Defects in mouse mammary gland development caused by conditional haploinsufficiency of Patched-1.
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In vertebrates, the hedgehog family of cell signaling proteins and associated downstream network components play an essential role in mediating tissue interactions during development and organogenesis. Loss-of-function or misexpression mutation of hedgehog network components can cause birth defects, skin cancer and other tumors. The mammary gland is a specialized skin derivative requiring epithelial-epithelial and epithelial-stromal tissue interactions similar to those required for development of other organs, where these interactions are often controlled by hedgehog signaling. We have investigated the role of the Patched-1 (Ptc1) hedgehog receptor gene in mammary development and neoplasia. Haploinsufficiency at the Ptc1 locus results in severe histological defects in ductal structure, and minor morphological changes in terminal end buds in heterozygous postpubescent virgin animals. Defects are mainly ductal hyperplasias and dysplasias characterized by multilayered ductal walls and dissociated cells impacting ductal lumens. This phenotype is 100% penetrant. Remarkably, defects are reverted during late pregnancy and lactation but return upon involution and gland remodeling. Whole mammary gland transplants into athymic mice demonstrates that the observed dysplasias reflect an intrisic developmental defect within the gland. However, Ptc1-induced epithelial dysplasias are not stable upon transplantation into a wild-type epithelium-free fat pad, suggesting stromal (or epithelial and stromal) function of Ptc1. Mammary expression of Ptc1 mRNA is both epithelial and stromal and is developmentally regulated. Phenotypic reversion correlates with developmentally regulated and enhanced expression of Indian hedgehog (Ihh) during pregnancy and lactation. Data demonstrate a critical mammary role for at least one component of the hedgehog signaling network and suggest that Ihh is the primary hedgehog gene active in the gland. (+info)
The expression of Jagged1 in the developing mammalian heart correlates with cardiovascular disease in Alagille syndrome.
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The establishment of the cardiovascular system represents an early, critical event essential for normal embryonic development, and defects in cardiovascular development are a frequent cause of both in utero and neonatal demise. Congenital cardio-vascular malformations, the most frequent birth defect, can occur as isolated events, but are frequently presented clinically within the context of a constellation of defects that involve multiple organs and that define a specific syndrome. In addition, defects can be a primary effect of gene mutations or result from secondary effects of altered cardiac physiology. Alagille syndrome (AGS) is an autosomal dominant disorder characterized by developmental abnormalities of the heart, liver, eye, skeleton and kidney. Congenital heart defects, the majority of which affect the right-sided or pulmonary circulation, contribute significantly to mortality in AGS patients. Recently, mutations in Jagged1 ( JAG1 ), a conserved gene of the Notch intercellular signaling pathway, have been found to cause AGS. In order to begin to delineate the role of JAG1 in normal heart development we have studied the expression pattern of JAG1 in both the murine and human embryonic heart and vascular system. Here, we demonstrate that JAG1 is expressed in the developing heart and multiple associated vascular structures in a pattern that correlates with the congenital cardiovascular defects observed in AGS. These data are consistent with an important role for JAG1 and Notch signaling in early mammalian cardiac development. (+info)
Living related donor liver transplantation in a patient with severe aortic stenosis.
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We report the successful anaesthetic management of a young girl with Alagille's syndrome and severe aortic stenosis (resting pressure gradient 88 mm Hg) undergoing living related donor liver transplantation (LRDLT). The patient had end-stage liver disease and LRDLT was performed before replacement of the aortic valve. Anaesthesia was conducted uneventfully with the aid of a pulmonary artery catheter. Intra-aortic balloon pumping was used in the perioperative period for protection against myocardial ischaemia. Total clamping of the inferior vena cava was avoided during surgery and volume administration was guided by the pulmonary artery pressure. A stable circulation was maintained in the reperfusion period. The patient was discharged from hospital on day 54 after operation with normal liver function. Two years later her aortic valve was replaced successfully. (+info)
JAGGED1 expression in human embryos: correlation with the Alagille syndrome phenotype.
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Alagille syndrome (AGS, MIM 118450) is an autosomal dominant disorder with a variable phenotype characterised by hepatic, eye, cardiac, and skeletal malformations and a characteristic facial appearance. Mutations within the gene JAGGED1 (JAG1), which encodes a ligand for NOTCH receptor(s), has been shown to cause Alagille syndrome. Interactions of NOTCH receptors and their ligands influence cell fate decisions in several developmental pathways. We report the tissue expression of JAG1 in human embryos. We have performed tissue in situ hybridisation on human embryos aged 32-52 days using (35)S labelled riboprobes for JAG1. JAG1 is expressed in the distal cardiac outflow tract and pulmonary artery, major arteries, portal vein, optic vesicle, otocyst, branchial arches, metanephros, pancreas, mesocardium, around the major bronchial branches, and in the neural tube. We conclude that JAG1 is expressed in the structures affected in Alagille syndrome, such as the pulmonary artery, anterior chamber of the eye, and face. (+info)
Does liver transplantation affect growth pattern in Alagille syndrome?
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Alagille syndrome (AGS) is frequently associated with growth failure, which has been attributed to concurrent congenital anomalies, cholestasis, and malabsorption and/or malnutrition. However, the underlying cause of the growth failure is not well understood. Our objective is to analyze the growth pattern in 26 patients with AGS and the possible effect that orthotopic liver transplantation (OLT) may have on this pattern. The standardized height, weight, and growth velocity of 26 pair-matched patients with AGS were compared. Thirteen patients underwent OLT. Repeated-measure ANOVA methods were used for the statistical analysis. The overall mean standardized height (z score) was -2.92 in the OLT group versus -1.88 in the non-OLT group (P =.03). The overall mean standardized weight was -1. 21 in the non-OLT group and -1.67 in the OLT group (P =.23). In 15 patients, birth weight was 2.82 +/- 0.4 kg, for a mean standardized weight of -0.95, and weight at diagnosis was 4.53 +/- 2.12 kg, for a mean standardized weight of -1.56. Bone age was delayed in the 9 patients who underwent bone-age analysis. Growth hormone therapy administered to 2 patients did not improve growth. Patients with AGS had growth failure secondary to other factors in addition to liver disease. Growth failure beginning in the prenatal period supports a genetic basis for this feature. Growth improvement up to normal levels should not be expected as a benefit of OLT in these patients. Growth failure as a primary indication for OLT should be cautiously examined in patients with AGS. (+info)
Defective intracellular transport and processing of JAG1 missense mutations in Alagille syndrome.
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Jagged1 (JAG1) is a cell surface ligand in the Notch signaling pathway and mutations in this gene cause Alagille syndrome (AGS). JAG1 mutations have been identified in 60-70% of AGS patients studied, and these include total gene deletions ( approximately 6%), protein-truncating mutations (insertions, deletions and nonsense mutations) (82%) and missense mutations (12%). Based on the finding that total JAG1 deletions cause AGS, haploinsufficiency has been hypothesized to be a mechanism for disease causation; however, the mechanism by which missense mutations cause disease is not understood. To date, 25 unique missense mutations have been observed in AGS patients. Missense mutations are non-randomly distributed across the protein with clusters at the 5' end of the protein, in the conserved DSL domain, and two clusters within the EGF repeats. To understand the effect of the missense mutations on protein localization and function, we have studied four missense mutations (R184H, L37S, P163L and P871R). In two assays of JAG1 function, R184H and L37S are associated with loss of Notch signaling activity relative to wild-type JAG1. Neither R184H or L37S is present on the cell surface and both are abnormally glycosylated. Furthermore, these mutations lead to abnormal accumulation of the protein, possibly in the endoplasmic reticulum. Both P163L and P871R are associated with normal levels of Notch signaling activity and are present on the cell surface, consistent with these changes being polymorphisms rather than disease-causing mutations. (+info)
Parental mosaicism of JAG1 mutations in families with Alagille syndrome.
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The Alagille syndrome (AGS), a congenital disorder affecting liver, heart, skeleton and eye in association with a typical face, is an autosomal dominant disease with nearly complete penetrance and variable expression. AGS is caused by mutations in the developmentally important JAG1 gene. In our mutation screening, where 61 mutations in JAG1 were detected, we identified five cases where mosaicism is present. Our results point to a significant frequency of mosaicism for JAG1 mutations in AGS of more than 8.2%. Because mosaicism may be associated with a very mild phenotype, the appropriate diagnosis of AGS and consequently the determination of the recurrence risk can be complicated. (+info)
Outcome of liver disease in children with Alagille syndrome: a study of 163 patients.
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BACKGROUND AND AIMS: Various opinions have been expressed as to the long term prognosis of liver disease associated with Alagille syndrome (AGS). PATIENTS AND METHODS: We reviewed the outcome of 163 children with AGS and liver involvement, investigated from 1960 to 2000, the end point of the study (median age 10 years (range 2 months to 44 years)) being death, liver transplantation, or the last visit. RESULTS: At the study end point, of the 132 patients who presented with neonatal cholestatic jaundice, 102 remained jaundiced, 112 had poorly controlled pruritus, and 40 had xanthomas; cirrhosis was found in 35/76 livers, varices in 25/71 patients, and liver transplantation had been carried out in 44 patients (33%). Forty eight patients died, 17 related to complications of liver disease. Of 31 patients who did not present with neonatal cholestatic jaundice, five were jaundiced at the study end point, 17 had well controlled pruritus, and none had xanthomas; cirrhosis was found in 6/18 patients, varices in 4/11, and none underwent liver transplantation. Nine patients died, two of liver disease. In the whole series, actuarial survival rates with native liver were 51% and 38% at 10 and 20 years, respectively, and overall survival rates were 68% and 62%, respectively. Neonatal cholestatic jaundice was associated with poorer survival with native liver (p=0.0004). CONCLUSIONS: The prognosis of liver disease in AGS is worse in children who present with neonatal cholestatic jaundice. However, severe liver complications are possible even after late onset of liver disease, demanding follow up throughout life. (+info)