Project description:The replication timing program, or the order in which DNA is duplicated during S-phase, is associated with various features of chromosome structure and function, including gene expression, histone modifications, and 3-D compartmentalization of chromatin.
Project description:The replication timing program, or the order in which DNA is duplicated during S-phase, is associated with various features of chromosome structure and function, including gene expression, histone modifications, and 3-D compartmentalization of chromatin. 3 cell types, with a total of 6 individual replicates
Project description:<p>In this study we used next generation deep sequencing technologies to analyze the genomes of Harvard University Stem Cell lines 63 and 64. We performed 101-bp paired-end whole genome sequencing of the two cell lines using Illumina HiSeq platforms. The sequence reads obtained were analyzed for copy number and used for replication timing analysis. Our data suggests that read depth profiles can be used to map replication timing in Embryonic Stem Cells (ESCs). Further we observe that replication profiles are highly correlated across ESCs but distinct from those of other cell types such as Lymphoblastoid Cell Lines (LCLs). These results demonstrated that read depth data from whole genome sequencing can be used to study variation in replication timing within the human population and across different cell types. Whole genome sequences from HUES63 and HUES64 used for this study are being submitted.</p>
Project description:Suz12 exon 4 encodes 23 amino acids (aa 129–152 in SUZ12-L) that partially overlap with the WD-binding domain 1 (WDB1, 110–145). We reasoned that exon 4 skipping might alter the structure of SUZ12 and, possibly, PRC2 composition. To explore this possibility, we generated ESCs that lack the Suz12 exon 4 via CRISPR-Cas9–induced deletion. In addition, to rule out any biases due to the expression levels and/or SUZ12 epitope masking, we generated Suz12 knockout (KO) ESCs (herein, KO) in which Suz12 expression was subsequently rescued by re-introducing either the Suz12-L or Suz12-S mouse isoform fused to a triple-Flag tag under the regulation of a CAG promoter (KO+L/S; Figures S2H–S2K). We performed SUZ12 immunoprecipitation coupled with mass spectrometry (IP-MS) in the WT and ∆ex4 clones to compare their interactomes and with a flag antibody in the KO and rescue cell lines. As expected, no peptides corresponding to exon 4 were retrieved in ∆ex4 samples, while the rest of the sequence displayed similar coverage. Comparison of interactors in the two conditions revealed that SUZ12 binding to AEBP2 and JARID2 was strongly reduced in ∆ex4 cells with respect to WT cells, whereas SUZ12 binding to most core components or to PRC2.1-specific factors was unchanged or only slightly increased . These observations were confirmed by SUZ12 IP followed by Western blot (WB). Flag IP-MS in rescue cells confirmed that, while the long isoform was able to correctly form comparable amounts of both PRC2.1 and PRC2.2 subtypes, interaction of the SUZ12-S with PRC2.2-specific factors was drastically reduced.
Project description:Lipid metabolism is recognized as a key process for stem cell maintenance and differentiation but genetic factors that instruct stem cell function by influencing lipid metabolism remain to be delineated. Here we identify Tnfaip2 as an inhibitor of reprogramming of mouse fibroblasts into induced pluripotent stem cells. Tnfaip2 knockout embryonic stem cells (ESCs) exhibit differentiation failure and knockdown of the planarian orthologue, Smed-exoc3, abrogates in vivo differentiation of somatic stem cells, tissue homeostasis, and regeneration. Tnfaip2 deficient ESCs fail to induce synthesis of cellular triacylglycerol (TAG) and lipid droplets (LD) coinciding with reduced expression of Vimentin (Vim) – a known inducer of LD formation. Knockdown of Vim and Tnfaip2 act epistatically in enhancing cellular reprogramming of mouse fibroblasts. Similarly, planarians devoid of Smed-exoc3 displayed acute loss of TAGs. Supplementation of palmitic acid (PA) and palmitoyl-L-carnitine (a mitochondrial carrier of PA) restores the differentiation capacity of Tnfaip2 deficient ESCs as well as stem cell differentiation and organ maintenance in Smed-exoc3-depleted planarians. Together, these results identify a novel pathway, which is essential for stem cell differentiation and organ maintenance by instructing lipid metabolism.
