Generation of meiomaps of genome-wide recombination and chromosome segregation in human oocytes.
We have developed a protocol for the generation of genome-wide maps (meiomaps) of recombination and chromosome segregation for the three products of human female meiosis: the first and second polar bodies (PB1 and PB2) and the corresponding oocyte. PB1 is biopsied and the oocyte is artificially activated by exposure to calcium ionophore, after which PB2 is biopsied and collected with the corresponding oocyte. The whole genomes of the polar bodies and oocytes are amplified by multiple displacement amplification and, together with maternal genomic DNA, genotyped for ∼300,000 single-nucleotide polymorphisms (SNPs) genome-wide by microarray. Informative maternal heterozygous SNPs are phased using a haploid PB2 or oocyte as a reference. A simple algorithm is then used to identify the maternal haplotypes for each chromosome, in all of the products of meiosis for each oocyte. This allows mapping of crossovers and analysis of chromosome segregation patterns. The protocol takes a minimum of 3-5 d and requires a clinical embryologist with micromanipulation experience and a molecular biologist with basic bioinformatic skills. It has several advantages over previous methods; importantly, the use of artificial oocyte activation avoids the creation of embryos for research purposes. In addition, compared with next-generation sequencing, targeted SNP genotyping is cost-effective and it simplifies the bioinformatic analysis, as only one haploid reference sample is required to establish phase for maternal haplotyping. Finally, meiomapping is more informative than copy-number analysis alone for analysis of chromosome segregation patterns. Using this protocol, we have provided new insights that may lead to improvements in assisted reproduction for the treatment of infertility.
The Bridge Centre, London, UK.|School of Biosciences, University of Kent, Canterbury, UK.
Christian S
CS
Ottolini
GENERA, Centers for Reproductive Medicine, Rome, Italy.|GENETYX, Molecular Genetics Laboratory, Marostica, Italy.
Antonio
A
Capalbo
Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, UK.
Louise
L
Newnham
GENERA, Centers for Reproductive Medicine, Rome, Italy.|GENETYX, Molecular Genetics Laboratory, Marostica, Italy.
Danilo
D
Cimadomo
Illumina, Cambridge, UK.
Senthilkumar A
SA
Natesan
Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, UK.|DNRF Center for Chromosome Stability, Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark.
Eva R
ER
Hoffmann
GENERA, Centers for Reproductive Medicine, Rome, Italy.|GENETYX, Molecular Genetics Laboratory, Marostica, Italy.
Filippo M
FM
Ubaldi
GENERA, Centers for Reproductive Medicine, Rome, Italy.|GENETYX, Molecular Genetics Laboratory, Marostica, Italy.
Laura
L
Rienzi
The Bridge Centre, London, UK.|School of Biosciences, University of Kent, Canterbury, UK.|Illumina, Cambridge, UK.
Alan H
AH
Handyside
D000328:Adult; D002874:Chromosome Mapping / Q000379:methods; D020090:Chromosome Segregation; D005260:Female; D015894:Genome, Human; D005838:Genotype; D060005:Genotyping Techniques / Q000379:methods; D006239:Haplotypes; D006801:Humans; D008540:Meiosis; D009865:Oocytes / Q000166:cytology* / Q000378:metabolism; D059705:Polar Bodies / Q000166:cytology* / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D011995:Recombination, Genetic