RESUMO
Essentials Monocytes (Mo) transdifferentiate into endothelial cell-like (ECL) cells. Mo induce tissue factor (TF) expression and secretion in microvascular endothelial cells (mECs). TF interacts with Mo in a paracrine fashion, inducing their transdifferentiation into ECL cells. TF generates a positive feedback crosstalk between Mo and mECs that promotes angiogenesis. SUMMARY: Background Monocytes (Mo) increase neovascularization by releasing proangiogenic mediators and/or transdifferentiating into endothelial cell-like (ECL) cells. Recently, we have reported that Mo-microvascular endothelial cells (mECs) crosstalk induces mEC-tissue factor (TF) expression and promotes angiogenesis. However, the effect of TF on Mo remains unknown. Objective Here, we analyzed whether TF might exert angiogenic effects by inducing transdifferentiation of Mo. Methods Full-length TF (flTF) and alternatively spliced TF (asTF) were overexpressed in mECs, and their supernatants were added to Mo cultures. CD16 positivity and expression of vascular endothelial cell (VEC) markers in Mo were analyzed by fluorescence activated cell sorting. The capacity to form tube-like structures were visualized in three-dimensional cultures. Results In mECs flTF and asTF expression and release were increased in cultures with Mo-conditioned media. TF variants induced expansion of a CD16+ Mo subset and Mo transdifferentiation into ECL-cells expressing VEC markers that can form new microvessels. CD16+ Mo exposed to TF showed an increased expression of VE-cadherin, von Willebrand factor (VWF) and eNOS. Mo cultured with supernatants obtained from TF-silenced mECs did not transdifferentiate to ECL-cells or expressed VEC markers. Blocking ß1-integrin in Mo significantly blocked the effects of the TF variants. Conclusions Mo induce mECs to express and release TF, which drives CD16- Mo to transform into CD16+ Mo and to transdifferentiate into ECL-cells that can form new microvessels. Our results reveal a TF-mediated positive feedback between mECs and Mo that stimulates Mo differentiation and induces angiogenesis.
Assuntos
Transdiferenciação Celular , Células Endoteliais/metabolismo , Monócitos/metabolismo , Tromboplastina/metabolismo , Antígenos CD/metabolismo , Caderinas/metabolismo , Linhagem Celular , Linhagem da Célula , Movimento Celular , Proliferação de Células , Meios de Cultivo Condicionados/metabolismo , Proteínas Ligadas por GPI/metabolismo , Humanos , Integrina beta1/metabolismo , Neovascularização Fisiológica , Óxido Nítrico Sintase Tipo III/metabolismo , Comunicação Parácrina , Fenótipo , Receptores de IgG/metabolismo , Transdução de Sinais , Tromboplastina/genética , Fatores de Tempo , Transfecção , Fator de von Willebrand/metabolismoRESUMO
The cytogenetic study of a case of cutaneous squamous cell carcinoma developed in a child affected by xeroderma pigmentosum is described. In this paratetraploid tumor, virtually all mitoses had the following rearrangements: i(1q), i(1p), t(3q14q), del(9p), and der(19)t(8;19). In addition, there were several deletions of 1p and 1q. The del(9p) likely occurred as the first rearrangement. The distal segment of the short arm of chromosome #9 and the long arm of #19 and #22 were the most underrepresented and chromosome #6 the most overrepresented chromosome or chromosome segment. The most striking anomaly detected was a jumping translocation of chromosome #14, involved with chromosomes #1, #3, #5, #7, #9, #14, and #22. The breakage of chromosome #14 always occurred on the short arm.
Assuntos
Carcinoma de Células Escamosas/genética , Cromossomos Humanos Par 14 , Neoplasias Cutâneas/genética , Translocação Genética , Xeroderma Pigmentoso/genética , Carcinoma de Células Escamosas/etiologia , Criança , Feminino , Marcadores Genéticos , Humanos , Cariotipagem , Neoplasias Cutâneas/etiologia , Xeroderma Pigmentoso/complicaçõesRESUMO
Cytogenetic studies of a skin squamous cell carcinoma from a xeroderma pigmentosum patient were performed at several passages. They show the existence of recurrent rearrangements: 53% were dicentrics, of which 67% were of the telomere-telomere type. The telomeric region of the long arm of chromosome 12 was the most involved (in 38% of dicentrics), followed by 22p. The origin of this type of jumping rearrangement and its possible role on cell proliferation are discussed.
Assuntos
Carcinoma de Células Escamosas/genética , Aberrações Cromossômicas , Neoplasias Cutâneas/genética , Xeroderma Pigmentoso/genética , Adolescente , Carcinoma de Células Escamosas/complicações , Centrômero , Bandeamento Cromossômico , Humanos , Cariotipagem , Masculino , Neoplasias Cutâneas/complicações , Xeroderma Pigmentoso/complicaçõesRESUMO
An increased risk of Alzheimer disease (AD) has been reported in young mothers of Down syndrome (DS) probands. Subsequently, an increased frequency of the apolipoprotein E (apoE) allele epsilon 4 has been found in mothers (< or = 32 years) of DS children due to meiosis II (MII) errors providing a potential explanation for the increased risk of AD in DS mothers. In the present study we genotyped apoE and determined the origin of non-disjunction of 132 mothers and the corresponding fathers and DS children from Spain. Unexpectedly no epsilon 4 alleles have been detected in MII mothers of < or = 32 years of age (P = 0.02). Thus our study not only fails to find the effect previously reported, but it detects an opposite correlation. An increase in the epsilon 4 frequency (0.227) is detected in MI mothers <28 as compared to the epsilon 4 frequency present in MI mothers >28 years of age (0.089), although the differences are not significant if correction for multiple comparisons is applied. The simplest overall interpretation of the previously reported and present findings is that the detected associations are due to random statistical variation rather than to some real effect of the epsilon 4 allele. However the important potential implications of alternative explanations imply that this issue deserves further clarification in independent studies in other populations.
Assuntos
Alelos , Apolipoproteínas E/genética , Síndrome de Down/genética , Meiose/genética , Não Disjunção Genética , Adolescente , Adulto , Doença de Alzheimer/genética , Apolipoproteína E4 , Criança , Pré-Escolar , Pai , Feminino , Frequência do Gene , Genótipo , Humanos , Lactente , Recém-Nascido , Masculino , Mães , Fatores de RiscoRESUMO
Although the majority of patients with Beckwith-Wiedemann syndrome (BWS) have a normal karyotype, the study of those rare patients with a cytogenetic abnormality has given considerable insight into the genetics of this condition. The karyotypic abnormalities found include partial chromosome duplications of paternal origin and maternally derived translocations which usually involve the 11p15 region and provide one of the lines of evidence for the location of the BWS gene(s). Because the extent of the duplicated region in these patients is variable, the phenotypic expression of BWS is presumably due to the presence of a common duplicated region. Two unrelated patients with BWS were both noted to have a similar unbalanced t(5;11)(p15;p14) translocation. The parents in both families were unaffected but both fathers carried a balanced translocation involving the same chromosomes. Since the extent and nature of the duplication apparently determines the complex phenotypes seen in these patients, we undertook a detailed analysis of the extent of the triplicated region using fluorescent in situ hybrisation (FISH). Despite having markedly different phenotypes and presenting in disimilar ways the two patients had apparently identical duplication breakpoints.
Assuntos
Síndrome de Beckwith-Wiedemann/genética , Quebra Cromossômica/genética , Cromossomos Humanos Par 11 , Cromossomos Humanos Par 5 , Translocação Genética , Linhagem Celular , Mapeamento Cromossômico , Evolução Fatal , Humanos , Hibridização in Situ Fluorescente , Lactente , Recém-Nascido , Masculino , Deleção de Sequência/genética , TrissomiaRESUMO
The transcription of the Low-density lipoprotein receptor-related protein (LRP1) is upregulated by aggregated LDL (agLDL) and angiotensin II (AngII) in human vascular smooth muscle cells (hVSMC). The polymorphism c.1-25C>G creates a new GC-box in the LRP1 promoter recognized by Sp1/Sp3 transcription factors. The aims of this study were 1) to evaluate the impact of c.1-25C>G polymorphism on LRP1 transcriptional activity and expression, and 2) to examine the response of c.1-25C>G LRP1 promoter to LDL and AngII. EMSA and Luciferase assays in HeLa cells showed that -25G promoter has enhanced basal transcriptional activity and specific Sp1/Sp3 binding. hVSMC with GG genotype (GG-hVSMC) had higher LRP1 mRNA and protein levels, respectively than CC genotype (CC-hVSMC). EMSA assays showed that the polymorphism determines scarce amount of SRE-B/SREBP-2 complex formation and the failure of agLDL to further reduce these SRE-B/SREBP-2 complexes. Taken together, these results suggest that c.1-25C>G, by difficulting SREBP-2 binding, prevents SREBP-2 displacement required for LRP1 promoter response to LDL. In contrast, c.1-25C>G strongly favours Sp1/Sp3 binding and AngII-induced activity in Sp1/Sp3 dependent manner in GG-hVSMC. This increase is functionally translated into a higher capacity of GG-hVSMC to become foam cells from agLDL in presence of AngII. These results suggest that c.1-25C>G determines a lack of response to agLDL and an exacerbated response to AngII. It is thus conceivable that the presence of the polymorphism would be easily translated to vascular alterations in the presence of the pro-hypertensive autacoid, AngII.
Assuntos
Proteína-1 Relacionada a Receptor de Lipoproteína de Baixa Densidade/genética , Regiões Promotoras Genéticas/genética , Fator de Transcrição Sp1/metabolismo , Fator de Transcrição Sp3/metabolismo , Angiotensina II/fisiologia , Sítios de Ligação , Células HeLa , Humanos , Lipoproteínas LDL/metabolismo , Proteína-1 Relacionada a Receptor de Lipoproteína de Baixa Densidade/biossíntese , Músculo Liso Vascular/citologia , Músculo Liso Vascular/metabolismo , Polimorfismo Genético , Proteína de Ligação a Elemento Regulador de Esterol 2/biossíntese , Ativação TranscricionalRESUMO
Sterol regulatory element-binding proteins (SREBPs) negatively modulate the expression of the CD91/low-density lipoprotein receptor-related protein (LRP1), a carrier and signaling receptor that mediates the endocytosis of more than 40 structurally and functionally distinct ligands. The aim of this work was to analyze whether lipopolysaccharide (LPS) can regulate LRP1 expression through SREBPs in human monocyte-derived macrophages (HMDM). LPS led to LRP1 mRNA and protein inhibition in a dose- and time-dependent manner. Concomitantly, a strong upregulation of SREBP-1 mRNA and SREBP-1 nuclear protein levels was observed in LPS-treated HMDM. The specific silencing of SREBP-1 efficiently prevented LRP1 reduction caused by LPS. SREBP-1 mRNA and nuclear protein levels remained high in HMDM treated with LPS unexposed or exposed to LDL. Native (nLDL) or aggregated LDL (agLDL) per se downregulated SREBP-2 expression levels and increased LRP1 expression. However, lipoproteins did not significantly alter the effect of LPS on SREBP-1 and LRP1 expression. Collectively, these data support that lipoproteins and LPS exert their modulatory effect on LRP1 expression through different SREBP isoforms, SREBP-2 and SREBP-1, respectively. These results highlight a crucial role of SREBP-1 as a mediator of the downregulatory effects of LPS on LRP1 expression in human macrophages, independently of the absence or presence of modified lipoproteins.
Assuntos
Lipopolissacarídeos/farmacologia , Proteína-1 Relacionada a Receptor de Lipoproteína de Baixa Densidade/biossíntese , Macrófagos/metabolismo , Proteína de Ligação a Elemento Regulador de Esterol 1/genética , Proteína de Ligação a Elemento Regulador de Esterol 2/genética , Regulação para Baixo , Humanos , Macrófagos/efeitos dos fármacos , Proteínas Nucleares/metabolismo , RNA Mensageiro/metabolismoRESUMO
BACKGROUND: Tissue factor (TF) and its signaling mediators play a crucial role in angiogenesis. We have previously shown that TF-induced endothelial cell (EC) CCL2 release contributes to neovessel formation. OBJECTIVE: In this study, we have investigated the signaling pathways involved in TF-induced EC tube formation. METHODS: The human microvascular endothelial cell line (HMEC-1) cultured onto basement membrane-like gel (Matrigel) was used to study TF signaling pathways during neovessels formation. RESULTS: Inhibition of endogenous TF expression in ECs using siRNA resulted in inhibition of a stable tube-like structure formation in three-dimensional cultures, associated with a down-regulation of Akt activation, an increased phosphorylation of Raf at Ser(259) with a subsequent reduction of Raf kinase and a reduction of ERK1/2 phosphorylation ending up in Ets-1 transcription factor inhibition. Conversely, overexpression of TF resulted in an increase in tube formation and up-regulation of Akt protein. Moreover, immunoprecipitation of Akt and western blotting of the immunoprecipitates with anti-TF antibody revealed a direct interaction between TF and Akt. The effects of silencing TF were partially reversed by a PAR2 agonist that rescued tube formation, indicating that the TF-Akt pathway induces PAR2-independent effector signaling. Finally, enforced expression of Akt in TF-silenced ECs rescued tube formation in a Matrigel assay and induced Ets-1 phosphorylation. CONCLUSIONS: In EC, TF forms a complex with Akt activating Raf/ERK and Ets-1 signaling induces microvessel formation.
Assuntos
Microvasos/crescimento & desenvolvimento , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transdução de Sinais , Tromboplastina/metabolismo , Linhagem Celular , Humanos , Imunoprecipitação , Fosforilação , Tromboplastina/químicaRESUMO
Low density lipoprotein receptor-related protein (LRP1) is upregulated in vascular smooth muscle cells by intravascular aggregated LDL (agLDL) - LDL trapped in the arterial intima and systemic LDL. LRP1 upregulation in hypercholesterolemic aortas is concomitant with SREBP downregulation. However, the specific role of SREBP isoforms in LRP1 transcription and LDL-induced LRP1 upregulation in human vascular smooth muscle cells (VSMC) is unknown. In the present study we report that specific silencing of either SREBP-1 or SREBP-2 enhanced LRP1 whereas overexpression of the active SREBP isoforms decreased LRP1 expression. Gel mobility shift and ChIP assays demonstrated that SREBP-1a, SREBP-1c and SREBP-2 were able to bind to three putative SRE sequences; SRE-A (-1042 to -1028), SRE-B (-115 to -101) and SRE-C (+226 to +234). ChIP assays demonstrated that agLDL (100µg/mL, 24h) significantly and specifically decreased SREBP-2 binding to the LRP1 promoter. Luciferase assays demonstrated that agLDL increased the transcriptional activity of A/B or A/C double mutants but failed to increase that of the double B/C mutant. Our results show that both SREBP-1 and SREBP-2 negatively modulated LRP1 transcription. Furthermore, agLDL exerted an upregulatory effect on LRP1 expression by decreasing SREBP-2 binding to LRP1 promoter. Two SRE-like sequences control the response of LRP1 to agLDL.
Assuntos
Proteína-1 Relacionada a Receptor de Lipoproteína de Baixa Densidade/biossíntese , Músculo Liso Vascular/metabolismo , Proteínas de Ligação a Elemento Regulador de Esterol/genética , Regulação para Baixo , Ensaio de Desvio de Mobilidade Eletroforética , Células HeLa , Humanos , Lipoproteínas LDL/metabolismo , Músculo Liso Vascular/citologia , Músculo Liso Vascular/efeitos dos fármacos , Isoformas de Proteínas/genética , RNA Mensageiro/metabolismo , RNA Interferente Pequeno/farmacologia , Proteína de Ligação a Elemento Regulador de Esterol 1/metabolismo , Proteína de Ligação a Elemento Regulador de Esterol 2/metabolismo , Regulação para CimaRESUMO
Mitochondrial HMG-CoA synthase deficiency is an inherited metabolic disorder caused by a defect in the enzyme that regulates the formation of ketone bodies. Patients present with hypoketotic hypoglycaemia, encephalopathy and hepatomegaly, usually precipitated by an intercurrent infection or prolonged fasting. The diagnosis may easily be missed as previously reported results of routine metabolic investigations, urinary organic acids and plasma acylcarnitines may be nonspecific or normal, and a high index of suspicion is required to proceed to further confirmatory tests. We describe a further acute case in which the combination of urinary organic acids, low free carnitine and changes in the plasma acylcarnitine profile on carnitine supplementation were very suggestive of a defect in ketone synthesis. The diagnosis of mitochondrial HMG-CoA synthase deficiency was confirmed on genotyping, revealing two novel mutations: c.614G > A (R188H) and c.971T > C (M307T). A further sibling, in whom the diagnosis had not been made acutely, was also found to be affected. The possible effects of these mutations on enzyme activity are discussed.
Assuntos
Hidroximetilglutaril-CoA Sintase/deficiência , Erros Inatos do Metabolismo/diagnóstico , Doenças Mitocondriais/diagnóstico , Carnitina/análogos & derivados , Carnitina/sangue , Carnitina/farmacologia , Análise Mutacional de DNA , Genótipo , Heterozigoto , Humanos , Lactente , Masculino , MutaçãoRESUMO
3-Hydroxy-3-methylglutaric aciduria is a rare autosomal recessive genetic disorder that affects ketogenesis and leucine metabolism. The disease is caused by mutations in the gene coding for 3-hydroxy-3-methylglutaryl-coenzyme A lyase (HL). To date 26 different mutations have been described. A (betaalpha)(8) TIM barrel structure has been proposed for the protein, and almost all missense mutations identified so far localize in the beta sheets that define the inside cavity. We report an Italian patient who bears homozygously a novel HL mutation, c.608G > A (p. G203E) in beta sheet six. A structural model of the mutated protein suggests that glutamic acid 203 impedes catalysis by blocking the entrance to the inner cavity of the enzyme. Loss of functionality has been confirmed in expression studies in E. coli, which demonstrate that the G203E mutation completely abolishes enzyme activity. Beta sheet six and beta sheet two are the two protein regions that accumulate most missense mutations, indicating their importance in enzyme functionality. A model for the mechanism of enzyme function is proposed.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos/genética , Meglutol/urina , Mutação de Sentido Incorreto , Oxo-Ácido-Liases/química , Oxo-Ácido-Liases/genética , Sequência de Aminoácidos , Animais , Criança , Análise Mutacional de DNA , Humanos , Masculino , Dados de Sequência Molecular , Conformação Proteica , Estrutura Secundária de Proteína , Homologia de Sequência de AminoácidosRESUMO
A cytogenetic study of the lymphocytes from 6 classic and 4 variant forms of xeroderma pigmentosum is reported. This study performed on 978 R-banded metaphases shows that there is no specific chromosomal rearrangement in this disorder. In UDS-deficient forms, the rates of deletions, chromatid gaps and chromosome gaps are significantly increased. The preferential involvement of G-bands is discussed.
Assuntos
Aberrações Cromossômicas/genética , Xeroderma Pigmentoso/genética , Transtornos Cromossômicos , Inversão Cromossômica , Mapeamento Cromossômico , Humanos , Linfócitos/ultraestrutura , Translocação GenéticaRESUMO
Eleven independent tumors (5 basa-cell carcinomas, 5 squamous-cell carcinomas and 1 malignant melanoma), 2 pretumoral lesions and one common nevus, developing in the skin of 10 unrelated XP patients were cytogenetically analyzed. No specific chromosomal changes were observed. Two features were relevant, however: emergence of several independent clones and over-involvement of telomeric and centromeric regions in the formation of chromosomal rearrangements. Jumping translocations were observed in 2 squamous-cell carcinomas involving telomeric and centromeric regions.
Assuntos
Aberrações Cromossômicas , Lesões Pré-Cancerosas/genética , Neoplasias Cutâneas/genética , Xeroderma Pigmentoso/genética , Adolescente , Adulto , Criança , Feminino , Humanos , MasculinoRESUMO
Mutations that cause deficiency of the 21-hydroxylase (21-OH) appear as a result of recombinations between the CYP21B coding gene and the highly homologous CYP21A pseudogene, which are tandemly arranged with the C4A and C4B genes. We report a detailed analysis of a major chromosomic rearrangement by Southern blot using 21-OH and complement C4 cDNA probes, in a wide sample of classic Spanish congenital adrenal hyperplasia (CAH) patients. This study made it possible to observe that 50% of the patients carried at least one allele with gross abnormalities and that the frequencies of alleles with large deletions (16.66%) and gene conversions (14.16%) in the CYP21B gene were very similar. Moreover, our analysis revealed the existence of sixteen different restriction patterns of C4/CYP21 genes. Besides the detection of a new haplotype, which does not seem to appear from unequal crossing-over mechanisms, we observed the highest frequency on CYP21A duplications reported, as well as no duplications of the CYP21B gene. We also observed that although gross abnormalities of the CYP21A pseudogene did not affect 21-OH activity, alleles carrying deleterious point mutations had more rearrangements of the CYP21A gene than normal alleles. Even though the 21-OH deficiency is an autosomic trait, boys in our sample carried 2.6 times more deletions than girls. In contrast, conversion alleles were found equally frequently.
Assuntos
Hiperplasia Suprarrenal Congênita/genética , Esteroide 21-Hidroxilase/genética , Southern Blotting , Criança , Complemento C4/genética , DNA Complementar , Feminino , Conversão Gênica , Deleção de Genes , Rearranjo Gênico , Haplótipos , Humanos , Masculino , Mutação Puntual , Polimorfismo Genético , Polimorfismo de Fragmento de Restrição , Pseudogenes/genética , EspanhaRESUMO
Neurofibromas are one of the most characteristic features of neurofibromatosis type 1 (NF1), an inherited autosomal-dominant neurogenetic disorder affecting 1 in 3500 individuals worldwide. These benign tumors mainly consist of Schwann cells (SCs) and fibroblasts. Recent evidence demonstrates that somatic mutations at the NF1 gene are found in neurofibromas, but it has not been demonstrated whether SCs, fibroblasts and/or both cell types bear a somatic loss of NF1. We recently established a cell culture system that allows selective expansion of human SCs from neurofibromas. We cultured pure populations of SCs and fibroblasts derived from 10 neurofibromas with characterized NF1 mutations and found that SCs but not fibroblasts harbored a somatic mutation at the NF1 locus in all studied tumors. Furthermore, by culturing neurofibroma-derived SCs under different in vitro conditions we were able to obtain two genetically distinct SC subpopulations: NF1(-/-) and NF1(+/-). These data strongly support the idea that NF1 mutations in SCs, but not in fibroblasts, correlate to neurofibroma formation and demonstrate that only a portion of SCs in neurofibromas have mutations in both NF1 alleles.
Assuntos
Genes da Neurofibromatose 1 , Neurofibroma/genética , Células de Schwann/fisiologia , Divisão Celular/efeitos dos fármacos , Separação Celular , Tamanho Celular/efeitos dos fármacos , Células Cultivadas , Colforsina/farmacologia , Fibroblastos/patologia , Fibroblastos/fisiologia , Genótipo , Mutação em Linhagem Germinativa , Humanos , Mutação , Neurofibroma/patologia , Células de Schwann/patologiaRESUMO
The distribution of spontaneous sister chromatid exchanges (SCEs) was studied in PHA-stimulated lymphocytes from 15 patients affected by xeroderma pigmentosum (XP). The study of unscheduled DNA synthesis (UDS) in twelve of these patients showed that seven were deficient and five proficient. The number of SCEs in XP patient cells was higher than in those of 19 controls, and the distributions of SCEs per cell were significantly different. However, the results varied when XP patients were considered in relation to their UDS: the group of XP patients with proficient UDS did not differ, whereas the group of XP patients with deficient UDS was very significantly different from controls. The group not tested for UDS was similar to the deficient UDS group. The possible relationship between the increase of SCEs and the type of DNA repair defect is discussed.
Assuntos
Reparo do DNA , Troca de Cromátide Irmã , Xeroderma Pigmentoso/genética , Adolescente , Adulto , Células Cultivadas , Criança , Pré-Escolar , Feminino , Humanos , Linfócitos/ultraestrutura , MasculinoRESUMO
This paper describes the characterization and chromosomal distribution of new long repetitive sequences present in all species of the genus Zea. These sequences constitute a family of moderately repetitive elements ranging approximately from 1350 to 1700 copies per haploid genome in modern maize (Zea mays ssp. mays) and teosinte (Zea diploperennis), respectively. The elements are long, probably larger than 9 kb, and they show a highly conserved internal organization among Zea subspecies and species. The elements are present in all maize chromosomes in an interspersed pattern of distribution, are absent from centromeric and pericentric heterochromatin, and with some clustering in the distal regions of chromosome arms.
RESUMO
The analysis of a sample of 100 isoacentric (IA) and isocentric (IC) chromosomes, which had originated from spontaneous or radiation-induced deletions in human lymphocytes, is reported. IC and also IA have a strong tendency to be formed after breakage in juxtacentromeric heterochromatin. When euchromatic regions are involved, the breaks are not distributed at random since they frequently occur at places where juxtacentromeric heterochromatin exists in other primate species. It is assumed that intercalary structures conserving some of the properties of heterochromatin exists in human chromosomes in intercalary positions.
Assuntos
Aberrações Cromossômicas , Deleção Cromossômica , Bandeamento Cromossômico , Heterocromatina/genética , Humanos , Cariotipagem , Linfócitos/ultraestruturaRESUMO
Deficiency of mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (mHMGS) is a recessive disorder of ketogenesis that has been previously diagnosed in two children with hypoglycaemic hypoketotic coma during fasting periods. Here, we report the results of molecular investigations in a third patient affected by this disease. Sequencing of the entire coding region of the HMGCS2 gene revealed two missense mutations, G212R and R500H. Mendelian inheritance was confirmed by the analysis of parental samples and neither of the mutations was found on 200 control chromosomes. Functional relevance was confirmed by in vitro expression studies in cytosolic HMGS-deficient cells. Whereas wild-type cDNA of the HMGCS2 gene reverted the auxotrophy for mevalonate, the cDNAs of the mutants did not. The disease may be recognised by specific clinical and biochemical features but it is difficult to confirm enzymatically since the gene is expressed only in liver and testis. Molecular studies may facilitate or confirm future diagnoses in affected patients.
Assuntos
Hidroximetilglutaril-CoA Sintase/deficiência , Hidroximetilglutaril-CoA Sintase/genética , Mitocôndrias/enzimologia , Animais , Sequência de Bases , Células CHO , Cricetinae , Análise Mutacional de DNA , Primers do DNA/genética , DNA Complementar/genética , Feminino , Expressão Gênica , Genes Recessivos , Humanos , Técnicas In Vitro , Lactente , Masculino , Mutagênese Sítio-Dirigida , Mutação de Sentido IncorretoRESUMO
Deletions of the 22q11.2 have been associated with a wide range of developmental defects (notably DiGeorge syndrome, velocardiofacial syndrome, conotruncal anomaly face syndrome and isolated conotruncal cardiac defects) classified under the acronym CATCH 22. A DiGeorge syndrome patient bearing a balanced translocation whose breakpoint maps within the critical region has been previously described. We report the construction of a cosmid contig spanning the translocation breakpoint and the isolation of a gene mapping 10 kb telomeric to the breakpoint. This gene encodes a novel putative adhesion receptor protein, which could play a role in neural crest cells migration, a process which has been proposed to be altered in DiGeorge syndrome.