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PubMed1999

Variable morbidity in alagille syndrome: a review of 43 cases.

BACKGROUND: Alagille syndrome is one of the most common inherited disorders that cause chronic liver disease in children. Early reports suggested a benign course in these patients. Subsequent reports showed significant morbidity and mortality. This study was designed to analyze the long-term clinical course in Alagille syndrome. METHODS: The records of children with Alagille syndrome seen during a 20-year period were reviewed. RESULTS: Forty-three patients were identified. Liver disease was diagnosed before 12 months of age in 95%. The frequencies of renal anomalies (50%) and intracranial hemorrhage (12%) were significant. The high incidence of chronic otitis media (35%) has not been reported previously. One patient had a renal transplant. Vascular compromise as a pathologic mechanism for some characteristics of the syndrome is also suggested by the presence of small bowel stenosis and atresia, tracheal and bronchial stenosis, renal artery stenosis, middle aortic syndrome, and avascular necrosis of the humeral and femoral heads. Twenty (47%) patients underwent liver transplantation. Five of six who underwent Kasai procedure required liver transplantation. Twelve died (28%), five after liver transplantation. One patient died of intracranial bleeding. Sixteen (37%) without liver transplantation and 15 (35%) who underwent liver transplantation are alive. CONCLUSIONS: Some patients with early-onset and more severe liver disease can benefit from liver transplantation. Careful and complete assessment should be made of infants with a cholestatic syndrome, to avoid misdiagnosis and unnecessary Kasai procedures. Our observation of vascular compromise in various organ systems suggests that notch signaling pathway defects affect angiogenesis in Alagille syndrome.

Adolescent↗
PubMed1999

Clinical and molecular genetics of Alagille syndrome.

Alagille syndrome (AGS) is a dominantly inherited disorder characterized by bile duct paucity and resultant liver disease in combination with cardiac, skeletal, ocular, and facial abnormalities. Jagged1 (JAG1) has been identified as the AGS disease gene. It encodes a ligand in the Notch signaling pathway that is involved in cell fate determination. AGS is the first developmental disorder to be associated with this pathway. It shows highly variable expressivity, and diagnosis in mildly affected persons can be difficult without molecular analysis. Currently, JAG1 mutations are detected in about 70% of patients with AGS and include total gene deletions as well as protein truncating, splicing, and missense mutations. Mutations are located across the gene within the evolutionarily conserved motifs of the protein. There is no phenotypic difference between patients with deletion of the entire JAG1 gene and those with intragenic mutations. This suggests that haploinsufficiency for JAG1 is a mechanism causing AGS.

Alagille Syndrome↗
PubMed2006

Molecular genetics of aortic valve disease.

PURPOSE OF REVIEW: Bicuspid aortic valve is the most common type of cardiac malformation and predisposes to aortic valve calcification, which is the third leading cause of heart disease in adults. These seemingly temporally disparate diseases have been described as having genetic influences but limited data exist on the precise genetic causes in humans. Several advances in the molecular genetics of aortic valve formation and calcification have recently been identified and are described here. RECENT FINDINGS: A large family with autosomal-dominant aortic valve disease consisting of bicuspid aortic valve and aortic valve calcification was studied using genome-wide linkage analysis. This led to the identification of a nonsense mutation in NOTCH1 in affected individuals. This finding was supported by the discovery of a NOTCH1 frameshift mutation in an unrelated family with similar aortic valve disease, suggesting that NOTCH1 haploinsufficiency was a genetic cause of aortic valve malformations and calcification. The NOTCH signaling pathway was linked to a molecular pathway for aortic valve calcification, as NOTCH1 was found to repress activation of Runx2 - a transcription factor critical for osteoblast cell fate that is up-regulated in calcified human aortic valves. SUMMARY: The recent genetic and biochemical findings provide novel insights into the molecular and genetic basis for aortic valve dysmorphogenesis and calcification. Future studies focusing on the identification of additional disease-causing and susceptibility genes will aid in the development of prevention strategies. Ultimately, it will be the careful dissection of these molecular pathways that will hopefully lead to novel therapeutic options.

Adult↗
PubMed2003

Matrix metalloproteinase-21 is expressed epithelially during development and in cancer and is up-regulated by transforming growth factor-beta1 in keratinocytes.

Human matrix metalloproteinase-21 (MMP-21), the newest member of the MMP gene family, has been suggested to play an important role in embryogenesis and tumor progression and to be a target of the Wnt, Pax, and Notch signaling pathways. Here we report detection of MMP-21 by RT-PCR in mouse embryos aged 10.5, 12.5, 13.5, and 16.5 days, as well as in various adult murine organs. In both humans and mice, MMP-21 protein was detected in the epithelial cells of developing kidney, intestine, neuroectoderm, and skin but not in normal adult skin using immunohistochemistry with two unrelated antibodies. However, it was present in invasive cancer cells of aggressive subtypes of basal and squamous cell carcinomas, although it was not expressed in skin disorders characterized by mere keratinocyte hyperproliferation. Of several cytokines tested, transforming growth factor-beta1 induced MMP-21 in vitro in HaCaTs and keratinocytes as judged by real-time quantitative TaqMan PCR. Although suprabasal differentiating keratinocytes expressed MMP-21 in developing skin in vivo, MMP-21-positive keratinocytes were detected by immunohistochemistry in both low and high calcium cultures. MMP-21 expression was not up-regulated by ras transformation in HaCaT cell lines (HaCaT, A5, II-4, and RT3); in skin and colon cancers, its expression did not associate with apoptosis, beta-catenin transactivation, or epithelial MMPs-9 and -10. However, MMP-21 protein was found in the same regions as MMP-7 but not in the same cells. Our results suggest that during development, MMP-21 expression is temporally and spatially tightly controlled. Unlike many classical MMPs, it is present in various normal adult tissues. Among epithelial MMPs, MMP-21 has a unique expression pattern in cancer.

Animals↗
PubMed2001

The winged helix transcription factor Foxc1a is essential for somitogenesis in zebrafish.

Previous studies identified zebrafish foxc1a and foxc1b as homologs of the mouse forkhead gene, Foxc1. Both genes are transcribed in the unsegmented presomitic mesoderm (PSM), newly formed somites, adaxial cells, and head mesoderm. Here, we show that inhibiting synthesis of Foxc1a (but not Foxc1b) protein with two different morpholino antisense oligonucleotides blocks formation of morphological somites, segment boundaries, and segmented expression of genes normally transcribed in anterior and posterior somites and expression of paraxis implicated in somite epithelialization. Patterning of the anterior PSM is also affected, as judged by the absence of mesp-b, ephrinB2, and ephA4 expression, and the down-regulation of notch5 and notch6. In contrast, the expression of other genes, including mesp-a and papc, in the anterior of somite primordia, and the oscillating expression of deltaC and deltaD in the PSM appear normal. Nevertheless, this expression is apparently insufficient for the maturation of the presumptive somites to proceed to the stage when boundary formation occurs or for the maintenance of anterior/posterior patterning. Mouse embryos that are compound null mutants for Foxc1 and the closely related Foxc2 have no morphological somites and show abnormal expression of Notch signaling pathway genes in the anterior PSM. Therefore, zebrafish foxc1a plays an essential and conserved role in somite formation, regulating both the expression of paraxis and the A/P patterning of somite primordia.

Amino Acid Sequence↗
PubMed2002

Activation of Wnt signaling bypasses the requirement for RTK/Ras signaling during C. elegans vulval induction.

During Caenorhabditis elegans vulval development, activation of receptor tyrosine kinase/Ras and Notch signaling pathways causes three vulval precursor cells (VPCs) to adopt induced cell fates. A Wnt signaling pathway also acts in cell fate specification by the VPCs, via regulation of the Hox gene lin-39. We show here that either mutation of pry-1 or expression of an activated BAR-1 beta-catenin protein causes an Overinduced phenotype, in which greater than three VPCs adopt induced cell fates. This indicates that pry-1, which encodes a C. elegans axin homolog, acts as a negative regulator of Wnt signaling in the VPCs. Loss of activity of the APC homolog apr-1 increases the penetrance of this Overinduced phenotype, suggesting that APR-1 may play a negative role in Wnt signaling in this process in C. elegans similar to APC proteins in other systems. The Overinduced phenotype is suppressed by reduction of function of the genes pop-1 TCF and lin-39 Hox. Surprisingly, the Overinduced phenotype caused by hyperactivated Wnt signaling is not dependent on signaling through the Ras pathway. These data suggest that hyperactivation of Wnt signaling is sufficient to cause VPCs to adopt induced fates and that a canonical Wnt pathway may play an important role during C. elegans vulval induction.

Adenomatous Polyposis Coli Protein↗
PubMed2002

Neurogenin 3 is essential for the proper specification of gastric enteroendocrine cells and the maintenance of gastric epithelial cell identity.

The notch signaling pathway is essential for the endocrine cell fate in various tissues including the enteroendocrine system of the gastrointestinal tract. Enteroendocrine cells are one of the four major cell types found in the gastric epithelium of the glandular stomach. To understand the molecular basis of enteroendocrine cell development, we have used gene targeting in mouse embryonic stem cells to derive an EGFP-marked null allele of the bHLH transcription factor, neurogenin 3 (ngn3). In ngn3(-/-) mice, glucagon secreting A-cells, somatostatin secreting D-cells, and gastrin secreting G-cells are absent from the epithelium of the glandular stomach, whereas the number of serotonin-expressing enterochromaffin (EC) cells is decreased dramatically. In addition, ngn3(-/-) mice display intestinal metaplasia of the gastric epithelium. Thus, ngn3 is required for the differentiation of enteroendocrine cells in the stomach and the maintenance of gastric epithelial cell identity.

Alleles↗
PubMed2004

Pseudodominant inheritance of spondylocostal dysostosis type 1 caused by two familial delta-like 3 mutations.

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.

Adult↗
PubMed2006

Liver transplantation in children with Alagille syndrome: indications and outcome.

An AGS is a dominant inherited multisystem disorder caused by mutations in the Notch signaling pathway (JAG1). In our center, 5.3% of liver transplantations (OLT) are performed in children with AGS. Some of the affected children fulfilled criteria for OLT, despite the absence of liver cirrhosis. The aim of our present study was to evaluate the indications and outcome for OLT in children with this complex disorder as clear criteria are difficult to establish in clinical practice. A total of 37 patients were included in a retrospective analysis. Twenty-four children underwent OLT for chronic end-stage liver failure (n = 8) or symptomatic liver disease (n = 16). Patient survival post-OLT was 91.7% after 1 yr, that of graft survival was 87.5%, respectively. Significant post-transplant vascular complications included a mid-aortic syndrome (n = 1) and severe lethal bleeding due to suspected vascular malformation (n = 1). Severe hypercholesterolemia (>800 mg/dL) and xanthomata resolved completely in affected patients. We conclude from our data that indications for OLT in AGS should be extended to patients with severe symptomatic liver disease, even in the absence of liver cirrhosis because of the significantly improved outcome after pediatric OLT in the last decade. Future studies must identify underlying mechanisms of hypercholesterolemia and vascular malformation.

Adolescent↗
PubMed2004

Activation of Notch1 in the hair follicle leads to cell-fate switch and Mohawk alopecia.

The Notch signaling pathway has been shown to control cell-fate decisions during mouse development. To study the role of Notch1 in epidermal differentiation and the development of the various cell types within the mouse hair follicle, we generated transgenic mice that express a constitutive activated form of Notch1 under the control of the involucrin promoter. Transgenic animals express the transgene in the suprabasal epidermal keratinocytes and inner root sheath of the hair follicle, and develop both skin and hair abnormalities. Notch1 overexpression leads to an increase of the differentiated cell compartment in the epidermis, delays inner root sheath differentiation, and leads to hair shaft abnormalities and alopecia associated with the anagen phase of the hair cycle.

Alopecia↗
PubMed1998

Multiple functions within the Epstein-Barr virus EBNA-3A protein.

Two regions of the EBNA-3A protein of Epstein-Barr virus were shown to be capable of binding to the cell protein RBP-Jk (also known as CBF-1), a component of the Notch signaling pathway. Consistent with this binding, EBNA-3A inhibited reporter gene expression from plasmids containing RBP-Jk DNA binding sites within their promoters, including the Cp promoter. When EBNA-3A was linked to a GAL4 DNA binding domain, it repressed the activity of a promoter containing GAL4 binding sites at all plasmid concentrations tested. However, a deletion mutant of EBNA-3A lacking amino acids 100 to 364 showed a biphasic response in the GAL4 assay: it inhibited transcription at low DNA concentrations but activated it at high DNA concentrations. There appears to be a gene activation function within EBNA-3A that is masked in the full-length protein in this assay. Current models for EBNA-3 function have stressed transcription repression through binding to RBP-Jk, but we consider an alternative scheme in which the role of the binding of EBNA-3A, -3B, and -3C to RBP-Jk is to buffer the levels of active EBNA-3 protein. We have also found that the behavior of EBNA-3A in a cell fractionation procedure that distinguishes insoluble matrix from soluble cell fractions is modified by EBNA-LP, indicating a further novel level of interplay between the EBNA proteins.

Binding Sites↗
PubMed2005

Induction of Kaposi's sarcoma-associated herpesvirus latency-associated nuclear antigen by the lytic transactivator RTA: a novel mechanism for establishment of latency.

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent contributing to development of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman desease. Following primary infection, latency is typically established. However, the mechanism by which KSHV establishes latency is not understood. We have reported that the latency-associated nuclear antigen (LANA) can repress RTA (for replication and transcription activator) expression by down-regulating its promoter. In this study, we show that RTA is associated with the virion particle. We also show that RTA can activate the LANA promoter and induce LANA expression in transient reporter assays. Additionally, the transcription of RTA correlates with LANA expression in the early stages of de novo infection of KSHV, and induction of LANA transcription is responsive to induction of RTA with an inducible system. This induction in LANA transcription was dependent on recombination signal sequence binding protein Jkappa (RBP-Jkappa), as a RBP-Jkappa-deficient cell line was significantly delayed and inefficient in LANA transcription with expression of RTA. These studies suggest that RTA contributes to establishment of KSHV latency by activating LANA expression in the early stages of infection by utilizing the major effector of the Notch signaling pathway RBP-Jkappa. This describes a feedback mechanism by which LANA and RTA can regulate each other and is likely to be a key event in the establishment of KSHV latency.

Antigens, Viral↗
PubMed2002

Functional requirement for histone deacetylase 1 in Caenorhabditis elegans gonadogenesis.

Histone acetylation and deacetylation have been implicated in the regulation of gene expression. Molecular studies have shown that histone deacetylases (HDACs) function as transcriptional repressors. However, very little is known about their roles during development in multicellular organisms. We previously demonstrated that inhibition of maternal and zygotic expression of histone deacetylase 1 (HDA-1) causes embryonic lethality in Caenorhabditis elegans. Here, we report the identification of an hda-1 genetic mutant which has also been called a gon-10 mutant (for gonadogenesis defective 10) and show that loss of HDA-1 zygotic expression results in specific postembryonic defects in gonadogenesis and vulval development. We provide evidence that the lag-2 gene, which plays a role in gonadogenesis and vulval development and encodes a Notch ligand, is derepressed in gon-10 animals, suggesting that lag-2 may be a target of HDA-1. Our findings reveal a novel and specific function for the ubiquitously expressed HDA-1 in C. elegans gonadogenesis and place hda-1 in the Notch signaling pathway.

Amino Acid Sequence↗
PubMed2005

Up-regulation of delta-like 4 ligand in human tumor vasculature and the role of basal expression in endothelial cell function.

The Notch signaling pathway and the delta-like 4 ligand (DLL4) play key roles in embryonic vascular development. Many of the pathways involved in embryonic vascular development also play important roles in tumor angiogenesis. In this study, we assessed the expression of DLL4 in primary renal cancer and investigated the biological function of DLL4 in primary endothelial cells. Using real-time quantitative PCR and in situ hybridization, we showed that the expression of DLL4 was up-regulated within the vasculature of clear cell-renal cell carcinoma almost 9-fold more than normal kidney and was correlated with the expression of vascular endothelial growth factor (VEGF). The expression of DLL4 in endothelial cells was up-regulated by VEGF and basic fibroblast growth factor synergistically, and by hypoxia through hypoxia-inducible factor 1alpha. Down-regulation of DLL4 expression with RNA interference led to decreased expression of HEY1 and EphrinB2, and the inhibition of endothelial cell proliferation, migration, and network formation, all of which are important processes in tumor angiogenesis. The inhibition of proliferation occurred via the induction of cell cycle arrest in G0-G1 by increased expression of p21 and decreased phosphorylation of retinoblastoma. We conclude that an optimal window of the DLL4 expression is essential for tumor angiogenesis and that selective modulation of the DLL4 expression within human tumors may represent a potential novel antiangiogenic therapy.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Up-regulation of endothelial delta-like 4 expression correlates with vessel maturation in bladder cancer.

PURPOSE: Angiogenesis and vascular endothelial growth factor (VEGF) expression are associated with a poor outcome in bladder cancer. To understand more about the mechanisms, we studied the role of delta-like 4 (DLL4), an endothelial-specific ligand of the Notch signaling pathway, in bladder cancer angiogenesis. EXPERIMENTAL DESIGN: The expression of DLL4, CD34, and VEGF were studied in a cohort of 60 bladder tumors and 10 normal samples using quantitative PCR. In situ hybridization was used to study the pattern of DLL4 expression in 22 tumor and 9 normal samples. Serial sections were also stained for CD34 and alpha-smooth muscle actin (alpha-SMA) using conventional immunohistochemistry. RESULTS: The expression of DLL4 was significantly up-regulated in superficial (P < 0.01) and invasive (P < 0.05) bladder cancers. DLL4 expression significantly correlated with CD34 (P < 0.001) and VEGF (P < 0.001) expression. The in situ hybridization studies showed that DLL4 was highly expressed within bladder tumor vasculature. Additionally, DLL4 expression significantly correlated with vessel maturation as judged by periendothelial cell expression of alpha-SMA, 98.7% of DLL4-positive tumor vessels coexpressed alpha-SMA, compared with 64.5% of DLL4-negative tumor vessels (P < 0.001). High DLL4 expression may have prognostic value in superficial and invasive bladder. CONCLUSION: DLL4 expression is associated with vascular differentiation in bladder cancer; thus, targeting DLL4 may be a novel antiangiogenic therapy.

Actins↗
PubMed2003

Gene expression profiling reveals a highly specialized genetic program of plasma cells.

The formation of terminally differentiated plasma cells represents the critical final step in B-cell differentiation. In this study, utilizing oligonucleotide microarray analysis, we describe the highly specialized genetic profile exhibited by terminally differentiated plasma cells. A total of 1476 known genes were differentially expressed by plasma cells compared with B cells. Plasma cells displayed an up-regulation, induction, or a selective retention of a unique constellation of transcription factors, including members of the AP-1, nuclear factor-kappaB (NF-kappaB), nuclear factor of activated T cells (NFAT), and octamer binding factor families. Interestingly, plasma cells also displayed a down-regulation of several RNA polymerase I- related factors, consistent with terminal differentiation, and exhibited a down-regulation of the TATA box binding protein. Furthermore, plasma cells displayed alterations in multiple components of the Wnt and Notch signaling pathways and showed a unique pattern of apoptosis and proliferation-associated genes. Unexpectedly, plasma cells displayed an up-regulation of 2 factors normally associated with microenvironmental positioning of neuronal cells, reelin and neuropilin-1. These results supply insight into the developmental genetics of plasma cell differentiation and provide a foundation for further analysis of plasma cell biology.

Animals↗
PubMed2003

Expression of the Hsp23 chaperone during Drosophila embryogenesis: association to distinct neural and glial lineages.

BACKGROUND: In addition to their strong induction following stress, small heat shock proteins (Hsp) are also expressed during development in a wide variety of organisms. However, the precise identity of cell(s) expressing these proteins and the functional contribution of small heat shock proteins in such developmental context remain to be determined. The present study provides a detailed description of the Drosophila small heat shock protein Hsp23 expression pattern during embryogenesis and evaluates its functional contribution to central nervous system development. RESULTS: Throughout embryogenesis, Hsp23 is expressed in a stage-specific manner by a restricted number of neuronal and glial lineages of the central nervous system. Hsp23 is also detected in the amnioserosa and within a single lateral chordotonal organ. Its expression within the MP2 lineage does not require the presence of a functional midline nor the activity of the Notch signaling pathway. Transactivation assays demonstrate that transcription factors implicated in the differentiation of the midline also regulate hsp23 promoter activity. Phenotypic analysis of a transgenic line exhibiting loss of Hsp23 expression in the central nervous system suggests that Hsp23 is not required for development and function of this tissue. Likewise, its overexpression does not cause deleterious effects, as development remains unaffected. CONCLUSIONS: Based on the presented data, we suggest that the tightly regulated developmental expression of Hsp23 is not actively involved in cell differentiation and central nervous system development per se but rather reflects a putative role in preventive "pre-stress" neuroprotection or in non-vital process(es) common to the identified cell lineages.

Animals↗
PubMed2025

A case of congenital heart defects and familial exudative vitreoretinopathy caused by activation of a cryptic splice donor in NOTCH1.

BACKGROUND: NOTCH1 is associated with two disorders of vascular development, Adams-Oliver Syndrome 5 (AOS5) and aortic valve disease 1 (AOVD1). Here we report a disease-causing variant in NOTCH1 that has a previously undemonstrated effect on splicing. Additionally, we found that the proband has the optic phenotype of familial exudative vitreoretinopathy (FEVR) which has been reported for probands with pathogenic variants in genes in the notch signaling pathway, but never for NOTCH1. CASE PRESENTATION: The proband presented with a ventricular septal defect, pulmonic stenosis, and ocular findings consistent with familial exudative vitreoretinopathy (FEVR), which NOTCH1 has not been associated with to date. Trio exome sequencing identified a paternally inherited variant of uncertain significance in NOTCH1:c.2153&#xa0;A&#x2009;>&#x2009;G. We assessed the variant's effect using RT-PCR, finding an increased use of a cryptic donor compared to the control. On this basis, we were able to re-classify this variant as pathogenic. CONCLUSIONS: We expand the phenotypic spectrum of NOTCH1 and contribute to the building evidence that variants in NOTCH1 cause a spectrum of disorders of vascular development.

Humans↗