RESUMO
There are limited data on mitochondrial DNA (mtDNA) variation in the Mexican mestizo population. To examine the genetic diversity and matrilineal ancestry, the full mtDNA hypervariable regions I and II were sequenced in 270 unrelated mestizos from different regions of Mexico. A total of 202 different haplotypes were identified and the haplotype diversity was 0.9945. Amerindian haplotypes predominated in the sample with a proportion of 93.3%, followed by European (6.0%) and African haplotypes (0.7%). The frequency of the Amerindian haplogroups A2, B2, C1 and D1 was 51.1, 17.8, 18.5 and 5.9%, respectively. The frequency of Amerindian haplogroups was higher in the central region than in Mexico City, whereas it was the contrary for European haplogroups. This difference was accounted principally by the high frequency of B2 haplotypes in the central region. The minimum spanning network, the mismatch distribution and Tajima's D neutrality test suggest a population expansion for each Amerindian haplogroup, which could be initiated more recently for haplogroups A2 and D1. The present knowledge combined with other nuclear genetic markers will be essential in future association studies to correct for genetic substructure in mestizo populations.
Assuntos
DNA Mitocondrial/genética , Variação Genética , Haplótipos , Indígenas Norte-Americanos/genética , População Negra/genética , DNA Mitocondrial/química , DNA Mitocondrial/classificação , Frequência do Gene , Genética Populacional , Geografia , Humanos , México , Filogenia , Análise de Sequência de DNA , População Branca/genéticaRESUMO
Gonadoblastoma (GB) is an in situ tumor consisting of a heterogeneous population of mature and immature germ cells, other cells resembling immature Sertoli/granulosa cells, and Leydig/lutein-like cells, may also be present. GB almost exclusively affects a subset of patients with intersex disorders and in 30% of them overgrowth of the germinal component of the tumor is observed and the lesion is term dysgerminoma/seminoma. Several pathways have been proposed to explain the malignant process, and abnormal OCT3/4 expression is the most robust risk factor for malignant transformation. Some authors have suggested that OCT3/4 and beta-catenin might both be involved in the same oncogenic pathway, as both genes are master regulators of cell differentiation and, overexpression of either gene may result in cancer development. The mechanism by which beta-catenin participates in GB transformation is not completely clear and exploration of the E-cadherin pathway did not conclusively show that this pathway participated in the molecular pathogenesis of GB. Here we analyze seven patients with mixed gonadal dysgenesis and GB, in an effort to elucidate the participation of beta-catenin and E-cadherin, as well as OCT3/4, in the oncogenic pathways involved in the transformation of GB into seminoma/dysgerminoma. We conclude that the proliferation of immature germ cells in GB may be due to an interaction between OCT3/4 and accumulated beta-catenin in the nuclei of the immature germ cells.
Assuntos
Caderinas/fisiologia , Disgerminoma/etiologia , Disgenesia Gonadal Mista/complicações , Gonadoblastoma/etiologia , Fator 3 de Transcrição de Octâmero/fisiologia , Neoplasias Ovarianas/etiologia , Neoplasias Testiculares/complicações , beta Catenina/fisiologia , Adolescente , Transformação Celular Neoplásica , Pré-Escolar , Feminino , Humanos , Imuno-Histoquímica , Lactente , MasculinoRESUMO
Klinefelter syndrome is a well documented abnormality of sex differentiation, with an incidence of 1 in 600 newborn males. It is characterized by a 47,XXY or a mosaic karyotype and clinical findings of hypergonadotrophic hypogonadism, small testes, infertility, reduced body hair, gynecomastia, and tall stature. Other conditions like venous disease, autoimmune disorders, mild neurobehavioral deficit, diabetes mellitus, sexual precocity, and osteoporosis may also affect these patients. Different malignancies such as breast cancer, testicular tumors, leukemia, and lymphomas occur in 1%-2% of the cases. Klinefelter syndrome has been associated with other malignancies such as extragonadal germ cell tumors; however, some authors consider this association an unusual finding. We report the molecular cytogenetic studies performed in 4 young males with mediastinal germ cell tumors. In 2 cases, a 47,XXY karyotype was recognized in different tissues by fluorescent in situ hybridization, whereas the other 2 had a normal XY karyotype. We propose that in young patients with mediastinal teratoma, a cytogenetic analysis must always be performed.
Assuntos
Germinoma/patologia , Síndrome de Klinefelter/patologia , Neoplasias do Mediastino/patologia , Teratoma/patologia , Adolescente , Adulto , Cromossomos Humanos X , Cromossomos Humanos Y , Evolução Fatal , Germinoma/genética , Germinoma/cirurgia , Humanos , Hibridização in Situ Fluorescente , Cariotipagem , Síndrome de Klinefelter/genética , Síndrome de Klinefelter/cirurgia , Masculino , Neoplasias do Mediastino/genética , Neoplasias do Mediastino/cirurgia , Teratoma/genética , Teratoma/cirurgiaRESUMO
Steroid sulfatase deficiency results in X-linked ichthyosis, an inborn error of metabolism in which the principal molecular defect is the complete deletion of the steroid sulfatase gene and flanking markers. Mosaicism for the steroid sulfatase gene has not yet been reported in X-linked ichthyosis. In this study we describe an X-linked ichthyosis patient with complete deletion of the steroid sulfatase gene and his mother with somatic and germinal mosaicism for this molecular defect. The family (X-linked ichthyosis patient, grandmother, mother, and sister) was analyzed through steroid sulfatase enzyme assay, polymerase chain reaction, DNA markers, and fluorescence in situ hybridization of the steroid sulfatase gene. Steroid sulfatase activity was undetectable in the X-linked ichthyosis patient, very low in the mother, and normal in the grandmother and sister. The X-linked ichthyosis patient showed a 2 Mb deletion of the steroid sulfatase gene and flanking regions from 5'DXS1139 to 3'DXF22S1. The mother showed one copy of the steroid sulfatase gene in 98.5% of oral cells and in 80% of leukocytes. The grandmother and sister showed two copies of the steroid sulfatase gene. The origin of the X chromosome with the deletion of the steroid sulfatase gene corresponded to the grandfather of the proband. We report the first case of somatic and germinal mosaicism of the steroid sulfatase gene in an X-linked ichthyosis carrier and propose DNA slippage as the most plausible mechanism in the genesis of this mosaicism.
Assuntos
Arilsulfatases/genética , Deleção de Genes , Ictiose Ligada ao Cromossomo X/genética , Mosaicismo/genética , Arilsulfatases/deficiência , Feminino , Heterozigoto , Humanos , Esteril-SulfataseRESUMO
Turner syndrome is a chromosomal disorder in which all or part of one X chromosome is missing. The meiotic or mitotic origin of most cases remains unknown due to the difficulty in detecting hidden mosaicism and to the lack of meiotic segregation studies. We analyzed 15 Turner patients, 10 with a 45,X whereas the rest had a second cell line with abnormal X-chromosomes: a pseudodicentric, an isochromosome, one large and one small ring, and the last with a long arm deletion. Our aims were: to detect X cryptic mosaicism in patients with a 45,X constitution; to determine the parental origin of the abnormality; to infer the zygotic origin of the karyotype and to suggest the timing and mechanism of the error(s) leading to the formation of abnormal X chromosomes from maternal origin. Molecular investigation did not revealed heterozygosity for any microsatellite, excluding X mosaicism in the 45,X cases. Parental origin of the single X chromosome was maternal in 90% of these patients. Three of the structurally abnormal Xs were maternally derived whereas the other two were paternal. These results allowed us to corroborate breakpoints in these abnormal X chromosomes and suggest that the pseudodicentric chromosome originated from post-zygotic sister chromatid exchange, whereas the Xq deleted chromosome probably arose after a recombination event during maternal meiosis.
Assuntos
Repetições de Microssatélites/genética , Síndrome de Turner/genética , Adolescente , Adulto , Criança , Bandeamento Cromossômico , DNA/genética , Saúde da Família , Feminino , Humanos , Recém-Nascido , Cariotipagem , Masculino , Linhagem , Aberrações dos Cromossomos Sexuais , Cromossomo X/genéticaRESUMO
Turner syndrome (TS) is a disorder caused by partial or complete X-chromosome monosomy. Studies in TS patients with different karyotypes have demonstrated the presence of Y-chromosome-derived sequences (4-61%). Early detection of Y-chromosome sequences in TS is of great importance because of the high risk of gonadal tumor development. We investigated the presence of Y-chromosome sequences in TS patients with a 45,X karyotype. One hundred seven unrelated 45,X Mexican TS patients recruited between 1992 and 2003 were included. Y-chromosome-derived sequences were found by polymerase chain reaction in 10 (9.3%) patients. Six subjects underwent gonadectomy and in one of them a gonadoblastoma was found; another developed a gonadoblastoma with dysgerminoma. Because of the high proportion (33%) of gonadal tumors in patients with Y-chromosome sequences found among our patients of mestizo origin, adequate counseling regarding a gonadectomy should be given.
Assuntos
Cromossomos Humanos X/genética , Cromossomos Humanos Y/genética , Gonadoblastoma/genética , Neoplasias Ovarianas/genética , Aberrações dos Cromossomos Sexuais , Síndrome de Turner/genética , Adolescente , Adulto , Criança , Pré-Escolar , Feminino , Gonadoblastoma/complicações , Gonadoblastoma/diagnóstico , Humanos , Hibridização in Situ Fluorescente , Lactente , Recém-Nascido , Cariotipagem , Mosaicismo , Orquiectomia , Síndrome de Turner/complicações , Síndrome de Turner/diagnósticoRESUMO
BACKGROUND AND AIMS: Rhabdomyosarcoma (RMS) is a pediatric tumor whose classification is based on histological criteria according to two main subgroups, embryonal RMS (ERMS) and alveolar RMS (ARMS). The majority but not all ARMS carry the specific PAX3(7)/FKHR translocation. The type of translocation in patients with ARMS defines the prognosis. METHODS: We retrospectively analyzed 30 cases of ARMS in Mexican patients and evaluated the fusion status of the genes using RT-PCR and fluorescence in situ hybridization (FISH) in formalin-fixed paraffin-embedded tissues (FFPET). RESULTS: From 25 samples (83%) with optimal RNA quality, RT-PCR revealed 15 cases (50%) with the t(2;13)/PAX3-FKHR. Only one case (3%) was positive to t(1;13)/PAX7-FKHR and nine cases (30%) were fusion-negative. Correspondingly, using FISH, the t(2;13)/PAX3-FKHR was found positive in 19 cases (63.5%), one case (3%) revealed the t(1;13)/PAX7/FKHR and ten cases (33.5%) were fusion-negative by this method. Five cases were not evaluable by RT-PCR but recovered by FISH. Only four of the total revealed t(2;13); the other was fusion-negative. CONCLUSIONS: FISH technique is more sensitive when FFPET is used to describe the chromosomal translocation of ARMS. These Latino patients showed an association of the t(2;13) in older patients (mean: 9 years) and negative translocation in younger patients (mean: 4 years) (p <0.05). Both t(2;13) and negative-fusion were present in patients with clinical stages III and IV (p <0.05). There was a nonsignificant trend of t(2;13) to lower overall survival than negative-fusion status.
Assuntos
Hibridização in Situ Fluorescente/métodos , Proteínas Recombinantes de Fusão/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodos , Rabdomiossarcoma/genética , Criança , Formaldeído , Humanos , Estimativa de Kaplan-Meier , México , Inclusão em Parafina , Estudos Retrospectivos , Rabdomiossarcoma/classificação , Rabdomiossarcoma/mortalidade , Rabdomiossarcoma/patologiaRESUMO
17alpha-Hydroxylase deficiency (17OHD) is a rare form of congenital adrenal hyperplasia caused by mutations in the CYP17A1 gene. This condition shows considerable clinical and biochemical variation. Molecular characterization of novel mutations in the CYP17A1 gene and detailed study of their structural, enzymatic, and clinical consequences are required to fully understand enzyme behavior. Here, we present the first molecular characterization of two novel mutations in CYP17A1 in a 15-year-old female Mexican mestizo 46,XY female with primary amenorrhea and lack of pubertal development and severe hypertension that manifested only after surgery. A complete clinical and biochemical evaluation was compatible with 17OHD. Structural anomalies in the CYP17A1 gene were discovered by direct automated sequencing, which revealed a novel compound heterozygous K110X/R362H mutation that leads to a complete lack of enzyme activity. Immunohistochemical analyses performed to determine protein expression and localization showed that cytochrome P450 17A1 was completely absent in the patient's testicular tissue. Studies of novel mutations, such as those described here, provide important information that allows us to better understand the effect of a given mutation on enzyme function and to observe the impact of the mutation on clinical phenotype.
Assuntos
Hiperplasia Suprarrenal Congênita/enzimologia , Mutação , Esteroide 17-alfa-Hidroxilase/genética , Acantose Nigricans/diagnóstico , Adolescente , Hiperplasia Suprarrenal Congênita/diagnóstico , Hormônio Adrenocorticotrópico , Sequência de Bases , DNA/sangue , DNA/química , Estradiol/sangue , Hormônio Foliculoestimulante/sangue , Disgenesia Gonadal/enzimologia , Disgenesia Gonadal/genética , Heterozigoto , Humanos , Hidrocortisona/sangue , Hormônio Luteinizante/sangue , Masculino , Fenótipo , Puberdade , Testículo/enzimologia , Testosterona/sangueRESUMO
We report a Mexican boy with isolated ectrodactyly (split hand malformation) in whom a new mutation was identified in exon 3 of the TP63 gene. In contrast to previously reported patients with isolated split hand/foot anomaly and mutations in the DNA binding domain of Tp63, the mutation described herein induce an amino acid substitution (R97C) in the canonical transactivation (TA) domain. To our knowledge, this is the first naturally occurring mutation described so far in this part of the protein. Based on the genotype-phenotype correlation observed in our patient, we hypothesize that integrity of the TA domain of Tp63 is critical for normal limb development.
Assuntos
Deformidades Congênitas da Mão/genética , Mutação de Sentido Incorreto , Fosfoproteínas/genética , Transativadores/genética , Sequência de Bases , Sítios de Ligação/genética , DNA/química , DNA/genética , Análise Mutacional de DNA , Proteínas de Ligação a DNA , Genes Supressores de Tumor , Deformidades Congênitas da Mão/patologia , Heterozigoto , Humanos , Lactente , Masculino , Fatores de Transcrição , Ativação Transcricional/genética , Proteínas Supressoras de TumorRESUMO
Otopalatodigital syndrome type 1 (OPD1) [OMIM 311300] is an X-linked dominant multiple congenital anomalies disease mainly characterized by a generalized skeletal dysplasia, mild mental retardation, hearing loss, cleft palate, and typical facial anomalies. OPD1 belongs to a group of X-linked skeletal dysplasias known as oto-palato-digital syndrome spectrum disorders that also include OPD2, Melnick-Needles syndrome (MNS), and frontometaphyseal dysplasia (FMD). Recently, it has been demonstrated that mutations in the gene encoding the cytoskeletal protein Filamin A (FLNA) are responsible for this group of clinically overlapping human syndromes. We present the phenotypic and molecular data of a sporadic female patient clinically diagnosed with an OPD1 syndrome who carried a novel FLNA point mutation resulting in an Asp203Tyr substitution in the actin-binding domain of the protein. X-inactivation analyses demonstrated an extremely skewed pattern towards her maternal chromosome. Our results add to the molecular spectrum of the oto-palato-digital related syndromes and contribute to the delineation of phenotype-genotype correlation in this group of X-linked skeletal disorders.
Assuntos
Anormalidades Múltiplas/genética , Cromossomos Humanos X/genética , Proteínas Contráteis/genética , Mecanismo Genético de Compensação de Dose , Proteínas dos Microfilamentos/genética , Mutação de Sentido Incorreto , Anormalidades Múltiplas/patologia , Adulto , Sequência de Bases , Doenças do Desenvolvimento Ósseo/patologia , Fissura Palatina/patologia , Anormalidades Craniofaciais , DNA/química , DNA/genética , Análise Mutacional de DNA , Feminino , Filaminas , Transtornos do Crescimento/patologia , Humanos , Sindactilia/patologia , SíndromeRESUMO
Mixed gonadal dysgenesis (MGD) is a developmental anomaly in which most of the patients have a dysgenetic testis, a contralateral streak and a 45,X/46,XY karyotype. This entity involves an heterogeneous group of gonadal and phenotypic abnormalities with a wide clinical spectrum. The phenotype depends on the ratio of testicular tissue which induces virilization. Although the karyotype in these patients is 45,X/46,XY, no genotype-phenotype correlation has been found to date. Müllerian ducts persistence (MDP) in MGD is rare; however, four patients with both entities and different karyotypes have been described. Here we present the data on a newborn patient with an atypical MGD associated with MDP, two left testes, a gonadal streak on the right, and absence of Wolffian derivatives. PCR analysis identified all the Y-derived sequence tested in the father, while the patient had them all except the AZF b,c regions which were lost. FISH analysis of the paternal Y chromosome documented Yq paracentric inversion while the patient's karyotype was 45,X/46,X,idic(Yp). No mutations were observed in MIS/MISRII genes.
Assuntos
Disgenesia Gonadal Mista/genética , Ductos Paramesonéfricos/anormalidades , Testículo/anormalidades , Bandeamento Cromossômico , Disgenesia Gonadal Mista/patologia , Humanos , Hibridização in Situ Fluorescente , Recém-Nascido , Cariotipagem , Masculino , Modelos GenéticosRESUMO
Gonadoblastoma is an unusual mixed germ cell-sex cord-stromal tumor that has the potential for malignant transformation and 30% of all patients with gonadoblastoma develop germ cell tumors mainly dysgerminoma/seminoma. An additional 10% gives rise to other malignant germ cell neoplasms. This tumor affects a subset of patients with intersex disorders. The age at diagnosis is variable ranging from birth to the fourth decade, but around 94% of cases are diagnosed during the first three decades of life and there are few cases with gonadoblastoma diagnosed in infants. In this paper, we present the histological and molecular findings of four patients with gonadal dysgenesis who developed gonadoblastoma in the first 2 years of life and one case with bilateral dysgerminoma diagnosed at 15 years of age. The sex chromosomes of mosaic patients do not distribute homogenously in dysgenetic gonads; however, statistical analysis of FISH results revealed significant differences between the XY cell line in the gonadoblastoma compared with the dysgenetic testis. Our cases demonstrate that tumors could be present at a very early age, so the prophylactic removal of the gonads is advised.
Assuntos
Cromossomos Humanos Y/genética , Disgenesia Gonadal Mista/genética , Gonadoblastoma/patologia , Neoplasias Ovarianas/patologia , Neoplasias Testiculares/patologia , Testículo/anormalidades , Adolescente , Pré-Escolar , Feminino , Disgenesia Gonadal Mista/patologia , Gonadoblastoma/genética , Humanos , Hibridização in Situ Fluorescente , Lactente , Cariotipagem , Masculino , Neoplasias Ovarianas/genética , Neoplasias Testiculares/genéticaRESUMO
PURPOSE: To describe the molecular defects in the Norrie disease protein (NDP) gene in two families with Norrie disease (ND). METHODS: We analysed two families with ND at molecular level through polymerase chain reaction, DNA sequence analysis and GeneScan. RESULTS: Two molecular defects found in the NDP gene were: a missense mutation (265C > G) within codon 97 that resulted in the interchange of arginine by proline, and a partial deletion in the untranslated 3' region of exon 3 of the NDP gene. Clinical findings were more severe in the family that presented the partial deletion. We also diagnosed the carrier status of one daughter through GeneScan; this method proved to be a useful tool for establishing female carriers of ND. CONCLUSION: Here we report two novel mutations in the NDP gene in Mexican patients and propose that GeneScan is a viable mean of establishing ND carrier status.
Assuntos
Cegueira/congênito , Proteínas do Olho/genética , Perda Auditiva Neurossensorial/genética , Deficiências da Aprendizagem/genética , Mutação de Sentido Incorreto , Proteínas do Tecido Nervoso/genética , Deleção de Sequência , Criança , Pré-Escolar , Análise Mutacional de DNA , Saúde da Família , Feminino , Triagem de Portadores Genéticos , Heterozigoto , Humanos , Masculino , Biologia Molecular , Linhagem , Reação em Cadeia da Polimerase , Retina/anormalidadesRESUMO
In the year 2002, the population of Mexico was approaching 103 million inhabitants. Approximately 74% of them live in the cities with a continuous migration from rural to urban areas. Genetic departments are concentrated in the capital and other big cities. In this paper we review the current status of genetic departments in Mexico City, emphasizing the main areas of genetic services offered to the public and involved in research. We also comment on the deficiencies identified and suggest recommendations to improve the quality of the genetic services offered to the Mexican population.
Assuntos
Serviços em Genética/organização & administração , Anormalidades Congênitas/prevenção & controle , Atenção à Saúde/organização & administração , Atenção à Saúde/normas , Doenças Genéticas Inatas/prevenção & controle , Serviços em Genética/ética , Serviços em Genética/normas , Ocupações em Saúde/educação , Humanos , MéxicoRESUMO
The World Health Organization sponsored a Consultation on Community Genetic Services and a Regional Network of Medical Genetics in Latin America in Porto Alegre, Brazil, on June 19, 2003. The main recommendations of the meeting included: (a) the call for government funding of services, research and education in medical genetics; (b) the conduct of epidemiological research on the prevalence and types of birth defects, genetic disorders and genetic predispositions to common diseases; (c) the education of health professionals in genetics; (d) the education of genetic professionals in community health and public health genetics; (e) the fostering of interactions between clinical geneticists, public health personnel, primary health care workers and community organizations, and (f) a better planning of regionalized services to avoid duplication and inefficiency.
Assuntos
Serviços em Genética/normas , Genética Médica/normas , Guias como Assunto , Organização Mundial da Saúde , Redes Comunitárias , Serviços em Genética/organização & administração , Técnicas Genéticas , Testes Genéticos , Genética Médica/organização & administração , Humanos , América LatinaRESUMO
INTRODUCTION: Müllerian agenesis, also named the Mayer-Rokitansky-Küster-Hauser syndrome (MRKHS) or vaginal aplasia, is the second most common cause of primary amenorrhea. It is characterized by the congenital absence of the Müllerian structures including the Fallopian tubes, the uterus, and the internal portion of the vagina in an otherwise normally feminized 46,XX subject. Most cases are sporadic in inheritance, but the occurrence of some patients with chromosomal translocations or even familial aggregates suggest a genetic basis for the disease, although the etiology of the disease is still unknown. It has been suggested that activating mutations in the anti-Müllerian hormone (AMH) or in its receptor (AMHRII) are potential sources for the defect. METHODS: In this study we describe the molecular analysis of both the AMH and AMHR genes in a group of 15 patients with Müllerian agenesis. After sequencing all exons and exon/intron junctions of both genes, we were not able to detect any deleterious mutation. RESULTS: Five new polymorphisms, 2 of them in the AMHRII gene and 3 of them in the AMH gene, were identified. No significant differences between patients and controls were observed in the frequency of a given polymorphism. CONCLUSION: This work reinforces the view that molecular defects in the AMH or AMHR are unlikely sources for the MRKHS syndrome.
Assuntos
Transtornos do Desenvolvimento Sexual/genética , Ductos Paramesonéfricos/anormalidades , Hormônio Antimülleriano , Estudos de Casos e Controles , Feminino , Glicoproteínas/genética , Humanos , Polimorfismo Genético , Receptores de Peptídeos/genética , Receptores de Fatores de Crescimento Transformadores beta , Síndrome , Hormônios Testiculares/genética , UTP-Hexose-1-Fosfato Uridililtransferase/genéticaRESUMO
BACKGROUND/AIMS: Mutations in the androgen receptor (AR) gene result in an X-linked recessive form of male pseudohermaphroditism known as the androgen-insensitivity syndrome (AIS). The alterations most frequently observed are missense or nonsense point mutations in exons 4-8 of the AR gene that affect the steroid-binding domain of the receptor in subjects with various degrees of androgen resistance. Despite the increasing number of AR mutations identified, a reliable genotype-phenotype correlation has not been established and individuals with the same molecular defect may exhibit different phenotypes. Here, we studied a patients with an AIS characterized by bilateral gynecomastia, normal male external genitalia, and normal sperm counts. METHODS: Exon-specific polymerase chain reaction, single-stranded conformational polymorphism, and sequencing analysis of the subject's AR gene were performed in addition to hormone-binding assays in skin fibroblasts from the patient. RESULTS: A point mutation at codon 870 of the AR, changing alanine to valine, was detected. CONCLUSION: As AR missense mutations changing alanine 870 to valine have been previously described in 3 unrelated patients showing severe AIS phenotypes, we conclude that phenotypic heterogeneity associated to identical mutations in the AR gene is probably due to individual functional differences in AR coregulator molecules.
Assuntos
Ginecomastia/genética , Mutação Puntual , Receptores Androgênicos/genética , Adulto , Sequência de Aminoácidos , Citosol/metabolismo , Di-Hidrotestosterona/metabolismo , Fibroblastos/citologia , Fibroblastos/metabolismo , Fibroblastos/patologia , Heterogeneidade Genética , Humanos , Cinética , Masculino , Fenótipo , Valores de Referência , Pele/citologia , Pele/patologia , Contagem de EspermatozoidesRESUMO
Androgen insensitivy syndrome (AIS) is the most frequent cause of male pseudohermaphroditism resulting from target-organ resistance to androgen action. Individuals bearing the complete form of the disease (CAIS) present a female phenotype and a lack of pubic and axillary hair. In the present study, four 46,XY patients born in two generations from a kindred with a history of AIS were examined for genetic abnormalities in the androgen receptor gene (AR). All eight exons encoding the AR protein were individually amplified from genomic DNA followed by a mutation screening with single-strand conformation polymorphism analysis. Sequencing of the mutant AR revealed a novel insertion/deletion mutation in exon 5. A deletion of 7 bp is replaced by an insertion of 11 nucleotides, which represents a duplication of the adjacent downstream sequence. The mutation g.2640_2646delAGGATGC/2652_2662insTTCGCCCCTGA, results in a frameshift that introduces a premature termination signal TGA, nine codons downstream. Such a rearrangement predicts a truncation of the AR, thereby deleting a large portion of the ligand-binding domain (amino acid position 768-919). Furthermore, although this mutation breaks the translational reading frame starting from codon 760, examination of the complementary DNA suggested that it does not disturb mRNA splicing. These changes have been found in all the patients and appear to account for the observed absence of detectable androgen binding to the AR in cultured fibroblasts and for the CAIS phenotype in the kindred. This disorder represents the first insertion/deletion mutation of the AR that probably arose by a slipped-strand mispairing mechanism.
Assuntos
Androgênios/metabolismo , Deleção de Genes , Mutação , Receptores Androgênicos/genética , Adulto , Sequência de Aminoácidos , Síndrome de Resistência a Andrógenos/genética , Sequência de Bases , Western Blotting , Células Cultivadas , Análise Mutacional de DNA , DNA Complementar/metabolismo , Éxons , Saúde da Família , Feminino , Fibroblastos/metabolismo , Humanos , Masculino , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Linhagem , Fenótipo , Polimorfismo Conformacional de Fita Simples , Ligação Proteica , Estrutura Terciária de Proteína , Splicing de RNA , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Sex differentiation in humans depends on the presence of the Y-linked gene SRY, which is activated in the pre-Sertoli cells of the developing gonadal primordium to trigger testicular differentiation. Occasionally testicular formation can take place in subjects lacking a Y chromosome resulting in a 46,XX sex reversal condition. True hermaphroditism (TH) is a rare form of intersexuality characterized by the presence of testicular and ovarian tissue in the same individual. Genetic heterogeneity has been proposed as a cause of dual gonadal development in some cases and recently, hidden mosaicism was reported to cause TH in some 46,XX SRY negative patients. Here we report a TH case in which hidden mosaicism for the Y and X chromosome was detected by PCR and FISH in peripheral blood and gonadal tissue, supporting the fact that mosaicism may cause TH and that molecular analysis of gonadal tissue should be performed in all 46,XX cases.
Assuntos
Deleção Cromossômica , Cromossomos Humanos X/genética , Cromossomos Humanos Y/genética , Transtornos do Desenvolvimento Sexual/genética , Mosaicismo , Aberrações dos Cromossomos Sexuais , Criança , Feminino , Genes sry/genética , Genitália Feminina/anormalidades , Genitália Feminina/cirurgia , Humanos , Hibridização in Situ Fluorescente , Cariotipagem , Masculino , Testículo/anormalidades , Testículo/cirurgiaRESUMO
True hermaphroditism (TH) is an unusual form of sex reversal, characterized by the development of testicular and ovarian tissue in the same subject. Approximately 60% of the patients have a 46,XX karyotype, 33% are mosaics with a second cell line containing a Y chromosome, while the remaining 7% are 46,XY. Molecular analyses have demonstrated that SRY is present in only 10% of TH with a 46,XX karyotype; therefore, in the remaining 90%, mutations at unknown X-linked or autosomal sex determining loci have been proposed as factors responsible for testicular development. True hermaphroditism presents considerable genetic heterogeneity with several molecular anomalies leading to the dual gonadal development as SRY point mutations or SRY hidden gonadal mosaicism. In order to identify genetic defects associated with subjects with the disease, we performed molecular analyses of the SRY gene in DNA from blood leukocytes and gonadal tissue in 12 true hermaphrodites with different karyotypes. Our results using PCR and FISH analyses reveal the presence of hidden mosaicism for SRY or other Y sequences in some patients with XX true hermaphroditism and confirms that mosaicism for SRY limited to the gonads is an alternative mechanism for testicular development in 46,XX true hermaphrodites.