Project description:Reprogramming of somatic cells into Induced Pluripotent Stem Cells (iPSCs) provided a major leap towards more personalized cellular models for disease modelling and offers great prospects for regenerative medicine. Despite their considerable success, we still lack the ability to control the state of iPSCs fully, especially at the epigenetic level. This can be appreciated at chromosomal regions regulated by genomic imprinting which provides a good read-out for epigenetic fidelity in iPSCs. Indeed, imprinting defects have already been reported in both mouse and human iPSCs. However, the extent, nature, causes and consequences of these defects still remain to be analysed in a systematic manner. To fill this gap in knowledge, we used a controlled secondary reprogramming system whereby the donor mouse embryonic fibroblasts (MEFs) contain a doxycycline (DOX)-inducible Yamanaka cassette and also Single Nucleotide Polymorphisms (SNPs) to distinguish between the two parental alleles. Several female and male isogenic mouse iPSCs (miPSCs) were obtained using independent culture conditions (defined versus serum) and screened by allelic-specific IMPLICON, a targeted next-generation method to measure DNA methylation at imprinted regions with unprecedented genomic coverage of 1000-fold. Our results showed that imprinting defects are remarkably common in miPSCs. Interestingly, we found important differences in gender responses to culture conditions. In particular, female iPSCs exhibit widespread hypomethylation defects regardless of culture conditions, while male miPSCs show tendency for hypomethylation defects under defined conditions, and hypermethylation defects under serum conditions in particular loci. As expected, methylation defects at imprinted regions resulted in dysregulation of monoallelic expression of imprinted genes. Our results are of utmost importance to devise future reprogramming strategies to generate epigenetic error-free iPSCs
Project description:Our knowledge of genomic imprinting in primates is lagging behand that of mice largely due to the difficulties of allelic analyses in outbred animals. To understand imprinting dynamics in primates, we profiled transcriptomes, DNA methylomes and H3K27me3 in uniparental monkey embryos. We further developed single-nucleotide polymorphisms (SNP)-free methods, TARSII and CARSII, to identify germline differentially methylated regions (DMRs) in somatic tissues. Our comprehensive analyses showed that allelic DNA methylation, but not H3K27me3, is a major mark that correlates with paternal-biasedly expressed genes (PEGs) in uniparental monkey embryos. Interestingly, primate germline DMRs are different from PEG-associated DMRs in early embryos and are enriched in placenta. Strikingly, most placenta-specific germline DMRs are lost in placenta of cloned monkey. Collectively, our study establishes SNP-free germline DMR identification methods, defines developmental imprinting dynamics in primates and demonstrates imprinting defects in cloned monkey placenta, which provides important clues for improving primate cloning.
Project description:Genomic imprinting is an allele-specific gene expression system important for mammalian development and function. The molecular basis of genomic imprinting is allele-specific DNA methylation 2. While it is well known that the de novo DNA methyltransferases Dnmt3a/b are responsible for the establishment of genomic imprinting, how the methylation mark is erased during primordial germ cell (PGC) reprogramming remains a mystery. Here we report that Tet1 plays a critical role in the erasure of genomic imprinting. We show that despite their identical genotype, progenies derived from mating between Tet1-KO males and wild-type females exhibit a number of variable phenotypes including placental, fetal and postnatal growth defects, and early embryonic lethality. These defects are, at least in part, caused by the dysregulation of imprinted genes, such as Peg10 and Peg3, which exhibit aberrant hypermethylation in the paternal allele of differential methylated regions (DMRs). RNA-seq reveals extensive dysregulation of imprinted genes in the next generation due to paternal functional loss of Tet1. Genome-wide DNA methylation analysis of E13.5 PGCs and sperm derived from Tet1-KO mice reveals hypermethylation of DMRs of imprinted genes in sperm, which can be traced back to PGCs. Dynamics of methylation change in Tet1-affected sites suggested that Tet1 swipes remaining methylation including imprinted genes at late reprogramming stage. We also revealed that Tet1play a role in paternal imprinting erasure in females germline. Thus, our study establishes a critical function for Tet1 in the erasure of genomic imprinting. Genome-wide DNA methylation analysis of E13.5 PGCs from control and Tet1-KO mice
Project description:Genomic imprinting is an allele-specific gene expression system important for mammalian development and function. The molecular basis of genomic imprinting is allele-specific DNA methylation 2. While it is well known that the de novo DNA methyltransferases Dnmt3a/b are responsible for the establishment of genomic imprinting, how the methylation mark is erased during primordial germ cell (PGC) reprogramming remains a mystery. Here we report that Tet1 plays a critical role in the erasure of genomic imprinting. We show that despite their identical genotype, progenies derived from mating between Tet1-KO males and wild-type females exhibit a number of variable phenotypes including placental, fetal and postnatal growth defects, and early embryonic lethality. These defects are, at least in part, caused by the dysregulation of imprinted genes, such as Peg10 and Peg3, which exhibit aberrant hypermethylation in the paternal allele of differential methylated regions (DMRs). RNA-seq reveals extensive dysregulation of imprinted genes in the next generation due to paternal functional loss of Tet1. Genome-wide DNA methylation analysis of E13.5 PGCs and sperm derived from Tet1-KO mice reveals hypermethylation of DMRs of imprinted genes in sperm, which can be traced back to PGCs. Dynamics of methylation change in Tet1-affected sites suggested that Tet1 swipes remaining methylation including imprinted genes at late reprogramming stage. We also revealed that Tet1play a role in paternal imprinting erasure in females germline. Thus, our study establishes a critical function for Tet1 in the erasure of genomic imprinting. Genome-wide DNA methylation analysis of sperm derived from control and Tet1-KO mice
Project description:Genomic imprinting is an allele-specific gene expression system important for mammalian development and function. The molecular basis of genomic imprinting is allele-specific DNA methylation 2. While it is well known that the de novo DNA methyltransferases Dnmt3a/b are responsible for the establishment of genomic imprinting, how the methylation mark is erased during primordial germ cell (PGC) reprogramming remains a mystery. Here we report that Tet1 plays a critical role in the erasure of genomic imprinting. We show that despite their identical genotype, progenies derived from mating between Tet1-KO males and wild-type females exhibit a number of variable phenotypes including placental, fetal and postnatal growth defects, and early embryonic lethality. These defects are, at least in part, caused by the dysregulation of imprinted genes, such as Peg10 and Peg3, which exhibit aberrant hypermethylation in the paternal allele of differential methylated regions (DMRs). RNA-seq reveals extensive dysregulation of imprinted genes in the next generation due to paternal functional loss of Tet1. Genome-wide DNA methylation analysis of E13.5 PGCs and sperm derived from Tet1-KO mice reveals hypermethylation of DMRs of imprinted genes in sperm, which can be traced back to PGCs. Dynamics of methylation change in Tet1-affected sites suggested that Tet1 swipes remaining methylation including imprinted genes at late reprogramming stage. We also revealed that Tet1play a role in paternal imprinting erasure in females germline. Thus, our study establishes a critical function for Tet1 in the erasure of genomic imprinting. Gene expression analysis of E9.5 embryos
Project description:Maternal-effect mutations in components of the subcortical maternal complex (SCMC) of the human oocyte can cause early embryonic failure, gestational abnormalities and recurrent pregnancy loss. Enigmatically, they are also associated with DNA methylation abnormalities at imprinted genes in conceptuses, in the devastating gestational abnormality biparental complete hydatidiform mole (BiCHM) or in multi-locus imprinting disease (MLID). However, the developmental timing, genomic extent and mechanistic basis of these imprinting defects are unknown. Here, we studied methylation level of a women reported with familial recurrent hydatidiform mole and multiple pregnancy loss. Genotype analysis revealed homozygous mutation in KHDC3L. We obtained biparental mole from patient (Patient D) and compared it’s whole-genome methylation profile with respect to control placentas and sporadic mole (AnCHM) using Infinium MethylationEPIC BeadChip (WG-317-1001, Illumina). We also used endometrium samples from their respective mother for the comparison purposes. Molar conceptuses were observed with methylation defects at genome-wide level and profound loss of methylation at multiple genome-derived differentially methylated regions (gDMRs) confirming MLID.
Project description:Through genome-wide transcriptional comparisons, this study interrogates the capacity of iPSCs to accurately model pathogenic signatures of structural cardiac defects. Herein, we studied the molecular etiology of structural cardiac defects in Nos3-/- mice via transcriptional analysis of stage-matched embryonic and iPSC-derived tissues. In vitro comparisons of differentiated embryoid bodies were calibrated to in utero benchmarks of health and disease. Integrated systems biology analysis of WT and Nos3-/- transcriptional profiles revealed 50% concordant expression patterns between in utero embryonic and ex vivo iPSC-derived tissue. In particular, up-regulation of glucose metabolism (p-value = 3.95x10-12) and down-regulation of fatty acid metabolism (p-value = 6.71x10-12) highlight a bioenergetic signature of early Nos3 deficiency during cardiogenesis that can be recapitulated in iPSC-derived tissues. The in vitro concordance of early Nos3-/- disease signatures supports the utility of iPSCs as a cell-autonomous model of structural heart defects. Moreover, this study supports the use of iPSCs as a platform to pinpoint initial stages of cardiac pathogenesis.