Biomedical subjects

N Porchet

Publications and source records attributed to N Porchet.

At least 55 records · Page 3Linked to original sources

PubMed1999

[MUC genes: a superfamily of genes? Towards a functional classification of human apomucins].

The MUC genes encode epithelial mucins. Eight different human genes have been well characterized, and two others identified more recently. Among them, a family of four genes, expressed in the respiratory and digestive tracts, is clustered to chromosome 11p15.5; and these genes encode gel-forming mucins which are structurally related to the superfamily of cystine-knot growth factors. A second group is composed of three independent genes encoding various isoforms of mucins including membrane-bound mucins associated to carcinomas. In this second group, MUC3 and MUC4 encode large apomucins containing EGF-like domains.

Amino Acid Sequence↗

PubMed1998

Genomic organization of the human mucin gene MUC5B. cDNA and genomic sequences upstream of the large central exon.

The complete structure of the DNA encoding the polypeptide chain of human mucin MUC5B has been determined. In this paper, we report the full-length cDNA (3886 bp) and genomic (15,143 bp) sequences upstream of the unusually large central exon of the human mucin gene MUC5B. This region, composed of 29 exons, encodes 1283 amino acid residues. Exon sizes vary from 44 to 262 bp, and intron sizes range from 87 to 1703 bp. We determined the 5'-end of MUC5B by performing rapid amplification of cDNA ends-polymerase chain reaction experiments leading to the same length of the amplified product and by using primer extension experiments. A putative translation start site was found at nucleotide +37. We compared the amino-terminal region of MUC5B with those of pro-von Willebrand Factor, MUC2 and MUC5AC, and animal mucins, RMuc2, PSM, and FIM-B.1. The primary amino acid sequence with a high content of cysteine residues demonstrates a high degree of similarity with other members of the 11p15 mucin gene family, particularly MUC5AC. The complete genomic organization and both full-length genomic and cDNA sequences of MUC5B have been elucidated. This gene contains 48 exons and encodes 5662 amino acid residues to give a polypeptide with a Mr approximately 600,000.

Amino Acid Sequence↗

PubMed1998

Genomic organization of the 3'-region of the human MUC5AC mucin gene: additional evidence for a common ancestral gene for the 11p15.5 mucin gene family.

The human mucin gene MUC5AC is mapped clustered with MUC2, MUC5B and MUC6 on chromosome 11p15.5. We report here the isolation and characterization of a genomic cosmid clone, designated ELO9, spanning the 3'-region of MUC5AC and the 5'-region of MUC5B, allowing us to conclude that MUC5AC and MUC5B have the same transcriptional orientation. We determined the genomic organization and the entire sequence of the 3'-region of MUC5AC. The comparative molecular analysis of MUC5AC and MUC5B points to a remarkable similarity in the size and the distribution of exons, and in the type of splice sites, supporting the notion that MUC5AC and MUC5B have evolved from a single common ancestral gene. The derivation of the four genes of the 11p15.5 mucin gene family from a single ancestral gene is discussed.

Amino Acid Sequence↗

PubMed1998

Human mucin gene MUC4: organization of its 5'-region and polymorphism of its central tandem repeat array.

In a previous study we isolated a partial cDNA with a tandem repeat of 48 bp, which allowed us to map a novel human mucin gene named MUC4 to chromosome 3q29. Here we report the organization and sequence of the 5'-region and its junction with the tandem repeat array of MUC4. Analysis of three overlapping genomic clones allowed us to obtain a partial restriction map of MUC4 and to locate the complete 48 bp tandem repeat domain on a PstI/EcoRI genomic fragment that exhibits a very large variation in number of tandem repeats (7-19 kb). cDNA clonal extension allowed us to obtain the entire 5' coding region of MUC4. Exon 1 consists of a 5' untranslated region and an 82 bp fragment encoding the signal peptide. This latter shows a high degree of similarity to the signal peptide of another apomucin, ASGP-1. Exon 2 is extremely large and contains a unique sequence that is followed by the whole tandem repeat domain. It encodes only one cysteine residue, making MUC4 different from mucin genes belonging to the 11p15.5 family. Moreover, an intron downstream from the tandem repeat array consists mainly of a 15 bp tandem repeat that exhibits a polymorphism in having a variable number of tandem repeats.

Amino Acid Sequence↗

PubMed1998

Human mucin genes MUC2, MUC3, MUC4, MUC5AC, MUC5B, and MUC6 express stable and extremely large mRNAs and exhibit a variable length polymorphism. An improved method to analyze large mRNAs.

Of the nine mucin genes that have been characterized, only MUC1 and MUC7 have been fully sequenced, and their transcripts can be detected as distinct bands of predicted size by Northern blot analysis. In contrast, the RNA patterns observed for each of the other MUC genes have usually shown a very high degree of polydispersity. This polydispersity has been believed to be one of the typical features of the mucin mRNAs, but until now, its origin has remained unexplained. In the work described in the present paper, we investigated two possible kinds of explanation for this phenomenon: namely that the extensive polydispersity results from a biological mechanism or that it is artifactual in origin. The data obtained, as a result of improving the purification and blotting methods, allowed us to show that in all of the tissues analyzed, each of the genes, MUC2-6, expresses mRNAs that are stable and are of an unusually large size to be found in eukaryotes (14-24 kilobases). Moreover, allelic variations in length of these mucin transcripts were observed. We demonstrate that these variations are directly related to the variable number of tandem repeat polymorphisms seen at the DNA level.

Apolipoprotein B-100↗

PubMed1998

Evolutionary history of the 11p15 human mucin gene family.

The four human mucin genes MUC6, MUC2, MUC5AC, and MUC5B are located at chromosome 11p15.5. It has been demonstrated that the three mucins MUC2, MUC5AC, and MUC5B contain several Cys-subdomains of 108 amino acid residues. In contrast, little information is available concerning MUC6. These Cys-subdomains contain 10 cysteine residues that have a highly conserved position. We present here a coherent probable evolutionary history of this human gene family after comparison of the nucleotide sequences of these Cys-subdomains. The three MUC loci MUC2, MUC5AC, and MUC5B may have evolved from a common ancestral gene by two successive duplications. Moreover, we can postulate that MUC5AC and MUC5B have evolved in a concerted manner, while MUC2 has evolved separately.

Base Sequence↗

PubMed1998

Variable number tandem repeat polymorphism of the mucin genes located in the complex on 11p15.5.

A family of four genes that encode major secreted mucins (MUC6, MUC2, MUC5AC and MUC5B) map to within 400 kb on chromosome 11p15.5. These genes contain long stretches of tandem repeats of sequence that encode serine- and threonine-rich domains but that otherwise show no similarity from gene to gene, and regions of unique sequence domains that do show evidence of sequence homology. We have previously reported the existence of polymorphism in three of these genes but the extent and nature of this allelic variation is now described here in detail. Variable number tandem repeat polymorphisms of MUC6, MUC2 and MUC5AC are predicted to encode mucin polypeptides that differ in length. In the case of MUC2 and MUC6 these length differences are substantial (up to twofold). MUC5B in contrast does not show common allele length variation. Three MUC2 mutations are reported, none of which are associated with the meiotic recombinations previously observed in this region of chromosome 11.

Child↗

PubMed1998

Germ-line mutation analysis in patients with multiple endocrine neoplasia type 1 and related disorders.

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant syndrome predisposing to tumors of the parathyroid, endocrine pancreas, anterior pituitary, adrenal glands, and diffuse neuroendocrine tissues. The MEN1 gene has been assigned, by linkage analysis and loss of heterozygosity, to chromosome 11q13 and recently has been identified by positional cloning. In this study, a total of 84 families and/or isolated patients with either MEN1 or MEN1-related inherited endocrine tumors were screened for MEN1 germ-line mutations, by heteroduplex and sequence analysis of the MEN1 gene-coding region and untranslated exon 1. Germ-line MEN1 alterations were identified in 47/54 (87%) MEN1 families, in 9/11 (82%) isolated MEN1 patients, and in only 6/19 (31.5%) atypical MEN1-related inherited cases. We characterized 52 distinct mutations in a total of 62 MEN1 germ-line alterations. Thirty-five of the 52 mutations were frameshifts and nonsense mutations predicted to encode for a truncated MEN1 protein. We identified eight missense mutations and five in-frame deletions over the entire coding sequence. Six mutations were observed more than once in familial MEN1. Haplotype analysis in families with identical mutations indicate that these occurrences reflected mainly independent mutational events. No MEN1 germ-line mutations were found in 7/54 (13%) MEN1 families, in 2/11 (18%) isolated MEN1 cases, in 13/19 (68. 5%) MEN1-related cases, and in a kindred with familial isolated hyperparathyroidism. Two hundred twenty gene carriers (167 affected and 53 unaffected) were identified. No evidence of genotype-phenotype correlation was found. Age-related penetrance was estimated to be >95% at age >30 years. Our results add to the diversity of MEN1 germ-line mutations and provide new tools in genetic screening of MEN1 and clinically related cases.

Amino Acid Substitution↗

PubMed1998

Abnormal mucus in cap polyposis.

BACKGROUND: Cap polyposis is a rare disease characterised by mucoid and bloody diarrhoea, with polyps covered by a cap of mucoid and fibrinopurulent exudate. The pathogenesis is not known. AIMS: To pour some light on cap polyposis pathogenesis, by examining the mucus of patients and analysing the expression of five mucin genes, MUC2, MUC3, MUC4, MUC5AC, and MUC5B. PATIENT AND METHODS: The study was performed on biopsy specimens taken from a patient with recurrent cap polyposis. Histochemical examination, electron microscopy, and mRNA in situ hybridisation were used. RESULTS: The mucus of cap polyposis differed in three respects from that of normal adult colon: abnormal ultrastructure of the mucus in the goblet cells, predominance of non-sulphated mucins, abnormal expression of the MUC4, MUC3, and MUC5AC genes. CONCLUSIONS: Most of these abnormalities have been reported for other pathological situations, suggesting that the abnormalities observed in the mucus of this patient with cap polyposis are probably secondary phenomena rather than primary. However, the mucin abnormalities detected, which reflect deregulation of the expression of three apomucin genes, abnormal glycosylation, and abnormalities of the secretion process, are also probably involved in the clinical manifestations of cap polyposis.

Adult↗

PubMed1998

Mucin gene expression in human embryonic and fetal intestine.

BACKGROUND: The intestinal epithelium is covered by a continuous layer of mucus which is secreted by well differentiated epithelial cells. Disregulation of the expression of mucins has been reported to have possible implications in the neoplastic process which affects intestinal mucosae. It is well known that preneoplastic and neoplastic tissues can express fetal phenotypic characteristics. AIMS: To assess whether the expression of mucin genes in the intestinal tract is linked to the stage of cellular differentiation and tissue development, by studying the expression of six mucin genes in human fetal small intestine and colon, and also adult tissues. METHODS: In situ hybridisation was used to study mRNA expression of MUC2, MUC3, MUC4, MUC5B, MUC5AC, and MUC6 in 32 human embryos and fetuses (6.5-27 weeks gestation). Normal adult mucosae were used as controls. RESULTS: Three mucin genes, MUC2, MUC4, and MUC5AC, were differently expressed in fetal intestine compared with expression in normal adults. CONCLUSION: These differences in mucin gene expression suggest a possible regulatory role for these products in intestinal epithelial cell differentiation.

Adult↗

PubMed1998

[Ovarian mucinous tumor of gastric and intestinal type associated with Peutz-Jeghers syndrome: in situ hybridization study of apomucin gene transcripts].

Occurrence of mucinous tumors is favored by Peutz-Jeghers syndrome (PJS). A case of bilateral ovarian mucinous tumor associated with ovarian mature teratoma occurring in a 22-year-old woman with PJS was reported. Tumor cells included 5 cell types: tall columnar mucinous pale cells with neutral mucins; goblet cells with acidic nonsulfated mucins; non mucinous columnar cells; mucinous cuboidal cells lining small glands; endocrine cells. Expression of the MUC2, MUC3, MUC5AC and MUC6 genes was demonstrated by in situ hybridization according to cell type. Some atypia and numerous mitotic figures were observed in basal glands. Diagnosis was ovarian borderline mucinous tumor with gastric and intestinal phenotype associated with PJS.

Adenocarcinoma, Mucinous↗

PubMed1998

[Clinicogenetic study of MEN1: recent physiopathological data and clinical applications. Study Group of Multiple Endocrine Neoplasia (GENEM)].

Multiple Endocrine Neoplasia type 1 (MEN1, OMIM 131100, Wermer syndrome) is characterized by inherited predisposition to primary hyperparathyroidism, endocrine pancreatic-duodenal, pituitary, adrenal glands tumors and benign and/or malignant proliferations of diffuse neuroendocrine tumors in thymus and bronchi, formerly defined as carcinoid tumors. Minor lesions have been observed in MEN1 patients such as cutaneous tumors (angiofibroma, lipoma, lentiginosis), thyroid epithelioma and tumors of the central nervous system, mainly spinal ependymoma. The MEN1 gene, a locus encompassing a 9 kb of genomic sequence contains 10 exons, the first exon being untranslated. The protein encoded by this gene was called menin and has been shown to contain two nuclear localization signals (NLS), suggesting a major function in the nucleus. Germline MEN1 mutations have been described in more than 150 families and are spread throughout the entire coding sequence. More than 70% of the mutations alter one or both NLS and no genotype-phenotype correlations were found to date. The MEN1 gene seems to be involved in a 20-30% of sporadic parathyroid and pancreatic/bronchic neuroendocrine tumors, but less than 1% of pituitary sporadic tumors. Further knowledge on the intracellular function of menin will be needed to understand the pathogenic effect of truncating and missense mutations of this gene in the initiation of endocrine cells tumorigenesis.

Humans↗

PubMed1997

Mucins secreted by a transformed cell line derived from human tracheal gland cells.

High-molecular-mass glycoconjugates are secreted by the continuous cell line MM-39, which has been obtained from cultured human tracheal gland cells transformed by simian virus 40. They were purified on Sepharose(R) CL-4B and then by two steps of density-gradient centrifugation. High-molecular-mass glycoproteins resistant to digestion by hyaluronidase, chondroitin ABC lyase and heparitinase were obtained, in addition to hyaluronic acid and proteoglycans. They were susceptible to beta-elimination. They contained polylactosaminoglycan chains as well as carbohydrate chains with a terminal sialic acid in the NeuAc alpha2-3 sequence. Most of them have a buoyant density of 1.45 g/ml in CsCl-density-gradient centrifugation, except for MUC1. The MM-39 cells were also characterized by a high expression of MUC1 and MUC4 genes, but they did not express MUC2, MUC3, MUC5B and MUC5AC. Therefore the MM-39 cells synthesized mucin-like glycoproteins as well as lysozyme and mucous proteinase inhibitor [Merten, Kammouni, Renaud, Birg, Mattéi and Figarella (1996) Am. J. Respir. Cell. Mol. Biol. 15, 520-528]; they should be considered as having a mixed, both serous and mucous, phenotype.

Cell Line, Transformed↗

PubMed1997

Genomic organization of the 3' region of the human mucin gene MUC5B.

MUC5B, mapped clustered with MUC6, MUC2, and MUC5AC to chromosome 11p15.5, is a human mucin gene of which the genomic organization is being elucidated. We have recently published the sequence and the peptide organization of its huge central exon, 10,713 base pairs (bp) in length. We present here the genomic organization of its 3' region, which encompasses 10,690 bp. The genomic sequence has been completely determined. The 3' region of MUC5B is composed of 18 exons ranging in size from 32 to 781 bp, contrasting thus with the very large central exon. The sizes of the 18 introns range from 114 to 1118 bp. Some repetitive sequences were identified in four introns. The peptide deduced from the sequence of the 18 exons consists of an 808-amino acid peptide. This carboxyl-terminal region exhibits extensive sequence similarity to MUC2, MUC5AC, and von Willebrand factor, particularly the number and the positions of the cysteine residues, suggesting that this domain may be derived from a common ancestral gene. The presence in these components of a cystine knot also found in growth factors such as transforming growth factor-beta is of particular interest. Moreover, one part of this peptide is identical to the 196-amino acid sequence deduced from the cDNA clone pSM2-1, which codes for a part of the high molecular weight mucin MG1 isolated from human sublingual gland. Considering the expression pattern of MUC5B and the origin of MG1, we can thus conclude that MUC5B encodes MG1.

Amino Acid Sequence↗

PubMed1997

Human mucin gene MUC5B, the 10.7-kb large central exon encodes various alternate subdomains resulting in a super-repeat. Structural evidence for a 11p15.5 gene family.

Human mucin gene MUC5B is mapped clustered with MUC6, MUC2, and MUC5AC on chromosome 11p15.5. We report here the isolation of three overlapping genomic clones of human MUC5B spanning approximately 40 kilobases. We have determined their partial restriction maps and the intron-exon boundaries of the central region encoding a single open reading frame. This coding region has been completely sequenced. Its length is 10,713 base pairs, and it encodes a 3570-amino acid peptide. Nineteen subdomains have been individualized. Some subdomains show similarity to each other, creating larger composite repeat units that we have called super-repeats. Four super-repeats of 528 amino acid residues are thus observed within the central exon. Each comprises (i) a subdomain composed of 11 repeats of the irregular repeat of 29 amino acid residues, (ii) a unique conserved subdomain with no typical repeat, and (iii) a cysteine-rich subdomain. This latter subdomain has high sequence similarity to the cysteine-rich domains described in MUC2 and MUC5AC. Sequence data of these three genes, together with their clustered organization, lead us to suggest that they may be a part of a multigene family. The super-repeat present in MUC5B is the largest ever determined in mucin genes and the central exon of this gene is, by far, the largest reported for a vertebrate gene.

Amino Acid Sequence↗

PubMed1997

Mucin gene expression in biliary epithelial cells.

BACKGROUND/AIMS: In recent years considerable advances have been made in our knowledge of human mucin genes. Although analysis of their genomic organization is still in progress, the pattern of their expression in different human mucosae is now fairly well established. However, little is known about their expression in the biliary tree. In this study we determined the pattern of expression of the different human mucin genes in gallbladder biliary epithelial cells, intrahepatic bile ducts and liver. METHODS: Two complementary methods were used: Northern-blot and in situ hybridization analyses. The experiments were performed with eight probes corresponding to MUC1, MUC2, MUC3, MUC4, MUC5AC, MUC5B, MUC6 and MUC7. RESULTS: Our results revealed a strong mRNA expression of MUC3, MUC6 and MUC5B, a weak expression of MUC1, MUC5AC and MUC2, and no expression of MUC4 and MUC7. Surprisingly, MUC3, which was the gene which was most expressed in the biliary tree, was also found in hepatocytes, suggesting another function for the MUC3 protein than that of a secreted mucin. CONCLUSIONS: We conclude that MUC3, MUC6 and MUC5B were the main mucin genes expressed in biliary epithelial cells.

Adult↗

PubMed1997

Genetic testing in presymptomatic diagnosis of multiple endocrine neoplasia.

Multiple endocrine neoplasias (MEN) are familial diseases characterized by endocrine neoplasms and transmitted in an autosomal dominant manner. In MEN type 1, the major lesions affect parathyroid glands, pancreatic islet cells and anterior pituitary. The MEN-1 gene has been mapped to chromosome 11q13 and a set of DNA-polymorphic markers localized close to this region provides a useful tool for presymptomatic diagnosis in MEN-1 families. MEN type 2 refers to the inherited forms of medullary thyroid carcinoma (MTC) associated or not with pheochromocytoma and hyperparathyroidism. In MEN-2, germinal mutations of the C-RET proto-oncogene which is localized on chromosome 10q11 have been found in the three clinical and allelic forms of the syndrome respectively, MEN-2 type A, B and familial isolated MTC. Mutations of C-RET are found in more than 90% of MEN-2 patients and genetic screening leads to accurate risk evaluation in families and consequently a preventive treatment of MTC and adrenal neoplasms. Recent discoveries on MEN syndromes and related familial endocrine disorders have a major clinical impact and allow a better understanding of the physiological pathways involved in familial as well as in sporadic endocrine tumor pathogenesis.

Chromosomes, Human, Pair 10↗

PubMed1996

Human mucin genes assigned to 11p15.5: identification and organization of a cluster of genes.

Four distinct genes that encode mucins have previously been mapped to chromosome 11p15.5. Three of these genes (MUC2, MUC5AC, and MUC6) show a high level of genetically determined polymorphism and were analyzed in the CEPH families. Linkage analysis placed all three genes on the genetic map in a cluster between HRAS and INS, and more detailed analysis of recombinant breakpoints revealed that MUC6 is telomeric to MUC2. Using these recombinants D11S150 was mapped close to MUC2. Ten of the 11 recombinant chromosomes studied in detail were paternal, and the recombinant events were distributed throughout the 11p15 region, suggesting that the high level of recombination observed in 11p15.5 is not due to a particular recombinational hot spot. Pulsed-field gel electrophoresis was used to make a detailed physical map of the MUC cluster and to integrate the physical and genetical maps. The gene order was determined to be HRAS-MUC6-MUC2-MUC5AC-MUC5B-IGF2. The MUC genes span a region of some 400 kb and the map extends 770 kb and contains 15 putative CpG islands. The order of the MUC genes on the map corresponds to the relative order of their expression along the anterior-posterior axis of the body, suggesting a possible functional significance to the gene order.

Adult↗