Ventajas y limitaciones de la citogenética en la medicina actual / Advantages and limitations of cytogenetics in current medicine

La citogenética es el estudio de los cromosomas tanto en número como en estructura. En 1882 Flemming publica las primeras primeras ilustraciones de los cromosomas humanos a partir de observaciones al microscopio y recién en el año 1953, Tjio y Levan determinaron el número real de cromosomas humanos por célula diploide (2n=46). El propósito de este trabajo es presentar el valor, uso actual e importancia de los estudios citogenéticos en aquellos casos en que el profesional de salud se enfrente a un paciente con una probable enfermedad de causa genética o síndrome dismórfico, además de exponer algunas experiencias de un laboratorio de Citogenética en el Paraguay, donde se realiza el estudio cromosómico. Aún con el advenimiento de la Biología Molecular y de la Citogenética Molecular, la citogenética convencional sigue siendo una herramienta de gran importancia, ya que permite realizar el diagnóstico de una enfermedad genética en pacientes con sospecha clínica de ser portadores de anomalías cromosómicas, y por tanto asesorar a las familias respecto de dicha enfermedad, proveer un pronóstico, riesgo de recurrencia y en casos que se requiera, un tratamiento(AU)

Cytogenetics is the study of chromosomes both in number and structure. The first publications about human cytogenetics were provided towards the end of the 19th century with the publication of Flemming in 1882 of the first figures of human chromosomes from observations under the microscope and only in 1953, Tjio and Levan determined the actual number of human chromosomes per diploid cell (2n = 46). The purpose of this paper is to present the value, current use and importance of cytogenetic studies in those cases in which the health professional faces a patient with a probable disease of genetic causes or dysmorphic syndrome, in addition to exposing some experiences from a Cytogenetics laboratory in Paraguay, where chromosomal study is carried out. Even with the arrival of Molecular Biology and Molecular Cytogenetics, conventional cytogenetics is a tool with a great importance, which allows the genetic disease diagnosis in patients with clinical suspicion of being carriers of chromosomal abnormalities, allowing to advice families about the disease, as well as to provide a prognosis, risk of recurrence and, in cases that requires it, a treatment(AU)

Anormalidades cromossômicas entre pacientes com cardiopatia congênita / Chromosomal abnormalities in patients with congenital heart disease

FUNDAMENTO: As anormalidades cromossômicas (ACs) representam importante causa de cardiopatia congênita (CC). OBJETIVO: Determinar a frequência, os tipos e as características clínicas de ACs identificadas em uma amostra prospectiva e consecutiva de pacientes com CC. MÉTODO: Nossa amostra foi composta por pacientes com CC avaliados em sua primeira hospitalização em uma unidade cardíaca de tratamento intensivo de um hospital pediátrico de referência do sul do Brasil. Todos os pacientes foram submetidos à avaliação clínica e citogenética, através do cariótipo de alta resolução. Os defeitos cardíacos foram classificados segundo Botto e cols. Na análise estatística utilizou-se o qui-quadrado, o teste exato de Fisher e odds ratio (p < 0,05). RESULTADOS: Nossa amostra foi composta de 298 pacientes, 53,4% do sexo masculino, com idades variando de um dia a 14 anos. Anormalidades cromossômicas foram observadas em 50 pacientes (16,8%), sendo que 49 deles eram sindrômicos. Quanto às ACs, 44 delas (88%) eram numéricas (40 pacientes com +21, dois com +18, um com triplo X e um com 45,X) e seis (12%) estruturais [dois pacientes com der(14;21), +21, um com i(21q), um com dup(17p), um com del(6p) e um com add(18p)]. O grupo de CCs mais associado a ACs foi o do defeito de septo atrioventricular. CONCLUSÕES: ACs detectadas pelo cariótipo são frequentes entre pacientes com CC. Assim, os profissionais - especialmente aqueles que trabalham em serviços de cardiologia pediátrica - devem estar cientes das implicações que a realização do cariótipo pode trazer, tanto para o diagnóstico, tratamento e prognóstico desses pacientes como para o seu aconselhamento genético.

BACKGROUND: Chromosomal abnormalities (CAs) are an important cause of congenital heart disease (CHD). OBJECTIVE: Determine the frequency, types and clinical characteristics of CAs identified in a sample of prospective and consecutive patients with CHD. METHOD: Our sample consisted of patients with CHD evaluated during their first hospitalization in a cardiac intensive care unit of a pediatric referral hospital in Southern Brazil. All patients underwent clinical and cytogenetic assessment through high-resolution karyotype. CHDs were classified according to Botto et al. Chi-square, Fisher exact test and odds ratio were used in the statistical analysis (p < 0.05). RESULTS: Our sample consisted of 298 patients, 53.4% males, with age ranging from 1 day to 14 years. CAs were observed in 50 patients (16.8%), and 49 of them were syndromic. As for the CAs, 44 (88%) were numeric (40 patients with +21, 2 with +18, 1 with triple X and one with 45,X) and 6 (12%) structural [2 patients with der(14,21), +21, 1 with i(21q), 1 with dup(17p), 1 with del(6p) and 1 with add(18p)]. The group of CHDs more often associated with CAs was atrioventricular septal defect. CONCLUSIONS: CAs detected through karyotyping are frequent in patients with CHD. Thus, professionals, especially those working in Pediatric Cardiology Services, must be aware of the implications that performing the karyotype can bring to the diagnosis, treatment and prognosis and for genetic counseling of patients and families.

Comparación de la calidad embrionaria entre fertilización in vitro (FIV) y cultivo intravaginal de ovocitos (INVO) en el Centro Colombiano de Fertilidad y Esterilidad - CECOLFES, Bogotá, Colombia / Comparing embryo quality between in vitro fertilization (IVF) and intravaginal ovocyte culture (INVO) in the Colombian Centre for Fertility and sterility - CECOLFES, Bogotá, Colombia

Objetivo: comparar la calidad embrionaria y describir las tasas de implantación, embarazo y aborto en las técnicas de fertilización in vitro (FIV) y el cultivo intravaginal de ovocitos. Materiales y métodos: cohortes históricas de pacientes con tratamiento de fertilización in vitro y el cultivo intravaginal de ovocitos en el Centro Colombiano de Fertilidad y Esterilidad (Cecolfes) durante el año 2010. Se incluyeron 137 pacientes aspiradas dentro de los cuatro grupos de estudio: Grupo 1, FIV/Incubadora; Grupo 2, FIV/INVO; Grupo 3, ICSI/INVO, y Grupo 4, ICSI/Incubadora. Se midió el peso de la paciente, el número de ovocitos recuperados y óvulos maduros (MII), la tasa de implantación y la tasa de embarazo y aborto en cada uno de los grupos. Se realizó análisis mediante la prueba de Kruskal-Wallis; la calidad embrionaria fue evaluada con un análisis de covarianza multivariado (MANOVA). Resultados: se observó diferencia significativa en la calidad embrionaria entre las dos técnicas FIV e INVO (p = 0,0388). En la técnica INVO se presentaron mayores tasas de división embrionaria (μ = 7,35/INVO frente a 6,64/Incubadora) y menor fragmentación (μ = 4,67/INVO frente a 4,59/ Incubadora). En cuanto a la tasa de implantación, embarazo y aborto se obtuvieron más altos porcentajes en los grupos INVO. Conclusión: la técnica INVO se asoció a mejor calidad embrionaria. Las tasas de implantación, embarazo y bajas tasas de aborto son semejantes a las descritas en la técnica FIV.

Objective: Comparing embryo quality and describing implantation, pregnancy and abortion rates regarding in vitro fertilization (IVF) and intravaginal oocyte culture (INVO) techniques. Materials and methods: The study involved historical cohorts of patients undergoing IVF and INVO treatment in the Colombian Fertility and Sterility Centre (Centro Colombiano de Fertilidad y Esterilidad – Cecolfes) during 2010. It involved 137 aspirated patients, covering four study groups: Group 1 IVF/incubator, Group 2 IVF/INVO, Group 3 ICSI/INVO and Group 4 ICSI/incubator. The patients’ weight, the number of ovocytes retrieved, mature ovules (M2), implantation rate, pregnancy and abortion rates were measured in each group. The Kruskal-Wallis test was used for statistical analysis; embryo quality was evaluated by multivariate covariance analysis (MANOVA). Results: A significant difference was observed regarding embryo quality between IVF and INVO (p = 0.0388), the INVO technique having higher embryo cleavage rates (μ = 7.35/INVO cf 6.64/ incubator) and lower embryo fragmentation (μ = 4.67/INVO cf 4.59/incubator). INVO groups also had higher percentages concerning their implantation, pregnancy and abortion rates. Conclusion: The INVO technique led to obtaining better quality embryos; implantation, pregnancy and abortion rates were similar to those described for the IVF technique.

Genomic imbalances detected through array CGH in fetuses with holoprosencephaly / Instabilidades genômicas detectadas através de array CGH em fetos com holoprosencefalia

OBJECTIVE: Holoprosencephaly (HPE) is heterogeneous in pathogenesis, integrating genetic susceptibility with the influence of environmental factors. Submicroscopic aberrations may contribute to the etiology of HPE. Our aim was to report the molecular analysis of 4 fetuses with HPE and normal metaphase karyotype. METHOD: A whole genome BAC-array based Comparative Genomic Hybridization (array CGH) was carried out in fetal blood samples. All potential cytogenetic alterations detected on the arrays were matched against the known copy number variations databases. RESULTS: The array CGH analysis showed copy number gains and losses in all cases. We found a recurrent deletion in 15q14 (clone RP11-23J11) and in 15q22 (clone RP11-537k8) in 2 out 4 cases analyzed. We also observed submicroscopic gain in 6p21 in 3 out of 4 fetuses in nearby clones. All these regions were tested in known databases and no copy number variations have been described for them. CONCLUSION: This is the first report of molecular characterization through a whole genome microarray CGH of fetuses with HPE. Our results may contribute to verify the effectiveness and applicability of the molecular technique of array CGH for prenatal diagnosis purposes, and contributing to the knowledge of the submicroscopic genomic instability characterization of HPE fetuses.

OBJETIVO: Holoprosencefalia (HPE) é uma malformação heterogênea na patogênese, integrando a suscetibilidade genética com a influência de fatores ambientais. Aberrações submicroscópicas podem contribuir para a etiologia da HPE. Nosso objetivo foi relatar a análise molecular de 4 fetos com HPE e cariótipo normal. MÉTODO: Foi realizado um estudo descritivo prospectivo dos achados da técnica de hibridação genômica comparativa baseada em microarranjos utilizando BAC clones de ampla cobertura genômica (BAC-array CGH) em amostras sanguíneas de fetos portadores de holoprosencefalia e com cromossomos numericamente normais ao bandamento G. Todas as potenciais alterações citogenéticas detectadas foram comparadas com bancos de dados com variações do número de cópias conhecidas. RESULTADOS: A análise de array CGH evidenciou ganhos e perdas do número de cópias em todos os 4 casos. Foram encontradas deleções recorrentes em 15q14 (clone RP11-23J11) e em 15q22 (clone RP11-537k8) em 2 dos 4 casos analisados. Observou-se em 3 fetos ganho genômico na região 6p21 em clones próximos. Todas estas regiões não apresentaram variações do número de cópias descritas em bancos de dados conhecidos. CONCLUSÃO: Este é o primeiro relato de caracterização molecular através de um microarray CGH de fetos com HPE. Nossos resultados podem contribuir para verificar a eficácia e aplicabilidade da técnica molecular de array CGH para fins de diagnóstico pré-natal, contribuindo para o conhecimento da caracterização de instabilidades genômicas submicroscópicas de fetos com HPE.

Cytogenetic aberrations in primary cell cultures of the ovarian surface epithelium / Aberraciones citogenéticas en cultivos primarios del epitelio superficial del ovario

Our objective was to determine the presence of chromosomal abnormalities in primary cultures of ovarian surface epithelial cells in women of different ages with no history of cancer. Throughout conventional cytogenetic techniques, we analyzed chromosome spreads of cultured ovarian epithelial cells from 10 donors who were 50 or more years old (B) and 16 controls between 20 and 49 years old (A), belonging to the mestizo population in Bogota DC, Colombia. Of the 26 cultures that were analyzed in passage 1, 61.5% had an abnormal chromosome complement (62.5% in A, and 60% in B). Abnormalities included polyploidies, endoduplications and monosomies. Deletions in chromosomes 3 and 11 were found in just one metaphase. None of the samples showed weaknesses or breakpoints. After transforming and applying the exact student’s t-test for variance heterogeneity, we found significant differences in the frequency of metaphases, that were higher in A than in B (p=0.05), and in the frequency of polyploidies, which were higher in B than in A (p=0.044). Through the application of the Mann-Whitney test, we determined that the frequency of endoduplications was higher in A than in B (p=0.126), without reaching significant differences. There were no significant differences in the frequency of monosomies. The level of significance was set at p £ 0.05. Taking into account that polyploidization is a marker of chromosomal instability and that the risk of cancer arising from the ovarian surface epithelium augments substantially after menopause, the increase in the frequency of age-associated polyploidies could be used as a predictor of ovarian cancer in women from an ethnically homogeneous population as the mestizo one in Bogota DC.

El objetivo del presente trabajo fue determinar la presencia de anormalidades cromosómicas en cultivos primarios de células del epitelio superficial ovárico en mujeres de diferentes edades, sin antecedentes de cáncer. Mediante técnicas de citogenética convencional fueron analizados extendidos de células epiteliales ováricas histológicamente normales, provenientes de cultivos primarios de 10 donantes de 50 o más años (B) y de 16 donantes entre 20 y 49 años que se utilizaron como grupo control (A), pertenecientes a la población mestiza de Bogotá DC, Colombia. De 26 cultivos examinados en pase 1, 61,5% presentó complemento cromosómico anormal, 62,5% en A y 60% en B. Las anomalías numéricas halladas, todas en mosaico, incluyeron poliploidías, endoduplicaciones y monosomías. En una única célula en metafase de un cultivo, se presentaron deleciones en los cromosomas 3 y 11. Ninguna muestra presentó fragilidades o roturas. Previa aplicación de transformaciones, con la prueba exacta t-student para varianzas heterogéneas, se encontraron diferencias significativas en la frecuencia de células con metafase normal, mayor en A que en B (p=0,05) y en la de poliploidías, mayor en B que en A (p=0,044). Con la prueba exacta de Mann-Whitney se determinó que la frecuencia de endoduplicaciones en A fue mayor que en B (p=0,126), sin alcanzar diferencias significativas y que no hubo diferencias significativas en la frecuencia de monosomías. El nivel de significación fue p £ 0,05. Si se tiene en cuenta que la poliploidización es un marcador de inestabilidad cromosómica y, que además, el riesgo de aparición de cáncer derivado del epitelio superficial del ovario aumenta sustancialmente después de la menopausia, el incremento en la frecuencia de poliploidías asociado con la edad podría ser utilizado como predictor de cáncer ovárico en mujeres de una población étnicamente homogénea como la población mestiza de Bogotá DC.

Immature oocyte quality and maturational competence of porcine cumulus-oocyte complexes subpopulations

Porcine immature oocyte quality (i.e., that of live oocytes at the germinal vesicle stage) was evaluated according to features of the surrounding cumulus, aiming to establish maturational competence of different subpopulations of such cumulus-oocyte complexes. Six subpopulations were identified: A1 (with a dense cumulus), A2 (with a translucent cumulus), B1 (with the corona radiata), B2 (partly naked oocytes), C (naked oocytes), D (with a dark cumulus). The percent incidence of live oocyte in these subpopulations changed significantly as related to cumulus features, however the occurrence of oocytes in the germinal vesicle stage was lower in class D only. Similar metaphase II rates achieved in A1, A2, B1 and B2 classes after in vitro maturation suggest that the nucleus may in fact mature in vitro, in spite of the different accompanying cumulus features which are typical of these classes. In contrast, a higher cytoplasmic maturation rate obtained in class A may indicate a stronger dependence of this variable upon cumulus features than that shown by nuclear maturation. When different types of cumulus expansion after in vitro maturation were considered (i.e., fully expanded cumulus, partly expanded cumulus, and partly naked oocyte), no differences were found in the percent of oocytes reaching metaphase II or cytoplasmic maturation. It is concluded that morphological features of the collected porcine cumulus-oocyte complexes (rather than cumulus behavior during culture) may be useful for selection of potentially competent oocytes for in vitro fertilization and embryo production.

Metaphase I orientation of Robertsonian trivalents in the water-hyacinth grasshopper, Cornops aquaticum (Acrididae, Orthoptera)

Trivalents resulting from polymorphic Robertsonian rearrangements must have a regular orientation in metaphase I if the polymorphisms are to be maintained. It has been argued that redistribution of proximal and interstitial chiasmata to more distal positions is necessary for a convergent orientation, the only one that produces viable gametes. Cornops aquaticum is a South-American grasshopper that lives and feeds on water-hyacinths, and has three polymorphic Robertsonian rearrangements in its southernmost distribution area in Central Argentina and Uruguay. The orientation of trivalents in metaphase I, the formation of abnormal spermatids and the frequency and position of chiasmata in the trivalents, was analysed in a polymorphic population of C. aquaticus. In this study we observed a correlation between the number of trivalents with the frequency of abnormal spermatids; additionally, the number of chiasmata, especially proximal and interstitial ones, was strongly correlated with the frequency of the linear orientation. Therefore we confirmed our previous assumption, based on other evidence, that the chiasmata redistribution in fusion carriers is essential to the maintenance of the polymorphisms.

Efecto del inhibidor de fosfodiesterasa tipo 4 —rolipram, sobre la maduración in vitro de oocitos bovinos / Efeito do inibidor de fosfodiesterasa tipo 4 —rolipram, sobre a maturação in vitro de oocitos bovinos / Effect of phosphodiesterase type 4-inhibitor rolipram on in vitro maturatrion of bovine oocytes

Durante el proceso de maduración in vitro de oocitos, las gonadotropinas FSH y LH inducen la producción de AMPc. El AMPc tiene efecto dual, donde los altos niveles de AMPc intraoocitario mantienen su bloqueo meiótico, mientras que en las células de la granulosa inducen la maduración del oocito. Los niveles de AMPc son regulados por hidrólisis mediada por fosfodiesterasas (PDE), las cuales presentan expresión específica en el folículo, el oocito expresa la PDE 3, mientras que las células de la granulosa PDE 4. Con el objetivo de evaluar el efecto del rolipram, un inhibidor específico de PDE 4, sobre el porcentaje de maduración nuclear in vitro (MNIV) de oocitos bovinos, 629 complejos cúmulo oocito (CCO) fueron cultivados a 38.5 ºC/5% CO2/24 h, en medio TCM-199 con la adición de pFSH y hrLH, o rolipram. Los grupos experimentales fueron: adición de gonadotropinas, rolipram (25, 50 ó 75 M), rolipram 50 M + gonadotropinas, o control sin estímulo. Los oocitos fueron teñidos con DAPI y evaluados bajo fluorescencia para determinar el porcentaje de maduración nuclear por la expulsión del primer cuerpo polar. El rolipram 50M estimuló la maduración nuclear de oocitos bovinos de una manera similar a la obtenida con las gonadotropinas (76.83 vs 79.46%, p>0.05), pero en mayor medida que la observada con rolipram 25 y 75 M (31.25, y 28.61%, respectivamente). Los CCOs cultivados en presencia de rolipram 50 M+Gonadotropinas maduraron en menor proporción (63.74%) comparada con gonadotropinas (p<0.01) o rolipram 50 M (p<0.05). Los resultados permiten concluir que el porcentaje de maduración nuclear in vitro de oocitos bovinos depende de la dosis de rolipram utilizada, donde la concentración de rolipram 50 M presentó un comportamiento similar a las gonadotropinas en la maduración del oocito...

Gonadotropic follicle stimulating hormone (FSH) and lutenizing hormone (LH) induce intracellular cyclic AMP (cAMP) production during the in vitro maturation (IVM) of bovine oocytes. Cyclic AMP exerts a dual effect, where high intraoocyte cAMP levels are responsible for oocyte meiotic blockage, while high cAMP levels into the granulose cells induce oocyte maturation. Intracellular cAMP levels are regulated by phosphodiesterases (PDE)-mediated hydrolysis, enzymes having a specific follicle expression pattern. Oocyte expresses typo 3 PDE (PDE 3), while granulose cells expresses type 4 PDE (PDE 4). With the aim to test the effect of the specific PDE 4 inhibitor rolliprom on percentage in vitro nuclear maturation (IVNM) of bovine oocytes, 629 cumulus-oocyte complexes (COC) were cultured at 38.5 ºC/CO2 5%/24 h on TCM-199 medium with pFSH and hrLH with or without rolipram. Experimental groups were: gonadotrophins alone, gonadotropins + rolipram (25, 50, or 75 M), rolipram 50 M + gonadotrophins, and control (media without stimulus). In order to determinate the nuclear maturation percentage by the first polar body expulsion, oocytes were dyed with DAPI and evaluated by fluorescence. Rolipram 50 M stimulated bovine oocyte nuclear maturation in a similar way to gonadotrophins stimulus (76.83 vs. 79.46%, p>0.05) did, but in a higher way than rolipram 25 M (31.25%) or 75 M (28.61%). The COC cultured with rolipram 50 M+gonadotrophins maturated in a lower proportion (63.74%) than did with gonadotropins (p<0.01) or rolipram 50 M (p<0.05). A dose-dependent response of percentage of IVNM of bovine oocytes was detected. Thus rolipram 50 M, exerts a similar effect of gonadotropins on oocyte maturation...

Durante o processo de maturação in vitro de oocitos, as gonadotrofinas FSH e LH induzem a produção de AMPc. O AMPc tem duplo efeito, pois os altos níveis de AMPc intraoocitario mantém o bloqueio meiótico, enquanto que nas células da granulosa induzem a maturação do oocito. Os níveis de AMPc são regulados pela hidrólise mediada das fosfodiesterasas (PDE), as quais apresentam expressão específica no folículo, o oocito expressa a PDE 3, enquanto que as células da granulosa PDE 4. Com o objetivo de avaliar o efeito do rolipram, um inibidor específico de PDE 4, sobre a percentagem de maturação nuclear in vitro (MNIV) de oocitos bovinos, 629 complexos cúmulo oocito (CCO) foram cultivados a 38.5 ºC/5% CO2/24 h, em meio TCM-199 com a adição de pFSH e hrLH, o rolipram. Os grupos experimentais foram: adição de gonadotrofinas, rolipram (25, 50 ó 75 M), rolipram 50 M + gonadotrofinas, ou controle sem estímulo. Os oocitos foram tingidos com DAPI e avaliados sob fluorescência para determinar a percentagem de maturação nuclear pela expulsão do primeiro corpo polar. O rolipram 50M estimulou a maturação nuclear de oocitos bovinos de maneira similar a obtida com as gonadotrofinas (76.83 vs 79.46%, p>0.05), porém em maior medida que a observada com rolipram 25 y 75 M (31.25, y 28.61%, respectivamente). Os CCOs cultivados na presença de rolipram 50 M+Gonadotrofinas maturaram em menor proporção (63.74%) quando comparado com gonadotrofinas (p<0.01) ou rolipram 50 M (p<0.05). Os resultados permitem concluir que a percentagem de maturação nuclear in vitro de oocitos bovinos depende da doses de rolipram utilizada, sendo que a concentração de rolipram 50 M apresentou um comportamento similar às gonadotrofinas na maturação do oocito...

Chromosome number and cytogenetics of Euphorbia heterophylla L

Euphorbia heterophylla L. (Euphorbiaceae) is a herbaceous species of great economic importance due to its invasive potential and consequent damage to agriculture and pasture land. For the first time, we provide information on its chromosome number, morphology, and behavior of mitotic chromosomes. Seeds were germinated and submitted to four treatments to obtain metaphases: 0.5% colchicine for 2 to 5 h, at ambient temperature; 0.5% colchicine for 16 to 24 h; 0.0029 M 8-hydroxyquinoline (8-HQ) for 2 to 5 h at ambient temperature, and 0.0029 M 8-HQ for 16 to 24 h at 4°C. The material was then fixed in methanol:acetic acid (3:1) and kept at -20°C for 24 h. Roots were macerated in the enzyme solution of Flaxzyme™ (NOVO FERMENT™)-distilled water (1:40) at 34°C for 2 h and later fixed again. Chromosome preparations were obtained by the dissociation of the apical meristems. The best chromosome preparations were obtained with the use of 8-HQ for 21 h 30 min at 4°C. E. heterophylla showed 2n = 28 chromosomes. The short arm of the largest pair of chromosomes of the complement (pair number 1) displayed a secondary constriction while the nucleolus was observed in the interphasic cell. Structural rearrangements were also observed in the E. heterophylla L. genome. The genomic instability associated with polyploidy may be the result of selection shaped by environmental adaptations and/or human-induced manipulation through agricultural practices.

Subtelomeric region of chromosome 2 in patients with autism spectrum disorders

Autism spectrum disorders are severe psychiatric diseases commonly identified in the population. They are diagnosed during childhood and the etiology has been much debated due to their variations and complexity. Onset is early and characterized as communication and social interaction disorders and as repetitive and stereotyped behavior. Austistic disorders may occur together with various genetic and chromosomal diseases. Several chromosomal regions and genes are implicated in the predisposition for these diseases, in particular those with products expressed in the central nervous system. There are reports of autistic and mentally handicapped patients with submicroscopic subtelomeric alterations at the distal end of the long arm of chromosome 2. Additionally, there is evidence that alterations at 2q37 cause brain malformations that result in the autistic phenotype. These alterations are very small and not identified by routine cytogenetics to which patients are normally submitted, which may result in an underestimation of the diagnosis. This study aimed at evaluating the 2q37 region in patients with autistic disorders. Twenty patients were studied utilizing the fluorescence in situ hybridization technique with a specific probe for 2q37. All of them were also studied by the GTC banding technique to identify possible chromosomal diseases. No alterations were observed in the 2q37 region of the individuals studied, and no patient presented chromosomal diseases. This result may be due to the small sample size analyzed. The introduction of routine analysis of the 2q37 region for patients with autistic disorders depends on further studies.

Karyotypic studies of Cratylia argentea (Desv.) O. Kuntze and C. mollis Mart. ex Benth. (Fabaceae - Papilionoideae)

Cratylia argentea and C. mollis (Fabaceae-Papilionoideae) are legume shrubs native to the Cerrado and Caatinga, respectively. Both species show great resistance to drought and high nutritive value, which makes them a valuable forage resource in tropical regions. Cytogenetic studies were carried out on accessions of C. argentea and C. mollis from Germplasm Banks of Embrapa Gado de Leite (Juiz de Fora, MG) and Embrapa Semi-Árido (Petrolina, PE), respectively. Root tips were treated with 3 mM 8-hydroxyquinoline and slides were made using the air-dry technique. Karyotype description for each accession took into account the following features: chromosome number; total length, relative length and arm ratio of each chromosome; haploid set length, and degree of asymmetry. Mitotic metaphases in both species showed 2n = 22 chromosomes, where this is the first report of diploid number for C. mollis. Chromosome length was also quite similar for the two species, ranging from 5.08 to 2.50 µm in C. argentea and 5.12 to 2.51 µm in C. mollis, with haploid sets of equal size, measuring 38.10 and 37.85 µm, respectively. However, they did not show the same karyotypic formula, which was 5 m + 4 sm + 2 st for C. argentea and 7 m + 2 sm + 2 st for C. mollis. This indicates the occurrence of rearrangements within chromosomes I and VI. Both karyotypes showed a tendency for asymmetry.

Cytogenetic characterization of Crenicichla (Pisces, Perciformes, Cichlidae) of the Iguaçu River

Three populations of the genus Crenicichla, namely Crenicichla iguassuensis, Crenicichla sp 1 and Crenicichla sp 2, from the Iguaçu River, were analyzed cytogenetically, and their nucleolus organizer regions, constitutive heterochromatin distribution and chromomycin A3 markings were studied. Karyotype analyses showed a diploid number of 48 chromosomes, made up of 2 metacentric pairs, 2 submetacentric pairs, 7 subtelocentric pairs, and 13 acrocentric pairs for the three Crenicichla species and no sexual chromosome differentiation. Nucleolus organizer regions showed strong interstitial marking on the first chromosome pair, coincident with a constriction presented by Giemsa and positive marking by chromomycin. Although constitutive heterochromatin patterns were also similar, with pericentromeric markings, small differences in the three species could be observed. Crenicichla sp 2 presented some chromosomes with bitelomeric markings absent in Crenicichla iguassuensis and Crenicichla sp 1.

Cytogenetic characterization of Rhamdiaquelen (Siluriformes, Heptapteridae) from the Bodoquena Plateau, Mato Grosso do Sul, Brazil

We made a cytogenetic study of the fish Rhamdia quelen collected from the Bodoquena Plateau, an isolated national park region in Mato Grosso do Sul State, Brazil. The diploid number was 2n = 58, with 36 metacentric + 16 submetacentric + 6 subtelocentric chromosomes. We found one to three B chromosomes, which were metacentric and submetacentric and of medium size, showing both intra- and interindividual variation. The nucleolus organizer region (NOR) was located in the terminal region of the short arm of submetacentric pair 20. Staining with CMA3 fluorochrome revealed the NOR location, while there was no evidence of fluorescent staining with DAPI. C banding revealed heterochromatin mainly in the terminal regions of the chromosome arms, including the NOR pair. In addition, metacentric pair 2 showed three heterochromatic blocks in the terminal portions and in the pericentromeric region. The B chromosomes appeared euchromatic. The CB + CMA3 staining combination demonstrated only one chromosome pair with fluorescence, probably the NOR-bearing one, while CB + DAPI gave various fluorescent signals, including metacentric pair 2, indicating that these heterochromatic regions are AT-rich in this population of R. quelen. The R. quelen population in this isolated region of Brazil is chromosomally distinct from that of other populations that have been studied.

Differentiation of Nijmegen breakage syndrome from Fanconi anemia

Nijmegen breakage syndrome (NBS) is a rare auto-somal recessive condition with chromosomal instability. Clinical and biological overlap between Fanconi anemia and ataxia telangiectasia has been reported. We report two cases of NBS born to consanguineous parents. Case one had NBS and Falconi anemia clinical features but relatively little chromosome breakage. The second case had mild NBS features, while cytogenetic evaluation with mitomycin C induction showed chromosome damage. Chromosomal analysis of bone marrow cells revealed tetraploidy, which indicates progression towards leukemia. On the basis of clinical and cytogenetic evaluation, these two cases were confirmed as NBS. However, detailed molecular studies are essential for accurate diagnosis and management of this disease.

A micro-spreading improvement for spermatogenic chromosomes from Triatominae (Hemiptera-Reduviidae)

Cytogenetics of triatomines have been a valuable biological tool for the study of evolution, taxonomy, and epidemiology of these vectors of Trypanosoma cruzi. Here we present a single microtube protocol that combines micro-centrifugation and micro-spreading, allowing high quality cytogenetic preparations from male gonadal material of Rhodnius prolixus and Triatoma lecticularia. The amount of cellular scattering can be modulated, which can be useful if small aggregates of synchronous cells are desired. Moreover, a higher number of slides per gonad can be obtained with fully flattened clean chromosomal spreads with minimum overlaps, optimal for classical and modern molecular cytogenetic analyses.

Evidence of allopolyploidy in Brachiaria brizantha (Poaceae: Paniceae) through chromosome arrangement at metaphase plate during microsporogenesis

In the hexaploid (2n = 6x = 54) accession B176 of Brachiaria brizantha, one cytological characteristic differentiated it from the other accessions previously analyzed with the same ploidy level. Nearly 40% of meiocytes displayed the chromosome set arranged at two metaphase plates at the poles of the cell, close to the membrane. In these cells, both metaphase plates were arranged in an angle to form a typical tripolar spindle. Therefore, cells did not show normal chromosome segregation at anaphase I. Only nine univalent chromosomes migrated from each plate to the opposite pole with the remainder staying immobile on the plate. As a result of such spindle orientation and chromosome behavior, trinucleate telophases I were recorded. After telophase, cytokinesis eliminated the small nuclei into a microcyte. The second division proceeded normally, with the presence of microcytes in all phases. The origin of such an abnormality was explained on the hexaploid level of the accession which could have resulted by chromosome doubling of a triploid derived from species that did not display the same behavior for spindle organization. The high percentage of meiotic abnormalities recorded in this accession compromises fertility and renders it inadequate for the breeding program.

A male-sterile mutation in soybean (Glycine max) affecting chromosome arrangement in metaphase plate and cytokinesis

A spontaneous male-sterile, female-fertile mutation affecting bivalent arrangement at the metaphase plate and cytokinesis was detected in line BR98-197 of the soybean breeding program developed by Embrapa - National Soybean Research Centre. Untill diakinesis, meiosis was normal with chromosome pairing as bivalents. From this phase, in several meiocytes, bivalents were not able to organize a single metaphase plate and remained scattered in the cytoplasm in a few or several groups. In these meiocytes, chromosomes segregated in both divisions giving rise to several micronuc1ei. However, the main cause of male sterility was the absence of cytokinesis after telophase II. Instead of the typical tetrads of microspores, four nucleate coenocytic microspores were formed. In the mutant, pollen mitoses did not occur, and after engorgement by starch, pollen underwent a progressive process of degeneration

Localization of rDNA sites in holocentric chromosomes of three species of triatomines (Heteroptera, Triatominae)

Chromatin organization in the holocentric chromosomes of three triatomines species was cytologically studied by fluorescent in situ hybridization with a 45S rDNA probe of Drosophila melanogaster to localize ribosomal genes. In Triatoma tibiamaculata, metaphases I showed telomeric highlights in a single, larger bivalent. In T. protacta, hybridization was detected in one of the telomeres of an autosomal chromosome. In T. platensis, there were highlights in a single, smaller chromosome (X chromosome). The results obtained did not agree with the expected localization of rDNA genes in the sex chromosomes of triatomines, as demonstrated by silver impregnation, and suggest that the chromosome reorganization that occurred in this group during evolution may be a more important mechanism involved in rDNA distribution.

Karyotype description of Pomacea patula catemacensis (Caenogastropoda, Ampullariidae), with an assessment of the taxonomic status of Pomacea patula

Mitotic chromosomes of the freshwater snail Pomacea patula catemacensis (Baker 1922) were analyzed on gill tissue of specimens from the type locality (Lake Catemaco, Mexico). The diploid number of chromosomes is 2n = 26, including nine metacentric and four submetacentric pairs, therefore, the fundamental number is FN = 52. No sex chromosomes could be identified. The same chromosome number and morphology were already reported for P. flagellata, i.e., the other species of the genus living in Mexico. The basic haploid number for family Ampullariidae was reported to be n = 14 in the literaure; so, its reduction to n = 13 is probably an apomorphy of the Mexican Pomacea snails. Lanistes bolteni, from Egypt, also shows n = 13, but its karyotype is much more asymmetrical, and seems to have evolved independently from P. flagellata and P. patula catemacencis. The nominotypical subspecies, P. patula patula (Reeve 1856), is a poorly known taxon, whose original locality is unknown. A taxonomical account is presented here, and a Mexican origin postulated as the most parsimonious hypothesis.