Efficient production of immunodeficient non-obese diabetic/Shi-scid IL2rγnull mice via the superovulation technique using inhibin antiserum and gonadotropin.

Severe immunodeficient mice are an essential tool for the examination of the efficacy and safety of new therapeutic technologies as a humanized model. Previously, non-obese diabetic (NOD)/Shi-scid IL2rγnull (NOG) mice were established as immunodeficient mice by combining interleukin-2 receptor-γ chain-knockout mice and NOD/Shi-scid mice. The NOG mice are used frequently in the research of therapeutic monoclonal antibodies and regenerative medicine for human diseases. Establishment of an efficient production system of NOG mice, using optimized reproductive techniques, is required to accelerate research. In this study, we investigated the efficacy of the superovulation technique using equine chorionic gonadotropin (eCG) and inhibin antiserum (IAS) in NOG mice of various ages (4, 8, 12, 24, or 54 weeks). Additionally, we examined the fertilizing and developmental ability of the oocytes through in-vitro fertilization using frozen-thawed sperm, embryo culture and embryo transfer. The results showed that NOG mice produced the highest number of oocytes at 12 weeks old following the co-administration of eCG and IAS (collectively IASe) (70 oocytes/female). IASe was more effective in increasing the number of oocytes v. eCG at all ages. The IASe-derived oocytes demonstrated the ability to fertilize and develop into blastocysts and pups. Finally, we demonstrated that three strains of genetically modified NOG mice were efficiently produced through the optimized reproductive techniques. In summary, we developed an efficient system for the production of immunodeficient mice using 12-week-old, IASe-treated female NOG mice.

Equine chorionic gonadotropin.

Cells from the chorionic girdle of the equine trophoblast invade the maternal endometrium at day 36 of gestation and become established as secretory elements known as the endometrial cups. These structures, which persist for 40-60 days, produce a gonadotropin which can be found in circulation until about day 130 of gestation. This glycoprotein has been identified in the horse and the donkey, with the former having received much better characterization. It consists of 2 noncovalently linked peptide chains; an alpha-subunit of 96 amino acids, which is common to that found in other horse glycoprotein hormones. The beta-subunit of 149 amino acids is identical to horse LH beta. Horse CG is the most heavily glycosylated of the known pituitary and placental glycoprotein hormones. The alpha-subunit has two and the beta-subunit one N-linked glycosylation site, and the beta-chain has in excess of four O-linked glycosylation sites. The N-linked glycans have some oligosaccharides that are not found on other glycoprotein hormones. The sialic component of glycosylation confers an exceptionally long half-life on CG compared to other glycoprotein hormones. Horse CG has LH-like activity in horse receptor and in vitro bioassays. In spite of the amino acid homology, it has lower LH activity than does horse LH. Its most intriguing, and as yet unexplained, characteristic is its pronounced FSH and LH activity in species other than the horse. Horse CG binds to FSH receptors of virtually all mammalian species, other than the horse, in which it has been tested and will produce biological effects peculiar to FSH. It has similar and potent interaction with LH receptors. The structural basis of this duality is not known but may be related to the region 90-110 of the beta-chain. Horse CG is believed to be constitutively expressed by the trophoblastic cells until the endometrial cups degenerate. The role of CG in equine gestation is not completely understood. It is believed to act as an LH-like hormone to induce supplementary ovulation and/or luteinization of follicles in the mare. It has not been established whether CG or the accessory corpora lutea are necessary for successful horse pregnancy. They may serve as a redundant system to assure that there is sufficient secretion of the primary corpus luteum to maintain pregnancy until the placenta assumes its role as the principal steroidogenic organ of gestation.

Expression of an in vitro biologically active equine LH/CG without C-terminal peptide (CTP) and/or beta26-110 disulphide bridge.

The C-terminal region of the beta subunit of the human chorionic gonadotrophin (hCG) is implied in heterodimer stability (beta26-110 disulphide bridge), in vitro LH bioactivity (region beta102-110) and in in vivo LH bioactivity (beta CTP). Like the hCG beta, the equine eLH and eCG beta subunits, also possess a C-terminal extension (CTP). But, in contrast to hCG, eLH and eCG bind to both LH and FSH receptors in species other than the horse. This allows investigation of the roles of the beta subunit C-terminal region of a eLH/CG recombinant molecule on both LH and FSH activities. To do so, the CTP was deleted and/or the beta26-110 disulphide bond was mutated and the resulting mutated beta subunits were transiently co-expressed with common alpha subunit in COS7 cells. These regions were also deleted in a betaalphaeLH/CG single chain also expressed in COS7 cells. The hormones produced were characterized by different ELISAs and in vitro LH and FSH bioassays. Mutation of the 26-110 disulphide bond and deletion of the betaCTP led to a decrease in eLH/CG heterodimer production. Double mutation promoted an additive effect on production of the heterodimer and of the corresponding tethered eLH/CG. The elimination of the beta26-110 disulphide bond in the betaalpha single chain had no effect on its production. However, neither the 26-110 disulphide bond nor the CTP mutations affected dimer stability and bioactivities of the secreted heterodimers and/or single chain molecules. Therefore, in contrast to hCG, the 26-110 S-S bond of the recombinant eLH/CG beta subunit does not seem to be essential for eLH/CG dimer stability upon secretion and expressing LH and FSH bioactivities.

Structure-function relationships and mechanism of action of pituitary and placental gonadotrophins.

Data from the author's laboratory on relationships between structure and function of equine luteinizing hormone, follicle-stimulating hormone and choriogonadotrophin as well as their mechanisms of action are reviewed and compared with their human counterparts. Polymorphism of these hormones and problems associated with their purification are discussed as well as the association and dissociation of their alpha- and beta-subunits. The affinity of receptor binding, the superactivity of membrane transduction and homologous desensitization of target cells by non-stimulatory doses of the gonadotrophins are also reviewed.

Gonadotropin preparations: past, present, and future perspectives.

This Educational Bulletin offers past, present and future perspectives on gonadotropin preparations.

Involvement of equine chorionic gonadotropin (eCG) carbohydrate side chains in its bioactivity; lessons from recombinant hormone expressed in insect cells.

Natural eCG consists of as much as 45% carbohydrate side chains. The present paper deals with the analysis of the roles of the N- and O-linked saccharides of this hormone in the different steps of its activity and its possible replacement by recombinant eCG expressed in baculovirus-insect cell systems.

The equine placenta and equine chorionic gonadotrophin--an overview.

Chorionic gonadotrophins seem to be unique for primate and equid species. Unlike primates, the equine conceptus does not implant in the maternal uterine endometrium until around day 37 of pregnancy. At this time specialized cells of the trophoblast, organized in the embryonic girdle, invade the endometrium and become established in the endometrial stroma, forming the so-called endometrial cups. This migration of girdle cells is accompanied by their morphological transformation into large decidual-like cells and by the appearance of a gonadotrophic hormone in the mare's blood. There is convincing evidence today that the hormone is of chorionic origin; therefore the term equine Chorionic Gonadotrophin (eCG) seems to be more appropriate than the formerly used term Pregnant Mare Serum Gonadotrophin (PMSG). Secretion of eCG peaks between days 60 and 80 in pregnant mares, to decline gradually until day 130 of gestation, with pronounced inter-individual variation. There appear to be no hormonal regulatory mechanisms controlling eCG synthesis and secretion, suggesting that the size and the morphology of the endometrial cups are the limiting factors. Equine CG is a glycoprotein hormone, composed of noncovalently bound alpha- and beta-subunits. The alpha-subunit consists of 96 amino acids and is identical for eCG and the pituitary hormones eLH, eFSH, and eTSH. The beta-subunit is similar to beta-hCG in that both have a C-terminal extension. It is comprised of 149 amino acids and the peptide primary structure is identical to that of beta-eLH.(ABSTRACT TRUNCATED AT 250 WORDS)

[Production of recombinant eCG with potent FSH-like activity by site-directed mutagenesis].

Equine chorionic gonadotropin (eCG) and luteinizing hormone (eLH) are encoded by a single gene and have identical peptide portions. They, however, differ in the structures of their attached oligosaccharides, which depend on the sites of their production. Recombinant eCG/LH (rec-eCG/LH) possesses dual LH and FSH activities. Mutant eCG/LH in which Asn 56 of the alpha-subunit was changed to Gln to remove the N-linked oligosaccharide showed complete loss of LH activity, whereas in contrast its FSH activity was more potent than that of the wild-type. Another mutant, which lacked the carboxyterminal portion of the beta-subunit to which O-linked oligosaccharides are attached, showed LH activity similar to that of the wild-type, whereas it had the most potent FSH activity. Thus, the oligosaccharides attached to eCG/LH play differential roles in the expression of biological activity.

A novel uterine protein that associates with the embryonic capsule in equids.

An apparently unique protein produced in large quantities by the endometrium of the mare which adheres to, or is incorporated into, the acellular capsule that surrounds the equine conceptus in early pregnancy, has been characterized and partially sequenced. It has a molecular mass of approximately 18 kDa on SDS-PAGE gels and is nonglycosylated as assessed by a sensitive carbohydrate detection kit. Comparison of its first 24 amino-terminal amino acids with all entries in the databases failed to show any significant identity with any other protein sequence. Secretion of the protein appears to be progesterone dependent, as its presence in uterine flushings correlates with peripheral serum progesterone profiles during the oestrous cycle and its secretion can be induced in anoestrous mares by administration of a synthetic progestagen. However, in pregnant mares, the protein disappears from the uterus after about day 20 (term = 320-340 days), despite the persistence of high serum concentrations of progesterone, indicating that additional mechanisms control its synthesis and secretion. The strong association of the protein with the glycoprotein capsule that surrounds the equine blastocyst suggests that it may be incorporated into the capsule as the capsule expands from day 11 after ovulation. Alternatively, or additionally, it may be involved in the transport of nutrients or other substances through the capsule, and may therefore play an important role in the maintenance of pregnancy.

Carbohydrate analysis of glycoprotein hormones.

Complete carbohydrate composition analysis of glycoprotein hormones, their subunits, and oligosaccharides isolated from individual glycosylation sites can be accomplished using high-pH anion-exchange chromatography combined with pulsed amperometric detection. Neutral and amino sugars are analyzed from the same hydrolyzate by isocratic chromatography on a Dionex CarboPAC PA1 column in 16 mM NaOH. Sialic acid is quantified following mild hydrolysis conditions on the same column in 150 mM sodium acetate in 150 mM NaOH. Ion chromatography on a Dionex AS4A column in 1.8 mM Na(2)CO(3)/1.7 mM NaHCO(3); postcolumn, in-line anion micromembrane suppression; and conductivity detection can be used to quantify sulfate, a common component of pituitary glycoprotein hormone oligosaccharides. Mass spectrometric analysis before and after elimination of oligosaccharides from a single glycosylation site can provide an estimate of the average oligosaccharide mass, which facilitates interpretation of oligosaccharide composition data. Following release by peptide N-glycanase (PNGase) digestion and purification by ultrafiltration, oligosaccharides can be characterized by a high-resolution oligosaccharide mapping technique using the same equipment employed for composition analysis. Oligosaccharide mapping can be applied to the entire hormone, individual subunits, or individual glycosylation sites by varying PNGase digestion conditions or substrates. Oligosaccharide release by PNGase is readily monitored by SDS-PAGE. Site-specific deglycosylation can be confirmed by amino acid sequence analysis. For routine isolation of oligosaccharides, addition of 2-aminobenzamide at the reducing terminus facilitates detection; however, the oligosaccharide retention times are altered. Composition analysis is also affected as the 2-aminobenzamide-modified GlcNAc peak overlaps the fucose peak.

Differential effects of alpha subunit Asparagine56 oligosaccharide structure on equine lutropin and follitropin hybrid conformation and receptor-binding activity.

The gonadotropins, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and chorionic gonadotropin (CG), are cysteine-knot growth-factor superfamily glycoproteins composed of a common alpha subunit noncovalently associated with a hormone-specific beta subunit. The cysteine-knot motifs in both subunits create two hairpin loops, designated L1 and L3, on one side of the knot, with the intervening long loop, L2, on the opposite side. As the average alpha-subunit loop 2 oligosaccharide mass increased from 1482 to 2327, LH and FSH receptor-binding affinities of the dual-specificity eLH declined significantly, while the decrease in FSH receptor-binding affinity for eFSH was not significant. In the present study, we characterized hormone-specific glycosylation of alphaL2 oligosaccharides in eLHalpha, eFSHalpha, and eCGalpha preparations. MALDI mass spectrometry revealed 28-57 structures, including high mannose, hybrid, bi-, and triantennary oligosaccharides. The same intact subunit preparations and their alphaL2 loop-deglycosylated derivatives were combined with either eLHbeta or eFSHbeta, and the circular dichroism (CD) spectrum for each preparation was determined. We predicted that hybrid hormone preparations obtained by combining intact eLHalpha, eFSHalpha, and eCGalpha preparations with eLHbeta might exhibit differences in conformation that would disappear when the alphaL2 oligosaccharide attached to alphaAsn(56) was removed by selective peptide-N-glycanase digestion (N(56)dg-alpha). CD data supported the first prediction; however, elimination of alphaL2 oligosaccharide actually increased the conformational differences. The intact alpha subunit:eFSHbeta hybrids had virtually identical CD spectra, as expected. However, the N(56)dg-alpha:eFSHbeta hybrid spectra differed from each other. Oligosaccharide removal altered the conformation of most hybrids, suggesting that alphaAsn(82) oligosaccharide (located in alphaL3) also influenced gonadotropin conformation.