Spindle abnormalities in normally developing and arrested human preimplantation embryos in vitro identified by confocal laser scanning microscopy

• Published in: Human reproduction (Oxford) Vol. 20; no. 3; pp. 672 - 682
• Main Authors: Chatzimeletiou, Katerina, Morrison, Ewan E., Prapas, Nikos, Prapas, Yannis, Handyside, Alan H.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.03.2005; Oxford Publishing Limited (England)
• Subjects: Acetylation; Biological and medical sciences; Blastocyst - physiology; Blastocyst - ultrastructure; cell cycle checkpoints; Cell Nucleus - ultrastructure; Chromosome Aberrations; Chromosome Segregation; Cleavage Stage, Ovum; confocal laser scanning microscopy; Embryonic Development; Gynecology. Andrology. Obstetrics; human preimplantation embryo; Humans; In Vitro Techniques; Interphase; Medical sciences; Microscopy, Confocal; mitotic spindle; nuclear abnormalities; Spindle Apparatus - metabolism; Spindle Apparatus - ultrastructure; Tissue Distribution; Tubulin - metabolism; nuclear abnormalities; cell cycle checkpoints; human preimplantation embryo; confocal laser scanning microscopy; mitotic spindle; Human; Vertebrata; Embryo; Mammalia; cell cycle checkpoints/confocal laser scanning microscopy/human preimplantation embryo/mitotic spindle/nuclear abnormalities; Blastocyst; Cell cycle; Laser; Development; Confocal microscopy; Mitotic spindle; In vitro
• DOI: 10.1093/humrep/deh652
• ISSN: 0268-1161

BACKGROUND: Despite recent technical improvements, many human preimplantation embryos fail to develop to the blastocyst stage or implant after transfer to the uterus. A possible cause for this developmental arrest is the high incidence of nuclear and postzygotic chromosomal abnormalities observed during cleavage, including chaotic chromosome complements, suggestive of defects in mitotic chromosomal segregation. The underlying mechanisms are largely unknown, but similarities with chromosome instability in human cancers led to the proposal that cell cycle checkpoints may not operate at these early stages. METHODS: To investigate this and to examine whether spindle abnormalities contribute to chromosome malsegregation, we have used fluorescence and confocal laser scanning microscopy, following immunolabelling with antibodies specific for α-tubulin, γ-tubulin, or acetylated tubulin, combined with a DNA fluorochrome to visualize nuclei, spindle and chromosome configurations in normal and arrested human embryos, from cleavage to blastocyst stages. RESULTS: In addition to frequent interphase nuclear abnormalities, we identify for the first time various spindle abnormalities including abnormal shape and chromosome loss and multipolar spindles at cleavage and blastocyst stages. CONCLUSIONS: We propose that a major pathway leading to postzygotic chromosomal abnormalities is the formation of binucleate blastomeres with two centrosomes which result either in a bipolar spindle and division to two tetraploid blastomeres, or in a multipolar spindle, chromosome malsegregation and chromosomal chaos.