RESUMO
The basic molecular mechanisms by which chromosomal rearrangements in heterozygous state produce spermatogenic disturbances are poorly understood. Testicular biopsies from five patients - one carrier of a Robertsonian translocation rob t(13;14), two carriers of two different Y-autosome translocations, a t(Y;6) and a t(Y;11), one carrier of a reciprocal translocation t(3;13) and one carrier of a heterochromatin duplication in chromosome 9 - were processed for histopathological analysis, electron microscopy and fluorescent immunolocalization of meiotic proteins. In all the patients, the asynaptic regions during pachytene are labelled by BRCA1 and retained RAD51 foci. The variant histone γ-H2AX is located on the chromatin domains of the asynaptic regions and the XY body. In contrast, these meiotic proteins are absent in those chromosomal segments that are non-homologously synapsed. The present observations on five new cases and a review of recent studies show that the common features shared by all these cases are the abnormal location of some meiotic proteins and the presence of transcriptionally silenced chromatin domains on asynaptic regions. The frequent association of these silenced regions with the XY body and the rescue of spermatocyte viability through non-homologous synapsis are also shared by all these carriers. A passive, random mechanism of clustering of asynaptic regions with the XY body is suggested.
Assuntos
Azoospermia/genética , Oligospermia/genética , Análise do Sêmen , Espermatogênese/genética , Espermatozoides/anormalidades , Adulto , Proteína BRCA1/genética , Cromatina , Histonas/genética , Humanos , Masculino , Meiose/genética , Estágio Paquíteno/genética , Rad51 Recombinase/genética , Translocação GenéticaRESUMO
BACKGROUND: Klinefelter syndrome is the most frequent chromosome abnormality in human males. This paper aims to investigate the ploidy of meiotic and pre-meiotic germ cells found in spermatogenic foci, and furthermore, the sex chromosome constitution of Sertoli cells which surround these germ cells in non-mosaic Klinefelter patients. METHODS AND RESULTS: A survey of 11 adult patients diagnosed with classical, non-mosaic Klinefelter syndrome who underwent testicular biopsies, showed that six of them had spermatogenesis foci. The topographical study of the biopsies showed that tubuli with germ cells are a minor fraction (8-24%) of all tubuli, although the overwhelming majority is devoid of germ cells. Using fluorescence in situ hybridization (FISH) with probes for the X-centromere and immunolocalization of meiotic proteins, the present work shows that all the 92 meiotic spermatocytes analyzed with FISH were euploid, 46,XY, and thus can form normal, haploid gametes. On the other hand, Sertoli cells show two marks for the X chromosome, meaning that they are 47,XXY. CONCLUSIONS: These results provide a rationale for the high rate of success in the testicular sperm extraction plus ICSI procedures when applied to Klinefelter patients. It is also in agreement with previous studies in the XXY-mouse model. These spermatogenic foci most probably originate from clones of spermatogonia that have randomly lost one of the X chromosomes, probably during periods of life when high spermatogonial mitotic activity occurs.
Assuntos
Células Germinativas/fisiologia , Síndrome de Klinefelter/fisiopatologia , Espermatogênese/fisiologia , Testículo/patologia , Adulto , Humanos , Hibridização in Situ Fluorescente , Cariotipagem , Síndrome de Klinefelter/patologia , Masculino , Células de Sertoli/patologia , Células de Sertoli/fisiologia , Espermatócitos/patologia , Espermatócitos/fisiologiaRESUMO
BACKGROUND: The mechanisms of meiotic arrest in human spermatogenesis are poorly known. METHODS AND RESULTS: A testicular biopsy from an azoospermic male showed complete spermatogenesis arrest at the spermatocyte stage, asynapsis, lack of formation of the XY body, partial reversion to a mitotic-like division and cell degeneration both at the prophase and at the abnormal cell divisions. Synaptonemal complex analysis showed minor segments of synapsis and mainly single axes. Fluorescent immunolocalization of meiotic proteins showed normal SYCP3, scarcity of SYCP1, null MLH1 foci, about 10 patches of gamma-H2AX, abnormal presence of BRCA1 among autosomal axes, absence of RAD51 in early and advanced spermatocytes and permanence of gamma-H2AX labelling up to the abnormal spermatocyte divisions that are the most advanced stage reached. There are at least six dominions of evenly packed chromatin resembling that of the normal XY body, but no true XY body. CONCLUSIONS: The protein phenotype and the fine structure of the nuclei are compatible with a deficiency of the processing of double-strand DNA breaks in the zygotene-like spermatocytes, but the features of this defect do not agree with Spo11, Sycp1, Atm and Dmc1 null mutations, which give absence of XY body, synapsis disturbances and spermatocyte apoptosis in mice.
Assuntos
Dano ao DNA , Reparo do DNA , Oligospermia/metabolismo , Espermatócitos/ultraestrutura , Espermatogênese , Complexo Sinaptonêmico/metabolismo , Proteínas Adaptadoras de Transdução de Sinal , Adenosina Trifosfatases/genética , Adulto , Proteínas Mutadas de Ataxia Telangiectasia , Proteína BRCA1/análise , Proteínas de Transporte , Proteínas de Ciclo Celular/análise , Proteínas de Ciclo Celular/genética , Núcleo Celular/química , Núcleo Celular/metabolismo , Núcleo Celular/ultraestrutura , Pareamento Cromossômico/genética , DNA/metabolismo , Dano ao DNA/genética , Proteínas de Ligação a DNA/análise , Proteínas de Ligação a DNA/genética , Endodesoxirribonucleases , Esterases/genética , Histonas/análise , Humanos , Masculino , Meiose/genética , Proteína 1 Homóloga a MutL , Mutação , Proteínas Nucleares/análise , Proteínas Nucleares/genética , Oligospermia/genética , Proteínas Serina-Treonina Quinases/análise , Rad51 Recombinase/análise , Espermatócitos/química , Espermatócitos/metabolismo , Espermatogênese/genética , Complexo Sinaptonêmico/química , Complexo Sinaptonêmico/genética , Testículo/patologia , Proteínas Supressoras de Tumor/análiseRESUMO
The meiotic cytology and fine structure of the sex multiples in males from two species of the genus Alouatta are presented and compared with descriptions from other species of this genus. As shown in pachytene by synaptonemal complex analysis and in metaphase I by spreading, there is a quadrivalent in male meiosis in A. caraya, which is formed by an X(1)X(2)Y(1)Y(2) complex, while in A. palliata there is a trivalent formed by an X(1)X(2)Y(1) complex. Chromosome painting with human probes shows that A. caraya sex multiples share the same components as those of A. seniculus sara and A. seniculus arctoidea. However, as shown here for A. palliata and by others in A. fusca, there are differences among the multiples of some species. It is shown that in this genus there are several varieties of sex multiples that share some features, and that the origin of these multiples is most probably a primitive development in the genus Alouatta.
Assuntos
Alouatta/genética , Meiose/genética , Cromossomos Sexuais/química , Cromossomos Sexuais/genética , Animais , Bandeamento Cromossômico/métodos , Cromossomos de Mamíferos/química , Cromossomos de Mamíferos/genética , Evolução Molecular , Variação Genética/genética , Cariotipagem , Linfócitos/química , Linfócitos/metabolismo , Masculino , Metáfase/genética , Microscopia Eletrônica/métodos , Mitose/genética , Especificidade da Espécie , Espermatócitos/química , Espermatócitos/metabolismo , Espermatócitos/ultraestrutura , Complexo Sinaptonêmico/genéticaRESUMO
Complex chromosome rearrangements are rare aberrations that frequently lead to reproductive failure and that may hinder assisted reproduction. A 25-year-old azoospermic male was studied cytogenetically with synaptonemal complex analysis of spermatocytes from a testicular biopsy and fluorescence in situ hybridization (FISH) of lymphocytes. The spermatocytes showed a pentavalent plus a univalent chromosome. Cell death occurred mainly at advanced pachytene stages. The sex chromosomes were involved in the multiple, as shown by their typical axial excrescences. Two autosomal pairs, including an acrocentric chromosome (15), were also involved in the multiple. FISH allowed the definite identification of all the involved chromosomes. An inverted chromosome 12 is translocated with most of one long arm of chromosome 15, while the centromeric piece of this chromosome 15 is translocated with Yqh, forming a small marker chromosome t(15;Y). The euchromatic part of the Y chromosome is joined to the remaining piece of chromosome 12, forming a neo-Y chromosome. The patient shows azoospermia and a normal phenotype. The disruption of spermatogenesis is hypothetically due to the extent of asynaptic segments and to sex-body association during pachytene. This CCR occurred 'de novo' during paternal spermatogenesis. Meiotic analysis and FISH are valuable diagnostic tools in these cases.
Assuntos
Aberrações Cromossômicas , Oligospermia/genética , Adulto , Análise Citogenética , Rearranjo Gênico , Loci Gênicos , Humanos , Hibridização in Situ Fluorescente , Masculino , Meiose , Proteínas de Plasma Seminal/genética , Deleção de Sequência , Espermatócitos/patologia , Espermatócitos/fisiologia , Espermatogênese/genética , Complexo Sinaptonêmico/genéticaRESUMO
The fine structure of the binucleate, parasitic protist Giardia lamblia during interphase and divisional stages was studied by serial thin sectioning and three-dimensional reconstructions. The earlier sign of nuclear division is the development of a few peripheral areas of densely packed chromatin directly attached to the inner nuclear envelope. An intracytoplasmic sheet of ventral disk components grows from the cell periphery towards one of the nuclei, apparently constricting this nucleus, which becomes located at a ventral bulge. After the basal bodies become duplicated, a full nuclear division occurs in trophozoites, giving two pairs of parent-daughter nuclei. This full division occurs in a dorsal-ventral direction, with the resulting nuclear pairs located at the sides of the two sets of basal bodies. A new ventral disk is formed from the disk-derived sheets in the cell harboring the four nuclei. Cytokinesis is polymorphic, but at early stages is dorsal-to-dorsal. Encysting trophozoites show the development of Golgi cisternae stacks and dense, specific secretory granules. 3-D reconstructions show that cysts contain a single pair of incompletely strangled nuclei. The dividing Giardia lacks a typical, microtubular spindle either inside or outside the nuclei. The nuclear envelope seems to be the only structure involved in the final division of the parent-daughter nuclei. (AU)
Assuntos
RESEARCH SUPPORT, NON-U.S. GOVT , Núcleo Celular/ultraestrutura , Giardia lamblia/ultraestrutura , Membrana Nuclear/ultraestrutura , Divisão Celular/fisiologia , Núcleo Celular/fisiologia , Cromatina/fisiologia , Cromatina/ultraestrutura , Citoplasma/fisiologia , Citoplasma/ultraestrutura , Giardia lamblia/fisiologia , Complexo de Golgi/fisiologia , Complexo de Golgi/ultraestrutura , Microscopia Eletrônica , Membrana Nuclear/fisiologia , Organelas/fisiologia , Organelas/ultraestrutura , Vesículas Secretórias/fisiologia , Vesículas Secretórias/ultraestruturaRESUMO
The fine structure of the binucleate, parasitic protist Giardia lamblia during interphase and divisional stages was studied by serial thin sectioning and three-dimensional reconstructions. The earlier sign of nuclear division is the development of a few peripheral areas of densely packed chromatin directly attached to the inner nuclear envelope. An intracytoplasmic sheet of ventral disk components grows from the cell periphery towards one of the nuclei, apparently constricting this nucleus, which becomes located at a ventral bulge. After the basal bodies become duplicated, a full nuclear division occurs in trophozoites, giving two pairs of parent-daughter nuclei. This full division occurs in a dorsal-ventral direction, with the resulting nuclear pairs located at the sides of the two sets of basal bodies. A new ventral disk is formed from the disk-derived sheets in the cell harboring the four nuclei. Cytokinesis is polymorphic, but at early stages is dorsal-to-dorsal. Encysting trophozoites show the development of Golgi cisternae stacks and dense, specific secretory granules. 3-D reconstructions show that cysts contain a single pair of incompletely strangled nuclei. The dividing Giardia lacks a typical, microtubular spindle either inside or outside the nuclei. The nuclear envelope seems to be the only structure involved in the final division of the parent-daughter nuclei.
Assuntos
Giardia lamblia/ultraestrutura , Membrana Nuclear , Núcleo Celular/ultraestrutura , Complexo de Golgi/fisiologia , Complexo de Golgi/ultraestrutura , Citoplasma/fisiologia , Citoplasma/ultraestrutura , Cromatina/fisiologia , Cromatina/ultraestrutura , Divisão Celular/fisiologia , Giardia lamblia/fisiologia , Microscopia Eletrônica , Membrana Nuclear , Núcleo Celular/fisiologia , Organelas/fisiologia , Organelas/ultraestrutura , Vesículas Secretórias/fisiologia , Vesículas Secretórias/ultraestruturaRESUMO
A multiple sex chromosome system was found in three unrelated individuals of the primate Alouatta caraya. This mechanism is originated by a translocation between the Y chromosome and one of the autosomes (A7). Mitotic karyotypes show two small, acrocentric chromosomes (AY and YA), which are the translocation products. In metaphase I of male meiosis, there is a very long chain quadrivalent in which the order of the element is: X-YA-A7-AY. Segregation in the quadrivalent is alternate and gives balanced products. Synaptonemal complex karyotypes at pachytene show the structure of the quadrivalent made by the four axes. There is a slight difference in the relative length of AY and YA and the kinetochore of A7 aligns with that of AY. The synaptic pattern and changes in the quadrivalent during pachytene are described. Thin sections of the quadrivalent body show that the chromatin packing in the sex chromosome region is different from that of the autosomal region. This X1X2Y1Y2/X1X1XX2 sex chromosome system may be extended among other members of the genus Alouatta.