Identification of a New Insulin-like Growth Factor 3 (igf3) in Turbot (Scophthalmus maximus): Comparison and Expression Analysis of IGF System Genes during Gonadal Development

Abstract

Fish reproduction is closely related to the regulation of the brain and liver, making it essential to identify the factors that control this process. The turbot (Scophthalmus maximus) is an economically significant species that has been successfully breeding through industrial aquaculture. Investigation of factors into the involvement of gonadal development is crucial for artificial breeding. In this study, a new insulin-like growth factor 3 igf3 gene was cloned and characterized. Additionally, all three types of turbot IGFs contain a distinct IGF domain, with IGF3 and IGF2 being grouped with other teleosts, demonstrating a closely related genetic relationship. The expression analysis showed that igf3 mRNA is predominantly expressed in the gonad and brain (specifically in the pituitary and hypothalamus), suggesting its effects at multiple levels in the brain–pituitary–gonadal axis. Furthermore, the mRNA levels of igfs during gonadal development were examined. In the gonad and liver of female turbots, the expression levels of igfs mRNA significantly increased from stage II to VI during the process of oogenesis, including maturation and degeneration. In the testis and liver of male turbots, igf3 mRNA maintained high expression levels during the proliferation of spermatogonia at stages II and III. In addition, the highest levels of igf1 and igf2 were observed at the beginning of spermatogenesis and during sperm production stages V and VI. All the results suggest that the IGFs were closely related to the gonadal development in turbot and improve a better understanding of the IGF system in the regulation of gonadal development in teleost.

Molecular Characteristics, Expression Patterns, and Response of Insulin-like Growth Factors Gene Induced by Sex Steroid Hormones in Blotched Snakehead (Channa maculata)

“…In the late juvenile stage of European eels (A. anguilla) [41] and the larval phase of tongue sole (C. semilaevis) [10], the expression levels of IGF1 and IGF2 are significantly higher in females compared to males. In addition to IGF1 and IGF2, a gonad-specific IGF family gene (IGF3) has been isolated in the gonads of turbot (Scophthalmus maximus) [4], zebrafish (D. rerio) [9], orange-spotted grouper (Epinephelus coioides) [43], and common carp (Cyprinus carpio) [44], uniquely expressed in ovaries and testes. IGF3 commences at the early stage of sex determination and differentiation and remains high in expression throughout gonadal development, offering insights into fish gonadal development, particularly in economically valuable species.…”

“…IGFs have garnered considerable attention across various species because of their vital role in growth regulation. IGFs are highly conserved and primarily include two types, IGF-1 and IGF-2 [4]. In mammals, IGF-1 primarily governs postnatal growth and development, while IGF-2 plays a crucial role during embryonic development, influencing processes such as cell proliferation, differentiation, migration, and apoptosis [5].…”

Identification of Insulin-like Growth Factor (IGF) Family Genes in the Golden Pompano, Trachinotus ovatus: Molecular Cloning, Characterization and Gene Expression

“…The third member of the IGF family, IGF3, was discovered around a decade ago in teleosts, and it plays an important role in regulating fish reproduction [ 4 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. The production of IGFs in fish is regulated by the endocrine system, which is composed of growth hormones, somatostatin, and insulin [ 17 , 18 , 19 , 20 , 21 , 22 ]. Due to the scarcity of research on the roles of IGF family genes in golden pompano, more information needs to be obtained.…”