epidermal-growth-factor and Growth-Disorders

Growth hormone (GH) transduction defect (GHTD) is a growth disorder with impaired signal transducer and activator of transcription 3 (STAT3) phosphorylation mediated by overexpression of cytokine-inducible SH2-containing protein (CIS), which causes increased growth hormone receptor (GHR) degradation. This study investigated the role of epidermal growth factor (EGF) in the restoration of normal GH signaling in GHTD.. Protein expression, cellular localization and physical contact of proteins of the GH and EGF signaling pathways were studied by Western immunoblotting, immunofluorescence and co-immunoprecipitation, respectively. These were performed in fibroblasts of one GHTD patient (P) and one control child (C) at the basal state and after induction with human GH (hGH) 200 μg/L (GH200), either with or without silencing of CIS mRNA, and after induction with hGH 1000 μg/L (GH1000) or 50 ng/mL EGF.. The membrane availability of the EGF receptor (EGFR) and the activated EGFR (pEGFR) was increased in P only after simultaneous GH200 and silencing of CIS mRNA or with GH1000, whereas this occurred in C after GH200 alone. After EGF induction, the membrane localization of GHR, STAT3 and that of EGFR were increased in P more than in C.. In conclusion, in GHTD, the EGFR seems to participate in successful GH signaling, but induction of GHTD fibroblasts with a higher dose of hGH is needed. The EGF/EGFR pathway, in contrast to the GH/GHR pathway, seems to function normally in P and is more primed compared to C. The involvement of the EGFR in successful GH signaling may explain the catch-up growth seen in the Ps when exogenous hGH is administered.

Topics: Biomarkers; Case-Control Studies; Child; Epidermal Growth Factor; ErbB Receptors; Female; Fibroblasts; Fluorescent Antibody Technique; Follow-Up Studies; Growth Disorders; Human Growth Hormone; Humans; Immunoblotting; Immunoprecipitation; Male; Phosphorylation; Prognosis; Receptors, Somatotropin; STAT3 Transcription Factor; Suppressor of Cytokine Signaling Proteins

Mice lacking epidermal growth factor (EGF), transforming growth factor alpha, and amphiregulin were used to identify roles for these EGF receptor (EGF-R) ligands in gastrointestinal development and mucosal integrity.. Gastrointestinal tract development was examined in knockout mice and correlated with expression of EGF-R protein and EGF family members throughout the gut. Crossfostering experiments addressed roles of maternal- and neonatal-derived ligands in pup growth and intestinal development. Cysteamine-induced ulceration in EGF(-/-) mice was used to examine its role in mucosal cytoprotection.. Neonatal mice lacking all 3 ligands were growth retarded, even when reared by wild-type dams; conversely, lack of maternal ligands transiently impaired wild-type pup growth. Triple null neonates displayed spontaneous duodenal lesions, and ileal villi were truncated and fragile with reduced cellular proliferation in the crypts. However, maturation of digestive enzymes was unaffected. Adult EGF(-/-) mice displayed more severe lesions in response to cysteamine treatment compared with wild-type counterparts, although triple null mice were not more susceptible to dextran sulfate sodium-induced colitis, suggesting a differential role for these ligands in the injury response.. EGF-R ligands are required for development and mucosal maintenance in mouse small intestine. Both maternal and neonatal sources of growth factors are required for optimal pup growth.

Topics: Amphiregulin; Animals; Body Weight; Duodenal Diseases; Duodenum; EGF Family of Proteins; Epidermal Growth Factor; Female; Glycoproteins; Growth Disorders; Growth Substances; Intercellular Signaling Peptides and Proteins; Mice; Reverse Transcriptase Polymerase Chain Reaction; Species Specificity; Transforming Growth Factors

Epidermal growth factor (EGF) repeat-containing proteins constitute an expanding family of proteins involved in several cellular activities such as blood coagulation, fibrinolysis, cell adhesion, and neural and vertebrate development. By using a bioinformatic approach, we have identified a new member of this family named MAEG (MAM- and EGF-containing gene; HGMW-approved gene symbol and gene name). Sequence analysis indicates that MAEG encodes a secreted protein characterized by the presence of five EGF repeats, three of which display a Ca(2+)-binding consensus sequence. In addition, a MAM domain is also present at the C-terminus of the predicted protein product. The human and murine full-length cDNAs were identified and mapped to human Xp22 and to the mouse syntenic region. Northern analysis indicates that MAEG is expressed early during development. Taken together, these data render MAEG a candidate for human and murine developmental disorders.

Topics: Amino Acid Sequence; Animals; Blotting, Northern; Calcium-Binding Proteins; Cell Adhesion Molecules; Chromosome Mapping; DNA; DNA, Complementary; Epidermal Growth Factor; Exons; Fetus; Gene Expression Regulation, Developmental; Genes; Glycoproteins; Growth Disorders; Growth Substances; Humans; Introns; Membrane Glycoproteins; Mice; Molecular Sequence Data; Neoplasm Proteins; Peptides; Sequence Alignment; Sequence Analysis, DNA; Sequence Homology, Amino Acid; X Chromosome

The epidermal growth factor (EGF) family of peptides signals through the erbB family of receptor tyrosine kinases and plays important roles in development and tumorigenesis. Both EGF and transforming growth factor (TGF)-alpha only bind to erbB1 and activate it. The precursor of EGF is distinct from that of TGF-alpha in having eight additional EGF-like repeats. We have recently shown that the EGF precursor without these repeats is biologically active and leads to hypospermatogenesis in transgenic mice. Here we present evidence that the growth of transgenic mice widely expressing this engineered EGF precursor is also stunted. These mice were consistently born at half the normal weight and reached almost 80% of normal weight at adulthood. The mechanism involved a reduction of serum insulin-like growth factor-binding protein-3. Chondrocyte development in the growth plate was affected, and osteoblasts accumulated in the endosteum and periosteum. Besides these novel findings on the in vivo effects of EGF on bone development, we observed no sign of tumor formation in our transgenic animals. In contrast to previous reports on TGF-alpha transgenic mice, we show that the biological functions of EGF and TGF-alpha are clearly distinct.

Topics: Actins; Animals; Body Weight; Bone Development; Epidermal Growth Factor; Growth Disorders; Hepatitis, Animal; Humans; Insulin-Like Growth Factor Binding Protein 3; Liver; Mice; Mice, Transgenic; Osteoblasts; Promoter Regions, Genetic

Leprechaunism is an autosomal recessive syndrome of severe insulin resistance and is characterized by intrauterine growth restriction, acanthosis nigricans, hirsutism, and loss of glucose homeostasis. Here we report a new female patient of Hispanic and Afro-American descent whose fibroblasts and lymphoblasts had markedly impaired insulin binding (less than 10% of that in controls). Insulin binding to lymphoblasts established from both unrelated parents was partially impaired. Insulin-like growth factor-I (IGF-I) and epidermal growth factor (EGF) binding to the patient's fibroblasts were within the normal range. Insulin stimulation of receptor autophosphorylation and kinase activity was markedly reduced in the patient's fibroblasts. The patient's fibroblasts had both a reduced number of immunoreactive insulin receptor (6% of those in controls) and concomitantly reduced amounts of insulin-receptor mRNA, suggesting that both mutations inherited by the patient reduced insulin-receptor mRNA. Sequencing of the insulin-receptor gene and cDNA indicated that the patient was heterozygous for a paternally derived mutation at bp 1333, converting Arg372 to a STOP codon. This nonsense mutation was observed in the insulin-receptor gene, but not in cDNA, indicating reduced amounts of mRNA for the allele containing this mutation. The coding sequence of the maternally inherited insulin-receptor allele was normal. Both the marked reduction in insulin-receptor mRNA in the compound heterozygous fibroblasts of the proband and the partially reduced insulin binding in maternal cells suggest that the maternally derived mutation is located in an insulin-receptor gene sequence that controls cellular mRNA content.

Topics: Base Sequence; Black People; Blotting, Northern; Cells, Cultured; Epidermal Growth Factor; Female; Growth Disorders; Heterozygote; Humans; Infant; Insulin; Insulin Resistance; Insulin-Like Growth Factor I; Molecular Sequence Data; Mutation; Phosphorylation; Phosphotransferases; Receptor, Insulin; RNA, Messenger

Comparative studies have shown that cultured vascular smooth muscle cells from spontaneously hypertensive rats (SHR) proliferate to a higher cell number, grow to a greater density, and have greater specific growth rate, particularly at a higher saturation density, than those of the normotensive Wistar-Kyoto (WKY) control rats. The growth difference was not due to varying cell survival nor to attachment ability after passage. The degree of DNA synthesis was estimated by [3H]thymidine incorporation into newly synthesized DNA. [3H]thymidine uptake increased with escalating concentrations of calf serum and reached a plateau at 5% calf serum in WKY rats, whereas an excessive, continuous rise was observed in SHR with up to a 20% concentration. [3H]thymidine incorporation into newly synthesized DNA was tested after stimulation by platelet-derived growth factor and epidermal growth factor. A significantly higher amount of newly synthesized DNA in vascular smooth muscle cells from SHR was noted when the cells were stimulated by platelet-derived growth factor or epidermal growth factor alone, and their simultaneous addition did not significantly change the 50% effective concentration but heightened the maximal response. These data provide evidence of increased aortic smooth muscle cell proliferation from aortas of SHR after mitogen stimulation and suggest a defect in growth stimulatory-inhibitory control.

Topics: Animals; Aorta; Cell Division; Cells, Cultured; DNA; Epidermal Growth Factor; Growth Disorders; Male; Muscle Development; Muscle, Smooth, Vascular; Platelet-Derived Growth Factor; Rats; Thymidine; Time Factors

Leprechaunism is a rare genetic disorder characterized by severe growth retardation and insulin resistance. Maximal epidermal growth factor (EGF) binding was reduced in fibroblasts from three unrelated patients with leprechaunism (Ark-1, Can-1, and Minn-1) compared with control (0.8-2.2%/mg protein vs. 5.5%/mg protein). This was due to a decrease in receptor affinity in Ark-1 and Can-1 and a decrease in receptor number in Minn-1. In all cell lines, EGF-stimulated receptor autophosphorylation was also decreased to 18-60% of control, whereas EGF internalization and degradation was normal. Sphingosine (40 microM), a protein kinase C inhibitor, increased EGF receptor affinity twofold in control cells and six- to nine-fold in cells of leprechaunism. However, sphingosine did not enhance EGF-stimulated receptor autophosphorylation in either the controls or the patients' cells. By contrast, only one of the three cell lines of patients with the type A syndrome demonstrated a decrease in EGF binding and all demonstrated normal or near normal EGF-stimulated receptor autophosphorylation. These data indicate that in patients with leprechaunism, there are functional abnormalities of the EGF receptor, as well as of the insulin receptor, that may contribute to the severity of the syndrome. These data also suggest a role for the insulin receptor in maintaining normal EGF receptor function in these cells.

Topics: Drug Resistance; Epidermal Growth Factor; ErbB Receptors; Fibroblasts; Growth Disorders; Humans; Insulin Resistance; Phosphorylation; Protein Kinase C; Receptor, Insulin; Sphingosine

To explore a possible mechanism for the diminished growth potential in a patient with an unusual form of insulin resistance, somatomedin C/insulin-like growth factor I (SM-C/IGF-I) and insulin stimulation of [3H]thymidine incorporation and cell replication were compared in skin fibroblasts from the patient (DF) and normal controls. There appeared to be no generalized abnormality in cellular responsiveness to growth factors. In both DF and control cells, SM-C/IGF-I (50 ng/ml), insulin (100 ng/ml), and epidermal growth factor (5 ng/ml) stimulated [3H]thymidine incorporation 5-, 2-, and 6-fold, respectively. Low concentrations of human hypopituitary serum (0.25%) enhanced the effectiveness of SM-C/IGF-I and insulin to a similar extent in both DF and control cells. On the other hand, 10% calf serum stimulated [3H]thymidine incorporation 37-fold in control cells, while DF cells were only 50% as responsive. Preincubation of control cells with dexamethasone (10(-7) M) caused a marked synergistic increase in SM-C/IGF-I stimulated [3H]thymidine incorporation (15- to 20-fold in serum-free medium; 50- to 80-fold in 0.25% human hypopituitary serum). In contrast, preexposure to dexamethasone did not augment SM-C/IGF-I stimulation of thymidine incorporation into DNA of DF cells. Furthermore, the stimulation of cell replication by SM-C/IGF-I and insulin was potentiated by dexamethasone in control but not DF cultures. These data suggest that impairment of the synergistic action of glucocorticoids with SM-C/IGF-I and insulin regulation of fibroblast growth may be involved in the pathology of this insulin-resistant growth disorder.

Topics: Cell Division; Cells, Cultured; Dexamethasone; Drug Synergism; Epidermal Growth Factor; Fibroblasts; Growth Disorders; Humans; Insulin Resistance; Insulin-Like Growth Factor I; Somatomedins; Thymidine

Topics: Abnormalities, Multiple; Child; Child, Preschool; Endocrine System Diseases; Epidermal Growth Factor; Female; Follow-Up Studies; Growth Disorders; Hirsutism; Humans; Phenotype; Syndrome