

We have recently reported the expression of murine Implantation Serine Proteinase genes in pre-implantation embryos (ISP1) and uterus (ISP1 and ISP2). These proteinases belong to the S1 proteinase family and are similar to mast cell tryptases, which function as multimers.

Results

Here, we report the purification and initial characterization of ISP1 and 2 with respect to their physico-chemical properties and physiological function. In addition to being co-expressed in uterus, we show that ISP1 and ISP2 are also co-expressed in the pre-implantation embryo. Together, they form a heterodimer with an approximate molecular weight of 63 kD. This complex is the active form of the enzyme, which we have further characterized as being trypsin-like, based on substrate and inhibitor specificities. In addition to having a role in embryo hatching and outgrowth, we demonstrate that ISP enzyme is localized to the site of embryo invasion during implantation and that its activity is important for successful implantation in vivo.

Conclusion

On the basis of similarities in structural, chemical, and functional properties, we suggest that this ISP enzyme complex represents the classical hatching enzyme, strypsin. Our results demonstrate a critical role for ISP in embryo hatching and implantation.

GRP78/BiP is required for cell proliferation and protecting the inner cell mass from apoptosis during early mouse embryonic development

GRP78, also known as BiP, is a central regulator of endoplasmic reticulum (ER) homeostasis due to its multiple functional roles in protein folding, ER calcium binding, and controlling of the activation of transmembrane ER stress sensors. ER stress induction of GRP78/BiP represents a major prosurvival arm of the unfolded protein response (UPR). However, the physiological role of GRP78 in development is not known. Using a transgenic approach, we discovered that the Grp78 promoter is activated in both the trophectoderm and inner cell mass (ICM) of embryos at embryonic day 3.5 via a mechanism requiring the ER stress elements. To reveal the function of the GRP78 in vivo, we created a tri-loxP Grp78 mutant allele, which was further crossed with EIIA-cre to create a knockout allele. The Grp78+/- mice, which express 50% of the wild-type level of the GRP78 protein, are viable. Interestingly, the heterozygous Grp78 cells up-regulate the ER proteins GRP94 and protein disulfide isomerase at both the transcript and protein levels, while other UPR targets such as CHOP and XBP-1 are not affected. Further studies revealed that mouse embryonic fibroblasts from Grp78+/- mice are capable of responding to ER stress. However, Grp78-/- embryos that are completely devoid of GRP78 lead to peri-implantation lethality. These embryos do not hatch from the zona pellucida in vitro, fail to grow in culture, and exhibit proliferation defects and a massive increase in apoptosis in the ICM, which is the precursor of embryonic stem cells. These findings provide the first evidence that GRP78 is essential for embryonic cell growth and pluripotent cell survival.

Role of prophet of Pit1 (PROP1) in gonadotrope differentiation and puberty

The prophet of Pit1 (PROP1) gene is essential for normal gonadotropin production in both humans and mice. Transgenic mice that overexpress PROP1 in gonadotropes and thyrotropes have transient hypogonadotropic hypogonadism and increased risk of pituitary adenomas. Here we report a temporal study of pituitary gonadotrope terminal differentiation and hypogonadism, delayed onset of puberty, and transient growth insufficiency in the transgenic males. The Prop1 transgenic mice recover from their abnormalities and exhibit normal size and fertility at 3 months. The relatively normal expression pattern of GnRH receptor (Gnrhr) suggests that the pituitary gonadotrope cell lineage is appropriately specified, but the ability to synthesize LH and FSH is impaired by excess PROP1. We report no obvious abnormalities in expression of the transcription factors early growth response 1, NR5A1, GATA2, TBX19, and NR0B1, or the TGFbeta pathway members including activin, inhibin, and activin receptors. Thus, overexpression of PROP1 may influence gonadotrope development by a novel mechanism. Microarray analysis identified the inhibitory transmembrane receptor gene Klrg1 and the protease gene Prss28 as candidates for involvement in this process. We hypothesize that variation in PROP1 expression could affect the growth spurt and the onset of puberty in humans.

Murine implantation serine proteinases 1 and 2: Structure, function and evolution

Implantation is a vital phase in pregnancy whereupon the hatched embryo invades into the uterine wall to establish intimate contacts with the mother for further development. Although it is generally believed that proteinases are major factors that confer the embryo its invasive character, the nature of proteinases involved in implantation remain mostly elusive. In this article, we review the organization, structure and postulated function of the implantation serine proteinase (ISP1 and 2) genes. The ISPs are embedded within a cluster of tryptase genes on mouse chromosome 17. They are most closely related to members of the mast cell tryptase family, indicating that they may possess some properties characteristic of tryptases including multimerization-dependent activation. The significant similarities found in regulatory regions of ISP genes, together with the observation that ISP proteins are co-expressed and heterodimerize in the embryo and uterus suggests that they are intimately co-regulated during implantation. Inhibition of ISP proteolytic function has implicated this enzyme in the processes of embryo hatching and implantation.

Identification of a subgroup of glycosylphosphatidylinositol-anchored tryptases

The tryptase locus on mouse chromosome 17A3.3 contains 13 genes that encode enzymatically active serine proteases with different tissue expression profiles and substrate specificities. Mouse mast cell protease (mMCP) 6, mMCP-7, mMCP-11/protease serine member S (Prss) 34, tryptase 6/Prss33, tryptase epsilon/Prss22, implantation serine protease (Isp) 1/Prss28, and Isp-2 are constitutively exocytosed enzymes. We now demonstrate that tryptase 5/Prss32, pancreasin/Prss27, and testis serine protease-1 are inserted into plasma membranes via glycosylphosphatidylinositol (GPI) anchors analogous to Prss21, and that these serine proteases can be released from the cell's surface by a phosphatidylinositol-specific phospholipase C. These data suggest that the C-terminal residues play key roles in determining where tryptases compartmentalize in cells. GPI-anchored proteins are targeted to lipid rafts. Thus, our identification of a number of GPI-anchored tryptases whose genes reside at mouse chromosome 17A3.3 also implicates important biological functions for this new family of serine proteases on the surfaces of cells.

Roles of Na,K-ATPase in Early Development and Trophectoderm Differentiation

Before implantation into the uterine wall, the mammalian embryo undergoes a period of cell division, cell shape change, and cell differentiation leading to the formation of an outer epithelium, the trophectoderm. The trophectoderm is the part of the embryo that initiates uterine contact and, after transformation to become the trophoblast, uterine invasion. Similar to the kidney nephron, the trophectoderm is a transporting epithelium with distinct apical and basolateral membrane domains; its function is to facilitate transepithelial Na+ and fluid transport for blastocoel formation. That transport is driven by Na,K-adenosine triphosphatase (ATPase) localized in basolateral membranes of the trophectoderm. Preimplantation embryos express multiple alpha and beta subunit isoforms of Na,K-ATPase, potentially constituting multiple isozymes, but the basolaterally located alpha1beta1 isozyme appears to function uniquely to drive fluid transport. Embryos unable to express alpha1 subunits because of targeted deletion of the gene are able to form a blastocoel, but they fail to maintain their integrity and expire during the peri-implantation period. Preimplantation embryos also express the gamma subunit, a modulator of Na,K-ATPase activity, but targeted deletion of that gene did not reveal an essential developmental role. The preimplantation embryo offers a unique model for understanding the roles of Na,K-ATPase subunit isoforms in epithelial development and transepithelial transport.

Stage-specific formation of the equine blastocyst capsule is instrumental to hatching and to embryonic survival in vivo

Early embryonic development in the horse is characterized by the formation of an unusual acellular glycoprotein "capsule" between the trophectoderm and the overlying zona pellucida. This structure is first detected between days 6 and 7 after ovulation and completely envelops the spherical conceptus until as late as day 23 of gestation. In the present study, a micromanipulator was used to remove the capsule from 15 embryos on day 6-7 after ovulation. None of these denuded embryos developed into ultrasonographically detectable pregnancies after surgical transfer into recipient mares whereas four of six control embryos handled and transferred similarly but without capsule removal developed normally, thereby demonstrating clearly a role for the capsule in embryonic survival. In addition, observation of the embryonic investments after embryo collection and during micromanipulation led to the hypothesis that hatching of the horse embryo from its zona pellucida is assisted by the force of the expanding capsule, which causes the attenuating zona to literally burst open.

Transcriptome analysis in blastocyst hatching by cDNA microarray*

BACKGROUND

Hatching is an important process for early embryo development, differentiation and implantation. However, little is known about its regulatory mechanisms. By integrating the technologies of RNA amplification and cDNA microarrays, it has become possible to study the gene expression profile at this critical stage.

METHODS

Pre-hatched and hatched ICR mouse embryos (25 blastocysts in each group were used in the triplicate experiments) were collected for RNA extraction, amplification, and microarray analysis (the mouse cDNA microarray, 6144 genes, including expressed sequence tags).

RESULTS

According to cDNA microarray data, we have identified 85 genes that were expressed at a higher level in hatched blastocyst than in pre-hatched blastocysts. In this study, 47 hatching-related candidate genes were verified via re-sequencing. Some of these genes have been selected and confirmed by real-time quantitative RT-PCR. These hatching-specific genes were also expressed at a lower level in the delayed growth embryos (morula or blastocyst without hatching at day 6 post hCG). These genes included: cell adhesion and migration molecules [E-cadherin, neuronal cell adhesion molecule (NCAM), lectin, galactose binding, soluble 7 (Lgals7), vanin 3 and biglycan], epigenetic regulators (Dnmt1, and SIN3 yeast homolog A), stress response regulators (heme oxygenase 1) and immunoresponse regulators [interleukin (IL)-2-inducible T-cell kinase, IL-4R, interferon-gamma receptor 2, and neurotrophin]. The immunostaining of E-cadherin and NCAM showed strong and specific localization in hatched blastocyst.

CONCLUSIONS

This work provides important information for studying the mechanisms of blastocyst hatching and implantation. These hatching-specific genes may have potential as new drug targets for controlling fertility.

Mastin is a gelatinolytic mast cell peptidase resembling a mini-proteasome

Mastin is a tryptic peptidase secreted by canine mast cells. This work reveals that mastin is composed of catalytic domain singlets and disulfide-linked dimers. Monomers unite non-covalently to form tryptase-like tetramers, whereas dimers aggregate with monomers into larger clusters stabilized by hydrophobic contacts. Unlike tryptases, mastin resists inactivation by leech-derived tryptase inhibitor, indicating a smaller central cavity, as confirmed by structural models. Nonetheless, mastin is strongly gelatinolytic while not cleaving native collagen or casein, suggesting a preference for denatured proteins threaded into its central cavity. Phylogenetic analysis suggests that mammalian mastins shared more recent ancestors with soluble alpha/beta/delta tryptases than with membrane-anchored gamma-tryptases, and diverged more rapidly. We hypothesize that gelatinase activity and formation of inhibitor-resistant oligomers are ancestral characteristics shared by soluble tryptases and mastins, and that secreted mastin is a mini-proteasome-like complex that breaks down partially degraded proteins without causing bystander damage to intact, native proteins.

Embryotrophic factor-3 from human oviductal cells enhances proliferation, suppresses apoptosis and stimulates the expression of the β1 subunit of sodium–potassium ATPase in mouse embryos

BACKGROUND

Embrytrophic factor-3 (ETF-3) from human oviductal cells enhanced the development of mouse preimplantation embryos. This report studied the embryotrophic mechanisms of the molecule.

METHODS AND RESULTS

Mouse embryos were incubated with ETF-3 for 24 h at different stages of development. ETF-3 treatment between 96 and 120 h post-HCG increased the cell count of blastocysts, whilst treatment between 72 and 96 h post-HCG enhanced the expansion and hatching of the blastocysts. ETF-3 increased the cell number of the embryos by suppressing apoptosis and increasing proliferation as determined by TUNEL and bromodeoxyuridine uptake assays, respectively. Real-time quantitative PCR showed that the in vivo developed and ETF-3-treated blastocysts had a significantly higher mRNA copy number of Na/K-ATPase-beta1, but not of hepsin, than that of blastocysts cultured in medium alone. The former gene was associated with cavitation of blastocysts while the latter was related to hatching of blastocyst. The beneficial effect of ETF-3 on blastocyst hatching was also seen when ETF-3-supplemented commercially available sequential culture medium for human embryo culture was used to culture mouse embryos.

CONCLUSIONS

ETF-3 improves embryo development by enhancing proliferation, suppressing apoptosis and stimulating expression of genes related to blastocyst cavitation. Supplementating human embryo culture medium with ETF-3 may improve the success rate in clinical assisted reproduction.

Trophoblast-uterine interactions at implantation

Implantation of the embryo in the uterus is a critical and complex event and its failure is widely considered an impediment to improved success in assisted reproduction. Depending on whether placentation is invasive or superficial (epitheliochorial), the embryo may interact transiently or undergo a prolonged adhesive interaction with the uterine epithelium. Numerous candidate interactions have been identified, and there is good progress on identifying gene networks required for early placentation. However no molecular mechanisms for the epithelial phase are yet firmly established in any species. It is noteworthy that gene ablation in mice has so far failed to identify obligatory initial molecular events.

Identification and characterization of human and mouse ovastacin: a novel metalloproteinase similar to hatching enzymes from arthropods, birds, amphibians, and fish

We have cloned and characterized human and mouse ovary cDNAs encoding a new protein of the astacin family of metalloproteinases, called ovastacin because of its predominant expression in ovarian tissues. Human and mouse ovastacins exhibit the same domain organization as other astacins, including signal sequence, propeptide, and metalloproteinase domain. However, ovastacins show an additional C-terminal domain of about 150 amino acids with no similarity to other ancillary domains present in the equivalent region of most astacins. Northern blot analysis of human tissues and cell lines revealed that ovastacin is only detected at significant levels in leukemia and lymphoma cells of different origin. In addition, RT-PCR analysis demonstrated that ovastacin is expressed in human and mouse ovary, in unfertilized mouse oocytes, and in 1.5-day-postcoitum preimplantation embryos. Further studies showed that superovulation caused a dramatic increase in the expression of mouse ovastacin, indicating that the production of this enzyme is under hormonal regulation. Human ovastacin was expressed in Escherichia coli and the purified recombinant protein hydrolyzed synthetic substrates used for assaying metalloproteinases. These activities were abolished by inhibitors of metalloproteinases, but not by inhibitors of other classes of proteases. On the basis of these results, we suggest that ovastacin could play in mammals a physiological function similar to that performed by hatching proteases in evolutionary distant species from arthropods to fish.

Quantitative expression analysis of blastocyst-derived gene transcripts in preimplantation developmental stages of in vitro-produced bovine embryos using real-time polymerase chain reaction technology

The main objective of the present study was to analyse the quantitative expression pattern of genes from a subtracted blastocyst transcriptome throughout the preimplantation developmental stages of in vitro-produced bovine oocytes and embryos. For this purpose, Day 5 morula (M) cDNAs were subtracted from Day 7 blastocyst (B) cDNAs (B–M) and used to establish a B–M subtracted cDNA library, as reported previously. From the total generated clones, 19 were analysed quantitatively. The mRNA samples isolated from pools of immature oocytes (n = 150), mature oocytes (n = 150) and two-cell (n = 80), four-cell (n = 40), eight-cell (n = 20), morula (n = 6) and blastocyst (n = 3) embryos were reverse transcribed and subjected to real-time polymerase chain reaction (PCR) using sequence-specific primers and SYBR green as the DNA dye. A relative standard curve method was used to analyse the real-time data taking the morula stage as a calibrator. Applying suppression subtractive hybridisation (SSH), a total of 71 clones, which represent 33 different expressed sequence tags, were generated and available for analysis. Most transcripts were analysed for the first time in bovine embryogenesis. The real-time PCR has validated the results of SSH positively for 84% (16/19) of transcripts, whereas 16% (3/19) showed deviation in the expression pattern from the one seen during SSH. Several transcript-specific expression patterns were observed for genes that play decisive roles in bovine embryogenesis. In addition to identification, accurately quantifying the expression profiles of transcripts during development will pave the way towards understanding the molecular mechanisms of embryogenesis and their potential role in early embryo development. Most importantly, the present study has contributed to the enrichment of bovine embryo gene collection by generating new transcripts involved in bovine embryo development.

Origin of the murine implantation serine proteinase subfamily

The S1 serine protease family is one of the largest gene families known. Within this family there are several subfamilies that have been grouped together as a result of sequence comparisons and substrate identification. The grouping of related genes allows for the speculation of function for newly found members by comparison and for novel subfamilies by contrast. Analysis of the evolutionary patterns of genes indicates whether or not orthologs are likely to be identified in other species as well as potentially indicating that hypothesized orthologs are in fact not. Looking at subtle differences between subfamily members can reveal intricacies about function and expression. Previously, we have described genes encoding two novel serine proteinases, ISP1 and ISP2, which are most closely related to tryptases. The ISP1 gene encodes the embryo-derived enzyme strypsin, which is necessary for blastocyst hatching and invasion in vitro. Additionally both ISP1 and ISP2 are co-expressed in the endometrial gland during the time of hatching, suggesting that they may also both participate in zona lysis from within the uterine lumen. Here, we demonstrate that the ISPs are tandemly linked within the tryptase cluster on 17A3.3. We suggest that remarkable similarities within the 5'-untranslated and first intron regions of ISP1 and ISP2 may explain their intimate co-regulation in uterus. We also suggest that ISP genes have evolved through gene duplication and that the ISP1 gene has also begun to adopt an additional new function in the murine preimplantation embryo.

Uterine expression of implantation serine proteinase 2 during the implantation period and in vivo inhibitory effect of its antibody on embryo implantation in mice

The aim of the present study was to examine the uterine expression pattern of implantation serine proteinase 2 (ISP2) protein during early pregnancy in mice and the effects of anti-ISP2 antibody on embryo implantation. Expression of ISP2 protein was found to be specifically up-regulated in mouse uterine endometrial glands following the initiation of embryo implantation. Similarly, ISP2 protein expression was observed during pseudopregnancy, indicating that its expression is not embryo dependent. In other experiments, rabbit anti-ISP2 IgG was infused into the mouse uterine lumen on Day 3 or 4 of pregnancy to examine its effects on embryo implantation, whereas vehicle (saline) or unspecific rabbit IgG served as controls. The mean number of implanted embryos from anti-ISP2-IgG-treated mice was significantly lower than that from control mice. These results suggest that ISP2 may play an important role during embryo implantation.

Uterine secretion of ISP1 & 2 tryptases is regulated by progesterone and estrogen during pregnancy and the endometrial cycle

We have described two novel implantation serine proteinase (ISP) genes that are expressed during the implantation period. The ISP1 gene may encode the embryo-derived enzyme strypsin, which is necessary for blastocyst hatching in vitro and the initiation of invasion. The ISP2 gene, which encodes a related tryptase, is expressed in endometrial glands and is regulated by progesterone during the peri-implantation period. Based on similarities between ISP2 gene expression and that of a progesterone-regulated lumenal serine proteinase activity associated with lysis of the zona pellucida, we have suggested that the strypsin related protein, ISP2, may encode a zona lysin proteinase. Recently strypsin has also been found within uterine fluid, suggesting a second potential role in hatching. Consistently, we have discovered that ISP1 is also expressed in the uterine secretory gland at the time of hatching. In this study we demonstrate that both ISP1 and ISP2 are secreted together into the uterine lumen at peri-implantation, and that the appearance of ISP protein is regulated positively at the transcriptional level by progesterone and negatively at the posttranscriptional level by estrogen. This negative regulation by estrogen may be overridden in pregnancy as ISP protein expression is restored during oil-induced decidualization. ISP1 and ISP2 proteins are also expressed in proestrous suggesting additional roles in the endometrial cycle.

Mouse chromosome 17A3.3 contains 13 genes that encode functional tryptic-like serine proteases with distinct tissue and cell expression patterns

Probing of the mouse EST data base at GenBank trade mark with known tryptase cDNAs resulted in the identification of undiscovered serine protease transcripts whose genes reside at a 1.5-Mb complex on mouse chromosome 17A3.3. Mouse tryptase-5 (mT5), tryptase-6 (mT6), and mast cell protease-11 (mMCP-11) are new members of this serine protease superfamily whose amino acid sequences are 36-54% identical to each other and to their other 10 family members. The 13 functional mouse proteases can be subdivided into two subgroups based on conserved features in their propeptides. Of the three new serine proteases, mT6 is most widely expressed in tissues. mT5 is preferentially expressed in smooth muscle, whereas mMCP-11 is preferentially expressed in the spleen and bone marrow. In contrast to mT5 and mT6, mMCP-11 is also expressed in mast cells. Although mT6 and mMCP-11 are constitutively secreted when expressed in mammalian and insect cells, mT5 remains membrane-associated. The fact that recombinant mT5, mT6, and mMCP-11 possess non-identical expression patterns and substrate specificities suggests that each protease has a unique function in vivo. Of the 13 functional mouse tryptase genes identified at the complex, 12 have orthologs that reside in the syntenic region of human chromosome 16p13.3. The establishment of these ortholog pairs helps clarify the evolutionary relationship of the serine protease locus in the two species. This information provides a useful framework for the functional analysis of each protease using gene targeting and other molecular approaches.

Embryonic hatching enzyme strypsin/ISP1 is expressed with ISP2 in endometrial glands during implantation

Embryo hatching and outgrowth are the first critical steps on the way to a successful pregnancy. It is generally held that serine proteases are responsible for this process, although the exact mechanisms of action are not clearly understood. Recently, we described two novel implantation serine proteinase (ISP) genes that are expressed during the implantation period. The ISP1 gene encodes the embryo-derived enzyme strypsin, which is necessary for blastocyst hatching in vitro and the initiation of invasion. The ISP2 gene, which encodes a related tryptase, is expressed in endometrial glands and is regulated by progesterone during the peri-implantation period. Based on similarities between ISP2 gene expression and that of a progesterone-regulated lumenal serine proteinase activity associated with lysis of the zona pellucida, we have suggested that the strypsin related protein, ISP2, may encode a zona lysin proteinase. As tryptases naturally assemble to form tetrameric structures, we have hypothesized that ISP1 and ISP2 tetramerize to form strypsin and lysin, respectively. In this study, we demonstrate that like ISP2, the ISP1 gene is also expressed in endometrial glands and is positively regulated by progesterone during implantation. Using in situ hybridization of adjacent tissue sections, we show that the ISP1 and ISP2 genes are co-expressed within the endometrial gland. Following evidence that ISP1 and 2 can efficiently form homotetramers and heterotetramers in silico, we suggest that ISP heterotetramers may be also be secreted into the uterine lumen during the implantation period. That the embryonic hatching enzyme, may also be secreted into the uterine lumen from uterus, may provide insight into the mechanisms of hatching and implantation initiation.

Subtilisin proprotein convertase-6 expression in the mouse uterus during implantation and artificially induced decidualization

During implantation, a balance of factors regulates the invasive properties of the embryo and the anti-invasive properties of uterine decidua. Although antiproteinases such as the metalloproteinase inhibitor TIMP-3 are thought to play critical roles in preventing the overaggressive invasion of trophoblasts, the mechanism of antiproteinase regulation is unknown. Recently, the prohormone convertase SPC-6 has been found to be co-expressed in embryo-proximal decidua in association with TIMP-3. As members of this serine proteinase family are known to activate latent TGFbeta family members which regulate decidual TIMP-3 levels, we sought to characterize the expression of SPC-6 during pregnancy and artificial decidualization. In this study, we demonstrate that the zone of SPC-6 gene expression exhibits a great degree of temporal and spatial overlap with TIMP-3 gene expression in uterine decidua from E5.5 through to E8.5. Like TIMP-3, we demonstrate that SPC-6 expression is induced during the decidual cell response using an in vivo model of artificial decidualization. Both the secreted and membrane bound forms of SPC-6 are expressed throughout the period of decidualization, suggesting that SPC-6 may play multiple roles during this developmental period. This is confirmed by our observation of the movement of SPC-6 expression to the presumptive placental region, as TIMP-3 expression regresses at the implantation site.