Six structurally distinct insulin-like growth factor binding proteins have been isolated and their cDNAs cloned: IGFBP1-6. The proteins
display strong sequence homologies, suggesting that they are encoded by a closely related family of genes. The IGFBPs
contain 3 structurally distinct domains each comprising approximately one-third of the molecule. The N-terminal
domain 1 and the C-terminal domain 3 of the 6 human IGFBPs show moderate to high levels of sequence identity
including 12 and 6 invariant cysteine residues in domains 1 and 3, respectively (IGFBP6 contains 10 cysteine residues
in domain 1), and are thought to be the IGF binding domains. Domain 2 is defined primarily by a lack of sequence
identity among the 6 IGFBPs and by a lack of cysteine residues, though it does contain 2 cysteines in IGFBP4. Domain 3
is homologous to the thyroglobulin type I repeat unit.
General function
Extracellular binding protein
Comment
Cellular localization
Secreted
Comment
Ovarian function
Follicle development, Steroid metabolism
Comment
Regulation and Function of Tissue Inhibitor of Metalloproteinases 1 (TIMP1) and Tissue Inhibitor of Metalloproteinases 3 (TIMP3) in Periovulatory Rat Granulosa Cells. Li F et al. In the ovary, the matrix metalloproteinases (MMPs) and the TIMPs have been postulated to regulate extracellular matrix remodeling associated with ovulation. In the present study, we investigated the regulatory mechanisms controlling expression of Timp1 and Timp3 mRNA in periovulatory granulosa cells. Granulosa cells were isolated from immature PMSG-primed (10 IU) rat ovaries and treated with hCG (1 IU/ml). At 4h after hCG treatment, Timp1 expression was highest and then decreased gradually over the remaining 24h of culture. In contrast, hCG induced a biphasic increase of Timp3 expression at 2h and 16h. The hCG stimulated expression of Timp1 and Timp3 mRNA was blocked by inhibitors of the PKA (H89), PKC (GF109203) and MAP kinase (SB2035850) pathways. To further explore Timp1 and Timp3 regulation, cells were cultured with the progesterone receptor antagonist RU486 which blocked the hCG induction of Timp3 expression while the EGF receptor tyrosine kinase inhibitor AG1478 blocked the hCG stimulation of both Timp1 and Timp3 expression. The prostaglandin-endoperoxide synthase 2 inhibitor NS-398 had no effect. The potential function of TIMP3 was investigated with Timp3-specific siRNA treatment. Timp3 siRNA resulted in a 20% decrease in hCG induced progesterone levels and microarray analysis revealed an increase in cytochrome P450 Cyp 17, ubiquitin conjugating enzyme E2T, and heat shock protein 70. IGFBP5, stearyl-CoA desaturase, and annexin A1 were decreased. The differential regulation between Timp1 and Timp3 may correlate with their unique roles in the processes of ovulation and luteinization. For TIMP3, this may include regulating fatty acid synthesis, steroidogenesis, and protein turnover.
Expression regulated by
FSH, Growth Factors/ cytokines
Comment
Ingman WV, Owens PC, Armstrong DT
( MOLECULAR AND CELLULAR ENDOCRINOLOGY
v. 164(#1-2) pp. 53-58 JUN 20, 2000) reported differential regulation by FSH and IGF-I of extracellular
matrix IGFBP-5 in bovine granulosa cells: effect of association
with the oocyte.
Inhibition of insulin-like growth factor (IGF)-I induced DNA synthesis in
bovine oocyte-cumulus complexes (OCCs) caused by follicle-stimulating hormone
(FSH) has been linked to changes in the extracellular matrix which do not
occur in mural granulosa cells (MGCs). OCCs
and MGCs from bovine ovaries were cultured in media supplemented with IGF-I
and FSH for 24 h. Culture media and extracellular matrix were analysed for
IGF-binding proteins by Western ligand blot and immunoblot and found to
contain principally IGFBP-3 and -5.
The combined treatment of IGF-I and FSH
increased the concentration of IGFBP-3 in OCC and MGC conditioned media by 4-
and 6-fold, respectively. Treatment of OCCs and not MGCs with IGF-I and FSH
together increased extracellular matrix IGFBP-5 by 2.5-fold. The differential
regulation of extracellular matrix IGFBP-5 in OCCs compared to MGCs suggest
involvement of changes in the extracellular matrix brought about by IGF-I and
FSH in overall regulation of IGF-I in the ovarian follicle.
Differential genome-wide gene expression profiling of bovine largest and second-largest follicles: identification of genes associated with growth of dominant follicles. Hayashi KG et al. ABSTRACT: BACKGROUND: Bovine follicular development is regulated by numerous molecular mechanisms and biological pathways. In this study, we tried to identify differentially expressed genes between largest (F1) and second-largest follicles (F2), and classifythem by global gene expression profiling using a combination of microarray and quantitative real-time PCR (QPCR) analysis. The follicular status of F1 and F2 were further evaluated in terms of healthy and atretic conditions by investigating mRNA localization of identified genes. METHODS: Global gene expression profiles of F1 (10.7 +/- 0.7 mm) and F2 (7.8 +/- 0.2 mm) were analyzed by hierarchical cluster analysis and expression profiles of 16 representative genes were confirmed by QPCR analysis. In addition, localization of six identified transcripts was investigated in healthy and atretic follicles using in situ hybridization. The healthy or atretic condition of examined follicles was classified by progesterone and estradiol concentrations in follicular fluid. RESULTS: Hierarchical cluster analysis of microarray data classified the follicles into two clusters. Cluster A was composed of only F2 and was characterized by high expression of 31 genes including IGFBP5, whereas cluster B contained only F1 and predominantly expressed 45 genes including CYP19 and FSHR. QPCR analysis confirmed AMH, CYP19, FSHR, GPX3, PlGF, PLA2G1B, SCD and TRB2 were greater in F1 than F2, while CCL2, GADD45A, IGFBP5, PLAUR, SELP, SPP1, TIMP1 and TSP2 were greater in F2 than in F1. In situ hybridization showed that AMH and CYP19 were detected in granulosa cells (GC) of healthy as well as atretic follicles. PlGF was localized in GC and in the theca layer (TL) of healthy follicles. IGFBP5 was detected in both GC and TL of atretic follicles. GADD45A and TSP2 were localized in both GC and TL of atretic follicles, whereas healthy follicles expressed them only in GC. CONCLUSION: We demonstrated that global gene expression profiling of F1 and F2 clearly reflected a difference in their follicular status. Expression of stage-specific genes in follicles may be closely associated with their growth or atresia. Several genes identified in this study will provide intriguing candidates for the determination of follicular growth.
Phenotypes
Mutations
1 mutations
Species: mouse
Mutation name: None
type: targeted overexpression fertility: subfertile Comment: Insulin-like growth factor-binding protein 5 (Igfbp5) compromises survival, growth, muscle development, and fertility in mice.
Salih DA, et al .
The insulin-like growth factors (IGFs) are essential for development; bioavailable IGF is tightly regulated by six related IGF-binding proteins (IGFBPs). Igfbp5 is the most conserved and is developmentally up-regulated in key lineages and pathologies; in vitro studies suggest that IGFBP-5 functions independently of IGF interaction. Genetic ablation of individual Igfbps has yielded limited phenotypes because of substantial compensation by remaining family members. Therefore, to reveal Igfbp5 actions in vivo, we generated lines of transgenic mice that ubiquitously overexpressed Igfbp5 from early development. Significantly increased neonatal mortality, reduced female fertility, whole-body growth inhibition, and retarded muscle development were observed in Igfbp5-overexpressing mice. The magnitude of the response in individual transgenic lines was positively correlated with Igfbp5 expression. Circulating IGFBP-5 concentrations increased a maximum of only 4-fold, total and free IGF-I concentrations increased up to 2-fold, and IGFBP-5 was detected in high M(r) complexes; however, no detectable decrease in the proportion of free IGF-I was observed. Thus, despite only modest changes in IGF and IGFBP concentrations, the Igfbp5-overexpressing mice displayed a phenotype more extreme than that observed for other Igfbp genetic models. Although growth retardation was obvious prenatally, maximal inhibition occurred postnatally before the onset of growth hormone-dependent growth, regardless of Igfbp5 expression level, revealing a period of sensitivity to IGFBP-5 during this important stage of tissue programming.