Maternal LSD1/KDM1A is an essential regulator of chromatin and transcription landscapes during zygotic genome activation.
Bottom Line: Upon fertilization, the highly specialised sperm and oocyte genomes are remodelled to confer totipotency.The mechanisms of the dramatic reprogramming events that occur have remained unknown, and presumed roles of histone modifying enzymes are just starting to be elucidated.At the transcriptional level, the switch of the maternal-to-zygotic transition fails to be induced properly and LINE-1 retrotransposons are not properly silenced.
Affiliation: Institut Curie, Paris, France.
Upon fertilization, the highly specialised sperm and oocyte genomes are remodelled to confer totipotency. The mechanisms of the dramatic reprogramming events that occur have remained unknown, and presumed roles of histone modifying enzymes are just starting to be elucidated. Here, we explore the function of the oocyte-inherited pool of a histone H3K4 and K9 demethylase, LSD1/KDM1A during early mouse development. KDM1A deficiency results in developmental arrest by the two-cell stage, accompanied by dramatic and stepwise alterations in H3K9 and H3K4 methylation patterns. At the transcriptional level, the switch of the maternal-to-zygotic transition fails to be induced properly and LINE-1 retrotransposons are not properly silenced. We propose that KDM1A plays critical roles in establishing the correct epigenetic landscape of the zygote upon fertilization, in preserving genome integrity and in initiating new patterns of genome expression that drive early mouse development.
No MeSH data available.
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Mentions: (A) Pie chart representing the percent of each category of repeats analyzed in our 16 RNA-seq data of individual embryos. (B) Box-plot for percent of LINEs, SINEs and LTR element expression for f/wt (white) or △m/wt (black) embryos over the total of reads mapping repeats for each of our 16 samples of RNA-seq. Details of the analysis are in experimental analysis. (C) qPCR analysis for LINE-1, SinesB1 and MuERV-L expression levels from individual two-cell stage cDNAs of f/wt (white) or △m/wt (black). Each embryo is represented as a single bar. Data are expressed as normalized expression to three house-keeping genes. On the right of each graph is represented the mean ± sem. Two asterisks indicate p<0.01 as calculated using a Student’s t-test. (D) Nascent LINE-1 transcripts are detected by RNA FISH (signal in red) using a TCN7 probe on f/wt or △m/wt two-cell stage embryos. RNAse A treated control embryos processed in parallel display no signal for RNA transcription. Also see Figure 5—figure supplement 1 for Atrx expression control. (E) Quantification of LINE-1 RNA FISH. On the left, the graph represents the fluorescent quantification with the mean intensity of fluorescence plotted on the x axis against the respective maximum intensity on the y axis) for each nucleus of the two–cell embryos for the two populations (white squares = f/wt controls and black square = △m/wt mutants). On the right, box-plot representation of the entropy levels analysis of the RNA FISH images for the control versus mutant embryos as defined by Haralick parameters measuring the pattern of the image with each dot corresponding to a f/wt (white) or △m/wt (black) nucleus.P value is calculated with a student T-test and indicated that the two populations are significantly different. (F) IF of two-cell stage embryos using anti-ORF1 antibodies (in red). A dotted line indicates the nucleus. Below is the graphical representation of the percentage of embryos displaying enriched fluorescent signal in either the cytoplasm (cy) or the nucleus (nu) for f/wt or △m/wt embryos. (G) IF of two-cell stage embryos using antibodies directed against phosphorylated histone H2A variant X (γH2AX, in green) for f/wt and △m/wt. Below is the corresponding quantification of embryo percentage according to the strength of γH2AX staining. DNA is counterstained by DAPI (blue). Number of processed embryos is indicated. Scale bar, 2 μm (D, G)) 10 μm (F).
No MeSH data available.