Catz D S, Fischer L M, Moschella M C, Tobias M L, Kelley D B
Department of Biological Sciences, Sherman Fairchild Center for the Life Sciences, Columbia University, New York, New York 10027.
Dev Biol. 1992 Dec;154(2):366-76. doi: 10.1016/0012-1606(92)90075-r.
Masculinization of the larynx in Xenopus laevis frogs is essential for the performance of male courtship song. During postmetamorphic (PM) development, the initially female-like phenotype of laryngeal muscle (slow and fast twitch fibers) is converted to the masculine form (entirely fast twitch) under the influence of androgenic steroids. To explore the molecular basis of androgen-directed masculinization, we have isolated cDNA clones encoding portions of a new Xenopus myosin heavy chain (MHC) gene. We have detected expression of this gene only in laryngeal muscle and specifically in males. All adult male laryngeal muscle fibers express the laryngeal myosin (LM). Adult female laryngeal muscle expresses LM only in some fibers. Expression of LM during PM development was examined using Northern blots and in situ hybridization. Males express higher levels of LM than females throughout PM development and attain adult levels by PM3. In females, LM expression peaks transiently at PM2. Treatment of juvenile female frogs with the androgen dihydrotestosterone masculinizes LM expression. Thus, LM appears to be a male-specific, testosterone-regulated MHC isoform in Xenopus laevis. The LM gene will permit analysis of androgen-directed sexual differentiation in this highly sexually dimorphic tissue.
非洲爪蟾喉部的雄性化对于雄性求偶鸣叫的表现至关重要。在变态后（PM）发育过程中，喉肌最初类似雌性的表型（慢肌纤维和快肌纤维）在雄激素类固醇的影响下转变为雄性形式（完全是快肌纤维）。为了探究雄激素导向的雄性化的分子基础，我们分离了编码一种新的非洲爪蟾肌球蛋白重链（MHC）基因部分片段的cDNA克隆。我们仅在喉肌中检测到了该基因的表达，且在雄性中特异性表达。所有成年雄性喉肌纤维都表达喉肌球蛋白（LM）。成年雌性喉肌仅在部分纤维中表达LM。使用Northern印迹法和原位杂交技术检测了PM发育过程中LM的表达。在整个PM发育过程中，雄性表达的LM水平高于雌性，并在PM3时达到成年水平。在雌性中，LM表达在PM2时短暂达到峰值。用雄激素双氢睾酮处理幼年雌性爪蟾会使LM表达雄性化。因此，LM似乎是非洲爪蟾中一种雄性特异性、受睾酮调节的MHC同工型。LM基因将有助于分析这种高度两性异形组织中雄激素导向的性别分化。
