Biology subjects

Munusamy, P.

Publications and source records attributed to Munusamy, P..

3 recordsLinked to original sources

bioRxiv2024

Sex chromosomes shape the transcriptional landscape of the preimplantation mouseembryo

Sex chromosomes are emerging as key regulators of adult health and disease in males (XY) and females (XX), but their impact on embryo development is poorly understood. Using single-cell RNA sequencing (scRNA-seq) on wild type and aneuploid mouse embryos, we show that sex chromosomes significantly shape the preimplantation embryo transcriptional landscape. A hierarchy of effects are identified, distinctly mediated by the Y chromosome, the dosage of X chromosomes, X-chromosome imprinting, and by Xist, the non-coding RNA that initiates X-inactivation. The sex chromosomes have strong trans effects on autosomal gene expression throughout preimplantation development. The Y chromosome has an unexpectedly pronounced impact on the trophectoderm, the precursor of the placenta, and this property is shared with genes expressed from the inactive X chromosome. The paternal and maternal X chromosomes differentially promote preimplantation growth, and we identify multiple novel candidate X-linked imprinted genes mediating this effect. Our findings show that sex chromosomes impact the embryo from the beginning of life, long before the appearance of overt sex differences.

developmental biology↗

bioRxiv2023

Single cell RNA-seq reveals protracted germ line X chromosome reactivation dynamics directed by a PRC2 dependent mechanism

Initiating soon after PGC specification, female germ cells undergo reactivation of the silenced X chromosome during genome wide reprogramming. However, the kinetics and dynamics of XCR in vivo have remained poorly understood. To address this here we perform a global appraisal of XCR using high-dimensional techniques. Using F1 B6 v CAST mouse embryos, we perform a detailed assessment, applying single-cell RNA-seq and chromatin profiling on germ cells purified from E10.5 to E16.5. While scRNA-seq profile showed that male and female germ cells are transcriptionally indistinct at E11.5, they are sexually dimorphic by E12.5, diverging further through development to E16.5. With allelic resolution, we show that the reactivating X chromosome is only partly active at E10.5, then reactivates gradually and reaches near parity in output to the constitutively active X chromosome at [~]E16.5 when developing oogonia are meiosis prophase I. Crucially, we show that sexually dimorphic dosage compensation patterns observed in germ cells, occur in tandem with an increase in the allelic proportion from the reactivating X chromosome. While Xist is extinguished from E10.5, the epigenetic memory of earlier XCI in female cells persists much longer, likely from self-sustained PRC2 complex (Ezh2 / Eed / Suz12) function. The reactivating X chromosome is enriched in the epigenetic silencing mark H3K27me3 at E13.5, which is removed by E16.5 permitting gene expression. Our findings link XCR, along with functional regulation of PRC2 in promoting female meiosis.

developmental biology↗

bioRxiv2021

Direct reprogramming of human embryonic to trophoblast stem cells

During the first week of development, human embryos form a blastocyst comprised of an inner cell mass and trophectoderm (TE) cells, the latter of which are progenitors of placental trophoblast. Here we investigated the expression of transcripts in the human TE from early to late blastocyst stages. We identified enrichment of transcription factors GATA2, GATA3, TFAP2C and KLF5 and characterised their protein expression dynamics across TE development. By inducible overexpression and mRNA transfection we determined that these factors, together with MYC, are sufficient to establish induced trophoblast stem cells (iTSCs) from primed human embryonic stem cells. These iTSCs self-renew and recapitulate morphological characteristics, gene expression profiles, and directed differentiation potential similar to existing human TSCs. Systematic omission of each, or combinations of factors, revealed the critical importance of GATA2 and GATA3 for iTSC transdifferentiation. Altogether, these findings provide insights into the transcription factor network that may be operational in the human TE and broaden the methods for establishing cellular models of early human placental progenitor cells, which may be useful in the future to model placental-associated diseases. Summary statementTranscriptional analysis of human blastocysts reveals transcription factors sufficient to derive induced trophoblast stem cells from primed human embryonic stem cells.

developmental biology↗