Characteristics of

Area of Science:

• * Molecular Endocrinology
• * Fish Reproduction
• * Genomics

Background:

• * Steroid hormones are essential for vertebrate reproduction.
• * The P450 side-chain cleavage enzyme (P450scc, Cyp11a) catalyzes the initial and rate-limiting step in steroidogenesis.
• * Understanding P450scc function in fish gonads is vital for aquaculture and reproductive biology.

Purpose of the Study:

• * To isolate and characterize the genomic DNA sequence of Cyp11a in the olive flounder (Paralichthys olivaceus).
• * To investigate the expression patterns and localization of Cyp11a during gonad differentiation and development.
• * To explore the regulatory mechanisms influencing Cyp11a expression in response to hormonal and environmental factors.

Main Methods:

• * DNA sequencing to determine the Cyp11a gene structure (5 exons, 4 introns).
• * Semi-quantitative and quantitative real-time PCR to analyze Cyp11a gene expression.
• * In situ hybridization and immunofluorescence to determine Cyp11a localization in gonadal tissues.
• * Hormone treatments (17β-estradiol, testosterone) and temperature manipulation to assess regulatory effects.
• * Cell transfection assays to investigate the role of nuclear receptors (NR5a2, NR0b1) and cyclic adenosine monophosphate (cAMP).

Main Results:

• * The olive flounder Cyp11a gene consists of 5 exons and 4 introns.
• * Cyp11a is primarily expressed in the gonad and head kidney, with higher levels in testis than ovary.
• * Cyp11a is localized in Leydig cells of the testis and thecal cells of the ovary.
• * Hormone treatments and high temperature significantly altered Cyp11a expression and steroid levels during gonad differentiation.
• * Nuclear receptors NR5a2 and NR0b1, as well as cAMP, significantly modulated Cyp11a gene expression.

Conclusions:

• * Cyp11a is dynamically expressed during olive flounder gonad differentiation and development.
• * Hormonal and environmental factors play a significant role in regulating Cyp11a expression in gonads.
• * Cyp11a is a key enzyme involved in steroid hormone synthesis and gonad development in olive flounder.
• * The findings provide insights into the molecular mechanisms underlying fish reproductive processes.