title: Selective Amplification of the Genome Surrounding Key Placental Genes in Trophoblast Giant Cells.
abstract: While most cells maintain a diploid state, polyploid cells exist in many organisms and are particularly prevalent within the mammalian placenta [1], where they can generate more than 900 copies of the genome [2]. Polyploidy is thought to be an efficient method of increasing the content of the genome by avoiding the costly and slow process of cytokinesis [1, 3, 4]. Polyploidy can also affect gene regulation by amplifying a subset of genomic regions required for specific cellular function [1, 3, 4]. This mechanism is found in the fruit fly Drosophila melanogaster, where polyploid ovarian follicle cells amplify genomic regions containing chorion genes, which facilitate secretion of eggshell proteins [5]. Here, we report that genomic amplification also occurs in mammals at selective regions of the genome in parietal trophoblast giant cells (p-TGCs) of the mouse placenta. Using whole-genome sequencing (WGS) and digital droplet PCR (ddPCR) of mouse p-TGCs, we identified five amplified regions, each containing a gene family known to be involved in mammalian placentation: the prolactins (two clusters), serpins, cathepsins, and the natural killer (NK)/C-type lectin (CLEC) complex [6-12]. We report here the first description of amplification at selective genomic regions in mammals and present evidence that this is an important mode of genome regulation in placental TGCs.
authors.affiliation: Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA.
authors.forename: Roberta L
authors.initials: RL
authors.lastname: Hannibal
authors.affiliation: Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA. Electronic address: jbaker@stanford.edu.
authors.forename: Julie C
authors.initials: JC
authors.lastname: Baker
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D015726:Giant Cells / Q000378:metabolism*; D051379:Mice; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D014327:Trophoblasts / Q000378:metabolism*