A novel profile of cumulus cell transcripts is associated with oocyte aneuploidy

Abstract

Listen

Translate article

OBJECTIVE: Molecular cytogenetic studies have estimated that greater than 20% of human oocytes are aneuploid. Preimplantation genetic testing of biopsied polar bodies has allowed for oocyte aneuploidy screening. However, biopsy procedures are invasive to the oocyte with potential impact on outcome. Recently, it has been shown that oocyte developmental competence may be determined by specific cumulus cell (CC) gene expression, a non-invasive approach. This study therefore investigated the potential association between the CC transcriptome and oocyte aneuploidy.DESIGN: Genomic analysis of human CCs.MATERIALS AND METHODS: CCs were donated with patient consent immediately after oocyte retrieval. CCs were sharply trimmed, washed in PBS and resuspended in lysis buffer. Comprehensive chromosome aneuploidy screening of both biopsied polar bodies was determined after whole genome amplification and hybridization to the Affymetrix 250K SNP microarray. Upon identification of aneuploidy status, total RNA was isolated from CCs belonging to 6 individual euploid oocytes and 6 individual aneuploid oocytes. In vitro transcription was performed followed by hybridization to Codelink Whole Genome Human Bioarray (n=12) (Applied Microrrays) and analysis with Genespring software (Agilent).RESULTS: Comprehensive human CC transcriptome analysis revealed expression of around 31,000 genes. Previously identified CC marker genes (n=24) were verified on this data set including RBL2, CYP19, CCND2 and PTGS2. Two novel gene sets were identified with greater than 2-fold differential expression that separated CCs originating from euploid oocytes with those from aneuploid oocytes. The first set contained 234 genes that were downregulated in CCs belonging to aneuploid oocytes; mainly involved in cell cycle, cell communication, chromosome organization, transport and metabolism. The second set contained 179 genes that were upregulated in CCs belonging to aneuploid oocytes; primarily involved in signal transduction, transport, cell communication and differentiation.CONCLUSIONS: This study has shown that oocyte aneuploidy could be associated with the expression profile of a novel set of CC genes. This form of analysis may potentially allow for non-invasive selection of euploid human oocytes based on the respective specific CC transcriptome profile. Improvements to oocyte selection are anticipated to improve embryo developmental competence, implantation rates and the success of single embryo transfer. OBJECTIVE: Molecular cytogenetic studies have estimated that greater than 20% of human oocytes are aneuploid. Preimplantation genetic testing of biopsied polar bodies has allowed for oocyte aneuploidy screening. However, biopsy procedures are invasive to the oocyte with potential impact on outcome. Recently, it has been shown that oocyte developmental competence may be determined by specific cumulus cell (CC) gene expression, a non-invasive approach. This study therefore investigated the potential association between the CC transcriptome and oocyte aneuploidy. DESIGN: Genomic analysis of human CCs. MATERIALS AND METHODS: CCs were donated with patient consent immediately after oocyte retrieval. CCs were sharply trimmed, washed in PBS and resuspended in lysis buffer. Comprehensive chromosome aneuploidy screening of both biopsied polar bodies was determined after whole genome amplification and hybridization to the Affymetrix 250K SNP microarray. Upon identification of aneuploidy status, total RNA was isolated from CCs belonging to 6 individual euploid oocytes and 6 individual aneuploid oocytes. In vitro transcription was performed followed by hybridization to Codelink Whole Genome Human Bioarray (n=12) (Applied Microrrays) and analysis with Genespring software (Agilent). RESULTS: Comprehensive human CC transcriptome analysis revealed expression of around 31,000 genes. Previously identified CC marker genes (n=24) were verified on this data set including RBL2, CYP19, CCND2 and PTGS2. Two novel gene sets were identified with greater than 2-fold differential expression that separated CCs originating from euploid oocytes with those from aneuploid oocytes. The first set contained 234 genes that were downregulated in CCs belonging to aneuploid oocytes; mainly involved in cell cycle, cell communication, chromosome organization, transport and metabolism. The second set contained 179 genes that were upregulated in CCs belonging to aneuploid oocytes; primarily involved in signal transduction, transport, cell communication and differentiation. CONCLUSIONS: This study has shown that oocyte aneuploidy could be associated with the expression profile of a novel set of CC genes. This form of analysis may potentially allow for non-invasive selection of euploid human oocytes based on the respective specific CC transcriptome profile. Improvements to oocyte selection are anticipated to improve embryo developmental competence, implantation rates and the success of single embryo transfer.