Molecular Characterization and Functional Analyses of IGFALS in the Chinese Soft-Shelled Turtle (<em>Pelodiscus sinensis</em>)

Abstract

The insulin-like growth factor (IGF) system plays a crucial role in the regulation of development, reproduction, and growth. Within this system, the IGF acid-labile subunit (<em>IGFALS</em>) plays a pivotal role in modulating IGF activity by stabilizing circulating IGF complexes. In this study, two <em>IGFALS</em> gene transcripts, named <em>IGFALSX1</em> and <em>IGFALSX2</em>, were identified for the first time in the Chinese soft-shelled turtle (<em>Pelodiscus sinensis</em>). The cDNA sequences of <em>IGFALSX1</em> and <em>IGFALSX2</em> were 2,452 bp and 2,520 bp, respectively, encoding 617 and 616 amino acids (AAs). The <em>IGFALS</em> gene was expressed in all tissues of <em>P. sinensis</em>, with particularly high expression in the liver, gonads, and lungs, and marked sexual dimorphism observed in the liver. Short-term stimulation of juvenile <em>P. sinensis</em> with sex steroids led to significant changes in <em>IGFALS</em> expression in the livers of both male and female individuals, suggesting its potential involvement in steroid-mediated growth modulation. These observations collectively indicate that <em>IGFALS</em> may function as a key molecular mediator in the steroid-responsive growth regulatory pathway of <em>P. sinensis</em>.