Aneuploidies: the embryo point of view

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1 Aneuploidies: the embryo point of view MC Magli, A. Pomante, AP Ferraretti, L. Gianaroli S.I.S.Me.. eproductive Medicine Unit, Bologna, Italy Bologna, May 8-11,

2 46 chromosomes????? 46 chromosomes? 2

3 TH IDAL SITUATIN uploid gametes uploid embryo 46n No implantation 3

4 FQUNCY F GAMT ANUPLIDY % 97.9% % Normo spermia Moderate AT bstructive azoospermia Moderate AT Non-bstructive azoospermia % Maternal age (yrs) n 47n 4

5 5 24n Mosaic 46/47n Mosaic 46/47n A N U P L I D Y S C U F M M I T I C S Mosaic 46/47n Mosaic 46/47n A N U P L I D Y S C U F M M I T T I C S

6 MSAICISM - ANUPLIDY SCU The clinical consequences of mosaicism depend on 1) when during development the error occurs, and 2) on the proportion of cells that continue to propagate. At the cleavage-stage embryo, the consequences of chromosomal mosaicism are more severe then if it occurs at later stages. Incidence of mosaicism from 15 to 90% at the cleavage stage from 15 to 30% at the blastocyst stage from 1 to 2% in prenatal diagnosis a selection mechanism against mosaicism / correction of aneuploidy in the later stages of development Taylor et al., 2014 MBY DVLPMNT Due to inactivation of the genome during embryo fertilization, genome stability until the third cell division is mainly controlled by the oocyte transcriptomes. mbryonic genome activation degradation of the oocyte s mna decreases fidelity of the cell division. 6

MBY DVLPMNT Short-end G1 in pluripotent status before differentiation is essential for rapid proliferation; however, it reduces the integrity of cell cycle check

ANUPLIDY TSTING N DAY 3 MBYS Chromosome instability Chromosome instability is a hallmark of tumorigenesis.

7 MBY DVLPMNT Short-end G1 in pluripotent status before differentiation is essential for rapid proliferation; however, it reduces the integrity of cell cycle check points. It seems that activation of genes responsible for cell division begins in the hatched blastocyst. ANUPLIDY TSTING N DAY 3 MBYS Chromosome instability Chromosome instability is a hallmark of tumorigenesis. Frequent segmental deletions, duplications and amplifications, often reciprocal in sister blastomeres, implying the occurrence of breakage-fusion-bridge cycles. Vanneste et al., 2009; Wells 7

8 MBY DVLPMNT The beginning of differentiation represents an important barrier for omitting mosaic embryos. Upon differentiation, reestablishment of a normal cell cycle would occur, giving aneuploid cells less chance for division. How does the embryo react to chromosome aneuploidy? 8

9 CCTIN F ANUPLIDY PB1 PB2 eciprocal errors at meiosis 2pn CCTIN F ANUPLIDY MICNUCLI: chromatid/chromosome lagging during division Chavez et al.,

10 CCTIN F ANUPLIDY The extra chromosome is encapsulated in micronuclei before being sequestered into fragments Intracellular fragments: some contain nuclear DNA Chromosome 16 Chavez et al., 2012 CCTIN F ANUPLIDY Chavez et al.,

, 2012 Fragmentation timing suggests an embryo response to chromosomal abnormalities.

11 CCTIN F ANUPLIDY As development proceeds, embryonic fragments may - remain as separate units that carry chromosomal DNA and cytoplasm - be reabsorbed by the same blastomere from which they were produced - fuse with a neighbouring blastomere Chavez et al., 2012 Fragmentation timing suggests an embryo response to chromosomal abnormalities. Chromosomally normal embryos display strict and tightly clustered cell cycle parameters, whereas chromosomally abnormal embryos exhibit more diverse parameters that may or may not overlap those of euploid embryos. Chavez et al.,

correction via anaphase lag, non-disjunction

apoptosis of aneuploid blastomeres and or

diploid/aneuploid blastomeres to embryonic or

, 2012 The high frequency of aneuploidy and

12 SLCTIN AGAINST CCTIN F ANUPLIDY Three underlying mechanisms suggested: - self correction via anaphase lag, non-disjunction or chromosome demolition; - cell arrest or apoptosis of aneuploid blastomeres and or embryos; - preferential allocation of diploid/aneuploid blastomeres to embryonic or extra-embryonic tissues Mantikou et al., 2012 The high frequency of aneuploidy and mosaicism in human embryos is a condition that seems to occur also in vivo. 12

13 Proliferation Invasivity uploidy / Normality Genetic diversity Chromosome instability Mosaicism mbryo Cancer cells Proliferate / Invade Invasiveness Proliferation Chromosome instability 13

Proliferation Invasiveness Chromosome instability -

implantation - Miscarriage - Aneuploid Invasiveness

14 Proliferation Invasiveness Chromosome instability - Development Healthy arrest implantation - No implantation - Miscarriage - Aneuploid Invasiveness pregnancy Proliferation Chromosome instability Proliferation Invasiveness Chromosome instability ANUPLIDY: TH MBY PINT F VIW Invasiveness Proliferation Chromosome instability 14

Blastocentesis: innovation in embryo biopsy

Blastocentesis: innovation in embryo biopsy L. Gianaroli, MC Magli, A. Pomante, AP Ferraretti S.I.S.Me.R. Reproductive Medicine Unit, Bologna, Italy Bologna, 8-11 May 2016 www.iiarg.com www.sismer.it 2013