RESUMO
Fibrinogen is a complex glycoprotein involved in the final step of the coagulation cascade as the precursor of fibrin monomers that participate in the formation of the haemostatic plug. Three genes (FGA, FGB, and FGG) clustered on chromosome 4q31.3-4q32.1 encode the three polypeptide chains (Aalpha, Bbeta, and gamma), which in a pairwise fashion form the hexameric circulating molecule. Among congenital fibrinogen deficiencies, quantitative defects (also called type I deficiencies; i.e. congenital afibrino-genemia [CAF] and hypofibrinogenemia) are characterized by the concomitant absence or reduction of coagulant activity and immunoreactive protein, while qualitative defects (type II deficiencies; i.e. dysfibrinogenemia and hypodysfibrino-genemia) show low clotting protein in contrast with normal or moderately reduced antigen. Patients affected by CAF (Mendelian Inheritance in Man, [MIM] #202400) or severe hypofibrinogenemia (MIM+134820, *134830, and *134850) may experience bleeding manifestations varying from mild to catastrophic. Although many cases of fibrinogen deficiencies have been described from a clinical point of view, only in a minority of cases the causal mutation was identified. The genetic defects so far described, most unique for any analyzed family, are invariantly located in the fibrinogen cluster; for only few of them the pathogenic role either at the protein or at the mRNA level has been investigated. This review, besides providing a concise description of the main structural and functional properties of fibrinogen and giving an overview of the clinical manifestations, the laboratory diagnosis and therapeutic approches, will be focused on the present knowledge on the genetic basis of quantitative fibrinogen deficiencies. Our systematic analysis of the available clinical and genetic data on these disorders evidences their high allelic heterogeneity, the existence of different pathogenic mechanisms, and the absence of strong genotype/phenotype correlations.
Assuntos
Afibrinogenemia/genética , Fibrinogênio/genética , Mutação , Afibrinogenemia/sangue , Testes de Coagulação Sanguínea , Fibrinogênio/química , Genótipo , Hemorragia , Humanos , Mutação/genética , Mutação/fisiologia , Fenótipo , Estrutura Secundária de ProteínaRESUMO
BACKGROUND: Several studies have evaluated the role of the multidrug resistance 1 gene (MDR1) polymorphism, which encodes the membrane-bound efflux transporter P-glycoprotein 170, in determining susceptibility to and disease behavior in inflammatory bowel disease (IBD), but with conflicting results. METHODS: A total of 211 patients with Crohn's disease (CD), 97 patients with ulcerative colitis (UC), and 212 control subjects were investigated for the presence of MDR1 G2677T/A and C3435T polymorphisms. Genotype frequencies of CD and UC patients were compared to those observed in a control population. Genotype-phenotype correlations with major clinical features were also established and estimated risks (odds ratio [OR] with 95% confidence interval [CI]) for the mutations were calculated by a logistic regression analysis and multiple correspondent analysis. RESULTS: No significant difference was observed for genotype frequencies for both MDR1 G2677T/A and C3435T polymorphisms on overall disease susceptibility for either CD or UC patients compared with control subjects. A significant association was found between the MDR1 C3435T polymorphism and patients with ileo-colonic CD (OR = 3.34; 95% CI: 1.34-8.27). Interestingly, a negative association was found between MDR1 C3435T polymorphism in patients with a positive family history for IBD (OR = 0.44; 95% CI: 0.20-0.95) and articular manifestations (OR = 0.29; 95% CI: 0.13-0.68). Both susceptible and protective effects were identified. No significant association between G2677T/A polymorphism and any specific subphenotypes was found, nor was there any association with subphenotypic categories of UC and both single nucleotide polymorphisms. CONCLUSIONS: The results of our study suggest that MDR1 gene polymorphism could have a role in determining susceptibility to IBD. The variability of this possible effect in the several studies reported so far may be the indirect expression of the complex role played by the MDR1 gene and its product, P-glycoprotein 170, in the regulation of host-bacteria interactions and in the pathogenesis of IBD.
Assuntos
Membro 1 da Subfamília B de Cassetes de Ligação de ATP/genética , Predisposição Genética para Doença , Doenças Inflamatórias Intestinais/genética , Polimorfismo Genético , Adulto , Colite Ulcerativa/genética , Feminino , Frequência do Gene , Genótipo , Humanos , Masculino , Fenótipo , Polimorfismo de Nucleotídeo ÚnicoRESUMO
Hereditary fibrinogen disorders include type I deficiencies (afibrinogenemia and hypofibrinogenemia, i.e. quantitative defects), with low or unmeasurable levels of immunoreactive protein; and type II deficiencies (dysfibrinogenemia and hypodysfibrinogenemia, i.e. qualitative defects), showing normal or altered antigen levels associated with reduced coagulant activity. While dysfibrinogenemias are in most cases autosomal dominant disorders, type I deficiencies are generally inherited as autosomal recessive traits. Patients affected by congenital afibrinogenemia or severe hypofibrinogenemia may experience bleeding manifestations varying from mild to severe. This review focuses on the genetic bases of type I fibrinogen deficiencies, which are invariantly represented by mutations within the three fibrinogen genes (FGA, FGB, and FGG) coding for the three polypeptide chains Aalpha, Bbeta, and gamma. From the inspection of the mutational spectrum of these disorders, some conclusions can be drawn: (i) genetic defects are scattered throughout the three fibrinogen genes, with only few sites appearing to represent relative mutational hot spots; (ii) several different types of genetic lesions and pathogenic mechanisms have been described in affected individuals (including gross deletions, point mutations causing premature termination codons, missense mutations affecting fibrinogen assembly/secretion, and uniparental isodisomy associated with a large deletion); (iii) the possibility to express recombinant fibrinogen mutants in eukaryotic cells is rapidly shedding light into the molecular mechanisms responsible for physiologic and pathologic properties of the molecule; (iv) though mutation analysis of the fibrinogen cluster does not yield precise information for predicting genotype/phenotype correlations, it still provides a valuable tool for diagnosis confirmation, identification of potential carriers, and prenatal diagnosis.
Assuntos
Afibrinogenemia/diagnóstico , Afibrinogenemia/genética , Fibrinogênio/biossíntese , Fibrinogênio/genética , Adolescente , Adulto , Criança , Pré-Escolar , Análise Mutacional de DNA , Feminino , Fibrinogênio/metabolismo , Deleção de Genes , Genótipo , Hemostasia , Humanos , Lactente , Recém-Nascido , Masculino , Fenótipo , Mutação PuntualRESUMO
Coagulation factor V (FV) is the protein cofactor required in vivo for the rapid generation of thrombin catalyzed by the prothrombinase complex. It also represents a central regulator in the early phases of blood clot formation, as it contributes to the anticoagulant pathway by participating in the downregulation of factor VIII activity. Conversion of precursor FV to either a procoagulant or anticoagulant cofactor depends on the local concentration of procoagulant and anticoagulant enzymes, so that FV may be regarded as a daring tight-rope walker gently balancing opposite forces. Given this dual role, genetic defects in the FV gene may result in opposite phenotypes (hemorrhagic or thrombotic). Besides a concise description on the structural, procoagulant and anticoagulant properties of FV, this review will focus on bleeding disorders associated with altered levels of this molecule. Particular attention will be paid to the mutational spectrum of type I FV deficiency, which is characterized by a remarkable genetic heterogeneity and by an uneven distribution of mutations throughout the FV gene.
Assuntos
Deficiência do Fator V/complicações , Hemorragia/etiologia , Transtornos Herdados da Coagulação Sanguínea , Fator V/genética , Fator V/fisiologia , Deficiência do Fator V/genética , Hemorragia/genética , Humanos , MutaçãoAssuntos
Afibrinogenemia/genética , Fibrinogênio/genética , DNA/genética , Análise Mutacional de DNA , Testes Genéticos , Genótipo , Homozigoto , Humanos , MutaçãoRESUMO
BACKGROUND: Type I fibrinogen deficiencies (hypofibrinogenemia and afibrinogenemia) are rare congenital disorders characterized by low or unmeasurable plasma fibrinogen antigen levels. Their genetic bases are represented by mutations within the three fibrinogen genes. Among the 11 reported missense mutations, a few have been characterized by expression studies and found to have an impaired fibrinogen assembly and/or secretion. Histopathological analyses were previously reported in two hypofibrinogenemic cases with discernible hepatic disease, revealing that both underlying mutations (gamma-Gly284Arg and gamma-Arg375Trp) were associated with hepatic fibrinogen endoplasmic reticulum storage disease (ERSD). OBJECTIVE: The objective of this study was to investigate the liver histology in an afibrinogenemic patient, homozygous for the Bbeta-Leu353Arg mutation, and to study the intracellular processing of the mutant protein. PATIENTS AND METHODS: Liver histology was evaluated by light microscopy, electron microscopy and immunocytochemistry. Intracellular processing of mutant fibrinogen was analyzed by pulse-chase labeling and immunoprecipitation experiments. Messenger RNA levels were determined by real-time reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: The histopathological characterization of the liver showed no signs of fibrinogen accumulation, a difference from the previously reported findings in two hypofibrinogenemic kindreds with ERSD. To evaluate whether the Bbeta-Leu353Arg mutation and the ERSD-associated gamma-Gly284Arg mutation affected intracellular fibrinogen trafficking differently, both mutant proteins were expressed in COS-1 cells. Bbeta-Leu353Arg led to a more severe secretion defect, but no differences that could explain phenotype-genotype correlation were found in the intracellular processing. Endoglycosidase-H analysis demonstrated a secretion block before translocation to the Golgi medial stacks. Real-time RT-PCR studies showed normal levels of the Bbeta mRNA in the patient's liver. CONCLUSIONS: The results confirm that Bbeta-Leu353Arg is associated with impaired fibrinogen secretion, but not with hepatic ERSD.
Assuntos
Retículo Endoplasmático/patologia , Fibrinogênio/genética , Hepatopatias/patologia , Fígado/patologia , Erros Inatos do Metabolismo/patologia , Mutação , Adolescente , Animais , Arginina/química , Células COS , DNA Complementar/metabolismo , Eletroforese em Gel de Poliacrilamida , Fibrinogênio/química , Genótipo , Glicosídeo Hidrolases/metabolismo , Humanos , Imuno-Histoquímica , Imunoprecipitação , Leucina/química , Fígado/metabolismo , Hepatopatias/genética , Masculino , Erros Inatos do Metabolismo/genética , Microscopia Eletrônica , Mutação de Sentido Incorreto , Fenótipo , RNA/metabolismo , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , TransfecçãoRESUMO
BACKGROUND: Severe factor V (FV) deficiency is a rare coagulation disorder, characterized by very low or unmeasurable plasma levels of functional and immunoreactive FV. Among rare inherited coagulopathies, FV deficiency is the least characterized from a molecular point of view (only 12 mutations have been reported). OBJECTIVES: The aim of this work was to investigate, at the molecular level, the pathogenetic mechanisms responsible for a case of severe FV deficiency. PATIENTS AND METHODS: A 19-year-old Iranian man showing unmeasurable FV activity and severely reduced FV antigen level in plasma was studied. Mutation screening was performed by sequencing. The effect of the identified mutation was investigated both at the mRNA and at the protein level. RESULTS: Molecular analysis of the factor V (FV) gene identified a novel homozygous A-->T transversion at position + 3 of the donor splice site of intron 19 (IVS19 + 3A-->T). Production of mutant mRNA in HeLa cells demonstrated that this mutation causes the entire exon 19 to be skipped from the FV mRNA. The mutant processed transcript codes for a deleted FV, lacking the first 24 amino acids of the C1 domain. Expression of the mutant FV protein in COS-1 cells showed that the deleted protein was synthesized but not secreted; moreover, the intracellular amount of deleted FV was reduced compared to wild type, suggesting intracellular degradation of mutant FV. CONCLUSIONS: This work reports the molecular characterization of the first mutation causing a partial deletion in the FV molecule, resulting in a severe impairment of protein secretion.
Assuntos
Éxons , Deficiência do Fator V/genética , Fator V/química , Fator V/genética , Deleção de Sequência , Adulto , Análise Mutacional de DNA , Fator V/metabolismo , Homozigoto , Humanos , Irã (Geográfico) , Masculino , Modelos Moleculares , Mutação Puntual , Estrutura Terciária de Proteína , Sítios de Splice de RNA/genética , RNA Mensageiro/genéticaRESUMO
Congenital afibrinogenemia is a rare coagulation disorder with autosomal recessive inheritance, characterized by the complete absence or extremely reduced levels of fibrinogen in patients' plasma and platelets. Eight afibrinogenemic probands, with very low plasma levels of immunoreactive fibrinogen were studied. Sequencing of the fibrinogen gene cluster of each proband disclosed 4 novel point mutations (1914C>G, 1193G>T, 1215delT, and 3075C>T) and 1 already reported (3192C>T). All mutations, localized within the first 4 exons of the A alpha-chain gene, were null mutations predicted to produce severely truncated A alpha-chains because of the presence of premature termination codons. Since premature termination codons are frequently known to affect the metabolism of the corresponding messenger RNAs (mRNAs), the degree of stability of each mutant mRNA was investigated. Cotransfection experiments with plasmids expressing the wild type and each of the mutant A alpha-chains, followed by RNA extraction and semiquantitative reverse-transcriptase-polymerase chain reaction analysis, demonstrated that all the identified null mutations escaped nonsense-mediated mRNA decay. Moreover, ex vivo analysis at the protein level demonstrated that the presence of each mutation was sufficient to abolish fibrinogen secretion.
Assuntos
Afibrinogenemia/congênito , Afibrinogenemia/genética , Códon , Fibrinogênio/genética , Mutação , RNA Mensageiro/metabolismo , Adulto , Animais , Barbados/etnologia , Células COS , Criança , Pré-Escolar , Estabilidade de Medicamentos , Éxons , Feminino , Fibrinogênio/química , Haplótipos , Humanos , Itália , Masculino , Mutagênese Sítio-Dirigida , Mutação Puntual , Regiões Promotoras Genéticas , Splicing de RNA , RNA Mensageiro/análise , RNA Mensageiro/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Análise de Sequência de DNA , TransfecçãoRESUMO
Genes coding for the alpha5, alpha3, and beta4 subunits (CHRNA5, CHRNA3, and CHRNB4) of the neuronal nicotinic acetylcholine receptors (nAChRs) are clustered on chromosome 15q24. Linkage of this chromosomal region to autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE), an idiopathic partial epilepsy, was reported in one family. Moreover, mutations in other neuronal nAChR subunit genes coding for the alpha4 (CHRNA4) and the beta2 (CHRNB2) subunits were associated with ADNFLE. Apart from the exon-intron structure of CHRNA3, the genomic organization of this gene cluster was unknown, making comprehensive mutational analyses impossible. The genomic structure of CHRNA5 and CHRNB4 is here reported. Moreover, two hitherto unknown introns were identified within the 3' untranslated region of CHRNA3, causing a partial tail-to-tail overlap with CHRNA5. Four novel intragenic polymorphisms were identified and characterized in the cluster.
Assuntos
Íntrons , Família Multigênica , Proteínas do Tecido Nervoso/genética , Neurônios/fisiologia , Polimorfismo Genético , Receptores Nicotínicos/genética , Sequência de Aminoácidos , Sequência de Bases , DNA/genética , Primers do DNA , Éxons , Humanos , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Sequências de Repetição em TandemRESUMO
A novel homozygous 3571C-->T nonsense mutation predicting the synthesis of a truncated factor V (FV) molecule was identified in exon 13 of the human coagulation factor V gene in two unrelated Italian probands with undetectable plasma levels of FV antigen and activity. Both patients were also homozygous for the FV Leiden mutation. Reverse transcription polymerase chain reaction studies showed strongly reduced mRNA levels of the mutant FV allele and FV heavy and light chains were not measurable in the plasma of the probands and reverse transcriptase. Haplotype analysis indicated that the nonsense mutation in both families had a common founder a long time ago.
Assuntos
Códon sem Sentido , Deficiência do Fator V/genética , Fator V/genética , Adolescente , Criança , Feminino , Haplótipos , Humanos , Masculino , RNA Mensageiro/análise , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Four novel polymorphisms were identified in the fibrinogen gene cluster. Three of them were localized in the promoter regions of the Aalpha-chain (alpha -128 C/G, alpha -58 G/A) or the gamma-chain (gamma -239 A/G) gene, while the remaining one was identified in intron 9 of the gamma-chain gene (gamma 7792 C/T). Genotype distributions for these polymorphisms were analyzed in 200 healthy Italian individuals and were in Hardy-Weinberg equilibrium. Since high levels of plasma fibrinogen have been associated with an increased risk of cardiovascular disease and genetic variations have been evaluated as thrombotic risk predictors, we analyzed their role in determining the plasma levels of this protein. Owing to the low frequency of the rare allele of alpha -128 C/G and gamma -239 A/G polymorphisms, association with plasma fibrinogen levels was investigated for only alpha -58 G/A and gamma 7792 C/T. We also investigated in the same population two previously identified polymorphisms in the fibrinogen gene cluster (alpha TaqI and beta -455 G/A) chosen for their widely studied association with plasma fibrinogen levels. In the multivariate linear regression analysis, no statistically significant association with plasma fibrinogen levels was found.
Assuntos
Fibrinogênio/genética , Polimorfismo Genético , Estudos Epidemiológicos , Fibrinogênio/metabolismo , Frequência do Gene , Ligação Genética , Genótipo , Humanos , Íntrons , Itália , Regiões Promotoras Genéticas , Análise de Sequência de DNARESUMO
Adrenomedullin, a potent vasoactive peptide, is actively secreted from primary cultures of human oral and skin keratinocytes, but nothing is known of the regulation of its release. This study describes the effects of a range of substances on adrenomedullin production from cultures of oral and skin keratinocytes. We have established that keratinocytes do not store adrenomedullin but secrete it constitutively. Cytokines interleukin-1alpha and -1beta, tumor necrosis factor-alpha and -beta, and the bacterial product, lipopolysaccharide, significantly stimulate adrenomedullin secretion from oral but not skin keratinocytes. Both transforming growth factor-beta1 and interferon-gamma are potent suppressors of adrenomedullin secretion from both cell types, as are forskolin, di-butyryl cyclic adenosine monophosphate, and adrenocorticotropin. The peptides thrombin and endothelin-1 increase adrenomedullin production, particularly from skin keratinocytes. These findings indicate that there are differences in the regulation of adrenomedullin production between oral and skin keratinocytes and that oral keratinocytes are particularly responsive to the action of inflammatory cytokines. This raises the possibility that adrenomedullin may serve a different functions in oral mucosa and skin.
Assuntos
Queratinócitos/metabolismo , Mucosa Bucal/citologia , Peptídeos/metabolismo , Pele/citologia , Hormônio Adrenocorticotrópico/farmacologia , Adrenomedulina , Bucladesina/farmacologia , Células Cultivadas , Colforsina/farmacologia , Endotelina-1/farmacologia , Hemostáticos/farmacologia , Humanos , Interferon gama/farmacologia , Interleucina-1/farmacologia , Queratinócitos/citologia , Queratinócitos/efeitos dos fármacos , Lipopolissacarídeos/farmacologia , Linfotoxina-alfa/farmacologia , Trombina/farmacologia , Fator de Crescimento Transformador beta/farmacologia , Fator de Crescimento Transformador beta1 , Fator de Necrose Tumoral alfa/farmacologiaRESUMO
Cultured epithelial grafts are used in the clinical treatment of both non-healing and acute partial-thickness wounds, owing to their ability to stimulate endogenous re-epithelialization. We have previously demonstrated that during the first 24 h following plating, human epidermal keratinocytes secrete an autocrine-acting mitogenic activity. Since the biological activity of cultured grafts is believed to decrease with cellular age, the effect of both in vivo and in vitro keratinocyte age on the secretion of this mitogenic activity, as well as on responsiveness to this activity, was studied. Keratinocytes from donors ranging in age from 2 to 81 years were analysed at increasing in vitro population doublings. Secretion into the medium of the mitogenic activity was not affected by either in vivo or in vitro cellular ageing, while responsiveness of keratinocytes to this mitogenic activity was age-related. These results suggest that cultured grafts from elderly donors may be effective in wound treatment.
Assuntos
Comunicação Autócrina/efeitos dos fármacos , Queratinócitos/efeitos dos fármacos , Queratinócitos/metabolismo , Mitógenos/metabolismo , Mitógenos/farmacologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Envelhecimento/fisiologia , Biópsia , Divisão Celular/efeitos dos fármacos , Células Cultivadas , Senescência Celular/fisiologia , Pré-Escolar , Meios de Cultivo Condicionados/metabolismo , Meios de Cultivo Condicionados/farmacologia , Feminino , Humanos , Queratinócitos/citologia , Queratinócitos/transplante , Masculino , Mitógenos/biossíntese , Cicatrização/efeitos dos fármacos , Ferimentos e Lesões/patologia , Ferimentos e Lesões/terapiaRESUMO
A new polymorphism in intron 1 of the neuronal nicotinic acetylcholine receptor alpha 4 subunit gene (CHRNA4) was identified. It consists of a G to T substitution located in the downstream flanking region of a previously reported CA repeat marker. This polymorphism whose frequency is about six percent in a control population occurs near the 3' end of the reverse primer generally used to type the CA repeat marker. Data are presented showing that the newly identified polymorphism causes erroneous genotyping of the CA repeat marker which can alter the results of linkage analysis for CHRNA4. The use of a different reverse primer located 34 nt downstream of the published sequence overcame errors in genotyping and identified two novel alleles of the CA repeat marker. Re-typing of the marker with the new proposed primer pair in a Caucasian control population of 107 unrelated individuals was also performed
Assuntos
Íntrons/genética , Polimorfismo Genético/genética , Receptores Nicotínicos/genética , Sequências de Repetição em Tandem/genética , Alelos , Sequência de Bases , Mapeamento Cromossômico , Primers do DNA/química , Família , Feminino , Marcadores Genéticos , Genótipo , Haplótipos , Humanos , Masculino , Dados de Sequência Molecular , Linhagem , Reação em Cadeia da PolimeraseRESUMO
Congenital afibrinogenemia is a rare autosomal recessive disorder characterized by the complete absence of plasma fibrinogen and by a bleeding tendency ranging from mild to moderately severe. Beside a deletion of the almost entire Aalpha-chain gene, only 2 missense mutations in the C-terminal domain of the Bbeta-chain have been very recently described as being associated with afibrinogenemia. We studied a Pakistani patient with unmeasurable plasma levels of functional and immunoreactive fibrinogen. Sequencing of the fibrinogen genes revealed a homozygous G-->A transition at position +5 of intron 1 of the gamma-chain gene. The predicted mutant fibrinogen gamma-chain would contain the signal peptide, followed by a short stretch of aberrant amino acids, preceding a premature stop codon. To demonstrate the causal role of the identified mutation, we prepared expression vectors containing a region of the fibrinogen gamma-chain gene spanning from exon 1 to intron 4 and carrying either a G or an A at position +5 of intron 1. Transient transfection of the mutated plasmid in HeLa cells, followed by RNA extraction and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, allowed us to demonstrate the production of an erroneously spliced messenger RNA (mRNA), retaining intron 1, as shown by direct sequencing. A normal splicing occurred in HeLa cells transfected with the wild-type plasmid. This is the first report of a mutation in the fibrinogen gamma-chain gene causing afibrinogenemia and indicates that, in addition to the Aalpha and Bbeta-chain genes, the gamma-chain gene must also be considered in mutation screening for afibrinogenemia.
Assuntos
Afibrinogenemia/genética , Fibrinogênio/genética , Mutação , Splicing de RNA , Sequência de Aminoácidos , Sequência de Bases , Pré-Escolar , Consanguinidade , Fibrinogênio/química , Células HeLa , Hemorragia/genética , Humanos , Masculino , Dados de Sequência Molecular , Paquistão , Linhagem , Reação em Cadeia da Polimerase , RNA Mensageiro/biossíntese , Análise de Sequência de DNA , TransfecçãoRESUMO
The chromosome 15q24 region, containing the CHRNA3/A5/B4 gene cluster, coding for the alpha3, alpha5 and beta4 subunits of neuronal nicotinic acetylcholine receptors, has been reported to be linked to autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) in one family. However, nor the gene nor the mutation involved have been identified. We report the refined mapping of CHRNA3/A5/B4 cluster. Segregation analyses of CHRNA3/A5/B4 polymorphisms in families showing recombinations for 15q24 G¿en¿ethon STR markers allowed to position the cluster in a 0.6 cM interval, between STRs D15S1027 and D15S1005. This location is external to the 15q24-ADNFLE-linked region, therefore excluding the involvement of this cluster in the pathogenesis of ADNFLE in the 15q24-linked family. Moreover, these data provide more precise information for further linkage studies.
Assuntos
Cromossomos Humanos Par 15 , Epilepsia do Lobo Frontal/genética , Família Multigênica , Polimorfismo Genético , Receptores Nicotínicos/genética , Mapeamento Cromossômico , Ritmo Circadiano , Consanguinidade , Epilepsia do Lobo Frontal/fisiopatologia , Feminino , Marcadores Genéticos , Humanos , Masculino , Repetições de Microssatélites , Linhagem , Subunidades ProteicasRESUMO
Isolation and sequencing of bovine and human intron-containing L3 ribosomal protein genes are here reported. They exhibit very similar organisation, both comprising 10 exons and nine introns. A polymorphic locus, involving a 19-bp deletion, was found in intron 6 of the human gene. The frequency of the two alleles has been estimated in 200 haploid genomes. In bovine and human genes intron sequences are rather different, except for limited regions, located in corresponding positions, which show a surprisingly high degree of identity. All these regions contain conserved features defining the box C/D class of small nucleolar RNAs. Demonstration is given that U43 small nucleolar RNA is encoded within the first intron of both bovine and human genes. Single nucleotide sequences, encoding two novel species of small nucleolar RNAs (U82, U83a and U83b), are located in introns 3, 5 and 7. Their expression has been investigated and a possible role of these molecules in 2'-O-ribose methylation of rRNAs is discussed.