Técnicas de substituição de DNA mitocondrial para reduzir a transmissão da Síndrome de Leigh / Mitochondrial DNA replacement techniques to reduce Leigh syndrome transmission

A Síndrome de Leigh (SL) é uma doença neuro-metabólica congênita, que faz parte do grupo das encefalopatias fatais, com progressão e morte dentro de 2 anos, em média. A SL é causada por mutações no DNA que causam alterações na geração de ATP celular pelas mitocôndrias. As mitocôndrias contêm seu próprio DNA (mtDNA) e, ao contrário do DNA nuclear, o mtDNA é herdado somente da mãe. Mulheres portadores de mutações causadoras da SL podem vivenciar experiências muito tristes ao tentarem realizar o sonho da maternidade. As técnicas de substituição de mtDNA mutado com mtDNA saudável de doadora, oferecem a essas mulheres a possibilidade de terem uma criança geneticamente relacionada sem a SL. O desenvolvimento e a aplicação clínica de terapias de substituição de mtDNA já são uma realidade, tendo o primeiro bebê gerado a partir da técnica nascido em 2016. Mas será que essas técnicas são seguras? Neste trabalho, revisamos a SL e algumas técnicas de substituição de mtDNA já aplicadas em humanos, que envolvem a transferência de pronúcleos de zigotos ou de fuso acromático de oócitos. Concluímos que, apesar dos resultados promissores, ainda é cedo para assegurar a aplicabilidade clínica de técnicas de substituição de mtDNA em seres humanos. (AU)

Leigh syndrome (SL) is a congenital neurometabolic disease included in the group of fatal encephalopathies, with progression and death within 2 years on average. SL is caused by mutations in the DNA that cause changes in the generation of cellular ATP by mitochondria. Mitochondria contain their own DNA (mtDNA) and, unlike nuclear DNA, mtDNA is inherited only from the mother. Women with SL mutations may experience mournful situations when attempting to fulfill the dream of motherhood. Techniques for replacing mutant mtDNA with healthy donor mtDNA provide these women with the possibility of having a genetically related child without SL. The development and clinical application of mtDNA replacement therapies is a reality, and the first baby generated using the technique was born in 2016. However, are these techniques safe? In this article, we review SL and some mtDNA replacement techniques that have been used in humans, which involve zygote pronuclear transfer or oocyte spindle transfer. We conclude that, despite the promising results, it is too early to ensure that mtDNA replacement techniques are clinically applicable to humans. (AU)

Study on expression profile of mRNA in brain of pronuclear transfer mice / 天津医药

Objective To investigate the expression profile of mRNAs in brain samples collected from pronuclear transfer (PNT) mice. Methods Female CD-1 mice were superovulated, and zygotes were collected after mating with adult male mice. Zygotes with two pronuclei were selected for pronuclear transfer manipulation, and then the reconstructed zygotes were transferred into the oviduct of pseudopregnant female mice. The infant mice obtained from pronuclear transfer were called PNT group, while the embryoes that were not performed pronuclear transfer was regarded as control group. Total RNA were extracted from brain samples of both PNT and control mice, and cDNA were labeled with fluorescent dye. Genes that were differentially expressed were identified using the Agilent mouse mRNA array. Gene ontology analysis and pathway analysis were also completed. Results Compared with control group, 392 mRNAs were expressed differentially, which showed more than 2.0 times variation and statistical significance, accounting for 1.7% of all mRNAs. Among those 366 mRNAs were up-regulated and 26 mRNAs were down-regulated. Eleven mRNAs came to 4.0 times variation in total. Gene ontology analysis indicated that differentially expressed genes were significantly enriched in alternative mRNA splicing, small GTPase mediated signal transduction, regulation of insulin receptor signaling pathway, hydrolase activity, transmembrane transporter activity and pyrophosphatase activity. Significant enriched pathway terms contained ion channel transport, fatty acid metabolism, butanoate metabolism, triacylglycerol and ketone body metabolism. Conclusion Pronuclear transfer might influence some key metabolism process in mouse brain.