epidermal-growth-factor and Scalp-Dermatoses

The Notch signaling pathway is highly conserved and essential for animal development. It is required for cell differentiation, survival, and proliferation. Regulation of Notch signaling is a crucial process for human health. Ligands initiate a signal cascade by binding to Notch receptors expressed on a neighboring cell. Notch receptors interact with ligands through their epidermal growth factor-like repeats (EGF repeats). Most EGF repeats are modified by

Topics: Animals; Ectodermal Dysplasia; Epidermal Growth Factor; Glycosylation; Humans; Limb Deformities, Congenital; N-Acetylglucosaminyltransferases; Receptors, Notch; Scalp Dermatoses

O-linked β-N-acetylglucosamine (O-GlcNAc) modification of epidermal growth factor (EGF) domains catalyzed by EGF domain O-GlcNAc transferase (EOGT) is the first example of GlcNAc modification in the lumen of the endoplasmic reticulum (ER).. This review summarizes current knowledge on the EOGT-catalyzed O-GlcNAc modification of EGF domains obtained through biochemical characterization, genetic analysis in Drosophila, and identification of human EOGT mutation. Additionally, this review discusses GTDC2-another ER protein homologous to EOGT that catalyzes the GlcNAc modification of O-mannosylated α-dystroglycan-and other components of the biosynthetic pathway involved in GlcNAc modification in the ER lumen.. GlcNAc modification in the ER lumen has been identified as a novel type of protein modification that regulates specific protein function. Moreover, abnormal GlcNAc modification in the ER lumen is responsible for Adams-Oliver syndrome and Walker-Warburg syndrome.. Elucidation of the biological function of GlcNAc modification in the ER lumen will provide new insights into the unique roles of O-glycans, whose importance has been demonstrated in multifunctional glycoproteins such as Notch receptors and α-dystroglyan.

Topics: Acetylglucosamine; Amino Acid Sequence; Animals; Drosophila Proteins; Ectodermal Dysplasia; Endoplasmic Reticulum; Epidermal Growth Factor; Glycosylation; Glycosyltransferases; Humans; Limb Deformities, Congenital; Molecular Sequence Data; Mutation; N-Acetylglucosaminyltransferases; Protein Conformation; Protein Processing, Post-Translational; Protein Structure, Tertiary; Scalp Dermatoses; Structure-Activity Relationship

Adams-Oliver syndrome is a rare disorder with varying degrees of scalp and cranial bone defects as well as limb anomalies, which can range from mild to more pronounced manifestations. In mild cases, closure of these defects can be achieved with a conservative approach. However, surgical closure is recommended in cases where the defect is extensive and includes cranial involvement. Several complicated cases of Adams-Oliver syndrome have been reported, in which flap failures were encountered and other alternatives had to be used to close critical scalp defects. Here, the case of a 4-year-old child with Adams-Oliver syndrome and a complex cranial defect with exposed titanium mesh is described. The patient was successfully treated with epidermal growth factor (EGF) infused foam dressings and subsequent split-thickness skin grafting. The EGF has been highlighted for its essential role in dermal wound repair through the stimulation of the proliferation and migration of keratinocytes, and showed accelerated wound healing when used in partial or full-thickness skin wounds.

Topics: Bandages; Child, Preschool; Ectodermal Dysplasia; Epidermal Growth Factor; Humans; Imaging, Three-Dimensional; Limb Deformities, Congenital; Scalp; Scalp Dermatoses; Skull; Surgical Flaps; Surgical Mesh; Titanium; Tomography, X-Ray Computed

Epidermal growth factor (EGF) domain-specific O-linked N-acetylglucosamine (EOGT) is an endoplasmic reticulum (ER)-resident O-linked N-acetylglucosamine (O-GlcNAc) transferase that acts on EGF domain-containing proteins such as Notch receptors. Recently, mutations in EOGT have been reported in patients with Adams-Oliver syndrome (AOS). Here, we have characterized enzymatic properties of mouse EOGT and EOGT mutants associated with AOS. Simultaneous expression of EOGT with Notch1 EGF repeats in human embryonic kidney 293T (HEK293T) cells led to immunoreactivity with the CTD110.6 antibody in the ER. Consistent with the GlcNAc modification in the ER, the enzymatic properties of EOGT are distinct from those of Golgi-resident GlcNAc transferases; the pH optimum of EOGT ranges from 7.0 to 7.5, and the Km value for UDP N-acetylglucosamine (UDP-GlcNAc) is 25 μm. Despite the relatively low Km value for UDP-GlcNAc, EOGT-catalyzed GlcNAcylation depends on the hexosamine pathway, as revealed by the increased O-GlcNAcylation of Notch1 EGF repeats upon supplementation with hexosamine, suggesting differential regulation of the luminal UDP-GlcNAc concentration in the ER and Golgi. As compared with wild-type EOGT, O-GlcNAcylation in the ER is nearly abolished in HEK293T cells exogenously expressing EOGT variants associated with AOS. Introduction of the W207S mutation resulted in degradation of the protein via the ubiquitin-proteasome pathway, although the stability and ER localization of EOGT(R377Q) were not affected. Importantly, the interaction between UDP-GlcNAc and EOGT(R377Q) was impaired without adversely affecting the acceptor substrate interaction. These results suggest that impaired glycosyltransferase activity in mutant EOGT proteins and the consequent defective O-GlcNAcylation in the ER constitute the molecular basis for AOS.

Topics: Acetylglucosamine; Amino Acid Sequence; Animals; Ectodermal Dysplasia; Endoplasmic Reticulum; Epidermal Growth Factor; Genetic Variation; Golgi Apparatus; HEK293 Cells; Hexosamines; Humans; Limb Deformities, Congenital; Mice; Molecular Sequence Data; Mutation; N-Acetylglucosaminyltransferases; Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; Proteasome Endopeptidase Complex; Protein Structure, Tertiary; Receptors, Notch; Recombinant Proteins; Scalp Dermatoses; Sequence Homology, Amino Acid; Signal Transduction; Ubiquitin

Autosomal recessive Adams-Oliver syndrome was diagnosed in three remotely related Bedouin consanguineous families. Genome-wide linkage analysis ruled out association with known Adams-Oliver syndrome genes, identifying a single-homozygosity ∼1.8-Mb novel locus common to affected individuals (LOD score 3.37). Whole-exome sequencing followed by Sanger sequencing identified only a single mutation within this locus, shared by all affected individuals and found in patients from five additional apparently unrelated Bedouin families: a 1-bp deletion mutation in a predicted alternative splice variant of EOGT, leading to a putative truncated protein. RT-PCR demonstrated that the EOGT-predicted alternative splice variant is ubiquitously expressed. EOGT encodes EGF-domain-specific O-linked N-acetylglucosamine transferase, responsible for extracellular O-GlcNAcylation of epidermal growth factor-like domain-containing proteins, and is essential for epithelial cell-matrix interactions. F-actin staining in diseased fibroblasts showed apparently intact cell cytoskeleton and morphology, suggesting the EOGT mutation acts not through perturbation of cytoskeleton but through other mechanisms yet to be elucidated.

Topics: Adolescent; Alternative Splicing; Child; Child, Preschool; Ectodermal Dysplasia; Epidermal Growth Factor; Female; Humans; Infant; Infant, Newborn; Limb Deformities, Congenital; Male; Mutation; N-Acetylglucosaminyltransferases; Pedigree; Scalp Dermatoses