α6 And α3 integrins arerequired for proper limb apical ectodermal ridge development in mice (original) (raw)
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Anatomy and Embryology, 2001
Growth hormone (GH) may act as a local growth factor in early embryonic development, since GH-and GH-receptor (GHR) immunoreactivity is present in all tissues and most cells of embryonic chicks during organogenesis. However, as GHR-immunoreactivity could, alternatively, reflect the presence of GH-binding proteins (GHBPs) rather than authentic receptors linked to signal transduction mechanisms, GHR immunoreactivity may not be indicative of GH target sites. The possibility that GH may act as an autocrine or paracrine factor during embryogenesis was therefore assessed in the present study by determining the presence and cellular localization of mRNA for a GH-responsive gene. The mechanism of GH action involves the induction of a number of specific GH-response genes. In chickens a novel GH-responsive gene (GHRG-1) has been identified as a marker of GH action. In situ hybridization, using a 860 bp probe for GHRG-1 mRNA, demonstrated widespread expression of the GHRG-1 gene in embryonic tissues known to contain GH-and GHR-immunoreactivity (e.g. in the spinal cord, skin, heart, liver, muscle, bone and lung). GHRG-1 mRNA was not, however, present in all cells of each tissue. It was, furthermore, not present in subepithelial cells of the esophagus and bronchus and was lacking in many spinal cord ependyma, which are also known to lack GH immunoreactivity. These results therefore support the possibility that GH acts as an autocrine/paracrine factor during early chick embryogenesis, which was hitherto thought to be a "growth-without-GH" syndrome.
Proceedings of The National Academy of Sciences, 1997
The results of this study challenge the widely held view that growth hormone (GH) acts only during the postnatal period. RNA phenotyping shows transcripts for the GH receptor and GH-binding protein in mouse preimplantation embryos of all stages from fertilized eggs (day 1) to blastocysts (day 4). An antibody specific to the cytoplasmic region of the GH receptor revealed receptor protein expression, first in two-cell embryos, the stage of activation of the embryonic genome (day 2), and in all subsequent stages. In cleavage-stage embryos this immunoreactivity was localized mainly to the nucleus, but clear evidence of membrane labeling was apparent in blastocysts. GH receptor immunoreactivity was also observed in cumulus cells associated with unfertilized oocytes but not in the unfertilized oocytes. The blastocyst receptor was demonstrated to be functional, exhibiting the classic bell-shaped dose-response curves for GH stimulation of both 3-O-methyl glucose transport and protein synthesis. Maximal stimulation of 40-50% was seen for both responses at less than 1 ng͞ml recombinant GH, suggesting a role for maternal GH. However mRNA transcripts for GH were also detected from the morula stage (day 3) by using reverse transcription-PCR, and GH immunoreactivity was seen in blastocysts. These observations raise the possibility of a paracrine͞autocrine GH loop regulating embryonic development in its earliest stages.
Journal of Clinical Investigation, 1989
The human growth hormone-variant (hGH-V) gene is one of five highly similar growth hormone-related genes clustered on the short arm of chromosome 17. Although the pattern of expression of the adjacent normal growth hormone (hGH-N) and chorionic somatomammotropin (hCS) genes in this cluster are well characterized, the expression of the hGH-V gene remains to be defined. In previous studies, we have demonstrated that the hGH-V gene is transcribed in the term placenta and expressed as two alternatively spliced mRNAs: one is predicted to encode a 22-kD hormone (hGH-V), the other retains intron 4 in its sequence resulting in the predicted synthesis of a novel 26-kD hGH-V-related protein (hGH-V2). In the present report, we document the expression of both of these hGH-V mRNA species in the villi of the term placenta, demonstrate an increase in their concentrations during gestation, and directly sublocalize hGH-V gene expression to the syncytiotrophoblastic epithelium of the term placenta by in situ cDNA-mRNA histohybridization. The demonstrated similarity in the developmental and tissue-specific expression of the hGH-V gene with that of the related hCS gene suggests that these two genes may share common regulatory elements.
Pediatric Research, 1992
Tissue responsiveness to growth hormone is likely to be regulated by local concentrations and availability of the membrane-bound growth hormone receptor (GHR) and perhaps by the actions of the soluble growth hormone binding protein (GHBP). To determine whether the developmental regulation of the GHR and GHBP might vary among tissues, we have measured the relative abundance of the 4.3-kb GHR and 1.3-kb GHBP mRNA in rat fetal and postnatal liver, kidney, lung, and ileum by Northern hybridization of polyadenylated RNA with a 32P-labeled antisense riboprobe prepared from a rat GHR cDNA. The GHR and GHBP mRNA were both present in the four tissues studied at fetal age 19 d (E19). In postnatal liver, both transcripts increased in abundance 3to 4-fold after 14 d to mature levels at 42 d ( p = 0.0001). Similar changes were seen in postnatal kidney for GHR mRNA abundance; however, GHBP mRNA abundance increased only 2-to 3-fold to mature levels by 28 d (kidney GHR versus GHBP mRNA profile, p = 0.0001). In lung, a 2fold linear increase in GHR mRNA abundance was observed (p = 0.0019), but the GHBP mRNA did not change (GHR versus GHBP mRNA profile, p = 0.0006). Both transcripts decreased in abundance by 2-to 3-fold from E l 9 to 42 d in ileum (p < 0.05). The abundance of both transcripts was three to 10 times greater in 60-d liver than in the other three tissues at 60 d. The variation in abundance and in the developmental profiles of the GHR and GHBP mRNA observed in these fetal and postnatal tissues suggests that the GHR and GHBP could mediate differences within and between tissues in the responsiveness to growth hormone. The differential regulation of the two transcripts evident in kidney and lung supports the emerging evidence that the GHBP may have a function distinct from that of the GHR. (Pediatr Res 31: 335-339, 1992) Abbreviations GH, growth hormone GHR, growth hormone receptor GHBP, growth hormone binding protein poly A+, polyadenylated RNA
Growth hormone as an early embryonic growth and differentiation factor
Anatomy and Embryology, 2004
In this review we consider the evidence that growth hormone (GH) acts in the embryo as a local growth, differentiation, and cell survival factor. Because both GH and its receptors are present in the early embryo before the functional differentiation of pituitary somatotrophs and before the establishment of a functioning circulatory system, the conditions are such that GH may be a member of the large battery of autocrine/paracrine growth factors that control embryonic development. It has been clearly established that GH is able to exert direct effects, independent of insulin-like growth factor-I (IGF-I), on the differentiation, proliferation, and survival of cells in a wide variety of tissues in the embryo, fetus, and adult. The signaling pathways behind these effects of GH are now beginning to be determined, establishing early extrapituitary GH as a bona fide developmental growth factor.
Biology of Reproduction, 1998
By reverse transcription-polymerase chain reaction, the transcript of the growth hormone receptor (GHR) was demonstrated in oocytes, follicular cells, and corpus luteum of the bovine ovary. Immunoblotting using the monoclonal antibody mAb 263 resulted in a distinct protein band at 120 kDa, confirming that translation of the mRNA takes place in the same cells. Nonradioactive in situ hybridization revealed that distribution of the mRNA encoding GHR was correlated with the developmental stage of the follicle. Whereas in primordial and primary follicles the oocyte showed distinct amounts of the transcript encoding GHR, in tertiary follicles the mRNA was predominantly localized in the cells of the cumulus oophorus. GHR mRNA was also expressed in the large granulosa lutein cells, in the germinal epithelium, and in the endothelial cells of ovarian vessels. Colocalization of the GHR protein showed a distribution pattern identical to that of the mRNA. In calves, oocyte and follicle cells changed GHR expression in the same way as in the adult ovary. During embryonic development of the ovary, distinct amounts of the mRNA encoding GHR were found in primordial follicles shortly before birth. Our results imply that the GHR is involved in ovarian ontogenesis, especially in early folliculogenesis.
Growth Hormone (GH)/GH Receptor Expression and GH-Mediated Effects During Early Bovine Embryogenesis
Biology of Reproduction, 2001
Pituitary growth hormone (GH) stimulates postnatal growth and metabolism. The role of GH and its receptor (GHR) during prenatal development, however, is still controversial. As shown by reverse transcription polymerase chain reaction (RT-PCR), bovine in vitro fertilization embryos synthesized the transcript of GHR from Day 2 of embryonic life onwards. Real time RT-PCR revealed that synthesis of GHR mRNA was increased 5.9-fold in 6-day-old embryos compared with 2-day-old embryos. Using in situ hybridization, the mRNA encoding GHR was predominantly localized to the inner cell mass of blastocysts. The GHR protein was first visualized 3 days after fertilization. GH-specific transcripts were first detected in embryos on Day 8 of in vitro culture. As shown by transmission electron microscopy, GH treatment resulted in elimination of glycogen storage in 6-to 8-dayold embryos and an increase in exocytosis of lipid vesicles. These results suggest that a functional GHR able to modulate carbohydrate and lipid metabolism is synthesized during preimplantation development of the bovine embryo and that this GHR may be subject to activation by embryonic GH after Day 8. conceptus, developmental biology, early development, growth hormone, IVF/ART 1 This work was supported by the Bundesminister fü r Bildung und Forschung, Bonn, Germany, as a part of a larger concerted project ''Fertilitätsstö rungen'' (01 KY 9103) and partly by the Deutsche Forschungsgemeinschaft (WO 685/2-1, WO 685/3-1).
Expression, Translation, and Localization of a Novel, Small Growth Hormone Variant
Endocrinology, 2007
A novel transcript of the GH gene has been identified in ocular tissues of chick embryos. It is, however, unknown whether this transcript (small chicken GH, scGH) is translated. This possibility was therefore assessed. The expression of scGH mRNA was confirmed by RT-PCR, using primers that amplified a 426-bp cDNA of its coding sequence. This cDNA was inserted into an expression plasmid to transfect HEK 293 cells, and its translation was shown by specific scGH immunoreactivity in extracts of these cells. This immunoreactivity was directed against the unique N terminus of scGH and was associated with a protein of 16 kDa, comparable with its predicted size. Most of the immunoreactivity detected was, however, associated with a 31-kDa moiety, suggesting scGH is normally dimerized. Neither protein was, however, present in media of the transfected HEK cells, consistent with scGH's lack of a signal sequence. Similar moieties of 16 and 31 kDa were also found in proteins extracted from ocular tissues (neural retina, pigmented epithelium, lens, cornea, choroid) of embryos, although they were not consistently present in vitreous humor. Specific scGH immunoreactivity was also detected in these tissues by immunocytochemistry but not in axons in the optic fiber layer or the optic nerve head, which were immunoreactive for full-length GH. In summary, we have established that scGH expression and translation occurs in ocular tissues of chick embryos, in which its localization in the neural retina and the optic nerve head is distinct from that of the full-length protein.
Metabolism, 1997
Adipose tissue is a growth hormone (GH)-responsive tissue in which GH regulates energy metabolism. GH exerts its effect by interacting with its specific GH receptor (GHR). In rodents, alternative splicing of the nascent transcript from the GHR gene produces two major transcripts: GHR mRNA and GHR binding protein (GHBP) mRNA. These two transcripts share the common extracellular ligand-binding domain, but differ in the C-terminal sequence. Since GHR plays an important role in mediating the actions of GH in adipose metabolism, we initiated these studies to examine GHR gene expression in the course of mouse 3T3-L1 preadipocyte-adipocyte conversion. GHR and GHBP transcripts were detected by RNase protection assay (RPA) using the antisense riboprobes complementary either to the specific sequence of the GHR Or to the sequence shared by both GHR and GHBP mRNAs. After stimulation of differentiation, mRNA abundance increased 28-fold and reached a maximal level by day 7 of adipogenesis. The GHR mRNA:GHBP mRNA ratio was 1.1 +--0.12 and remained unchanged during differentiation. The decay rate for both mRNAs, estimated by treating the cells with actinomycin D, was approximately 24 hours and showed no significant difference between preadipocytes and adipocytes. Thus, GHR gene expression is dramatically upregulated during preadipocyte-adipocyte differentiation.
Prenatal and Adult Growth Hormone Gene Expression in Rat Lymphoid Organs
Journal of Histochemistry & Cytochemistry, 2001
Growth hormone (GH) exerts its immune effects on mature lymphocytes through an autocrine/paracrine mechanism. We investigated the prenatal synthesis of GH mRNA in rat lymphoid organs using the sensitive in situ RT-PCR methodology. We show that GH transcripts are detectable in the thymus and liver of the 18-day fetus. At this stage, all thymocytes are immature and express the GH gene. In fetal liver, GH gene expression was localized in circulating lymphocytes and in hematopoietic cells surrounding GH mRNAnegative hepatocytes. In situ GH gene expression in fetal lymphoid organs was confirmed by in vitro RT-PCR showing that the amplified product from fetal lymphoid tissues was similar to the product obtained from the pituitary. Moreover, GH gene expression was detected in the thymus, spleen, and ileum Peyer's patches of adult rat, with a localization restricted to the lymphocytes and endothelial and smooth muscle cells of blood vessels. The autocrine/paracrine expression of the GH gene by lymphoid and hematopoietic cells during fetal growth might influence the generation of regulatory cells involved in immunity and hematopoiesis.