# Comparison of Nucleosome Landscapes Between Porcine Embryonic Fibroblasts and GV Oocytes

## TL;DR

This study compares chromatin structure and gene expression in pig oocytes and fibroblasts, revealing differences in nucleosome positioning that could aid in nuclear transplantation.

## Contribution

The study identifies unique nucleosome patterns and gene expression profiles in porcine oocytes versus fibroblasts, offering insights for cell reprogramming.

## Key findings

- Nucleosome occupancy in BF promoters was significantly higher (4.85%) than in PEF (3.3%).
- 51 genes were uniquely expressed in BF, and 80 in PEF, based on transcriptome reanalysis.
- Nucleosome distribution around TSSs correlated with expression in PEF but not in BF.

## Abstract

Nucleosomes serve as the basic structural components of chromatin and act as key regulators of gene expression and cellular function. In this study, we compared the nucleosome occupancy, distribution, and transcription of genes between two types of cells: fully grown germinal vesicle (GV) oocytes from big follicles (BF) and somatic cells (porcine embryonic fibroblast, PEF). The nucleosome occupancy in the BF promoter was significantly higher than in PEF. A reanalysis of published transcriptomes of fully grown GV oocytes and PEF identified 51 uniquely expressed genes in BF and 80 in PEF. The nucleosome distribution around gene transcription start sites (TSSs) correlated with expression levels in somatic cells, but results differed between BF and PEF. This research reveals the dynamic changes and crucial roles of nucleosome positioning and chromatin organization in different cell types, providing a theoretical basis for nuclear transplantation.

(1) Background: Nucleosomes represent the essential structural units of chromatin and serve as key regulators of cell function and gene expression. Oocytes in the germinal vesicle (GV) stage will later undergo meiosis and become haploid cells ready for fertilization, while somatic cells undergo mitosis after DNA replication. (2) Purpose: To furnish theoretical insights and data that support the process of cell reprogramming after nuclear transplantation. (3) Methods: We compared the nucleosome occupancy, distribution, and transcription of genes between two types of cells: fully grown GV oocytes from big follicles (BF) and somatic cells (porcine embryonic fibroblast, PEF). (4) Results: The nucleosome occupancy in the promoter of BF was 4.85%, which was significantly higher than that of 3.3% in PEF (p < 0.05), and the nucleosome distribution showed a noticeable increase surrounding transcriptional start sites (TSSs) in BF. Next, we reanalyzed the currently published transcriptome of fully grown GV oocytes and PEF, and a total of 51 genes in BF and 80 genes in PEF were identified as being uniquely expressed. The nucleosome distribution around gene TSSs correlated with expression levels in somatic cells, yet the results in BF differed from those in PEF. (5) Conclusion: This study uncovers the dynamic nature and significance of nucleosome positioning and chromatin organization across various cell types, providing a basis for nuclear transplantation.