Fig. 3.

Schematic illustration of mechanisms of oocyte maturation and related long non-coding RNAs (lncRNAs) regulation. In humans and animals, many factors have been identified, including epigenetic molecules like lncRNAs and their various signaling pathways, that are critical for oocyte maturation. They not only regulate oocyte maturation, but also coordinate each other (balance) to ensure physiological conditions. For instance, gonadotropin hormone-releasing hormone (GnRh) and insulin-like growth factor (IGF) system influences important elements of reproductive system development, including oocyte maturation. IGF-1 is a polypeptide hormone produced mainly by the liver which stimulates GnRH release directly from neuroendocrine brain regions. IGF-1/GnRh system is under the control of the regulatory activities of lncRNAs and their downstream signaling pathways, providing a balance for normal oocyte development/maturation. Note: SEMA7A, Semaphorin 7A; PI3K, Phosphoinositide 3-kinases; Akt, serine/threonine kinase family; LH, Luteinizing hormone; 17α-OHP, 17α-Hydroxyprogesterone; MIH-R, Maturation-inducing hormone receptor; MIH, Maturation-inducing hormone; LH-R, Luteinizing hormone receptor; GJ, Gap junctions; IGF-R, Insulin-like growth factor type 1 receptor; PKA, Protein kinase A; PKC, Protein kinase C; cAMP, Human cathelicidin antimicrobial peptide; PKA, Protein kinase A; EGF-R, Epidermal growth factor receptor; EGF, Epidermal growth factor; DA, Dopamine.