Cell
ArticleCompletion of mouse embryogenesis requires both the maternal and paternal genomes
Abstract
Transplantation of pronuclei between one-cell-stage embryos was used to construct diploid mouse embryos with two female pronuclei (biparental gynogenones) or two male pronuclei (biparental androgenones). The ability of these embryos to develop to term was compared with control nuclear-transplant embryos in which the male or the female pronucleus was replaced with an isoparental pronucleus from another embryo. The results show that diploid biparental gynogenetic and androgenetic embryos do not complete normal embryogenesis, whereas control nuclear transplant embryos do. We conclude that the maternal and paternal contributions to the embryonic genome in mammals are not equivalent and that a diploid genome derived from only one of the two parental sexes is incapable of supporting complete embryogenesis.
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A genetic basis for facultative parthenogenesis in Drosophila
2023, Current BiologyFacultative parthenogenesis enables sexually reproducing organisms to switch between sexual and asexual parthenogenetic reproduction. To gain insights into this phenomenon, we sequenced the genomes of sexually reproducing and parthenogenetic strains of Drosophila mercatorum and identified differences in the gene expression in their eggs. We then tested whether manipulating the expression of candidate gene homologs identified in Drosophila mercatorum could lead to facultative parthenogenesis in the non-parthenogenetic species Drosophila melanogaster. This identified a polygenic system whereby increased expression of the mitotic protein kinase polo and decreased expression of a desaturase, Desat2, caused facultative parthenogenesis in the non-parthenogenetic species that was enhanced by increased expression of Myc. The genetically induced parthenogenetic Drosophila melanogaster eggs exhibit de novo centrosome formation, fusion of the meiotic products, and the onset of development to generate predominantly triploid offspring. Thus, we demonstrate a genetic basis for sporadic facultative parthenogenesis in an animal.
Differentiation of uniparental human embryonic stem cells into granulosa cells reveals a paternal contribution to gonadal development
2023, Stem Cell ReportsGenomic imprinting underlies the mammalian requirement for sexual reproduction. Nonetheless, the relative contribution of the two parental genomes during human development is not fully understood. Specifically, a fascinating question is whether the formation of the gonad, which holds the ability to reproduce, depends on equal contribution from both parental genomes. Here, we differentiated androgenetic and parthenogenetic human pluripotent stem cells (hPSCs) into ovarian granulosa-like cells (GLCs). We show that in contrast to biparental and androgenetic cells, parthenogenetic hPSCs present a reduced capacity to differentiate into GLCs. We further identify the paternally expressed gene IGF2 as the most upregulated imprinted gene upon differentiation. Remarkably, while IGF2 knockout androgenetic cells fail to differentiate into GLCs, the differentiation of parthenogenetic cells supplemented with IGF2 is partly rescued. Thus, our findings unravel a surprising essentiality of genes that are only expressed from the paternal genome to the development of the female reproductive system.
Mechanisms of transgenerational epigenetic inheritance: lessons from animal model organisms
2023, Current Opinion in Genetics and DevelopmentEpigenetic inheritance is a phenomenon whereby stochastic or signal-induced changes to parental germline epigenome modulate phenotypic output in one or more subsequent generations, independently of mutations in the genomic DNA. While the number of reported epigenetic inheritance phenomena across phyla is exponentially growing, much remains to be elucidated about their mechanistic underpinnings, and their significance for organismal homeostasis and adaptation. Here, we review the most recent epigenetic inheritance examples in animal models, outlining molecular details behind environmental sensing by the germline, and the functional relationships connecting epigenetic mechanisms and phenotypic traits after fertilization. We touch upon the experimental challenges associated with studying the scope of environmental input on phenotypic outcomes between generations. Finally, we discuss the implications of mechanistic findings from model organisms for the emergent examples of parental effects in human populations.
Comparative single-cell transcriptomic profiles of human androgenotes and parthenogenotes during early development
2023, Fertility and SterilityTo unravel the differential transcriptomic behavior of human androgenotes (AGs) and parthenogenotes (PGs) throughout the first cell cycles, analyze the differential expression of genes related to key biologic processes, and determine the time frame for embryonic genome activation (EGA) in AGs and PGs.
Laboratory study.
Private fertility clinic.
Mature oocytes were retrieved from healthy donors and subjected to artificial oocyte activation using calcium ionophore and puromycin to generate PGs (n = 6) or enucleated and subjected to intracytoplasmic sperm injection to generate AGs (n = 10).
Uniparental constructs at different early stages of development were disaggregated into constituent single cells (we suggest the terms parthenocytes and androcytes) to characterize the single-cell transcriptional landscape using next-generation sequencing.
Transcriptomic profiles comparison between different stages of early development in AGs and PGs.
The uniparental transcriptomic profiles at the first cell cycle showed 68 down-regulated and 26 up-regulated differentially expressed genes (DEGs) in PGs compared with AGs. During the third cell cycle, we found 60 up-regulated and 504 down-regulated DEGs in PGs compared with AGs. In the fourth cell cycle, 1,771 up-regulated and 1,171 down-regulated DEGs were found in PGs compared with AGs. The AGs and PGs had reduced EGA profiles during the first 3 cell cycles, and a spike of EGA at the fourth cell cycle was observed in PGs.
Transcriptomic analysis of AGs and PGs revealed their complementary behavior until the fourth cell cycle. Androgenotes undergo a low wave of transcription during the first cell cycle, which reflects the paternal contribution to cell cycle coordination, mechanics of cell division, and novel transcription regulation. Maternal transcripts are most prominent in the third and fourth cell cycles, with amplification of transcription related to morphogenic progression and embryonic developmental competence acquisition. Regarding EGA, in PGs, a primitive EGA begins at the 1-cell stage and gradually progresses until the 4-cell stage, when crucial epigenetic reprogramming (through methylation) is up-regulated. In addition, our longitudinal single-cell transcriptomic analysis challenges that the zygote and early cleavage stages are the only totipotent entities, by revealing potential totipotency in cleavage-stage AGs and implications of paternal transcripts.
Perfiles transcriptómicos comparativos unicelulares de androgenotas y partogenotas humanas durante el desarrollo temprano.
Descifrar el comportamiento transcriptómico diferencial de androgenotas (AGs) y partenogenotas (PGs) humanos a través de los primeros ciclos celulares, analizar la expresión diferencial de los genes relacionados con procesos biológicos claves, y determinar los tiempos de la activación del genoma embrionario (EGA) en AGs y PGs.
Estudio en laboratorio.
Clínica privada de fertilidad.
Se recuperaron óvulos maduroos de donantes sanas y fueron sujetos a activación ovocitaria usando ionóforos de calcio y puromicina para generar PGs (n=6) o fueron enucleados y sujetos a inyección espermática intracitosplásmica para generar AGs (n=10).
Construcciones uniparentales de diferentes etapas de desarrollo temprano fueron desagregados en células únicas constituyentes (sugerimos los términos partenocitos y androcitos) para caracterizar el panorama transcripcional unicelular usando secuenciación de nueva generación.
Comparación de los perfiles transcriptómicos entre diferentes etapas del desarrollo embrionario en AGs y PGs.
Los perfiles transcriptómicos uniparentales en el primer ciclo celular mostró 68 regulaciones a la baja y 26 regulaciones a la alta de genes diferencialmente expresados (DEGs) en los PGs en comparación con los AGs. Durante el tercer ciclo celular, encontramos 60 regulaciones a la alta y 504 regulaciones a la baja de DEGs. En el cuarto ciclo celular, hubo 1,771 regulaciones a la alta y 1,171 regulaciones a la baja de DEGs en PGs en comparación con AGs. Los AGs y los PGs tuvieron un perfil de EGA reducidos durante los tres primeros ciclos celulares, y un pico de EGA en el cuarto ciclo celular se observó en los PGs.
El análisis transcriptómico de los AGs y los PGs revelaron su comportamiento complementario hasta la cuarta fase del ciclo celular. Las androgenotas pasaron una transcripción de onda baja durante la primera fase del ciclo celular, lo cual refleja la contribución paterna a la coordinación del ciclo celular, al mecanismo de la división celular y la regulación novedadosa de la transcripción. Las transcripciones maternas son mas prominentes en la tercera y cuarta fase del ciclo celular, con amplificaciones en transcripción relacionada a la progresión morfogénica y la adquisición de competencia del desarrollo embrionario. En relación a EGA en las PGs, una EGA primitiva empieza en el fase de 1 célula y gradualmente progresa hasta la fase de 4 células, cuando se produce una reprogramación epigenética (a través de metilación) es regulación a la alta. Además, nuestro análisis longitudinal transcriptómico unicelular cuestionan que el cigoto y las etapas de clivaje temprano son entidades exclusivamente totipotenciales, al revelar potencial totipotencial en clivaje temprano de AGs y las implicaciones de transcripción paterna.
Whole genome bisulfite sequencing of sperm reveals differentially methylated regions in male partners of idiopathic recurrent pregnancy loss cases
2023, Fertility and SterilityTo study the genome wide alterations in sperm DNA methylation in male partners of idiopathic recurrent pregnancy loss (iRPL) cases and note regions as potential diagnostic markers.
Case-control study and methylome analysis of human sperm.
Obstetrics and Gynaecology clinics.
Control group consists of apparently healthy fertile men having fathered a child within the last 2 years (n = 39); and case group consists of male partners of iRPL cases having ≥2 consecutive 1st trimester pregnancy losses (n = 47).
None.
Sperm DNA samples of controls and cases were selected for whole genome bisulfite sequencing analysis based on the previously set thresholds of global methylation levels and methylation levels of imprinted genes (KvDMR and ZAC). Whole genome bisulfite sequencing of selected sperm genomic DNA was performed to identify differentially methylated CpG sites of iRPL cases compared with fertile controls. Pathway analysis of all the differentially methylated genes was done by Database for Annotation, Visualization, and Integrated Discovery annotation tool and Kyoto Encyclopedia of Genes and Genomes tool. Differentially methylated CpGs within genes relevant to embryo and placenta development were selected to further validate their methylation levels in study population by pyrosequencing.
A total of 9497 differentially methylated CpGs with highest enrichment in intronic regions were obtained. In addition, 5352 differentially methylated regions and 2087 differentially methylated genes were noted. Signaling pathways involved in development were enriched on pathway analysis. Select CpGs within genes PPARG, KCNQ1, SETD2, and MAP3K4 showed distinct hypomethylated subpopulations within iRPL study population.
Our study highlights the altered methylation landscape of iRPL sperm, and their possible implications in pathways of embryo and placental development. The CpG sites that are hypomethylated specifically in sperm of iRPL subpopulation can be further assessed as predictive biomarkers.
La secuenciación del genoma completo del esperma por bisulfito revela regiones metiladas en parejas masculinas de casos de pérdida idiopática.
Estudiar las alteraciones a nivel del genoma en la metilación del ADN espermático en parejas masculinas de casos de pérdida idiopática recurrente del embarazo (iRPL) y señalar regiones como posibles marcadores diagnósticos.
Estudio de caso control y análisis del metiloma del esperma humano.
Clínica de obstetricia y ginecología.
El grupo control está formado por hombres fértiles aparentemente sanos que han tenido un hijo en los últimos 2 años (n= 39) y el grupo de casos está formado por parejas masculinas de casos de iRPL que han tenido ≥ 2 pérdidas de embarazo consecutivas en el primer trimestre (n= 47).
Ninguna.
Se seleccionaron muestras de ADN espermático de controles y casos para el análisis de secuenciación de bisulfito de genoma completo basándose en los umbrales previamente establecidos de niveles de metilación global y niveles de metilación de genes improntados (KvDMR y ZAC). Se realizó la secuenciación de bisulfito del genoma completo del ADN genómico de espermatozoides seleccionados para identificar los sitios CpG diferencialmente metiladas de los casos de iRPL en comparación con los controles fértiles. El análisis de rutas de todos los genes diferencialmente metilados se realizó mediante la herramienta de anotación “Database for Annotation, Visualization”, and “Integrated Discovery” y la herramienta “Kyoto Encyclopedia of Genes and Genomes”. Las CpGs diferencialmente metiladas dentro de los genes relevantes para el desarrollo del embrión y la placenta fueron seleccionadas para validar sus niveles de metilación en la población de estudio mediante pirosecuenciación.
Se obtuvo un total de 9497 CpGs diferencialmente metiladas con mayor enriquecimiento en regiones intrónicas. Además, se observaron 5352 regiones diferencialmente metiladas y 2087 genes diferencialmente metilados. Las vías de señalización implicadas en el desarrollo fueron enriquecidas en el análisis de rutas. CpGs seleccionadas dentro de los genes PPARG, KCNQ1, SETD2 y MAP3K4 mostraron distintas subpoblaciones hipometiladas dentro de la población de estudio iRPL.
Nuestro estudio destaca la metilación alterada de los espermatozoides en iRPL, y sus posibles implicaciones en las vías de desarrollo embrionario y placentario. Los sitios CpG que están hipometilados concretamente en el esperma de la subpoblación iRPL pueden ser evaluados como biomarcadores predictivos.
Parental genome and brain functions: The case of genomic imprinting
2023, Principles of Gender-Specific Medicine: Sex and Gender-Specific Biology in the Postgenomic EraGenomic imprinting is an epigenetic phenomenon producing a monoallelic parental-specific expression in a subset of mammalian genes. Typically, these genes are arranged in clusters, which are governed by an imprinting control region (ICR) characterized by differential methylation of the two alleles (differentially methylated regions, DMRs). Besides DNA methylation, additional regulatory mechanisms for imprinted expression include histone modifications, chromatin remodeling, and long noncoding RNAs. Canonically, the imprinted allele is completely repressed in most of the body tissues. However, notable exceptions (noncanonical imprinting) are emerging, with biased expression in different tissues or periods throughout the lifespan. Imprinting marks are erased and re-established in the germline with a precise regulation and timing. Then, they must be preserved after the fertilization despite the extensive reprogramming of the mammalian genome. Perturbances of these processes or alterations of imprinted loci cause congenital developmental abnormalities known as imprinting disorders. Indeed, imprinted genes act as key regulator of placental and fetal growth during development, but also provide life-long effects in metabolic, cognitive, and behavioral processes. Furthermore, we have recently proposed that genomic imprinting plays a crucial role in the biology of sleep, including both its homeostatic regulatory component and the formation of the internal (circadian) clock. Both sleep and genomic imprinting robustly influence fundamental aspects of mammalian survival, including mother-infant interactions and the regulation of metabolism and body temperature, highlighting the role of imprinting in cognitive functions. As a result, common evolutionary drivers are hypothesized for imprinting and sleep role in higher brain processes.