Nakamura Yoji, Higuchi Kentaro, Kumon Kazunori, Yasuike Motoshige, Takashi Toshinori, Gen Koichiro, Fujiwara Atushi
Bioinformatics and Biosciences Division, Fisheries Stock Assessment Center, Fisheries Resources Institute, Japan Fisheries Research and Education Agency, 2-12-4 Fuku-ura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan.
Tuna Aquaculture Division, Aquaculture Research Department, Fisheries Technology Institute, Japan Fisheries Research and Education Agency, 1551-8 Taira-machi, Nagasaki 851-2213, Japan.
Int J Genomics. 2021 Dec 14;2021:7226353. doi: 10.1155/2021/7226353. eCollection 2021.
Fish species have a variety of sex determination systems. Tunas (genus ) have an XY genetic sex determination system. However, the Y chromosome or responsible locus has not yet been identified in males. In a previous study, a female genome of Pacific bluefin tuna () was sequenced, and candidates for sex-associated DNA polymorphisms were identified by a genome-wide association study using resequencing data. In the present study, we sequenced a male genome of Pacific bluefin tuna by long-read and linked-read sequencing technologies and explored male-specific loci through a comparison with the female genome. As a result, we found a unique region carrying the male-specific haplotype, where a homolog of estrogen sulfotransferase gene was predicted to be encoded. The genome-wide mapping of previously resequenced data indicated that, among the functionally annotated genes, only this gene, named , was paternally inherited in the males of Pacific bluefin tuna. We reviewed the RNA-seq data of southern bluefin tuna () in the public database and found that of southern bluefin tuna was expressed in all male testes, but absent or suppressed in the female ovary. Since estrogen sulfotransferase is responsible for the inactivation of estrogens, it is reasonable to assume that the expression of in gonad cells may inhibit female development, thereby inducing the individuals to become males. Thus, our results raise a promising hypothesis that is the sex determination gene in fishes or at least functions at a crucial point in the sex-differentiation cascade.
鱼类具有多种性别决定系统。金枪鱼（属）具有XY型遗传性别决定系统。然而，雄性中的Y染色体或相关基因座尚未被确定。在之前的一项研究中，对太平洋蓝鳍金枪鱼（）的雌性基因组进行了测序，并通过使用重测序数据的全基因组关联研究确定了与性别相关的DNA多态性候选基因。在本研究中，我们通过长读长和连锁读长测序技术对太平洋蓝鳍金枪鱼的雄性基因组进行了测序，并通过与雌性基因组比较探索了雄性特异性基因座。结果，我们发现了一个携带雄性特异性单倍型的独特区域，预计该区域编码一种雌激素磺基转移酶基因的同源物。对之前重测序数据的全基因组定位表明，在功能注释基因中，只有这个名为的基因在太平洋蓝鳍金枪鱼雄性中是父系遗传的。我们查阅了公共数据库中南方蓝鳍金枪鱼（）的RNA测序数据，发现南方蓝鳍金枪鱼的在所有雄性睾丸中表达，但在雌性卵巢中不存在或受到抑制。由于雌激素磺基转移酶负责雌激素的失活，因此可以合理推测在性腺细胞中的表达可能会抑制雌性发育，从而诱导个体发育为雄性。因此，我们的结果提出了一个有前景的假设，即 是 鱼类的性别决定基因，或者至少在性别分化级联反应的关键节点发挥作用。
