Cromossomo B: comportamento meiótico e padrões de segregação em Astatotilapia latifasciata
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Data
2018-03-09
Autores
Venturelli, Natália Bortholazzi [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
As células possuem um conjunto regular de cromossomos denominados cromossomos do complemento A e, eventualmente cromossomos extras a esse complemento. Uma destas classes de elementos extras é denominada de cromossomos B (Bs) e ocorrem em uma ampla diversidade de eucariotos incluindo fungos, plantas e animais. Desde sua descrição, os Bs tem atraído a atenção dos pesquisadores. Para ser classificado com um um cromossomo B, este deve apresentar algumas características como: ter uma morfologia distinta dos cromossomos As, número da cópia pode variar entre os indivíduos que o possuem, muitas vezes são heterocromáticos, não são homólogos ao complemento A, não se pareiam ou se recombinam aos As, e frequentemente exibem herança não-Mendeliana. Os cromossomos B tem sido descritos em diversos vertebrados, incluindo o peixe ciclídeo Astatotilapia latifasciata, natural dos lagos Kyoga e Nawampasa, lagos satélites ao lago Vitória no leste Africano, este ciclídeo possui 44 cromossomos e a presença de 1 a 2 cromossomos B. O objetivo deste trabalho foi investigar o comportamento meiótico dos cromossomos B via imunocoloração com anticorpos específicos contra proteínas do complexo sinaptonêmico, coesinas e modificações de histonas; cruzamentos direcionados entre machos e fêmeas com e sem B; e análise de expressão dos genes synaptonemal complex protein 2-like, mitochondrial cardiolipin hydrolase-like, separin-like, tubulin beta-1 chain-like e kinesin-like. A imunocoloração com os anticorpos H3K27me3 e H3K4me3 apresentou uma distribuição global na fase de paquíteno. Já o anticorpo H3K9ac apresentou-se de forma dispersa ao longo de todas as regiões da cromatina interfásica e mantido até o paquíteno da prófase I, onde está associada ao complexo sinaptonêmico. Utilizando-se da tecnologia de super resolução de iluminação estruturada (SIM) observamos, com o dobro da resolução, anticorpos específicos contra coesinas e proteínas do complexo sinaptonêmico. Todos os cromossomos, incluindo o B, apresentam a estrutura regular de complexo sinaptonêmico sendo estas fundamentais para garantir a progressão meiótica e a manutenção do cromossomo B na célula. A hipótese do auto pareamento do cromossomo B investigado foi confirmada e esse auto-pareamento é um mecanismo que possibilita que o cromossomo B se mantenha nas células durante a divisão meiótica. A partir dos dados de cruzamentos direcionados e análise estatística podemos inferir que existe um drive meiótico atuando na espécie A. latifasciata, sendo este mais intenso nas fêmeas. Além disso, a expressão de alguns genes presentes no cromossomo B apresentam-se mais intensa em fêmeas, evidênciando o envolvimento desses genes no controle da transmissão meiótica deste cromossomo.
The cells have a regular set of chromosomes known as A chromosomes. However, there are extra chromosomes and one of them is the extra elements called B-chromosomes (Bs) that occurs in a wide variety of eukaryotes including fungi, plants and animals. Since its description, Bs have attracted the attention of the researchers. To be classified as a B, some characteristics must be present such as: distinct morphology of A chromosomes, number of copy can vary between the individuals bearing it, they are often heterochromatic, they are not homologous to the A complement set, they did not pare or recombine with As, and often exhibit non-Mendelian heritage. B chromosomes have been described in several vertebrates, including the cichlid fish Astatotilapia latifasciata, native to Kyoga and Nawampasa lakes, satellite lakes to Victoria lake in East Africa, which has 44 chromosomes and the presence of 1 to 2 B chromosomes. This work aimed to investigate the meiotic behavior of B chromosomes via immunostaining with specific antibodies against synaptonemic complex proteins, coesins and histone modifications; directed crosses between males and females with and without B; and gene expression analysis: synaptonemal complex protein 2-like, mitochondrial cardiolipin hydrolase-like, separin-like, tubulin beta-1 chain-like and kinesin-like. Immunostaining with antibodies H3K27me3 and H3K4me3 showed a global distribution in the pachytene phase. The H3K9ac antibody was dispersed throughout all the regions of the interphase chromatin and maintained until the pachytene, where it is associated with the synaptonemic complex. Using structured lighting super-resolution (SIM) technology, we observed, with double of the resolution, specific antibodies against coesins and proteins of the synaptonemic complex. All chromosomes, including B, present the regular structure of the synaptonemic complex, which are fundamental to guarantee the meiotic progression and maintenance of the B chromosome in the cell. The selfpairing hypothesis of the investigated chromosome B has been confirmed and this self-pairing is a mechanism that allows the B chromosome to be maintained in the cells during the meiotic division. From the data of directed crossings and statistical analysis we can infer that there is a meiotic drive acting in the species A. latifasciata, being this more evidentin females. In addition, the expression of some intact B chromosome genes is more intense in females, evidencing the involvement of these genes in the control of the meiotic transmission of chromosome B.
The cells have a regular set of chromosomes known as A chromosomes. However, there are extra chromosomes and one of them is the extra elements called B-chromosomes (Bs) that occurs in a wide variety of eukaryotes including fungi, plants and animals. Since its description, Bs have attracted the attention of the researchers. To be classified as a B, some characteristics must be present such as: distinct morphology of A chromosomes, number of copy can vary between the individuals bearing it, they are often heterochromatic, they are not homologous to the A complement set, they did not pare or recombine with As, and often exhibit non-Mendelian heritage. B chromosomes have been described in several vertebrates, including the cichlid fish Astatotilapia latifasciata, native to Kyoga and Nawampasa lakes, satellite lakes to Victoria lake in East Africa, which has 44 chromosomes and the presence of 1 to 2 B chromosomes. This work aimed to investigate the meiotic behavior of B chromosomes via immunostaining with specific antibodies against synaptonemic complex proteins, coesins and histone modifications; directed crosses between males and females with and without B; and gene expression analysis: synaptonemal complex protein 2-like, mitochondrial cardiolipin hydrolase-like, separin-like, tubulin beta-1 chain-like and kinesin-like. Immunostaining with antibodies H3K27me3 and H3K4me3 showed a global distribution in the pachytene phase. The H3K9ac antibody was dispersed throughout all the regions of the interphase chromatin and maintained until the pachytene, where it is associated with the synaptonemic complex. Using structured lighting super-resolution (SIM) technology, we observed, with double of the resolution, specific antibodies against coesins and proteins of the synaptonemic complex. All chromosomes, including B, present the regular structure of the synaptonemic complex, which are fundamental to guarantee the meiotic progression and maintenance of the B chromosome in the cell. The selfpairing hypothesis of the investigated chromosome B has been confirmed and this self-pairing is a mechanism that allows the B chromosome to be maintained in the cells during the meiotic division. From the data of directed crossings and statistical analysis we can infer that there is a meiotic drive acting in the species A. latifasciata, being this more evidentin females. In addition, the expression of some intact B chromosome genes is more intense in females, evidencing the involvement of these genes in the control of the meiotic transmission of chromosome B.
Descrição
Palavras-chave
Cromossomo B, meiose, Citogenética