Bm-muted, orthologous to mouse muted and encoding a subunit of the BLOC-1 complex, is responsible for the otm translucent mutation of the silkworm Bombyx mori

• Published in: Gene Vol. 629; pp. 92 - 100
• Main Authors: Zhang, Haokun, Kiuchi, Takashi, Wang, Lingyan, Kawamoto, Munetaka, Suzuki, Yutaka, Sugano, Sumio, Banno, Yutaka, Katsuma, Susumu, Shimada, Toru
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 20.09.2017
• Subjects: Animals; BLOC-1; Bm-muted; Bombyx - genetics; Bombyx - growth & development; Bombyx mori; Carrier Proteins - metabolism; Cloning, Molecular; Insect Proteins - genetics; Insect Proteins - metabolism; Multiprotein Complexes - metabolism; Mutation; Organdy; RNA Interference; Urate granule; Uric Acid - metabolism; Vesicular Transport Proteins - genetics; Vesicular Transport Proteins - metabolism; BC; BLOC; ABC; ORF; RPKM; Bombyx mori; AP-3; EGFP; Urate granule; HotSHOT; RT-PCR; KD; qPCR; Bm-muted; XDH; AA; RNAi; TSD; LROs; MITE; otm; MoCo; siRNA; Organdy; TIRs; BLOC-1; rp49; RACE; PCR
• ISSN: 0378-1119; 1879-0038
• DOI: 10.1016/j.gene.2017.07.071

“Tanaka's mottled translucent” (otm) is a mutation of the silkworm Bombyx mori that exhibits translucent skin during larval stages. We performed positional cloning of the gene responsible for otm and mapped it to a 364-kb region on chromosome 5 that contains 22 hypothetical protein-coding genes. We performed RNA-seq analysis of the epidermis and fat body of otm larvae and determined that the gene BGIBMGA002619 may be responsible for the otm mutation. BGIBMGA002619 encodes the biosynthesis of lysosome-related organelles complex 1 (BLOC-1) subunit 5, whose ortholog is responsible for the Muted mutant in mouse. Accordingly, we named this gene Bm-muted. We discovered that the expression of Bm-muted in the epidermis and fat body of otm mutants was dramatically suppressed compared with the wild type. We determined the nucleotide sequences of the full-length cDNA and genomic region corresponding to Bm-muted and found that a 538-bp long DNA sequence similar to B. mori transposon Organdy was inserted into the 3′ end of the first intron of Bm-muted in two otm strains. The Bm-muted cDNA of otm mutants lacked exon 2, and accordingly generated a premature stop codon in exon 3. In addition, short interfering RNA (siRNA)-mediated knockdown of this gene caused localized partial translucency of larval skin. These data indicate that the mutation in Bm-muted caused the otm-mutant phenotype. We propose that the insertion of Organdy caused a splicing disorder in Bm-muted in the otm mutant, resulting in a null mutation of Bm-muted. This mutation is likely to cause deficiencies in urate granule formation in epidermal cells that result in translucent larval skin. [Display omitted] •We identified Bm-muted as the gene responsible for Tanaka's mottled translucent (otm) mutation•Bm-muted encodes a subunit of the Bombyx mori biogenesis of lysosome-related organelles complex 1 (BLOC-1)•Insertion of Bombyx transposon Organdy induced aberrant splicing and caused a null mutation in Bm-muted of the otm mutant•Lysosome-related organelles (LROs) genes govern the accumulation of uric acid in silkworm larval epidermis