# Identification of ActivinβA and Gonadotropin Regulation of the Activin System in the Ovary of Chinese Sturgeon Acipenser sinensis

## TL;DR

This study identifies ActivinβA and its role in regulating ovarian development in Chinese sturgeon, showing how gonadotropins influence this system.

## Contribution

The study identifies and characterizes the activinβA gene in Chinese sturgeon and demonstrates its regulation by gonadotropins.

## Key findings

- ActivinβA was identified with a full-length cDNA sequence of 1572 base pairs in Chinese sturgeon.
- Activin A and gonadotropin stimulate activin system-related genes and ovary development-related genes in sturgeon ovarian cells.
- Activin signaling is conserved across vertebrates and plays a role in ovarian maturation regulation in A. sinensis.

## Abstract

Activin is a dimeric growth factor with diverse biological activities in vertebrates. This study aimed to investigate the regulatory role of the activin signaling pathway in the ovary of cultured Acipenser sinensis. One activinβA subunit with a full-length cDNA sequence of 1572 base pairs was identified. Multiple sequence alignment and phylogenetic analyses indicated the conserved evolution of ActivinβA from mammals to fish species. Transcripts of activinβA were distributed ubiquitously in ovary and non-ovarian tissues. The in vitro human recombinant Activin A incubation stimulated not only the activin system-related gene transcriptions of activinβA, follistatin, its receptors activinRIIA and activinRIIB, and smad2, smad3, and smad4, but also the ovary development-related genes cyp19a1a, erα, and erβ. Gonadotropin activated activin signaling by recruiting activinβA, follistatin, activinRIIA, and smad2. These results were helpful for not only the molecular exploration of activin signaling in fish species, but also the ovarian maturation regulation of A. sinensis.

Activin is a dimeric growth factor with diverse biological activities in vertebrates. This study aimed to investigate the regulatory role of the activin signaling pathway in the ovary of the endangered, cultured sturgeon species Acipenser sinensis. One activinβA subunit was identified, with a full-length complementary DNA (cDNA) sequence of 1572 base pairs. Multiple sequence alignment suggested that ActivinβA shared high sequence identities with its counterparts in four other sturgeon species. Phylogenetic analysis indicated the conserved evolution of ActivinβA among vertebrates from mammals to fish species. Transcripts of activinβA were distributed ubiquitously in the liver, kidney, intestine, ovary, midbrain, hypothalamus, and pituitary, with the highest transcription found in the pituitary. In Chinese sturgeon ovarian cells, in vitro human recombinant Activin A incubation stimulated the activin system-related gene transcriptions of activinβA, follistatin, its receptors -activinRIIA and activinRIIB, and drosophila mothers against decapentaplegic proteins (smads) smad2, smad3, and smad4. Ovary development-related mRNA levels of cyp19a1a and aromatase receptors of erα and erβ were enhanced by Activin A or human chorionic gonadotropin (hCG) incubation. Furthermore, 15 IU/mL hCG treatment increased the transcription levels of activinβA, follistatin, activinRIIA, and smad2. This suggested that the activin system was functional for the regulation of ovary development in Chinese sturgeon, possibly under the regulation of gonadotropin, by recruiting activinβA, follistatin, activinRIIA, and smad2. These results were helpful for the molecular exploration of activin signaling in fish species, as well as the ovarian maturation regulation of A. sinensis.