Tree Genetics and Molecular Breeding 2024, Vol.14, No.4, 166-176 http://genbreedpublisher.com/index.php/tgmb 167 implications of these findings for forest management and conservation, emphasizing the importance of preserving the regenerative potential of trees in the face of environmental changes. 2 Molecular Level Regulation 2.1 Genetic control of stem cell maintenance and differentiation Genetic control of stem cell maintenance and differentiation is primarily governed by a network of transcription factors and signaling pathways. Key transcription factors such as NANOG, OCT4, and SOX2 play crucial roles in maintaining stem cell pluripotency and regulating differentiation. These factors form a mutual regulatory circuit with polycomb repressive complexes and microRNAs, ensuring a balance between self-renewal and differentiation (Kashyap et al., 2009). Additionally, the interplay between cell cycle regulators and transcription factors is essential for coordinating stem cell proliferation and differentiation, highlighting the evolutionary significance of these interactions (Engström, 2021). 2.2 Role of transcription factors in stem cell regulation Transcription factors are pivotal in regulating stem cell behavior by modulating gene expression. NANOG, for instance, enhances embryonic stem cell self-renewal by promoting chromatin accessibility and maintaining repressive histone marks at developmental regulators (Heurtier et al., 2018). The integration of signaling pathways with transcriptional networks further influences stem cell fate, as seen in the dynamic regulation of chromatin-modifying enzymes and nucleosome occupancy (Figure 1) (Fagnocchi et al., 2015). This intricate network of transcription factors and signaling pathways ensures the precise control of stem cell pluripotency and differentiation. Figure 1 Signaling affecting stem cells identity and their interplay with chromatin (Adopted from Fagnocchi et al., 2015) Image caption: Key signaling pathways and relative factors contributing to the maintenance of mESCs (a) or hESCs/EpiSCs (b) identity or to their differentiation (see details in the main text). Black circles in (a) indicate the two chemicals used in the 2i culturing medium (CHIR99021 and PD03). Solid black arrows and lines indicate positive or negative modulation, respectively. Dashed black lines indicate indirect effects. Colored circles with “P” indicate phosphorylation. (c) Key examples of signaling to chromatin in ESCs. The upper panels are relative to a more differentiated state in which the LIF/Stat3 and Nanog targets are repressed while developmental genes are active. Lower panels, instead, describe embryonic stem cells chromatin features. On the right, effect of Jak2, or its constitutive active form Jak2V617F, on H3Y41P and HP1 loading on chromatin. In the middle, interconnection between Erk1/2 and the loading of PRC2 and RNA polymerase II activity at developmental genes. On the left, interplay between the esBAF complex and Stat3 in regulating LIF/Stat3 signaling pathway targets (Adopted from Fagnocchi et al., 2015)
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