Int. J. Dev. Biol. 55: 619 - 625 (2011)

https://doi.org/10.1387/ijdb.103181rm

Vol 55, Issue 6

Differentiation of steroid-producing cells during ovarian differentiation in the protogynous Malabar grouper, Epinephelus malabaricus

Developmental Expression Pattern | Published: 6 September 2011

Ryosuke Murata*^,1, Hirofumi Karimata², Yasuhisa Kobayashi¹, Ryo Horiguchi³, Kazuo Kishimoto⁴, Motofumi Kimura⁴, Tohru Kobayashi⁵, Kiyoshi Soyano⁶ and Masaru Nakamura^1,7

¹Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, ²Okinawa Prefectural Department of Agriculture, Forestry and Fisheries, Fisheries Division, ³Laboratory of Reproductive Biology, National Institute for Basic Biology, ⁴Okinawa Prefectural Fisheries and Ocean Research Center Ishigaki Laboratory, ⁵Laboratory of Molecular Reproductive Biology, Institute for Environmental Sciences and Graduate School of Nutritional and Environmental Sciences, University of Shizuoka, ⁶Institute for East China Sea Research, Nagasaki University and ⁷Solution Oriented Research for Science Technology (SORST) Japan Science and Technology Corporation, Honcho Kawaguchi, Saitama, Japan

Abstract

To understand the mechanism of sex differentiation in the protogynous Malabar grouper Epinephelus malabaricus, we performed an immunohistochemical investigation of the expression of three steroidogenic enzymes, cholesterol-side-chain-cleavage enzyme (CYP11a), aromatase (CYP19a1a), and cytochrome P45011beta-hydroxylase (CYP11b), in the gonads during ovarian differentiation. Strong positive immunoreactivity against CYP11a, the key enzyme of steroidogenesis, and CYP19a1a which is essential for estrogen (17beta-estradiol) production, appeared first in the somatic cells surrounding gonial germ cells in undifferentiated gonads and throughout ovarian differentiation. However, positive immunoreactivity against CYP11b, which is important for androgen (11-ketotestosterone) production, first appeared in the cluster of somatic cells in the ovary tunica near the dorsal blood vessel after differentiation. CYP19a1a and CYP11b did not co-localize in any cells. These results indicate that there are two types of steroid-producing cells, estrogen-producing cells and androgen-producing cells, in the gonads of this fish, and they are distributed differently, suggesting that these cells are derived from different somatic cells. Estrogen-producing cells appeared prior to ovarian differentiation, while androgen-producing cells were first detected after ovarian differentiation. These results suggest that endogenous estrogen is involved in ovarian differentiation.

Keywords

Steroid-producing cell, 17beta-estradiol, 11-ketotestosterone, Protogynous hermaphrodite, Grouper