Frequency of gray coat color in native Chinese horse breeds.

Gray horses are born colored, and they then gradually lose their hair pigmentation. Tremendous progress has been made in identifying the genes responsible for graying with age in horses in recent years. Results show that gray coat color in horses is caused by a 4.6-kb duplication in intron 6 of the syntaxin 17 gene (STX17), which constitutes a cis-acting-regulatory mutation. However, little is known about the gray phenotype in native Chinese horses. This study was conducted to explore the frequency distribution of the gray mutation in native Chinese horse breeds. A total of 489 samples from 14 native Chinese horse breeds were genotyped for the STX17 duplication using a simplified conventional PCR-based method. The results show that the gray mutation was present in 12 native Chinese horse breeds, except the Balikun and Guanzhong breeds. The Chakouyi and Hequ breeds had the highest frequency of the gray mutation (P(G) = 0.367 and P(G) = 0.274, respectively). There was no significant geographical difference in the distribution of gray coat color across native Chinese horse breeds. Our results suggest that gray is a common coat color in Chinese horses.

Localization of dystrophin relative to acetylcholine receptor domains in electric tissue and adult and cultured skeletal muscle.

Two high-affinity mAbs were prepared against Torpedo dystrophin, an electric organ protein that is closely similar to human dystrophin, the gene product of the Duchenne muscular dystrophy locus. The antibodies were used to localize dystrophin relative to acetylcholine receptors (AChR) in electric organ and in skeletal muscle, and to show identity between Torpedo dystrophin and the previously described 270/300-kD Torpedo postsynaptic protein. Dystrophin was found in both AChR-rich and AChR-poor regions of the innervated face of the electroplaque. Immunogold experiments showed that AChR and dystrophin were closely intermingled in the AChR domains. In contrast, dystrophin appeared to be absent from many or all AChR-rich domains of the rat neuromuscular junction and of AChR clusters in cultured muscle (Xenopus laevis). It was present, however, in the immediately surrounding membrane (deep regions of the junctional folds, membrane domains interdigitating with and surrounding AChR domains within clusters). These results suggest that dystrophin may have a role in organization of AChR in electric tissue. Dystrophin is not, however, an obligatory component of AChR domains in muscle and, at the neuromuscular junction, its roles may be more related to organization of the junctional folds.

Molecular cloning, expression analysis, and function of decorin in goat ovarian granulosa cells.

Decorin (DCN), a component of the extracellular matrix (ECM), participates in ECM assembly and influences cell proliferation and apoptosis in many mammalian tissues and cells. However, expression and function of DCN in the ovary remain unclear. This study cloned the full-length cDNA of goat DCN obtained from the ovary of an adult goat. Sequence analysis revealed that the putative DCN protein shared a highly conserved amino acid sequence with known mammalian homologs. The tissue distribution of DCN mRNA expression was evaluated by real-time PCR, and the results showed that DCN was widely expressed in the tissues of adult goat. Immunohistochemistry results suggested that DCN protein existed in the granulosa cells and oocytes from all types of follicles and theca cells of antral follicles. Moreover, hCG-induced DCN mRNA expression was significantly reduced by the inhibitors of protein kinase A, PI3K, or p38 kinase (P < 0.05), which are key mediators involved in hCG-induced DCN expression. Overexpression of DCN significantly increased apoptosis and blocked cell cycle progression in cultured granulosa cells (P < 0.05). Western blot analysis also showed that overexpression of DCN upregulated the expression levels of p21 protein (P < 0.05), whereas no effects were observed on the expression of Bax and Bcl-2 and on Bcl-2/Bax ratio (P > 0.05). These findings suggested that DCN regulates the apoptosis and cell cycle of granulosa cells.

MicroRNA-10b suppresses goat granulosa cell proliferation by targeting brain-derived neurotropic factor.

Brain-derived neurotropic factor (BDNF) and its high-affinity receptor, tyrosine kinase receptor B, have been assumed to be involved in female reproduction and have recently shown to play an essential role in follicle activation and oocyte maturation. In this study, we analyzed the expression of miR-10b and BDNF in the ovary and discovered that the expression of miR-10b was higher in monotocous goat ovaries than in polytocous goat ovaries, whereas the expression pattern of BDNF in ovary was opposite. Moreover, human chorionic gonadotropin induced rapid and transient expression of BDNF messenger RNA and protein. In contrast, human chorionic gonadotropin upregulated miR-10b expression in a time-dependent manner. The BDNF gene was identified as a direct target of miR-10b using a dual-luciferase reporter assay. Transfection of granulosa cells with miR-10b decreased BDNF messenger RNA and protein levels. MiR-10b overexpression inhibited cell proliferation, whereas BDNF promoted cell proliferation. However, a combined treatment with miR-10b and BDNF promoted cell proliferation, indicating that the reintroduction of BDNF reversed the suppressive effect of miR-10b. These results demonstrate that miR-10b downregulates BDNF expression in granulosa cells by directly targeting the 3' untranslated regions and plays an important role in inhibiting granulosa cell proliferation by targeting BDNF.

Immunohistochemical localization of bovine placental retinol-binding protein.

An immunogold staining method was used in combination with epipolarization microscopic detection to demonstrate the presence of bovine placental retinol-binding protein in bovine extraembryonic membranes. Amnion, chorion and allantois were fixed in Bouin fixation fluid and embedded in polyethylene glycol 1500. Sections (5 mm) were cut and transferred onto Digene silanated slides and immunostained using rabbit antiserum raised against bovine placental retinol-binding protein followed by goat anti-rabbit IgG labeled with 1 nm gold. Gold particles after silver enhancement were viewed and photographed under epipolarization microscopy. Epithelial cells of all three membranes (i.e. amniotic ectoderm, chorionic trophectoderm, and allantoic endoderm) were immunoreactive, while mesodermal cells, collagen, and blood cells were not. These data, together with our previous observation that these three placental membranes synthesize and secrete retinol-binding protein, indicate that epithelial cells lining the amnion, chorion and allantois are the major sources of this protein. The presence of retinol-binding protein in placental membranes and their fluids may be indicative of an important role for retinol in placental differentiation and development.

Molecular characterization and hormonal regulation of tissue inhibitor of metalloproteinase 1 in goat ovarian granulosa cells.

Tissue inhibitor of metalloproteinase 1 (TIMP1) belongs to a group of endogenous inhibitors that control the activity of matrix metalloproteinases and other metalloproteinases. TIMP1 is ubiquitously expressed and implicated in many physiological and pathologic processes. In this study, the full-length complementary DNA of goat (Capra hircus) Timp1 was cloned from adult goat ovary for the first time to better understand the regulatory role of TIMP1. The putative TIMP1 protein shared a high amino acid sequence identity with other species. Real-time polymerase chain reaction results showed that Timp1 was widely expressed in adult goat tissues, and messenger RNA expression was higher in the ovary than in other tissues; meanwhile, increasing expression of Timp1 was also discovered during the process of follicle growth and corpus luteum. We then investigated Timp1 expression patterns in different types of ovarian follicular cells from goats. In small or large antral follicles, Timp1 expression was higher (P < 0.05) in theca cells than in granulosa cells, cumulus cells, and oocytes. Increasing expression of Timp1 in theca and granulosa cells was observed as the variation of the follicle size. Immunohistochemical analyses further revealed the presence of the TIMP1 proteins in follicles at all antral stages of development. The most intense staining for TIMP1 was observed in the theca cells and granulosa cells of large antral follicles and corpus luteum. Timp1 was highly (P < 0.05) induced in granulosa cells in vitro after treatment with the luteinizing hormone agonist, human chorionic gonadotropin. Treatments with forskolin, phorbol 12-myristate 13-acetate, or phorbol 12-myristate 13-acetate + forskolin could also stimulate Timp1 messenger RNA expression. The effects of human chorionic gonadotropin were reduced (P < 0.05) by the inhibitors of protein kinase A, protein kinase C, MAPK kinase, or p38 kinase, indicating that Timp1 expression could be adjusted by luteinizing hormone-initiated activation of these signaling mediators. Our results suggested that TIMP1 may be involved in regulating ovarian follicle development and ovulation.

Preparation of colloidal gold-labeled agarose-gelatin microspherules for electron microscopic studies of phagocytosis in cultured cells.

Agarose-gelatin microspherules about 0.5 micron or larger are prepared with emulsification of 4% agarose-gelatin sol containing 0.2 M N-octylglucoside in an organic phase composed of cyclohexane, egg lecithin, Span 80, and ethanol, followed by extraction of lipophilic components with cyclohexane and ether. Colloidal gold particles are then introduced into microspherules using gold chloride reacting at room temperature with tannic acid in a specified concentration range. After they have been coated with bovine serum albumin or mouse IgG, colloidal gold-labeled microspherules can be readily phagocytized by mouse L-cells and P388 cells after incubation for several hours. In addition to their use as a novel marker for phagocytosis, we discuss other potential uses for these colloidal gold-labeled microspherules.

A new method for transfer of polyethylene glycol-embedded tissue sections to silanated slides for immunocytochemistry.

Polyethylene glycol (PEG) is an excellent embedding medium for immunohistochemical studies. It provides structural preservation superior to frozen sections and increased sensitivity of antigen detection compared with paraffin sections. One limitation of PEG embedment is that PEG sections are difficult to handle and adhere poorly to glass slides. Here we present a simple and effective method for embedding tissues in PEG and transferring the resultant sections onto silanated glass slides. In addition, a method for silver enhanced colloidal gold immunostaining was combined with common dye staining to demonstrate the excellent structure preservation and sensitive antigen detection. Bovine chorionic membrane was fixed with Bouin's fixative, embedded in polyethylene glycol (PEG) 1500, cut into 5-microns sections, flattened over agarose blocks (10 x 10 x 2 mm3), and blotted onto Digene silanated slides. Slides were then washed in PBS, which removed the PEG and agarose blocks. Tissue sections were immunocytochemically stained with dilute antiserum raised in a rabbit against purified bovine placental retinol binding protein (bpRBP). Sections were washed and incubated with 1-nm colloidal gold-labeled goat anti-rabbit IgG. The immunogold particles were enhanced by silver staining (IGSS). Specimens were observed and photographed with an Olympus epipolarization microscope. The new method offered excellent morphological preservation of cell structure and the epipolarization microscopy provided high sensitivity for detection of specific immunogold-silver particles.

Phagocytosis of protein coated colloidal-gold-agarose-gelatin microbeads by cultured uterine glandular epithelial and stromal cells.

A procedure for fixing and immunostaining whole cells from primary cultures of ovine and bovine uterine gland fragments was used to identify keratin in intermediate filaments of epithelial cells to distinguish them from stromal cells. Colloidal gold encapsulated agarose-gelatin microbeads were coated with different proteins and used to investigate uptake by epithelial and stromal cells in culture. Microbeads were taken up by stromal cells and by epithelial cells on the outskirts of colonies. These cells formed ridges where they contacted and grew above stromal cells. Electron microscopy demonstrated that the microbeads had been internalized and appeared to be nontoxic. Individual cells could harbor more than 90 microbeads within their cytoplasm for at least seven to ten days with no apparent harm. Some cells with microbeads were seen to divide.

Development of acetylcholinesterase induced by basic polypeptide-coated latex beads in cultured Xenopus muscle cells.

The formation of acetylcholine receptor (AChR) clusters can be induced by basic polypeptide-coated latex beads in cultured Xenopus muscle cells. Here we investigated the development of acetylcholinesterase (AChE) at the bead-induced AChR clusters. AChE activity began to appear at the clusters after 1 day of bead-muscle coculture and was present at all of the bead-induced clusters within 4-7 days. Electron microscopy revealed that AChE reaction products were discretely localized within the cleft and the membrane invaginations at the bead-muscle contacts. Thus, the beads can mimic the nerve in inducing a local accumulation of both the AChRs and AChE, suggesting that the development of both specializations can be effected by a common stimulus.

Purification and immunolocalization of ovine placental retinol-binding protein.

A retinol-binding protein (RBP), synthesized and secreted by ovine allantois in vitro, was purified from culture medium. The protein consisted of three isoelectric variants (pI 5.3-6.1) of identical molecular masses of about 23,000 Da as determined by two-dimensional PAGE under reducing conditions. Thirty-one of the first 34 N-terminal amino acids of the purified protein were sequenced and shown to have complete homology with bovine placental and bovine plasma RBP. The ultraviolet absorption spectrum and fluorescence excitation and emission spectra of the purified ovine placental RBP indicated the presence of bound retinol. Metabolic labeling studies demonstrated that the protein was synthesized by placental membranes. Using antiserum to bovine placental RBP, ovine placental RBP was immunolocalized in trophectoderm of 13-day-old blastocysts and trophectodermal cells of the chorion, endodermal cells lining the allantois, and ectodermal cells lining the amnion of 23-, 45-, and 53-day-old conceptuses. Results from this study suggest that ovine placental membrane epithelia synthesize and secrete RBP. Transport, storage, and metabolism of retinol mediated by placental RBP may be essential for normal embryonic development during pregnancy.