Telangiectasia-ectodermal dysplasia-brachydactyly-cardiac anomaly syndrome is caused by de novo mutations in protein kinase D1.

BACKGROUND: We describe two unrelated patients who display similar clinical features including telangiectasia, ectodermal dysplasia, brachydactyly and congenital heart disease. METHODS: We performed trio whole exome sequencing and functional analysis using in vitro kinase assays with recombinant proteins. RESULTS: We identified two different de novo mutations in protein kinase D1 (PRKD1, NM_002742.2): c.1774G>C, p.(Gly592Arg) and c.1808G>A, p.(Arg603His), one in each patient. PRKD1 (PKD1, HGNC:9407) encodes a kinase that is a member of the protein kinase D (PKD) family of serine/threonine protein kinases involved in diverse cellular processes such as cell differentiation and proliferation and cell migration as well as vesicle transport and angiogenesis. Functional analysis using in vitro kinase assays with recombinant proteins showed that the mutation c.1808G>A, p.(Arg603His) represents a gain-of-function mutation encoding an enzyme with a constitutive, lipid-independent catalytic activity. The mutation c.1774G>C, p.(Gly592Arg) in contrast shows a defect in substrate phosphorylation representing a loss-of-function mutation. CONCLUSION: The present cases represent a syndrome, which associates symptoms from several different organ systems: skin, teeth, bones and heart, caused by heterozygous de novo mutations in PRKD1 and expands the clinical spectrum of PRKD1 mutations, which have hitherto been linked to syndromic congenital heart disease and limb abnormalities.

Activated Braf induces esophageal dilation and gastric epithelial hyperplasia in mice.

Germline mutations in BRAF are a major cause of cardio-facio-cutaneous (CFC) syndrome, which is characterized by heart defects, characteristic craniofacial dysmorphology and dermatologic abnormalities. Patients with CFC syndrome also commonly show gastrointestinal dysfunction, including feeding and swallowing difficulties and gastroesophageal reflux. We have previously found that knock-in mice expressing a Braf Q241R mutation exhibit CFC syndrome-related phenotypes, such as growth retardation, craniofacial dysmorphisms, congenital heart defects and learning deficits. However, it remains unclear whether BrafQ241R/+ mice exhibit gastrointestinal dysfunction. Here, we report that BrafQ241R/+ mice have neonatal feeding difficulties and esophageal dilation. The esophagus tissues from BrafQ241R/+ mice displayed incomplete replacement of smooth muscle with skeletal muscle and decreased contraction. Furthermore, the BrafQ241R/+ mice showed hyperkeratosis and a thickened muscle layer in the forestomach. Treatment with MEK inhibitors ameliorated the growth retardation, esophageal dilation, hyperkeratosis and thickened muscle layer in the forestomach in BrafQ241R/+ mice. The esophageal dilation with aberrant skeletal-smooth muscle boundary in BrafQ241R/+ mice were recovered after treatment with the histone H3K27 demethylase inhibitor GSK-J4. Our results provide clues to elucidate the pathogenesis and possible treatment of gastrointestinal dysfunction and failure to thrive in patients with CFC syndrome.

N-acetylglucosamine modification in the lumen of the endoplasmic reticulum.

BACKGROUND: O-linked ß-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). SCOPE OF REVIEW: 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. MAJOR CONCLUSIONS: 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. GENERAL SIGNIFICANCE: 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.

Behavioral profile in RASopathies.

Here, we describe neurobehavioral features in patients with RASopathies (i.e., Noonan syndrome, LEOPARD syndrome, Costello syndrome, and cardiofaciocutaneous syndrome), developmental disorders caused by mutations in genes coding transducers participating in the RAS-MAPK signaling cascade. Parents of 70 individuals with a RASopathy were asked to fill out the following questionnaires: Child Behavior Checklist (CBCL), Social Communication Questionnaire version lifetime (SCQ-L), and Modified Checklist for Autism in toddlers (M-CHAT). Data analysis indicated high rates of internalizing (37%) and externalizing problems (31%) on CBCL. Scores over the cut-off were documented in 64% of patients with cardiofaciocutaneous syndrome, 44% with Costello syndrome, and 12% with Noonan syndrome on SCQ-L/M-CHAT. Our findings indicate that mutations promoting dysregulation of the RAS-MAPK cascade mark an increased psychopathological risk and highlight that autistic-like behavior could be underdiagnosed in patients with RASopathies.

Autosomal recessive Adams-Oliver syndrome caused by homozygous mutation in EOGT, encoding an EGF domain-specific O-GlcNAc transferase.

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.

Focal facial dermal dysplasia, type IV, is caused by mutations in CYP26C1.

Focal facial dermal dysplasia (FFDD) Type IV is a rare syndrome characterized by facial lesions resembling aplasia cutis in a preauricular distribution along the line of fusion of the maxillary and mandibular prominences. To identify the causative gene(s), exome sequencing was performed in a family with two affected siblings. Assuming autosomal recessive inheritance, two novel sequence variants were identified in both siblings in CYP26C1-a duplication of seven base pairs, which was maternally inherited, c.844_851dupCCATGCA, predicting p.Glu284fsX128 and a missense mutation, c.1433G>A, predicting p.Arg478His, that was paternally inherited. The duplication predicted a frameshift mutation that led to a premature stop codon and premature chain termination, whereas the missense mutation was not functional based on its in vitro expression in mammalian cells. The FFDD skin lesions arise along the sites of fusion of the maxillary and mandibular prominences early in facial development, and Cyp26c1 was expressed exactly along the fusion line for these facial prominences in the first branchial arch in mice. Sequencing of four additional, unrelated Type IV FFDD patients and eight Type II or III TWIST2-negative FFDD patients revealed that three of the Type IV patients were homozygous for the duplication, whereas none of the Type II or III patients had CYP26C1 mutations. The seven base pairs duplication was present in 0.3% of healthy controls and 0.3% of patients with other birth defects. These findings suggest that the phenotypic manifestations of FFDD Type IV can be non-penetrant or underascertained. Thus, FFDD Type IV results from the loss of function mutations in CYP26C1.

Continual low-level MEK inhibition ameliorates cardio-facio-cutaneous phenotypes in zebrafish.

Cardio-facio-cutaneous (CFC) syndrome is caused by germline mutations in KRAS, BRAF and MEK1/2. The highly selective and potent MEK inhibitors that have been developed as anti-cancer agents hold potential as therapeutics for CFC syndrome. We have previously shown that the effects of CFC mutations on zebrafish gastrulation can be prevented by a 1-hour treatment with MEK inhibitors within a specific developmental time-window. However, MEK activity is essential for normal development and PD0325901 treatment outside this treatment window leads to additional developmental defects in MEK-dependent tissues. We now test ten different doses of PD0325901 at six developmental time points and assess the effects on body axis length, heart development and craniofacial structures in zebrafish embryos. Notably, we find that a continuous low-level dose of PD0325901 that has only minor inhibition of MEK activity can prevent the action of both the common CFC BRAF(Q257R) kinase-active allele and the BRAF(G596V) kinase-impaired mutant allele through the first 5 days of development. These results provide a detailed study of the effects of PD0325901 in development and show that, unlike in cancer, which requires robust inhibition of MAPK signalling, a partial reduction in phospho-ERK1/2 activity is sufficient to moderate the developmental effects of BRAF(CFC) mutations.

Constitutive activation of B-Raf in the mouse germ line provides a model for human cardio-facio-cutaneous syndrome.

RASopathies are a class of developmental syndromes that result from congenital mutations in key elements of the RAS/RAF/MEK signaling pathway. A well-recognized RASopathy is the cardio-facio-cutaneous (CFC) syndrome characterized by a distinctive facial appearance, heart defects, and mental retardation. Clinically diagnosed CFC patients carry germ-line mutations in four different genes, B-RAF, MEK1, MEK2, and K-RAS. B-RAF is by far the most commonly mutated locus, displaying mutations that most often result in constitutive activation of the B-RAF kinase. Here, we describe a mouse model for CFC generated by germ-line expression of a B-RafLSLV600E allele. This targeted allele allows low levels of expression of B-RafV600E, a constitutively active B-Raf kinase first identified in human melanoma. B-Raf+/LSLV600E mice are viable and display several of the characteristic features observed in CFC patients, including reduced life span, small size, facial dysmorphism, cardiomegaly, and epileptic seizures. These mice also show up-regulation of specific catecholamines and cataracts, two features detected in a low percentage of CFC patients. In addition, B-Raf+/LSLV600E mice develop neuroendocrine tumors, a pathology not observed in CFC patients. These mice may provide a means of better understanding the pathophysiology of at least some of the clinical features present in CFC patients. Moreover, they may serve as a tool to evaluate the potential therapeutic efficacy of B-RAF inhibitors and establish the precise window at which they could be effective against this congenital syndrome.

Dendritic cells from humans with hypomorphic mutations in IKBKG/NEMO have impaired mitogen-activated protein kinase activity.

The covalent attachment of lysine 63-linked polyubiquitin to the zinc-finger domain of IKBKG/NEMO (also known as IKKγ) is necessary for full activation of NF-κB. Impairments of this biochemical mechanism explain the deleterious effects of hypomorphic NEMO mutations on NF-κB signaling function in humans suffering from X-linked ectodermal dysplasia and immunodeficiency. Nevertheless, the biological function of the NEMO zinc-finger domain in the regulation of mitogen-activated protein kinase (MAPK) activity is poorly understood. Here we show that dendritic cells from patients with EDI caused by a C-terminal E391X deletion of the zinc finger of NEMO exhibit impaired MAPK activation in response to lipopolysaccharide (LPS) stimulation. Interestingly, DCs from patients with a C417R missense mutation within the zinc finger domain of NEMO in which ubiquitination of NEMO is preserved are also defective in JNK and ERK activity following LPS stimulation. Our findings indicate that the structural integrity of the NEMO ZF domain is more important than its polyubiquitination for full activation of the MAPK. Furthermore, phosphorylation and polyubiquitination of upstream TAK1 were significantly reduced in the E391X zinc-finger deleted patients, indicating that the NEMO zinc finger may play an important role in assembling the proximal signaling complex for MAPK activation.

CNS imaging is a key diagnostic tool in the evaluation of patients with CFC syndrome: two cases and literature review.

Cardio-facio-cutaneous (CFC) syndrome is characterized by a variable degree of cognitive impairment, and multiple congenital anomalies including characteristic facies, cardiac, and ectodermal abnormalities. CFC syndrome is caused by mutations in the genes BRAF, MEK1, or MEK2. Here we provide a follow-up report on two patients presenting distinct facial appearance and other features of the syndrome, and we present the first molecular evidence of paternal origin for a CFC-causing germline mutation. Brain imaging revealed a lipoma of the corpus callosum and periventricular leukoencephalopathy as well as a hypoplastic corpus callosum, and defects in myelinization, in each patient, respectively. A review of the literature showed that, although non-specific, ventriculomegaly, hydrocephalus, and cortical atrophy represent the most frequent imaging findings of brain anomalies in CFC syndrome. CNS abnormalities are significant diagnostic features of CFC syndrome and a brain MRI is recommended in individuals diagnosed with CFC or suspected of having CFC syndrome.

Mutational and functional analysis in human Ras/MAP kinase genetic syndromes.

The Ras/mitogen-activated protein kinase (MAPK) pathway is essential in regulation of the cell cycle, cell differentiation, growth, and cell senescence, each of which are critical to normal development. A class of developmental disorders, the "RASopathies," is caused by germline mutations in genes that encode protein components of the Ras/MAPK pathway which result in dysregulation of the pathway and profound deleterious effects on development. One of these syndromes, cardiofaciocutaneous (CFC) syndrome, is caused by germline mutations in BRAF, MAP2K1 (MEK1) and MAP2K2 (MEK2), and possibly KRAS genes. Here, we describe the laboratory protocols and methods that we used to identify mutations in BRAF and MEK1/2 genes as causative for CFC syndrome. In addition, we present the techniques used to determine the effect these mutations have on activity of the Ras/MAPK pathway through Western blot analysis of the phosphorylation of endogenous ERK1/2, as well as through the use of an in vitro kinase assay that measures the phosphorylation of Elk-1.

Association of genetic polymorphisms of aldehyde dehydrogenase-2 with esophageal squamous cell dysplasia.

AIM: To demonstrate the possible associations between genetic polymorphisms of aldehyde dehydrogenase-2 (ALDH2) and esophageal squamous cell dysplasia (ESCD). METHODS: All participants came from an area of high incidence of esophageal cancer and underwent an endoscopic staining examination; biopsies were taken from a non-staining area of the mucosa and diagnosed by histopathology. Based on the examinations, the subjects were divided into the control group with normal esophageal squamous epithelial cells and the ESCD group. ALDH2 genotypes of 396 cases were determined including 184 ESCD cases and 212 controls. The odds ratio (OR) and 95% confidence intervals (95% CI) were calculated by binary logistic regression models. RESULTS: The distribution of ALDH2 genotypes showed significant differences between the two groups. The adjustment factors were gender and age in the logistic regression models. Compared with 2*2/2*2 genotype, 2*1/2*1 genotype was found to be a risk factor for ESCD, and the OR (95% CI) was 4.50 (2.21-9.19). There were significant correlations between ALDH2 genotypes and alcohol drinking/smoking/history of esophageal cancer. CONCLUSION: The ALDH2 polymorphism is significantly associated with ESCD.

Deficient natural killer cell cytotoxicity in patients with IKK-gamma/NEMO mutations.

NF-kappaB essential modifier (NEMO), also known as IKK-gamma, is a member of the I-kappaB kinase complex responsible for phosphorylating I-kappaB, allowing the release and activation of NF-kappaB. Boys with an expressed NEMO mutation have an X-linked syndrome characterized by hypohidrotic ectodermal dysplasia with immune deficiency (HED-ID). The immunophenotype resulting from NEMO mutation is highly variable, with deficits in both T and B cell responses. We evaluated three patients with NEMO mutations (L153R, Q403X, and C417R) and HED-ID who had evidence of defective CD40 signaling. All three patients had normal percentages of peripheral blood NK cells, but impaired NK cell cytotoxic activity. This was not due to a generalized defect in cytotoxicity because antibody-dependent cellular cytotoxicity was intact. This abnormality was partially reversed by in vitro addition of IL-2, which was also able to induce NF-kappaB activation. In one patient with recurrent cytomegalovirus infections, administration of IL-2 partially corrected the NK cell killing deficit. These data suggest that NEMO participates in signaling pathways leading to NK cell cytotoxicity and that IL-2 can activate NF-kappaB and partially overcome the NK cell defect in patients with NEMO mutations.