Biology subjects

Makedonski, K.

Publications and source records attributed to Makedonski, K..

4 recordsLinked to original sources

bioRxiv2022

Fibroblasts-derived from Pluripotent Cells Harboring a Single Allele Knockout in Two Pluripotency Genes Exhibit DNA Methylation Abnormalities and pluripotency induction Defects

A complete knockout (KO) of a single key pluripotency gene has been shown to drastically affect embryonic stem cell (ESC) function and epigenetic reprogramming. However, knockin (KI)/KO of a reporter gene only in one of two alleles in a single pluripotency gene is considered harmless and is largely used in the stem cell field. Here, we sought to understand the impact of simultaneous elimination of a single allele in two ESC key genes on pluripotency potential and acquisition. We established multiple pluripotency systems harboring KI/KO in a single allele of two different pluripotency genes (i.e. Nanog+/-; Sall4+/-, Nanog+/-; Utf1+/-, Nanog+/-; Esrrb+/- and Sox2+/-; Sall4+/-). Interestingly, although these double heterozygous mutant lines maintain their stemness and contribute to chimeras equally to their parental control cells, fibroblasts derived from these systems show a significant reduction in their capability to induce pluripotency either by Oct4, Sox2, Klf4 and Myc (OSKM) or by nuclear transfer (NT). Tracing the expression of Sall4 and Nanog, as representative key pluripotency targeted genes, at early phases of reprogramming could not explain the seen delay/blockage. Further exploration identifies abnormal methylation landscape around pluripotent and developmental genes in the double heterozygous mutant fibroblasts. Accordingly, treatment with 5-azacytidine two days prior to transgene induction rescues the reprogramming defects. This study emphasizes the importance of maintaining two intact alleles for pluripotency induction and suggests that insufficient levels of key pluripotency genes leads to DNA methylation abnormalities in the derived-somatic cells later on in development.

cell biology↗

bioRxiv2021

Pluripotency-Independent Induction of Human Trophoblast Stem Cells from Fibroblasts

Recent studies demonstrated that human trophoblast stem-like cells (hTS-like cells) can be derived from naive embryonic stem cells or be induced from somatic cells by the pluripotency factors, OSKM. This raises two main questions; (i) whether human induced TSCs (hiTSCs) can be generated independently to pluripotent state or factors and (ii) what are the mechanisms by which hTSC state is established during reprogramming. Here, we identify GATA3, OCT4, KLF4 and MYC (GOKM) as a pluripotency-independent combination of factors that can generate stable and functional hiTSCs, from both male and female fibroblasts. By using single and double knockout (KO) fibroblasts for major pluripotency genes (i.e. SOX2 or NANOG/PRDM14) we show that GOKM not only is capable of generating hiTSCs from the KO cells, but rather that the efficiency of the process is increased. Through H3K4me2 and chromatin accessibility profiling we demonstrate that GOKM target different loci and genes than OSKM, and that a significant fraction of them is related to placenta and trophoblast function. Moreover, we show that GOKM exert a greater pioneer activity compared to OSKM. While GOKM target many specific hTSC loci, OSKM mainly target hTSC loci that are shared with hESCs. Finally, we reveal a gene signature of trophoblast-related genes, consisting of 172 genes which are highly expressed in blastocyst-derived TSCs and GOKM-hiTSCs but absent or mildly expressed in OSKM-hiTSCs. Taken together, these results imply that not only is the pluripotent state, and SOX2 specifically, not required to produce functional hiTSCs, but that pluripotency-specific factors actually interfere with the acquisition of the hTSC state during reprogramming.

cell biology↗

bioRxiv2020

Comparative Parallel Multi-Omics Analysis During the Induction of Pluripotent and Trophectoderm States

Following fertilization, totipotent cells divide to generate two compartments in the early embryo: the inner cell mass (ICM) and trophectoderm (TE). It is only at the 32-64 -cell stage when a clear segregation between the two cell-types is observed, suggesting a T-shaped model of specification. Here, we examine whether the acquisition of these two states in vitro by nuclear reprogramming share similar dynamics/trajectories. We conducted a comparative parallel multi-omics analysis on cells undergoing reprogramming to Induced pluripotent stem cells (iPSCs) and induced trophoblast stem cells (TSCs), and examined their transcriptome, methylome, chromatin accessibility and activity and genomic stability. Our analysis revealed that cells undergoing reprogramming to pluripotency and TSC state exhibit specific trajectories from the onset of the process, suggesting V-shaped model. Using these analyses, not only we could describe in detail the various trajectories toward the two states, we also identified previously unknown stage-specific reprogramming markers as well as markers for faithful reprogramming and reprogramming blockers. Finally, we show that while the acquisition of the TSC state involves the silencing of embryonic programs by DNA methylation, during the acquisition of pluripotency these specific regions are initially open but then retain inactive by the elimination of the histone mark, H3K27ac.

developmental biology↗

bioRxiv2018

Germline DNA replication timing shapes mammalian genome composition

Mammalian DNA is replicated in a highly organized and regulated manner. Large, Mb-sized regions are replicated at defined times along S phase. DNA Replication Timing (RT) has been suggested to play an important role in shaping the mammalian genome by affecting mutation rates. Previous analyses relied on somatic DNA RT profiles, while to fully understand the influences of RT on the mammalian genome, germ cell RT information is necessary, as only germline mutations are passed to offspring and thus affect genomic composition. Using an improved RT mapping technique that allows mapping the RT from limited amounts of cells, we measured RT from two stages in the mouse germline - primordial germ cells (PGCs) and spermatogonial stem cells (SSCs). The germ cell RT profiles were distinct from those of both somatic and embryonic tissues. The correlations between RT and both mutation rate and recombination hotspots were not only confirmed in the germline tissues, but were shown to be stronger compared to correlations with RT of somatic tissues, emphasizing the importance of using RT profiles from the correct tissue of origin. Expanding the analysis to additional genetic features such as GC content, transposable elements (SINEs and LINEs) and gene density, also revealed a stronger correlation with the germ cell RT maps. GC content stratification along with multiple regression analysis revealed the independent contribution of RT to SINE, gene, mutation and recombination hotspot densities. Taken together, our results point to the centrality of RT in shaping multiple levels of mammalian genome composition.

genomics↗