Fish Growth Hormone Genes: Structure and Divergence
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Fish Growth Hormone Genes: Structure and Divergence1 D. N. Kamenskayaa and V. A. Brykova, b, * a
Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia b School of Natural Sciences, Far Eastern Federal University, Vladivostok, 690012 Russia *e-mail: [email protected] Received December 4, 2019; revised March 2, 2020; accepted March 19, 2020
Abstract—This review provides information on the structure of growth hormone genes (GHGs) in fish and the divergence of coding, intron, and adjacent flanking regions; original data obtained in our laboratory are also considered. In most fish species, GHGs are represented by a single copy, while some taxonomic groups have two paralogous genes. The coding sequences of GHGs are conserved. Gene length variations depend on the length of non-coding and flanking regions and introns. The divergence rate of gene sequences varies not only between different taxonomic groups, but also in the time of divergence within groups. In flanking regions, only the regulatory elements are conserved. Keywords: growth hormone gene, regulatory regions, divergence DOI: 10.1134/S1063074020040033
GENERAL VIEWS ON THE STRUCTURE OF VERTEBRATE GROWTH HORMONE GENES Growth hormone (somatotropic hormone, STH, or somatotropin) is one of the hormones of the anterior pituitary gland. It belongs to the class of polypeptide hormones and regulates growth and other physiological processes. Growth hormone, along with prolactin and somatolactin, is a member of the family of pituitary hormones. Genes of growth hormones of humans, some mammals, and a number of other vertebrates have been the best studied and characterized. In the human genome, the growth hormone (hGH) and placental lactogen (hPL) genes, also known as chorionic somatomammotropin (hCS) genes, form a cluster of five closely located genes. This cluster includes two hGH and three hPL genes [14, 36]. The human growth hormone normal (hGH-N) gene encodes pituitary growth hormone and is expressed only in somatotrophes, which are specialized cells of the adenohypophysis. The human growth hormone variant (hGH-V) gene encodes an alternative version of growth hormone that replaces the pituitary growth hormone in the late trimester of pregnancy and is expressed along with hPLs in the placenta [23, 36, 59]. The complete nucleotide sequences determined for all five genes, including their closest flanking regions [29, 36], are 1 Invited paper published in connection with the 50th anniversary
of the foundation of Zhirmunsky Institute of Marine Biology (now Zhirmunsky NSCMB).
more than 95% conserved. The complete nucleotide sequence of the hGH locus spans over 66 495 bp and contains sequences of all five genes. Each of the five genes in the cluster consists of five exons and four introns. The genes are separated by intergenic sequences of 6000 to 13000 base pairs (bp) in length. Since the cluster genes are expressed in different tissues and at different time intervals the expression is contro
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