RESUMEN
The pine woods treefrog, Hyla femoralis, is unique among North American hylid frogs in having a metacentric chromosome 6 and heteromorphic sex chromosomes of the XY/XX type. The X chromosome is distinguished by having a nucleolar organizing region (NOR) in the short arm. The Y chromosome does not possess an NOR. Until the present study, it was not known if the NOR was not present on the Y chromosome or inactive and therefore not detectable by conventional cytogenetic methods like silver staining. Exclusive of its unique features the karyotype of H. femoralis closely resembles those of North American frogs with karyotypes like H. chrysoscelis. We used replication banding and fluorescence in situ hybridization (FISH) with a DNA probe to the 18S + 28S ribosomal genes, which are located at the NOR, to characterize the H. femoralis karyotype. Our analysis revealed that the 18S + 28S ribosomal genes are not present on the Y chromosome, and that the karyotype of H. femoralis was derived from an H. chrysoscelis-like karyotype by relocation of the NOR to the X chromosome from chromosome 6 and either a concurrent or subsequent pericentric inversion of chromosome 6.
Asunto(s)
Anuros/genética , Bandeo Cromosómico/métodos , Hibridación Fluorescente in Situ/métodos , Cromosomas Sexuales/genética , Animales , Replicación del ADN/genética , Evolución Molecular , Femenino , Cariotipificación , Masculino , Región Organizadora del Nucléolo/genética , Cromosoma X/genética , Cromosoma Y/genéticaRESUMEN
The location of rDNA genes on the chromosomes of most species is identical within that species, usually occurring on the same chromosome or chromosomes. This is not the case in Cope's gray treefrog, Hyla chrysoscelis, where the rDNA genes are polymorphic for chromosome location. The occasions leading to this polymorphism have yet to be determined. The first step in understanding the nature of the polymorphism is the characterization of the ribosomal gene array. Here we describe the cloning, sequencing, and confirmation, by fluorescence in situ hybridization, of the 18S rDNA gene, a region which includes the end of the 18S rDNA gene, an internal transcribed spacer, and a portion of the 5' end of the 28S rDNA gene in H. chrysoscelis.
Asunto(s)
Regiones no Traducidas 5'/genética , Bufonidae/genética , ADN Espaciador Ribosómico/genética , ADN Ribosómico/genética , ARN Ribosómico 18S/genética , ARN Ribosómico 28S/genética , Animales , Secuencia de Bases , Clonación Molecular , Hibridación Fluorescente in Situ , Cariotipificación , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa , Polimorfismo Genético/genética , Alineación de Secuencia , Análisis de Secuencia de ADN , Transcripción Genética/genéticaRESUMEN
Populations of the diploid-tetraploid treefrogs Hyla chrysoscelis and H. versicolor can be defined by the polymorphic positions of the nucleolar organizing regions (NORs) on their chromosomes. Evidence from NOR positions and interstitial telomere sequence data shows that gene flow between H. chrysoscelis populations appears to be restricted, with contact occurring only in narrow "hybrid" zones. Hyla versicolor appears to have had multiple origins from H. chrysoscelis populations, and this, too, is reflected in the NOR positions. We used replication banding to determine if genetic isolation of H. chrysoscelis populations was accompanied by karyotype evolution in the populations or in contact zones. We also sought to detect karyotype alteration or replication differences associated with polyploidy in H. versicolor. Homologous chromosome pairs of all H. chrysoscelis studied displayed no differences in replication banding patterns, nor did they differ from those of H. versicolor. Although NOR positions differed between the populations studied, no disturbance of the replication banding patterns was found, indicating that structural rearrangements were not involved in creating the multiple NOR positions seen in populations of H. versicolor and H. chrysoscelis.
Asunto(s)
Anuros/genética , Bandeo Cromosómico , Cromosomas/genética , Replicación del ADN/genética , Diploidia , Poliploidía , Animales , Artefactos , Bromodesoxiuridina/farmacología , Cromosomas/efectos de los fármacos , Femenino , Pool de Genes , Hibridación Genética/genética , Cariotipificación , Masculino , Región Organizadora del Nucléolo/genética , Polimorfismo Genético/genéticaRESUMEN
Angelman syndrome (AS) is associated with a loss of maternal genetic information, which typically occurs as a result of a deletion at 15q11-q13 or paternal uniparental disomy of chromosome 15. We report a patient with AS as a result of an unbalanced cryptic translocation whose breakpoint, at 15q11.2, falls within this region. The proband was diagnosed clinically as having Angelman syndrome, but without a detectable cytogenetic deletion, by using high-resolution G-banding. FISH detected a deletion of D15S11 (IR4-3R), with an intact GABRB3 locus. Subsequent studies of the proband's mother and sister detected a cryptic reciprocal translocation between chromosomes 14 and 15 with the breakpoint being between SNRPN and D15S10 (3- 21). The proband was found to have inherited an unbalanced form, being monosomic from 15pter through SNRPN and trisomic for 14pter to 14q11.2. DNA methylation studies showed that the proband had a paternal-only DNA methylation pattern at SNRPN, D15S63 (PW71), and ZNF127. The mother and unaffected sister, both having the balanced translocation, demonstrated normal DNA methylation patterns at all three loci. These data suggest that the gene for AS most likely lies proximal to D15S10, in contrast to the previously published position, although a less likely possibility is that the maternally inherited imprinting center acts in trans in the unaffected balanced translocation carrier sister.
Asunto(s)
Síndrome de Angelman/genética , Deleción Cromosómica , Cromosomas Humanos Par 15 , Ribonucleoproteínas Nucleares Pequeñas , Translocación Genética , Autoantígenos/genética , Niño , Mapeo Cromosómico , Cromosomas Humanos Par 14 , ADN/metabolismo , Sondas de ADN , Femenino , Impresión Genómica/genética , Humanos , Metilación , Proteínas Nucleares snRNPRESUMEN
Constitutional nonreciprocal translocations are extremely rare, and even their existence is controversial. We report on a newborn infant with a de novo nonreciprocal translocation between chromosomes 1 and 8 resulting in 1q42.3 deletion syndrome. Fluorescent in situ hybridization with whole chromosome paints confirmed the conventional cytogenetic diagnosis.
Asunto(s)
Anomalías Múltiples/genética , Cromosomas Humanos Par 1 , Cromosomas Humanos Par 8 , Translocación Genética , Mapeo Cromosómico , Eliminación de Gen , Humanos , Hibridación Fluorescente in Situ , Recién Nacido , CariotipificaciónAsunto(s)
Aberraciones Cromosómicas/patología , Cromosomas Humanos Par 4 , Leucemia-Linfoma Linfoblástico de Células Precursoras/patología , Adolescente , Aneuploidia , Bandeo Cromosómico , Trastornos de los Cromosomas , Humanos , Hibridación Fluorescente in Situ , Masculino , Translocación GenéticaRESUMEN
Tamoxifen has found extensive use in the treatment of all stages of human breast cancer. The efficacy of tamoxifen treatment for the prevention of second primary tumors and its chemosuppressive action in animal models have led to initiation of clinical trials to test its efficacy for prevention of this disease in women. Recently, tamoxifen has been shown to induce hepatocellular carcinomas in rats. For determination of the mechanism of induction of these tumors and assessment of the possibility of risk of human cancer development from tamoxifen treatment, female Sprague-Dawley rats (five rats per treatment) were administered tamoxifen at doses ranging from 0.3 to 35 mg/kg. One day after treatment, the rats were sacrificed, and the hepatocytes were isolated and cultured for 50 h. Colcemid was added 3 h prior to harvest, and the hepatocytes were then prepared for karyotypic evaluation. One hundred metaphase spreads were examined per animal. Tamoxifen treatment resulted in the induction of aneuploidy in approximately 70% of the examined hepatocytes at the doses used. In addition, premature condensation (2-10%) and endoreduplication (5-10%) were observed in hepatocytes of rats treated with tamoxifen. Furthermore, exchanges between chromosomes as well as chromosome breakage were observed. Examination of the cultured hepatocytes from rats treated with tamoxifen by electron microscopy demonstrated both unipolar spindles and incompletely elongated spindles. Exposure of rats to a single in vivo dose of tamoxifen produced multiple changes in rat hepatocytes including clastogenic damage at doses comparable to that administered to humans. The occurrence of aneuploidy induction, premature condensation, chromosome breakage, and improper mitotic spindle formation indicates that risk versus benefit of tamoxifen treatment should be carefully evaluated.
Asunto(s)
Aneuploidia , Aberraciones Cromosómicas/inducido químicamente , Hígado/efectos de los fármacos , Huso Acromático/efectos de los fármacos , Tamoxifeno/efectos adversos , Animales , Trastornos de los Cromosomas , Relación Dosis-Respuesta a Droga , Femenino , Piridinas/efectos adversos , Ratas , Ratas Sprague-Dawley , Tamoxifeno/administración & dosificaciónRESUMEN
The severe phenotype of human females whose karyotype includes tiny ring X chromosomes has been attributed to the inability of the small ring X chromosome to inactivate. The XIST locus is expressed only from the inactive X chromosome, resides at the putative X inactivation center, and is considered a prime player in the initiation of mammalian X dosage compensation. Using PCR, Southern blot analysis, and in situ hybridization, we have looked for the presence of the XIST locus in tiny ring X chromosomes from eight females who have multiple congenital malformations and severe mental retardation. Our studies reveal heterogeneity within this group; some rings lack the XIST locus, while others have sequences homologous to probes for XIST. However, in the latter, the locus is either not expressed or negligibly expressed, based on reverse transcription-PCR analysis. Therefore, what these tiny ring chromosomes have in common is a level of XIST transcription comparable to an active X. As XIST transcription is an indicator of X chromosome inactivity, the absence of XIST transcription strongly suggests that tiny ring X chromosomes in females with severe phenotypes are mutants in the X chromosome inactivation pathway and that the inability of these rings to inactivate is responsible for the severe phenotypes.
Asunto(s)
Hominidae/genética , Aberraciones Cromosómicas Sexuales , Diferenciación Sexual/genética , Síndrome de Turner/genética , Cromosoma X , Adolescente , Adulto , Animales , Niño , Preescolar , Mapeo Cromosómico , Femenino , Marcadores Genéticos , Humanos , Hibridación Fluorescente in Situ , Cariotipificación , Persona de Mediana Edad , Fenotipo , Reacción en Cadena de la PolimerasaRESUMEN
Interstitial hybridization sites for the (TTAGGG)n telomeric repeat sequence were present in all seven species of hylid frogs examined and in a triploid hybrid between two of the species. Intra- and interspecific differences and similarities in hybridization sites agreed with what is known about the systematics of these species. Chromosome fusions, fissions, and inversions do not appear to have played a role in the evolution of the interstitial sites for the telomeric repeat in the species examined.
Asunto(s)
Anuros/genética , Secuencias Repetitivas de Ácidos Nucleicos/genética , Telómero , Animales , Evolución Biológica , Fluorescencia , América del Norte , Hibridación de Ácido NucleicoRESUMEN
We report on an infant girl born with findings of CHARGE association who proved to be a genetic male (46,XY) on cytogenetic study. Further investigation of the genitalia demonstrated partially female internal organs but absence of gonads by ultrasonography, hormone studies, and absence of ZFY by DNA probe of Yp. Pelvic exploration confirmed lack of gonadal tissue and uterus. Facial phenotype was compatible with CHARGE appearance.
Asunto(s)
Anomalías Múltiples/genética , Disgenesia Gonadal 46 XY/genética , Atresia de las Coanas/genética , Sondas de ADN , Oído Externo/anomalías , Encefalocele/genética , Trastornos del Crecimiento/genética , Cardiopatías Congénitas/genética , Humanos , Técnicas In Vitro , Lactante , Masculino , FenotipoRESUMEN
We evaluated the diagnostic contribution of adjunct studies performed on aspirated material in the work-up of pediatric fine-needle aspiration (FNA) biopsies. Ancillary studies were performed on 54 of 136 (39.7%) pediatric FNA biopsies during a 5-year period. In 23 (16.9%) cases, immunocytochemical (ICC) studies, consisting of immunoperoxidase staining of direct smears and/or cell blocks or flow cytometric immunophenotyping, were performed. The studies were adequate in 14 cases (60.9%), suboptimal in five cases (21.7%), and inadequate in four cases (17.4%). Of the adequate and suboptimal cases, the ICC data helped to narrow the differential diagnosis or classify the disease process in eight cases (42.1%), confirmed cytologic impression in nine cases (47.4%), and gave contradictory results in two cases (10.5%). Adequate material for electron microscopy (EM) was obtained in 14/19 cases (73.7%). Ultrastructural studies were diagnostic, or helped classify the disease process in five cases (35.7%), confirmed the cytologic impression in four cases (28.6%), helped exclude diagnostic considerations in three cases (21.4%), and were judged to be non-contributory in two cases (14.3%). Cytogenetic studies revealed six of seven cases (all neoplasms) to have abnormal karyotypes. Special stains for organisms performed on smears from 25 cases including Ziehl-Neelsen, Gomori methenamine silver (GMS), Gram, and Warthin-Starry (WS) were negative except for 1/16 GMS and 4/9 Gram stains. In summary, we found that with appropriate case selection, ancillary studies performed on aspirated material can provide useful information in pediatric FNA cytology.
Asunto(s)
Biopsia con Aguja , Técnicas Citológicas , Neoplasias/patología , Neoplasias Abdominales/patología , Adolescente , Neoplasias de las Glándulas Suprarrenales/patología , Niño , Preescolar , Citogenética , Femenino , Citometría de Flujo , Humanos , Inmunohistoquímica , Lactante , Linfoma no Hodgkin/patología , Masculino , Microscopía Electrónica , Neoplasias de Células Germinales y Embrionarias/patología , Feocromocitoma/patología , Neoplasias Torácicas/patologíaRESUMEN
Individual specimens of Bufo terrestris were discovered that possessed ribosomal gene locations in addition to those normally found. Every specimen from an island population that was examined had extra sites, whereas fewer individuals from coastal mainland populations and none from inland populations had them. Although the extra ribosomal gene locations probably did not arise through gross structural chromosome rearrangements, their origin remains unclear.
Asunto(s)
Bufonidae/genética , ADN Ribosómico/genética , Polimorfismo Genético , ARN Ribosómico 18S/genética , ARN Ribosómico 28S/genética , Animales , Bandeo Cromosómico , Familia de Multigenes/genética , North Carolina , Hibridación de Ácido NucleicoRESUMEN
Normal human foreskin fibroblasts (HSF4) were transfected using the pSV3-neo plasmid. A pool of 10 G418-resistant colonies, HSF4-T12, showed a progressive increase in the expression of a number of in vitro transformation markers with passage in culture and became immortalized. Although no tumors were formed when cells were injected subcutaneously into nude mice, this cell line produced progressive tumors when cells were injected into preimplanted Gelfoam sponges in the mice. When these tumors were cultured in vitro and subsequently injected subcutaneously, progressive tumors were produced with median latency periods as short as 4 weeks. Three phases of cytogenetic change could be distinguished. At early passages after transfection. HSF4-T12 exhibited many random chromosomal changes. At a time just after immortalization, both flow karyotype and G-banded analyses showed the appearance of balanced clonal rearrangements. These included t(2;4), t(2;14), t(3;?), 6p-, i(6p), 8p-, t(14;15), i(15), and t(18;?). These clonal rearrangements were stable with passage in culture, and less variability from cell to cell was noted. The only consistent chromosomal loss observed was -Y. Analysis of three independent tumors showed characteristic loss of chromosomal material rather than balanced chromosomal rearrangements. Frequent loss of 6q and chromosomes #13, 15, 20, and Y was noted.
Asunto(s)
Transformación Celular Viral , Aberraciones Cromosómicas , Virus 40 de los Simios , Animales , Transformación Celular Neoplásica , Deleción Cromosómica , ADN de Neoplasias/análisis , Fibroblastos , Humanos , Cariotipificación , Ratones , Ratones Desnudos , Trasplante de Neoplasias , Neoplasias Experimentales/etiología , Plásmidos , TransfecciónRESUMEN
The intrachromosomal distribution of non-telomeric sites of the (TTAGGG)n telomeric repeat was determined for 100 vertebrate species. The most common non-telomeric location of this sequence was in the pericentric regions of chromosomes. A variety of species showed relatively large amounts of this sequence present within regions of constitutive heterochromatin. We discuss possible relationships between the non-telomeric distribution of the (TTAGGG)n sequence and the process of karyotype evolution, during which these sites may provide potential new telomeres.
Asunto(s)
Cromosomas , ADN , Secuencias Repetitivas de Ácidos Nucleicos , Vertebrados/genética , Anfibios/genética , Animales , Secuencia de Bases , Evolución Biológica , Aves/genética , Bandeo Cromosómico , Peces/genética , Cariotipificación , Mamíferos/genética , Hibridación de Ácido Nucleico , Reptiles/genética , Especificidad de la EspecieRESUMEN
Two white females, age 2 1/2 and 33 years, respectively, were investigated because of severe mental retardation associated with neurologic abnormalities, coarse face, and soft tissue syndactyly involving upper and lower limbs. Each had cytogenetic findings of a mosaic variant of Ullrich-Turner syndrome with X ring chromosome in peripheral lymphocyte and skin fibroblasts. Early X replication occurred in one-third of the X ring chromosomes; there was no evidence for X-autosome translocation involving either X and an autosomal duplication; results of studies for fragility of the X chromosomes were unremarkable. In situ hybridization with an X centromere probe was positive for the ring. To our knowledge, the unusual constellation of cytogenetic, physical, and mental findings seen in these 2 individuals has not been reported previously.
Asunto(s)
Discapacidad Intelectual/genética , Síndrome de Noonan/genética , Sindactilia/genética , Cromosoma X , Adulto , Preescolar , Femenino , Técnicas Genéticas , Humanos , Mosaicismo , Cromosomas en AnilloRESUMEN
A human colon carcinoma cell line resistant to mitomycin C (MMC) was obtained by repeated exposure of a previously described sensitive parental line, HCT 116, to MMC in vitro. Xenografts grown from the MMC-resistant phenotype were not inhibited in MMC-treated animals, while MMC treatment produced growth inhibition in parental cell xenografts. The MMC-resistant phenotype exhibited a greater amount of a Mr 148,000 cell surface protein than did the parental line. The increase in this Mr 148,000 cell surface protein correlated positively with the degree of MMC resistance. Alkaline elution of filter-bound DNA from resistant cells exposed to MMC in vitro showed a decrease in DNA cross-link formation such that a 10-fold higher MMC concentration was required to produce similar cross-link formation in the resistant cell as compared to the parental cell. The development of MMC resistance was not associated with in vitro cross-resistance to other natural product cytotoxic drugs. This model for resistance to MMC will be useful in future studies to define the mechanisms for MMC action and resistance in human colon carcinoma cells.
Asunto(s)
Antibióticos Antineoplásicos/toxicidad , Neoplasias del Colon/patología , Proteínas de la Membrana/metabolismo , Mitomicinas/toxicidad , Animales , Línea Celular , Membrana Celular/efectos de los fármacos , Membrana Celular/metabolismo , Supervivencia Celular/efectos de los fármacos , Resistencia a Medicamentos , Femenino , Humanos , Cariotipificación , Ratones , Ratones Desnudos , Mitomicina , Trasplante de Neoplasias , Fenotipo , Trasplante HeterólogoRESUMEN
Six different techniques were evaluated to define better those technical factors that are most critical for obtaining prometaphase cells for banding analysis. Our results demonstrate: colcemid exposures of 30 min or less have no effect on increasing the yield of prometaphase cells, colcemid exposures of greater than 0.1 microgram/ml can be toxic, methotrexate depresses the mitotic index significantly and seems to increase the incidence of prometaphase cells only because it suppresses later forms; and (d) the optimum number of cytogenetically satisfactory prometaphase cells can be obtained with a 4-h exposure to a combination of low concentration actinomycin D (0.5 microgram/ml) and colcemid (0.1 microgram/ml). This technique inhibits chromosome condensation while permitting prometaphase cells to accumulate for 4 h.