RESUMO
The way in which transcriptional activity overcomes the physical DNA structure and gene regulation mechanisms involves complex processes that are not yet fully understood. Modifications in the cytosine-guanine sequence of DNA by 5-mC are preferentially located in heterochromatic regions and are related to gene silencing. Herein, we investigate evidence of epigenetic regulation related to the B chromosome model and transposable elements in A. scabripinnis. Indirect immunofluorescence using anti-5-mC to mark methylated regions was employed along with quantitative ELISA to determine the total genomic DNA methylation level. 5-mC signals were dispersed in the chromosomes of both females and males, with preferential accumulation in the B chromosome. In addition to the heterochromatic methylated regions, our results suggest that methylation is associated with transposable elements (LINE and Tc1-Mariner). Heterochromatin content was measured based on the C-band length in relation to the size of chromosome 1. The B chromosome in A. scabripinnis comprises heterochromatin located in the pericentromeric region of both arms of this isochromosome. In this context, individuals with B chromosomes should have an increased heterochromatin content when compared to individuals that do not. Although, both heterochromatin content and genome methylation showed no significant differences between sexes or in relation to the occurrence of B chromosomes. Our evidence suggests that the B chromosome can have a compensation effect on the heterochromatin content and that methylation possibly operates to silence TEs in A. scabripinnis. This represents a sui generis compensation and gene activity buffering mechanism.
Assuntos
Characidae/metabolismo , Cromossomos/metabolismo , Citidina/análogos & derivados , Metilação de DNA , Elementos de DNA Transponíveis , Inativação Gênica , Heterocromatina/metabolismo , Animais , Citidina/farmacologia , Citogenética , Ensaio de Imunoadsorção Enzimática , Epigênese Genética , Feminino , Hibridização in Situ Fluorescente , Isocromossomos , Masculino , MetilaçãoRESUMO
STUDY QUESTION: Are copy number variations (CNVs) in the pseudoautosomal regions (PARs) frequent in subjects with Y-chromosome microdeletions and can they lead to abnormal stature and/or neuropsychiatric disorders? SUMMARY ANSWER: Only subjects diagnosed with azoospermia factor (AZF)b+c deletions spanning to the end of the Y chromosome (i.e. terminal deletions) harbor Y isochromosomes and/or cells 45,X that lead to pseudoautosomal gene CNVs, which were associated with abnormal stature and/or neuropsychiatric disorders. WHAT IS KNOWN ALREADY: The microdeletions in the long arm of the Y chromosome (Yq) that include the loss of one to three AZF regions, referred to as Yq microdeletions, constitute the most important known etiological factor for primary spermatogenic failure. Recently, controversy has arisen about whether Yq microdeletions are associated with gain or loss of PAR genes, which are implicated in skeletal development and neuropsychiatric function. STUDY DESIGN, SIZE, DURATION: We studied a cohort of 42 Chilean patients with complete AZF deletions (4 AZFa, 4 AZFb, 23 AZFc, 11 AZFb+c) from a university medical center, diagnosed over a period of 15 years. The subjects underwent complete medical examinations with special attention to their stature and neuropsychiatric function. PARTICIPANTS/MATERIALS, SETTING, METHODS: All subjects were characterized for Yq breakpoints by PCR, and for CNVs in PARs by multiplex ligation-dependent probe amplification (MLPA), followed by qPCR analysis for genes in PAR1 (SHOX and ZBED1), PAR2 (IL9R) and two single copy genes (SRY and DDX3Y, respectively located in Yp11.3 and AZFa). In addition, karyotypes revision and fluorescence in situ hybridization (FISH) for SRY and centromeric probes for X (DXZ1) and Y (DYZ3) chromosomes were performed in males affected with CNVs. MAIN RESULTS AND THE ROLE OF CHANCE: We did not detect CNVs in any of the 35 AZF-deleted men with interstitial deletions (AZFa, AZFb, AZFc or AZFb+c). However, six of the seven patients with terminal AZFb+c deletions showed CNVs: two patients showed a loss and four patients showed a gain of PAR1 genes, with the expected loss of VAMP-7 in PAR2. In these patients, the Yq breakpoints localized to the palindromes P8, P5 or P4. In the four cases with gain of PAR1, qPCR analysis showed duplicated signals for SRY and DDX3Y and one copy of IL9R, indicating isodicentric Yp chromosomes [idic(Y)] with breakpoint in Yq11.22. The two patients who had loss of PAR1, as shown by MLPA, had an additional reduction for SRY and DDX3Y, as shown by qPCR, associated with a high proportion of 45,X cells, as determined by FISH and karyotype. In agreement with the karyotype analysis, we detected DYZ3++ and DYZ3+ cells by FISH in the six patients, confirming idic(Y) and revealing additional monocentric Y chromosome [i(Y)]. Five patients had a history of major depressive disorders or bipolar disorder, and three had language impairment, whereas two patients showed severe short stature (Z score: -2.75 and -2.62), while a man with bipolar disorder was very tall (Z score: +2.56). LARGE SCALE DATA: N/A. LIMITATIONS, REASONS FOR CAUTION: The number of males studied with Y-chromosome microdeletions and normozoospermic controls with normal karyotypes may not be enough to rule out an association between AZF deletions and PAR abnormalities. The prevalence of Y isochromosomes and/or 45,X cells detected in peripheral blood does not necessarily reflect the variations of PAR genes in target tissues. WIDER IMPLICATIONS OF THE FINDINGS: This study shows that CNVs in PARs were present exclusively in patients with terminal AZFb+c deletions associated with the presence of Y isochromosomes and 45,X cells, and may lead to neuropsychiatric and growth disorders. In contrast, we show that men with interstitial Yq microdeletions with normal karyotypes do not have an increased risk of PAR abnormalities and of phenotypical consequences. Moreover, our results highlight the importance of performing molecular studies, which are not considered in the usual screening for patients with Yq microdeletions. STUDY FUNDING/COMPETING INTERESTS: This work was supported by the National Fund for Scientific and Technological Development of Chile (FONDECYT), grant no. 1120176 (A.C.). The authors declare that no conflicting interests exist.
Assuntos
Cromossomos Humanos Y , Transtornos do Crescimento/psicologia , Isocromossomos , Transtornos Mentais/genética , Oligospermia/genética , Regiões Pseudoautossômicas/genética , Adolescente , Adulto , Estatura/genética , Deleção Cromossômica , Variações do Número de Cópias de DNA , Humanos , Masculino , Adulto JovemRESUMO
IKZF1 deletion (ΔIKZF1) is an important predictor of relapse in childhood B-cell precursor acute lymphoblastic leukemia. Because of its clinical importance, we previously mapped breakpoints of intragenic deletions and developed a multiplex PCR assay to detect recurrent intragenic ΔIKZF1. Since the multiplex PCR was not able to detect complete deletions (IKZF1 Δ1-8), which account for ~30% of all ΔIKZF1, we aimed at investigating the genomic scenery of IKZF1 Δ1-8. Six samples of cases with IKZF1 Δ1-8 were analyzed by microarray assay, which identified monosomy 7, isochromosome 7q, and large interstitial deletions presenting breakpoints within COBL gene. Then, we established a multiplex ligation-probe amplification (MLPA) assay and screened copy number alterations within chromosome 7 in 43 diagnostic samples with IKZF1 Δ1-8. Our results revealed that monosomy and large interstitial deletions within chromosome 7 are the main causes of IKZF1 Δ1-8. Detailed analysis using long distance inverse PCR showed that six patients (16%) had large interstitial deletions starting within intronic regions of COBL at diagnosis, which is ~611 Kb downstream of IKZF1, suggesting that COBL is a hotspot for ΔIKZF1. We also investigated a series of 25 intragenic deletions (Δ2-8, Δ3-8 or Δ4-8) and 24 relapsed samples, and found one IKZF1-COBL tail-to-tail fusion, thus supporting that COBL is a novel hotspot for ΔIKZF1. Finally, using RIC score methodology, we show that breakpoint sequences of IKZF1 Δ1-8 are not analog to RAG-recognition sites, suggesting a different mechanism of error promotion than that suggested for intragenic ΔIKZF1.
Assuntos
Deleção de Genes , Fator de Transcrição Ikaros/genética , Proteínas dos Microfilamentos/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Adolescente , Sequência de Aminoácidos , Sequência de Bases , Pré-Escolar , Pontos de Quebra do Cromossomo , Deleção Cromossômica , Cromossomos Humanos Par 7/genética , Variações do Número de Cópias de DNA , Feminino , Humanos , Lactente , Isocromossomos/genética , Masculino , Técnicas de Amplificação de Ácido Nucleico/métodos , Homologia de Sequência de Aminoácidos , Homologia de Sequência do Ácido NucleicoRESUMO
The combination of Turner syndrome with other genetic disorders such as congenital cataract has been reported, but its association with a congenital form with autosomal dominant inheritance and incomplete penetrance has not been previously reported in the literature. There are no reports on its presentations with rearrangements on chromosome 17. We report the exceptional case of a 20 months old girl with a constellation of major and minor anomalies, diagnosed with mosaic Turner syndrome by isochromosome Xq associated with a microduplication 17p13.3p13.2, who also had bilateral congenital nuclear cataract autosomal dominant with incomplete penetrance. We reviewed in the literature the origin and cause of these genetic alterations and we provided an approach to the hypothesis of the pathogenesis of the association of two of these genetic disorders in the same patient.
Assuntos
Catarata/congênito , Catarata/genética , Síndrome de Turner/genética , Catarata/complicações , Duplicação Cromossômica , Feminino , Humanos , Lactente , Isocromossomos/genética , Cariótipo , Linhagem , Fenótipo , Síndrome de Turner/complicaçõesRESUMO
La combinación del síndrome de Turner con otros trastornos genéticos, como la catarata congénita, ha sido reportada. Sin embargo, su asociación con una forma de catarata nuclear congénita con herencia autosómica dominante y penetrancia incompleta no ha sido reportada previamente en la literatura. Tampoco existen reportes de su presentación junto con rearreglos en el cromosoma 17. A continuación, presentamos el excepcional caso de una paciente con una constelación de anomalías mayores y menores, diagnosticada con síndrome de Turner en mosaico por isocromosoma Xq, asociado a una microduplicación 17p13.3p13.2, quien además presenta catarata nuclear congénita bilateral de herencia autosómica dominante con penetrancia incompleta. Se realiza una revisión acerca del origen y la causa de estas alteraciones genéticas y una aproximación a la hipótesis de la patogénesis de la asociación de dos de estos trastornos genéticos en una misma paciente.
The combination of Turner syndrome with other genetic disorders such as congenital cataract has been reported, but its association with a congenital form with autosomal dominant inheritance and incomplete penetrance has not been previously reported in the literature. There are no reports on its presentations with rearrangements on chromosome 17. We report the exceptional case of a 20 months old girl with a constellation of major and minor anomalies, diagnosed with mosaic Turner syndrome by isochromosome Xq associated with a microduplication 17p13.3p13.2, who also had bilateral congenital nuclear cataract autosomal dominant with incomplete penetrance. We reviewed in the literature the origin and cause of these genetic alterations and we provided an approach to the hypothesis of the pathogenesis of the association of two of these genetic disorders in the same patient.
Assuntos
Feminino , Lactente , Síndrome de Turner , Catarata , Isocromossomos , MosaicismoRESUMO
Particular sonographic fetal malformations are common in chromosome 18 aberrations, requiring invasive prenatal tests to confirm the diagnosis. Karyotyping is the gold standard assay in these cases, although it is a high complexity, expensive and approximately 2 weeks turnaround time test. On the contrary, quantitative fluorescent PCR is considered an accurate, simple, low cost and rapid assay, particularly useful for the diagnosis of aneuploidies of chromosomes 13, 18 and 21 and for the detection of maternal cell contamination of the sample. Clinical presentation of two cases of rare chromosome 18 defects, diagnosed using both techniques. One case was an isochromosome and the other was a partial duplication. Quantitative fluorescent PCR was an invaluable tool for the cytogenetics laboratory.
Assuntos
Isocromossomos , Trissomia/diagnóstico , Cromossomos Humanos Par 18 , Feminino , Fluorescência , Humanos , Gravidez , Diagnóstico Pré-Natal , Reação em Cadeia da Polimerase em Tempo Real/métodosRESUMO
Isochromosome 17q is a relatively common karyotypic abnormality in medulloblastoma, gastric, bladder, and breast cancers. In myeloid disorders, it is observed during disease progression and evolution to acute myeloid leukemia in Philadelphia-positive chronic myeloid leukemia. It has been reported in rare cases of myelodysplastic syndrome, with an incidence of 0.4-1.57%. Two new agents have been approved for treatment of myelodysplastic syndrome/chronic myelomonocytic leukemia. These are the hypomethylating agents, 5-azacytidine and decitabine, recommended by consensus guidelines for high-risk myelodysplastic syndrome patients not eligible for hematopoietic stem cell transplantation. We present a case of chronic myelomonocytic leukemia with normal cytogenetics at diagnosis treated with decitabine (with good response); however, the patient evolved to acute myeloid leukemia with i(17q) shortly after suspending treatment. To the best of our knowledge, this is the first report of acute myeloid leukemia with myelodysplasia-related changes with i(17q) after the use of a hypomethylating agent.
Assuntos
Azacitidina/análogos & derivados , Cromossomos Humanos Par 17/genética , Metilação de DNA/genética , Isocromossomos/genética , Leucemia Mieloide Aguda/induzido quimicamente , Leucemia Mieloide Aguda/genética , Síndromes Mielodisplásicas/induzido quimicamente , Azacitidina/efeitos adversos , Transformação Celular Neoplásica/patologia , Decitabina , Evolução Fatal , Humanos , Cariotipagem , Leucemia Mieloide Aguda/complicações , Masculino , Pessoa de Meia-Idade , Síndromes Mielodisplásicas/complicações , Síndromes Mielodisplásicas/genéticaRESUMO
The presence of a supernumerary 18p isochromosome is a rare chromosomal abnormality that results in 18p tetrasomy. This is a report on the clinical, cytogenetic and molecular findings of 2 non-related patients with a supernumerary 18p isochromosome. Both patients present some features of the 18p tetrasomy syndrome (strabismus, low-set ears, long and narrow fingers and toes), but additional characteristics were also observed. Cytogenetic analysis, FISH, MLPA and SNP array techniques showed that one of the isochromosomes is symmetric and monocentric, while the other is asymmetric and dicentric, yet resulting in a similar tetrasomy of the 18pter-18p10 region, followed by a partial 18q11.2 trisomy, an unprecedented finding in the literature.
Assuntos
Isocromossomos , Trissomia/genética , Criança , Cromossomos Humanos Par 18/genética , Análise Citogenética , Epigênese Genética , Feminino , Humanos , LactenteRESUMO
Chronic myelogenous leukemia (CML) is a common myeloproliferative disease that is characterized by the clonal expansion of marrow stem cells, and is associated with the Philadelphia chromosome. As the disease progresses, additional chromosome abnormalities may arise. The prognostic impact of secondary chromosomal abnormalities in CML is complex, heterogeneous, and sometimes related to previous treatment. Here, we describe a CML patient in lymphoid blast crisis associated with a new chromosomal abnormality identified, dic(7;12)(p12.21;p12.2) and i(12)(q10) using classical cytogenetics and spectral karyotype analysis. To the best of our knowledge, this is the first report of t(7;12)(p11.1;q11.1) and i(12)(q10) in a CML patient with lymphoid evolution.
Assuntos
Crise Blástica/genética , Cromossomos Humanos Par 12 , Cromossomos Humanos Par 7 , Isocromossomos , Leucemia Mielogênica Crônica BCR-ABL Positiva/genética , Translocação Genética , Adulto , Proteínas de Homeodomínio/genética , Humanos , Masculino , Cromossomo FiladélfiaRESUMO
Background: The Isochromosome 18q and chromosome 18 short arm deletion (18p-) constitute structural anomalies that are reported with certain frequency in the literature. However, the association of both abnormalities in a patient is very uncommon. Objective: Description of a clinical case of Isochromosome 18 with emphasys in the few phenotypic manifestations. Case-report: Female infant 18 months-old, with short stature, minor dysmorphic features and a slight psychomotor developmental delay, whose chromosomal study in peripheral blood showed a chromosomal mosaicism with two cell lines: chromosome 18 long arm isochromosome and deletion of chromosome 18 short arm. The chromosomal analysis of both parents did not show numerical neither morphological alterations. Discussion: This case illustrates the importance of requesting a karyotype in patients with small stature, dysmorphic features and/or malformations. The patient clinical features are compared with other similar cases described in the literature. The coexistence of both structural abnormalities (mosaicism) is extremely uncommon.
Introducción: El Isocromoma 18q y la deleción del brazo corto del cromosoma 18 (18p-), son anomalías estructurales que se reportan con cierta frecuencia en la literatura. Sin embargo, la asociación de ambas alteraciones en una misma paciente es muy infrecuente. Objetivo: Descripción de un caso clínico de Isocromosoma 18 con énfasis en la escasas manifestaciones fenotípicas. Caso Clínico: Lactante femenino de 18 meses de edad portador de talla baja, dismorfias menores y un leve retraso del desarrollo sicomotor, cuyo estudio cromosómico en sangre periférica mostró un mosaico compuesto por un isocromosoma del brazo largo del cromosoma 18 y otro cromosoma 18 con deleción del brazo p. El análisis cromosómico de ambos padres no mostró alteraciones numéricas ni morfológicas. Discusión: Este caso ilustra la importancia de solicitar un cariograma en pacientes con talla baja, dismorfias y/o malformaciones. Se describen las malformaciones encontradas y se compara con otros casos similares descritos en la literatura. La alteración estructural en mosaico reportada es sumamente infrecuente.