Studies on the molecular structure, organization, and expression of novel bombyxin genes of the silkmoth Bombyx mori カイコガゲノムより同定した新規ボンビキシン遺伝子の構造と発現に関する研究
Studies on the molecular structure, organization, and expression of novel bombyxin genes of the silkmoth Bombyx mori
Aslam Abu Faiz Md
アスラム アブ ファイズ エムディー
Insulin family peptide members play a pivotal role in regulation of growth, metabolism, and reproduction in vertebrates. Insulin-like peptides (ILPs) have also been identified from invertebrates, including several insect species. Bombyxin, isolated from the silkmoth Bombyx mori was the first ILP identified in insects. To gain insight into the role of bombyxin genes, the full genome of B. mori was analyzed, identified six novel bombyxin genes and grouped to five novel families: bombyxin-V through Z. All of these genes encoded preprobombyxin, the precursor molecule for bombyxin. Amino acid sequence comparison showed that these prepropeptides have 21 to 50% and 21 to 26% identities with previously characterized preprobombyxins and human preproinsulin, respectively. Genomic organization and chromosomal location of the genes were characterized. Each of bombyxin-V1 and -V2 had one intervening intron at 5' untranslated region (UTR), whereas Z1 had three introns - two at 5' UTR and one in C- peptide region. Human insulin and relaxin genes have intervening introns at almost the same position of these bombyxin genes. Reverse transcription-PCR and whole-mount in situ hybridization in different tissues and developmental stages were performed to observe temporal and spatial expression pattern. Newly identified bombyxin genes were expressed in diversified tissues. Bombyxin-V1, -W1 and -Y1 genes were predominantly expressed in four pairs of the medial neurosecretory cells of brain, which are the expression sites of other bombyxin genes also. The appearance of a short C-peptide, an extended A chain, appearance of high expression in non-feeding stages fat body, and induction upon starvation of bombyxin-X1 indicates its growth function and some structural similarities with insulin-like growth factors (IGFs). Bombyxin-Z1 was prejudiced to female insect. High level expression of Z1 in the follicular cells of ovary may suggest its function in reproduction. These results therefore demonstrate that bombyxin gene might have been originated from a vertebrate insulin-like common ancestral gene, and evolved into a diverse gene family with multiple functions.
学位取得年月日：2010年9月, 取得学位：博士(理学), 授与大学：Division of Life Sciences, Kanazawa University, Japan(金沢大学), Chief supervisor Prof. Dr. Masafumi Iwami(岩見雅史)