Biomedical subjects

Claudine Junien

Publications and source records attributed to Claudine Junien.

29 records · Page 2Linked to original sources

PubMed2003

Mutations in PCSK9 cause autosomal dominant hypercholesterolemia.

Autosomal dominant hypercholesterolemia (ADH; OMIM144400), a risk factor for coronary heart disease, is characterized by an increase in low-density lipoprotein cholesterol levels that is associated with mutations in the genes LDLR (encoding low-density lipoprotein receptor) or APOB (encoding apolipoprotein B). We mapped a third locus associated with ADH, HCHOLA3 at 1p32, and now report two mutations in the gene PCSK9 (encoding proprotein convertase subtilisin/kexin type 9) that cause ADH. PCSK9 encodes NARC-1 (neural apoptosis regulated convertase), a newly identified human subtilase that is highly expressed in the liver and contributes to cholesterol homeostasis.

Amino Acid Substitution↗

PubMed2003

The genetics of neonatal hyperinsulinism.

Congenital hyperinsulinism (CHI) is the most important cause of persistent hypoglycaemia in the neonate and infant. It is a clinically and genetically heterogeneous entity. The clinical heterogeneity is manifested by severity ranging from extremely severe life-threatening disease to very mild clinical symptoms which may even be difficult to identify. Furthermore, clinical responsiveness to medical and surgical management is extremely variable. Two histopathological forms have been described: a diffuse form of CHI and a focal form of CHI. Recent discoveries have begun to clarify the molecular aetiology of the disease and therefore the mechanisms responsible for its clinical heterogeneity are becoming clearer. Mutations in four different genes have been identified in patients with CHI. Most cases are caused by mutations in genes coding for either of the two subunits of the beta-cell K(ATP) channel (ABCC8 and KCNJ11). In the diffuse form of CHI, the hyperinsulinism is due to a recessive mutation of both alleles of these genes (rare dominant mutations have been described). In the focal form of CHI, two events intervene: first, the inheritance of a paternal ABCC8/KCNJ11 mutation; second, the focal reduction to homozygosity of the mutation during pancreatic development by a localized loss of the maternal 11p15 region. Others cases of CHI are due to rare mutations in the beta-cell enzymes glucokinase (only one family described) and glutamate dehydrogenase in hyperammonaemia-associated hyperinsulinism. However, in as many as 50% of cases, no genetic aetiology has yet been identified.

Chromosomes, Human, Pair 11↗

PubMed2003

The focal form of persistent hyperinsulinemic hypoglycemia of infancy: morphological and molecular studies show structural and functional differences with insulinoma.

Paternal mutation of ATP-sensitive K(+) (K(ATP)) channel genes and loss of heterozygosity (LOH) of the 11p15 region including the maternal alleles of ABCC8, IGF2, and CDKN1C characterize the focal form of persistent hyperinsulinemic hypoglycemia of infancy (FoPHHI). We aimed to understand the actual nature of FoPHHI in comparison with insulinoma. In FoPHHI, the lesion consists in clusters of beta-cells surrounded by non-beta-cells. Compared with adjacent islets, proinsulin mRNA is similar and proinsulin production higher (P < or = 0.02), indicating regulation at a translational level, with slightly lower insulin stock and lower ABCC8 peptide labeling (P<0.05). Insulinomas, composed of beta-cell nests or cords, have similar proinsulin mRNA compared with adjacent islets, highly variable proinsulin production, lower insulin stock (P < or = 0.02), and higher ABCC8 peptide labeling (P<0.05). Proinsulin mRNA is lower than in FoPHHI (P<0.001). Islets adjacent to FoPHHI appear to be resting, in contrast to those adjacent to insulinomas, evidencing intrapancreatic regulation of islet beta-cell activity. IGF2 peptide is present inside and outside both lesions, but IGF2 mRNA is restricted to the lesions. The 11p15 LOH and absence of CDKN1C peptide staining are demonstrated in all FoPHHI but also in three of eight insulinomas. Despite some molecular similarities, FoPHHI is thus fundamentally different from insulinoma.

ATP-Binding Cassette Transporters↗

PubMed2002

Changes in WT1 splicing are associated with a specific gene expression profile in Wilms' tumour.

Wilms' tumour (WT) or nephroblastoma is the most frequent kidney cancer in children. In a previous study, we reported alterations to WT1 transcription in 90% of WT tested, with decreased exon 5 +/- isoform ratio being the most frequent alteration (56% of WT). We now report an approach based on cDNA profiling of tumour pools to identify genes likely to be dysregulated in association with a decreased WT1 exon 5 +/- ratio. We compared the expression profiles of pools of tumours classified according to whether this isoform imbalance was present (five tumours) or not (four tumours), using Atlas Cancer cDNA expression arrays. Fourteen of 588 genes tested displayed specific up-regulation (CCND2, PCNA, N-MYC, E2F3, TOP2A, PAK1, DCC and PCDH2) or down-regulation (VEGF, IGFBP5, TIMP3, ARHB, C-FOS and CD9) in the pool of tumours with decreased exon 5 +/- ratio. These results were validated by RT-PCR analysis of four genes (CCND2, PCNA, VEGF and IGFBP5). We extended the analysis of VEGF expression to 51 tumours by real-time RT-PCR and ascertained differential expression of this gene associated with WT1 expression pattern. Moreover, our results suggest that the VEGF expression level may be of prognosis relevance for relapsed patients.

Alternative Splicing↗

PubMed2002

Facial appearance in persistent hyperinsulinemic hypoglycemia.

Persistent hyperinsulinism is the most common cause of recurrent hypoglycemia in infancy because of inappropriate oversecretion of insulin by the pancreas. Pancreatic lesions can be either focal or diffuse, and they have distinct molecular bases. We have studied the facial features in 17 unrelated patients presenting with neonatal (n = 8) or infancy-onset (n = 9) hyperinsulinism. Hyperinsulinism was related to focal adenomatous hyperplasia (n = 7), diffuse hyperinsulinism (n = 5), non-operated hyperinsulinism (n = 2), and hyperinsulinism with hyperammonemia (n = 3). SUR1 or Kir6.2 mutations were found in six of seven focal adenomatous hyperplasia and three of five diffuse hyperinsulinism. A loss of the maternal allele from chromosome 11p15 in the lesion was found in all focal adenomatous hyperplasia. GLUD1 mutations were found in all patients with hyperammonemia. Large birth weight (mean > 3,800 g) was consistently observed (11/17) but protruding tongue, exomphalos, or visceromegaly were never noted and Wiedemann-Beckwith syndrome could always be ruled out. All patients presented with high forehead, small nasal tip, and short columella giving the impression that the nose is large and bulbous, smooth philtrum, and thin upper lip. A square appearance to the face was more obvious in younger patients. These specific facial features, observed in patients with hyperinsulinism of various molecular mechanisms, could be the consequence of fetal intoxication by insulin. However, to date, facial anomalies have not been noted in infants of diabetic mothers and inversely, malformations that are commonly reported in infants of diabetic mothers were not present in our hyperinsulinemic patients.

ATP-Binding Cassette Transporters↗

PubMed2002

The UMD-LDLR database: additions to the software and 490 new entries to the database.

Mutations in the LDL receptor gene (LDLR) cause familial hypercholesterolemia (FH), one of the most frequent hereditary dominant disorders. The protein defect was identified in 1973, the gene was localized by in situ hybridization in 1985, and since, a growing number of mutations have been reported. The UMD-LDLR database is customized software that has been developed to list all mutations, and also to provide means to analyze them at the nucleotide and protein levels. The database has been recently modified to fulfill the recommendations of the Nomenclature Working Group for human gene mutations. However, in the current version, both the nomenclature and usual LDLR gene mutation names are reported since the latter are more commonly used. The software has also been modified to accommodate the splicing mutations and alleles that carry two nucleotide variations. The current version of UMD-LDLR contains 840 entries, of which 490 are new entries. Point mutations account for 90% of all mutations in the LDLR gene; the remaining are mostly major rearrangements, due to the presence of Alu sequences. Three new routines have been implemented in the software, thus giving users access to 13 sorting tools. In addition to the database, a Web site containing information about polymorphisms, major rearrangements, and promoter mutations is available. Both are accessible to the scientific community (www.umd.necker.fr) and should help groups working on LDLR to check their mutations and identify new ones, and greatly facilitate the understanding of functional classes/genotype relationships and of genotype/phenotype correlations.

Databases, Genetic↗

PubMed2002

Heterogeneity of persistent hyperinsulinaemic hypoglycaemia. A series of 175 cases.

UNLABELLED: Hyperinsulinism is a heterogeneous disorder characterised by severe hypoglycaemia due to an inappropriate oversecretion of insulin. In a personal series of 175 patients investigated for hyperinsulinaemic hypoglycaemia over the last 20 years, we review clinical presentations, molecular studies and therapeutic management of hyperinsulinism. There were 98 neonatal-onset patients, including 86 permanent hyperinsulinism and 12 transient forms, 68 with infancy-onset and nine with childhood-onset. Hyperammonaemia was found in 12 out of 69 patients tested, 4 neonates and 8 infants. Neonates were clinically more severely affected than infants. Diagnosis of infancy-onset hyperinsulinism was often delayed because of less profound hypoglycaemia and better tolerance to hypoglycaemia. Neonates required higher rates of i.v. glucose than infants to maintain normal plasma glucose levels (16 mg/kg per min versus 12 mg/kg per min). Only 16% of neonates were diazoxide-sensitive compared to 66% of the infants. Neonates with hyperammonaemia or transient hyperinsulinism were diazoxide-sensitive. Most neonates were pancreatectomised whereas 65% of the infants were treated medically. Among surgically-treated patients, 47% had a focal adenomatous hyperplasia (31 neonates and 13 infants) and 53% a diffuse form of hyperinsulinism (39 neonates and 11 infants). Diazoxide-responsiveness in the focal and diffuse forms did not differ in both neonates and infants; it depended only upon the age of onset of hypoglycaemia. One or two mutations, SUR1 or KIR6.2, were found in 41 of 73 neonates who were investigated and in 13/38 infants using polymerase chain reaction-single strand conformational polymorphism analysis of both genes. Almost all patients with SUR1 (38/41) or KIR6.2 (5/7) mutations were resistant to diazoxide. Ten patients with hyperinsulinism-hyperammonaemia syndrome had a mutation in the glutamate dehydrogenase gene (three neonates and seven infants) after reverse transcriptase-polymerase chain reaction and sequence analysis of cDNA. No mutation was found by polymerase chain reaction-single strand conformational polymorphism in the glucokinase gene. Eight of nine patients with childhood onset hyperinsulinism were treated surgically and histological examination confirmed an adenoma in each case. CONCLUSION: the clinical severity of hyperinsulinism varies mainly with age at onset of hypoglycaemia. The heterogeneity of hyperinsulinism has major consequences in terms of therapeutic outcome and genetic counselling.

Age of Onset↗

PubMedDate not supplied

Impact of diets and nutrients/drugs on early epigenetic programming.

Specific, often unbalanced diets are used to circumvent the metabolic defects of patients with monogenic inborn errors of metabolism. Human epidemiological studies and appropriately designed dietary interventions in animal models have provided considerable evidence to suggest that nutritional imbalance and metabolic disturbances, during critical time windows of developmental programming, may have a persistent effect on the health of the child and later in adulthood. Thus patients with monogenic inborn errors of metabolism may also suffer additional types of alterations due to the lack or excess of key nutrients. Interactions of nutrients with the epigenetic machinery lead to epigenetic changes associated with chromatin remodelling and regulation of gene expression that underlie the developmental programming of pathological consequences in adulthood. Today, with the explosion of new technologies, we can explore on a large scale the effects of nutrients on the level of expression of thousands of expressed genes (nutritional genomics and epigenomics), the corresponding protein products and their posttranslationally modified derivatives (proteomics), and the host of metabolites (metabolomics) generated from endogenous metabolic processes or exogenous dietary nutrients and can establish the relationship between these biological entities and diet, health or disease. The combination of these various lines of research on epigenetic programming processes should highlight new strategies for the prevention and treatment of inborn errors of metabolism.

Acetylation↗

PubMedDate not supplied

ABCC8 (SUR1) and KCNJ11 (KIR6.2) mutations in persistent hyperinsulinemic hypoglycemia of infancy and evaluation of different therapeutic measures.

Persistent hyperinsulinemic hypoglycemia of infancy (PHHI) can occur as a result of mutations in the subunits that form the ATP-sensitive potassium channel (K+ATP) in pancreatic beta-cells which play a major role in modulating insulin secretion from the beta-cells. Mutations have been shown in the genes for these subunits, namely for the plasma membrane sulfonylurea receptor (SUR1), ABCC8, and its associated inwardly rectifying potassium channel (KIR6.2) KCNJ11. Drugs which act on K+ATP channels, such as diazoxide, seem to need intact ABCC8 to be able to show their effects. Thus, it would be desirable to know the exact locus of the abnormality in the beta-cell to be able to choose the right therapeutic agent or to perform early pancreatectomy. The aim of this study was to search for the correlation between the mutations of the K+ATP channel and the outcome of therapeutic measures in patients with PHHI followed for a duration of 4 months to 7.3 years. Thirteen patients (5 F, 8 M) with PHHI with a median age of 2.5 months (8 days-12.1 years) were included in the study. Therapy for PHHI was initiated either with diazoxide (n = 9) or with calcium channel blocker (n = 4) as the agent of first choice. Three patients unresponsive to drugs underwent 95% pancreatectomy. Mutation analysis was performed by polymerase chain reaction (PCR) and single strand conformation polymorphism (SSCP) in DNA samples extracted from patients' peripheral leukocytes. The PCR products were directly sequenced. Screening of ABCC8 and KCNJ11 for mutations revealed abnormalities in the ABCC8 gene in three patients out of 13: homozygosity for the 155del1 mutation, compound heterozygosity for T267-->G/A4612-2-->G, and compound heterozygosity for G4310-->A/ R1494Q. No mutations in the KCNJ11 gene were identified. Of the three patients who underwent pancreatectomy, two had identified mutations and one did not have any known mutation. In two patients in whom hyperinsulinism recurred after surgery and in the rest of the children, therapy with either diazoxide or calcium channel blocker proved to be effective in controlling hypoglycemia over the follow-up period. Thus it may be concluded that mutations in the ABCC8 gene were not predictive of the response to drugs. Unidentified mutations in the K+ATP channels other than those screened or other functional abnormalities in these channels may account for the different therapeutic responses.

ATP-Binding Cassette Transporters↗

PubMedDate not supplied

Cadherins in Wilms' tumor: E-cadherin expression despite absence of WT1.

Loss of heterozygosity of chromosome 16q occurs in 17-25% of Wilms' tumors. Two cadherin genes mapping to 16q22 were chosen as candidate gens: E-CAD, encoding epithelial cadherin, because it is involved in kidney development and it was recently reported to be a WT1 target; and KSP-CAD because it encodes a kidney-specific cadherin. By RT-PCR analysis in a series of 39 Wilms' tumors, we identified a very low expression of E-CAD and KSP-CAD in 72% and 95% of the tumors, respectively. To ascertain whether down-expression of these genes could be related to WT1 alterations in tumors, we looked for a relationship between WT1 and CAD expression. Our data suggest (i) the existence of alternative mechanisms for regulating E-CAD expression, and (ii) that E-CAD does not belong to the WT1 pathway that is altered in Wilms' tumorigenesis.

Cadherins↗

PubMedDate not supplied

Delineation of a 2.8 megabases region harboring a potential tumor suppressor gene involved in renal cell carcinoma, that is commonly deleted from chromosome 14.

MATERIALS AND METHODS: To investigate the genetic alterations that occur during the development of renal cell carcinomas (RCC), we used 20 microsatellite markers to examine 48 renal cell carcinomas for allelic losses of chromosome arm 14q. RESULTS: We identified 14q LOH in 31% of cases. Twelve tumors were entirely lacking the 14q arm and three were partially deleted. For the first time on fresh tumors, these findings led to the delineation of a 17.9 Mb region between markers D14S281 and D14S277 that is commonly deleted. Interestingly, this segment overlaps with the previously reported 37.8 Mb commonly deleted region. CONCLUSION: Taken together these results allowed us to define a new 2.8 Mb segment between markers D14S588 and D14S277 that potentially harbors a tumor suppressor gene involved in the development of RCC which can be reached by positional cloning.

Adult↗