epidermal-growth-factor and Syndrome

Topics: Epidermal Growth Factor; Homeostasis; Humans; Ion Transport; Kidney; Magnesium; Magnesium Deficiency; Models, Biological; Renal Tubular Transport, Inborn Errors; Signal Transduction; Syndrome

The major manifestations of Rieger syndrome (RS), an autosomal dominant disorder, include absent maxillary incisor teeth, malformations of the anterior chamber of the eye, and umbilical anomalies [Aarskog et al., 1983: Am J Med Genet 15:29-38; Gorlin et al., 1990: "Syndromes of the Head and Neck" 3rd ed.]. Linkage of RS to human chromosome 4q markers has been identified with tight linkage to epidermal growth factor (EGF) [Murray et al., 1992: Nat Genet 2:46-48]. Mutations associated with genes of the EGF superfamily are implicated in malformations arising from abnormal development of the first branchial arch [Ardinger et al., 1989: Am J Hum Genet 45:348-353; Sassani et al., 1993: Am J Med Genet 45:565-569]. Down-regulation of EGF during early mouse development results in ablation of tooth formation [Kronmiller et al., 1991: Dev Biol 147:485-488]. Since EGF, TGF-alpha, and EGF receptor (EGFr) transcripts are expressed in the mouse first branchial arch and derivatives, experimental strategies were employed to investigate the consequences of down-regulation of EGF translation and inhibition of EGF receptor during embryonic mandibular morphogenesis. Antisense inhibition of EGF expression produces mandibular dysmorphogenesis with decreased tooth bud size; these effects are reversed by the addition of exogenous EGF to the culture medium [Shum et al., 1993: Development 118:903-917]. Tyrphostin RG 50864, which inhibits EGF receptor kinase activity, inhibits EGF or TGF-alpha stimulation of tyrosine phosphorylation in a concentration-dependent manner and severely retards mandibular development [Shum et al., 1993: Development 118:903-917].(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Base Sequence; Catechols; Disease Models, Animal; DNA, Antisense; Epidermal Growth Factor; ErbB Receptors; Facial Bones; Gene Expression; Humans; Mice; Molecular Sequence Data; Nitriles; Protein-Tyrosine Kinases; Signal Transduction; Skull; Syndrome; Tooth Abnormalities; Transforming Growth Factor alpha; Tyrphostins

Lichen planus (LP) and discoid lupus erythematosus (DLE) are separate disease entities. Nevertheless, patients with a so-called "overlap syndrome" have been described occasionally. The aim of the present study was to establish whether the LE/LP overlap syndrome, based on clinical and routine histological features, could be delineated from DLE or LP using immunohistochemical techniques. Formalin-fixated, paraffin-embedded skin biopsies of patients with DLE, LP and the overlap syndrome were compared regarding immunohistochemical markers for epidermal growth and differentiation and extracellular matrix components. With the markers for extracellular matrix proteins, it was possible to delineate the overlap syndrome from LP. This was not possible for the overlap syndrome and DLE. These findings might indicate that the LE/LP overlap syndrome could be considered as LP-like DLE rather than as a distinct disease entity.

Topics: Adult; Aged; Biomarkers; Biopsy, Needle; Culture Techniques; Diagnosis, Differential; Epidermal Growth Factor; Extracellular Matrix Proteins; Female; Humans; Immunohistochemistry; Keratins; Lichen Planus; Lupus Erythematosus, Discoid; Male; Middle Aged; Syndrome

To determine the galectin-3 (Gal3), interleukin-1 (IL-1), interleukin-6 (IL-6), and epidermal growth factor (EGF) levels in corneal epithelium of patients with recurrent corneal erosion (RCE) syndrome and compare them with healthy controls.. In this prospective interventional case control study, 32 eyes of 32 patients with RCE syndrome who had corneal epithelial erosions and 28 eyes of 28 healthy participants scheduled for photorefractive keratectomy (control group) were included. Exclusion criteria included corneal dystrophies, ectasia, dry eye, previous ocular surgery or topical medications, and systemic diseases. Epithelial samples were obtained during epithelial debridement in the study group and mechanical epithelial keratectomy in the control group. Galectin-3 levels were studied by the chemiluminescent microparticle immunoassay method. IL-1, IL-6, and EGF levels were determined using corresponding ELISA kits.. The median Gal3 levels were 132.25 ng/mL in the study group and 106.50 ng/mL in the control group. The median IL-1 and IL-6 levels were 6.24 pg/mL and 10.16 pg/mL, respectively, in the study group which were higher than that in the control group. The median EGF level in the study group was lower than that the control group with 1.30 pg/mL versus 2.67 pg/mL. In the control group, there was a significant positive correlation between EGF and IL-6 (r = 0.554; P = 0.040). A similar correlation was not observed in patients with RCE (r = -0.071; P = 0.794).. The lack of increased EGF expression and the imbalance between growth factors, adhesion molecules, and interleukins may be the reason for the impaired wound healing response in RCE syndrome.

Topics: Adult; Biomarkers; Corneal Dystrophies, Hereditary; Epidermal Growth Factor; Epithelium, Corneal; Female; Galectin 3; Humans; Interleukin-6; Male; Photorefractive Keratectomy; Prospective Studies; Syndrome

Valosin containing protein (VCP) disease (also known as Inclusion Body Myopathy, Paget Disease of Bone and Frontotemporal Dementia [IBMPFD] syndrome) is caused by mutations in the gene encoding VCP classically affecting the muscle, bone and brain. Although the genetic cause has been identified, details regarding the pathogenesis of IBMPFD have not been fully determined. Muscle wasting observed in VCP disease is suggestive of cytokine imbalance. We hypothesized that dysfunctional protein homeostasis caused by VCP mutations leads to cytokine imbalances thereby contributing to the muscle wasting phenotype. Circulating levels of interleukin-4 (IL-4), interleukin-6 (IL-6), tumor necrosis factor alpha (TNF a) and epidermal growth factor (EGF) were measured in plasma of patients with VCP disease or controls. TNF a and EGF were significantly altered in VCP disease as compared to control. TNF a was up-regulated, consistent with a cachexia phenotype and EGF levels were increased. No significant differences were observed in IL-4 and IL-6. Cytokine imbalances may be associated with VCP disease and may play a contributory role in VCP myopathy. Further understanding of how VCP dysfunction leads to aberrant protein homeostasis and subsequent cytokine imbalances may also aid in the understanding of other proteinopathies and in the development of novel treatments.

Topics: Adenosine Triphosphatases; Case-Control Studies; Cell Cycle Proteins; Cytokines; Epidermal Growth Factor; Frontotemporal Dementia; Humans; Interleukin-4; Interleukin-6; Muscle Development; Muscular Atrophy; Muscular Dystrophies, Limb-Girdle; Mutation; Myositis, Inclusion Body; Osteitis Deformans; Signal Transduction; Syndrome; Tumor Necrosis Factor-alpha; Valosin Containing Protein

We have previously described a syndrome characterized by facial dysmorphism, lens dislocation, anterior-segment abnormalities, and spontaneous filtering blebs (FDLAB, or Traboulsi syndrome). In view of the consanguineous nature of the affected families and the likely autosomal-recessive inheritance pattern of this syndrome, we undertook autozygosity mapping and whole-exome sequencing to identify ASPH as the disease locus, in which we identified two homozygous mutations. ASPH encodes aspartyl/asparaginyl β-hydroxylase (ASPH), which has been found to hydroxylate aspartic acid and asparagine residues on epidermal growth factor (EGF)-domain-containing proteins. The truncating and missense mutations we identified are predicted to severely impair the enzymatic function of ASPH, which suggests a possible link to other forms of ectopia lentis given that many of the genes implicated in this phenotype encode proteins that harbor EGF domains. Developmental analysis of Asph revealed an expression pattern consistent with the proposed link to the human syndrome. Indeed, Asph-knockout mice had a foreshortened snout, which corresponds to the facial abnormalities in individuals with Traboulsi syndrome. These data support a genetic basis for a syndromic form of ectopia lentis and the role of aspartyl hydroxylation in human development.

Topics: Amino Acid Sequence; Animals; Anterior Eye Segment; Calcium-Binding Proteins; Craniofacial Abnormalities; DNA Mutational Analysis; Ectopia Lentis; Epidermal Growth Factor; Exome; Female; Humans; Iris; Membrane Proteins; Mice; Mice, Knockout; Mixed Function Oxygenases; Molecular Sequence Data; Muscle Proteins; Pedigree; Protein Structure, Tertiary; Syndrome; Young Adult

Costello syndrome (CS) is a rare congenital disorder characterized by failure to thrive, craniofacial dysmorphisms, cardiac and skin abnormalities, mental retardation, and predisposition to malignancies. CS is caused by heterozygous gain-of-function mutations in HRAS that also occur as somatic alterations in human tumors. HRAS is one of the three classical RAS proteins and cycles between an active, GTP- and an inactive, GDP-bound conformation. We used primary human skin fibroblasts from patients with CS as a model system to study the functional consequences of HRAS mutations on endogenous signaling pathways. The GTP-bound form of HRAS was significantly enriched in CS compared with normal fibroblasts. Active HRAS is known to stimulate both the RAF-MEK-ERK and the PI3K-AKT signaling cascade. Phosphorylation of MEK and ERK was normal in CS fibroblasts under basal conditions and slightly prolonged after epidermal growth factor (EGF) stimulation. Interestingly, basal phosphorylation of AKT was increased yet more in CS fibroblasts. Moreover, AKT phosphorylation was diminished in the early and enhanced in the late phase of EGF stimulation. Taken together, these results document that CS-associated HRAS mutations result in prolonged signal flux in a ligand-dependent manner. Our data suggest that altered cellular response to growth factors rather than constitutive activation of HRAS downstream signaling molecules may contribute to some of the clinical features in patients with CS.

Topics: Abnormalities, Multiple; Cells, Cultured; Chromones; Craniofacial Abnormalities; Enzyme Inhibitors; Epidermal Growth Factor; Failure to Thrive; Fibroblasts; Guanosine Triphosphate; Humans; Immunoblotting; Intellectual Disability; MAP Kinase Kinase 1; MAP Kinase Kinase 2; Morpholines; Mutation; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins p21(ras); Signal Transduction; Skin; Skin Abnormalities; Syndrome

The epithelial sodium channel (ENaC) is expressed in a variety of tissues, including the renal collecting duct, where it constitutes the rate-limiting step for sodium reabsorption. Liddle's syndrome is caused by gain-of-function mutations in the beta and gamma subunits of ENaC, resulting in enhanced Na reabsorption and hypertension. Epidermal growth factor (EGF) causes acute inhibition of Na absorption in collecting duct principal cells via an extracellular signal-regulated kinase (ERK)-dependent mechanism. In experiments with primary cultures of collecting duct cells derived from a mouse model of Liddle's disease (beta-ENaC truncation), it was found that EGF inhibited short-circuit current (Isc) by 24 +/- 5% in wild-type cells but only by 6 +/- 3% in homozygous mutant cells. In order to elucidate the role of specific regions of the beta-ENaC C terminus, Madin-Darby canine kidney (MDCK) cell lines that express beta-ENaC with mutation of the PY motif (P616L), the ERK phosphorylation site (T613A), and C terminus truncation (R564stop) were created using the Phoenix retroviral system. All three mutants exhibited significant attenuation of the EGF-induced inhibition of sodium current. In MDCK cells with wild-type beta-ENaC, EGF-induced inhibition of Isc (<30 min) was fully reversed by exposure to an ERK kinase inhibitor and occurred with no change in ENaC surface expression, indicative of an effect on channel open probability (P(o)). At later times (>30 min), EGF-induced inhibition of Isc was not reversed by an ERK kinase inhibitor and was accompanied by a decrease in ENaC surface expression. Our results are consistent with an ERK-mediated decrease in ENaC open probability and enhanced retrieval of sodium channels from the apical membrane.

Topics: Amiloride; Amino Acid Motifs; Animals; Butadienes; Cell Line; Disease Models, Animal; Dogs; Down-Regulation; Epidermal Growth Factor; Epithelial Sodium Channel Blockers; Epithelial Sodium Channels; Hypertension; Kidney; Membrane Potentials; Mice; Mice, Transgenic; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Mutation; Nitriles; Phosphorylation; Protein Kinase Inhibitors; Protein Structure, Tertiary; Protein Transport; Sodium; Sodium Channel Blockers; Syndrome; Transfection

Osteoporosis pseudoglioma syndrome (OPPG) is an autosomal recessive disorder due to mutations in the low-density lipoprotein receptor-related protein 5 (LRP5) gene. Here, we report two novel missense mutations found in a southern Chinese family of a non-consanguineous marriage. Three out of four children had blindness, low bone mineral density (BMD) and multiple fractures in their childhood. Genotyping by DNA sequencing demonstrated 2 new mutations in exon 7 of the LRP5 gene. Tryptophans at amino acid residue positions 478 and 504 were replaced by arginine (W478R) and cysteine (W504C), respectively. While the parents that possessed either heterozygous W478R or W504C were apparently normal, all affected subjects were compound heterozygotes for the W478R and W504C mutations in the LRP5 gene. W478R is located immediately C-terminal to the third YWTD repeat of the second YWTD/EGF domain in LRP5, while W504C is located between the third and the fourth YWTD repeats of the second YWTD/EGF domain in LRP5. Using LRP5-related proteins, such as the low-density lipoprotein receptor (LDLR) and nidogen as reference models, a homology model of LRP5 suggested that the observed mutations may affect the molecular interactions of LRP5 and so lead to the observed OPPG phenotypes.

Topics: Adolescent; Base Sequence; Child; Epidermal Growth Factor; Exons; Female; Glioma; Heterozygote; Humans; Introns; LDL-Receptor Related Proteins; Low Density Lipoprotein Receptor-Related Protein-5; Male; Middle Aged; Models, Molecular; Mutation; Osteoporosis; Pedigree; Polymorphism, Genetic; Protein Structure, Quaternary; Syndrome

Spondylocostal dysostoses (SCD) are a heterogeneous group of disorders of axial skeletal malformation characterized by multiple vertebral segmentation defects and rib anomalies. Sporadic cases with diverse phenotypes, sometimes including multiple organ abnormalities, are relatively common, and monogenic forms demonstrating autosomal recessive (AR) and, more rarely, autosomal dominant (AD) inheritance have been reported. We previously showed that mutations in delta-like 3 (DLL3), a somitogenesis gene that encodes a ligand for the notch signaling pathway, cause AR SCD with a consistent pattern of abnormal segmentation. We studied an SCD family previously reported to show AD inheritance, in which the phenotype is similar to that in AR cases. Direct DLL3 sequencing of individuals in two generations identified the affected father as homozygous for a novel frameshift mutation, 1440delG. His two affected children were compound heterozygotes for this mutation and a novel missense mutation, G504D, the first putative missense mutation reported in the transmembrane domain of DLL3. Their two unaffected siblings were heterozygotes for the 1440delG mutation. Pseudodominant inheritance has been confirmed, and the findings raise potential consequences for genetic counseling in relation to the SCD disorders.

Topics: Adult; Aged; Aged, 80 and over; DNA Mutational Analysis; Dysostoses; Epidermal Growth Factor; Female; Humans; Intracellular Signaling Peptides and Proteins; Male; Membrane Proteins; Mutation; Mutation, Missense; Pedigree; Protein Structure, Tertiary; Radiography; Sequence Deletion; Siblings; Syndrome; Thoracic Vertebrae

We have investigated and compared GH and epidermal growth factor (EGF) signaling in primary human skin fibroblasts from normal subjects and subjects with GH-binding protein-positive Laron syndrome (LS). In normal human fibroblasts, GH and EGF activate the tyrosine phosphorylation of signal transducer and activator of transcription (STAT)1 and STAT5b; in LS fibroblasts, EGF does, but GH does not. GH also activates the tyrosine phosphorylation of Janus kinase (JAK)2 in normal, but not LS, fibroblasts. Similarly, both GH and EGF activate MAPK in normal fibroblasts, but only EGF does in the LS fibroblasts. As in the 3T3-F442A mouse preadipocyte cell line, GH signaling to mitogen-activated protein kinase is partially inhibited by wortmannin treatment, indicating a role for phosphatidylinositol 3-kinase (PI3K) in this signaling pathway. The exogenous expression of the GH receptor in one family of LS fibroblasts (H1) but not the other (M) restores signaling to a STAT5 reporter element. Together, these results indicate that the mechanism of defective GH signaling in two families of LS fibroblasts are different but that both occur at a level close to, and specific for, the GH receptor.

Topics: Abnormalities, Multiple; Androstadienes; Blotting, Western; Child; Epidermal Growth Factor; Female; Fibroblasts; Growth Hormone; Humans; Indicators and Reagents; Janus Kinase 2; Luciferases; Mitogen-Activated Protein Kinases; Phosphorylation; Precipitin Tests; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Receptors, Somatotropin; Signal Transduction; Syndrome; Transfection; Tyrosine; Wortmannin

Microdeletions Glu767(1-bp del), Thr967(1-bp del), and Leu1446(2-bp del) in the human USH2A gene have been reported to cause Usher syndrome type II, a disorder characterized by retinitis pigmentosa (RP) and mild-to-severe hearing loss. Each of these three frameshift mutations is predicted to lead to an unstable mRNA transcript that, if translated, would result in a truncated protein lacking the carboxy terminus. Here, we report Cys759Phe, a novel missense mutation in this gene that changes an amino-acid residue within the fifth laminin-epidermal growth factor-like domain of the USH2A gene and that is associated with recessive RP without hearing loss. This single mutation was found in 4.5% of 224 patients with recessive RP, suggesting that USH2A could cause more cases of nonsyndromic recessive RP than does any other gene identified to date.

Topics: Alleles; Amino Acid Sequence; Base Sequence; Deafness; Epidermal Growth Factor; Extracellular Matrix Proteins; Female; Genes, Recessive; Humans; Laminin; Male; Molecular Sequence Data; Mutation, Missense; Pedigree; Protein Structure, Tertiary; Retinitis Pigmentosa; Syndrome

During the immediate-early response of mammalian cells to mitogens, histone H3 is rapidly and transiently phosphorylated by one or more unidentified kinases. Rsk-2, a member of the pp90rsk family of kinases implicated in growth control, was required for epidermal growth factor (EGF)-stimulated phosphorylation of H3. RSK-2 mutations in humans are linked to Coffin-Lowry syndrome (CLS). Fibroblasts derived from a CLS patient failed to exhibit EGF-stimulated phosphorylation of H3, although H3 was phosphorylated during mitosis. Introduction of the wild-type RSK-2 gene restored EGF-stimulated phosphorylation of H3 in CLS cells. In addition, disruption of the RSK-2 gene by homologous recombination in murine embryonic stem cells abolished EGF-stimulated phosphorylation of H3. H3 appears to be a direct or indirect target of Rsk-2, suggesting that chromatin remodeling might contribute to mitogen-activated protein kinase-regulated gene expression.

Topics: 3T3 Cells; Abnormalities, Multiple; Animals; Calcium-Calmodulin-Dependent Protein Kinases; Cell Line, Transformed; Cell Nucleus; Cells, Cultured; Epidermal Growth Factor; Gene Expression Regulation; Gene Targeting; Histones; Humans; Mice; Mitosis; Mutation; Phosphorylation; Ribosomal Protein S6 Kinases; Signal Transduction; Stem Cells; Syndrome

Usher syndrome type IIa (OMIM 276901), an autosomal recessive disorder characterized by moderate to severe sensorineural hearing loss and progressive retinitis pigmentosa, maps to the long arm of human chromosome 1q41 between markers AFM268ZD1 and AFM144XF2. Three biologically important mutations in Usher syndrome type IIa patients were identified in a gene (USH2A) isolated from this critical region. The USH2A gene encodes a protein with a predicted size of 171.5 kilodaltons that has laminin epidermal growth factor and fibronectin type III motifs; these motifs are most commonly observed in proteins comprising components of the basal lamina and extracellular matrixes and in cell adhesion molecules.

Topics: Amino Acid Sequence; Animals; Cell Adhesion Molecules; Chromosome Mapping; Chromosomes, Human, Pair 1; Cochlea; Epidermal Growth Factor; Extracellular Matrix Proteins; Female; Fibronectins; Frameshift Mutation; Gene Expression; Genes, Recessive; Glycosylation; Hearing Loss, Sensorineural; Humans; Laminin; Male; Molecular Sequence Data; Pedigree; Retina; Retinitis Pigmentosa; Syndrome; Tumor Cells, Cultured

We have evaluated the 4q25-4q26 region where the autosomal dominant disorder Rieger syndrome has been previously mapped by linkage. We first excluded epidermal growth factor as a candidate gene by carrying out SSCP analysis of each of its 24 exons using a panel of seven unrelated individuals with Rieger syndrome. No evidence for etiologic mutations was detected in these individuals, although four polymorphic variants were identified, including three that resulted in amino acid changes. We next made use of two apparently balanced translocations, one familial and one sporadic, to identify a narrow physical localization likely to contain the gene or to be involved in regulation of gene function. Somatic cell hybrids were established from individuals with these balanced translocations, and these hybrids were used as a physical mapping resource for, first, preliminary mapping of the translocation breakpoints using known sequence tagged sites from chromosome 4 and then, after creating YAC and cosmids contigs encompassing the region, for fine mapping of those breakpoints. A cosmid contig spanning these breakpoints was identified and localized the gene to within approximately 150 kb of D4S193 on chromosome 4. The interval between the two independent translocations is approximately 50 kb in length and provides a powerful resource for gene identification.

Topics: Chromosome Mapping; Chromosomes, Human, Pair 4; Craniofacial Abnormalities; Epidermal Growth Factor; Genetic Markers; Glaucoma; Humans; Polymorphism, Single-Stranded Conformational; Sequence Analysis, DNA; Syndrome; Tooth Abnormalities; Translocation, Genetic; Umbilicus

To study the structural requirements for factor IXa binding to platelets, we have carried out equilibrium binding studies with human factor IXa after replacing the second epidermal growth factor (EGF) domain by the corresponding polypeptide region of factor X. The chimeric protein, factor IX(Xegf2), and the wild-type, factor IXwt, produced in embryonic kidney cells 293 were radiolabelled with 125I and activated with factor XIa. Direct binding studies with thrombin-activated platelets showed normal stoichiometry and affinity of binding of factor IXawt in the presence of factor VIIIa (2 units/ml) and factor X (1.5 microM). However, under similar experimental conditions, factor IXa(Xegf2) was bound to a smaller number of sites (396 sites/platelet) with decreased affinity, i.e. a dissociation constant (Kd) of 1.4 nM, compared with normal factor IXa, factor IXaN (558 sites/platelet; Kd 0.67 nM), or factor IXawt (590 sites/platelet; Kd 0.61 nM). The concentrations of factor IXaN and factor IXawt required for half-maximal rates of factor-X activation were 0.63 nM and 0.7 nM, indicating a close correspondence of the Kd,app. for binding of factor IXawt to the factor-X activating complex on activated platelets to the Kd obtained in equilibrium binding studies. In contrast, kinetic parameters for factor-X activation by factor IXa(Xegf2) showed a decreased affinity (Kd 1.5 nM), in agreement with results of binding studies. These studies with factor IX(Xegf2) suggest that the EGF-2 domain may be important for specific high-affinity factor IXa binding to platelets in the presence of factor VIIIa and factor X.

Topics: Binding Sites; Binding, Competitive; Blood Platelet Disorders; Blood Platelets; Cell Line; Embryo, Mammalian; Epidermal Growth Factor; Factor IXa; Factor X; Humans; Kidney; Kinetics; Oligopeptides; Recombinant Fusion Proteins; Reference Values; Syndrome; Thrombin

Topics: Atrophy; Diarrhea; Epidermal Growth Factor; Female; Humans; Infant; Injections, Intravenous; Intestinal Mucosa; Microvilli; Peptide Fragments; Recombinant Proteins; Syndrome

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

Postreceptor defects in insulin action have been reported in fibroblasts isolated from two patients with Leprechaunism, Leprechaun/Ark-1 and Leprechaun NC-1. We have extended the published reports on glucose, aminoisobutyric acid, and thymidine uptake in these cells to measurements of protein synthesis and protein breakdown. We found a remarkably consistent pattern of responsiveness between the two Leprechaun fibroblast lines. First, protein synthesis proceeded at a low basal rate that was only slightly stimulated by insulin. Second, basal rates of protein breakdown were significantly higher than in normal skin fibroblasts, with approximately equal inhibitory effects produced by 100 nM insulin. Third, the responses of protein synthesis and protein breakdown to insulin required higher concentrations of the hormone to elicit half-maximal effects. Fourth, both Leprechaun cell lines were slow growing in complete medium, a situation that results from low rates of protein synthesis and high rates of protein breakdown. Fifth, the abnormal rates of protein metabolism in the presence of serum were caused not by the inability of serum to produce anabolic responses but because the unstimulated rates reflect a more catabolic basal state. Taken together with previous published results, our measurements suggest a generalized metabolic defect in Leprechaun fibroblasts that can only partly be explained by the reduced sensitivity of the cells to insulin.

Topics: Blood; Cell Division; Epidermal Growth Factor; Face; Fibroblasts; Humans; In Vitro Techniques; Infant; Insulin; Insulin Resistance; Proteins; Skin; Syndrome

Leprechaunism is a rare inherited disorder characterized by severe intrauterine growth retardation and insulin resistance. Cultured skin fibroblasts from an infant with Leprechaunism were previously reported to show decreased stimulation of DNA synthesis by insulin despite apparently normal binding of [125I]insulin and [125I]somatomedin C. We have now further investigated the growth of this patient's fibroblasts and compared their metabolic responses to insulin and various peptide growth factors with responses in normal foreskin-derived fibroblasts. The doubling time of Leprechaun fibroblasts was prolonged (90 vs. 29 h), and their morphology was abnormal. Stimulation of [3H]glucose uptake was minimal with low insulin levels (1--10 ng/ml) relative to controls, but was comparable at higher insulin concentrations (1--10 micrograms/ml). Stimulation of [3H] aminoisobutyric acid uptake by insulin, epidermal growth factor (EGF), multiplication-stimulating activity, and somatomedin C (Sm-C) in Leprechaun cells was diminished relative to control cells at all concentrations tested. Furthermore, stimulation of [3H]thymidine incorporation in Leprechaum cells by EGF, Sm-C, and fibroblast growth factor was also subnormal. Binding of [125I]EGF to Leprechaun fibroblasts was not decreased. It is concluded that fibroblasts from this patient are resistant to the metabolic effects of insulin, EGF, Sm-C, and fibroblast growth factor. Since receptors for three of these peptides are apparently normal, it is likely that the defect in these cells is at the postreceptor level, perhaps involving a metabolic pathway common to the action of multiple growth factors.

Topics: Aminoisobutyric Acids; Cell Division; Cells, Cultured; Drug Resistance; Dwarfism; Epidermal Growth Factor; ErbB Receptors; Fibroblast Growth Factors; Fibroblasts; Glucose; Humans; Infant; Insulin Resistance; Insulin-Like Growth Factor I; Peptides; Receptors, Cell Surface; Somatomedins; Syndrome; Thymidine