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Mech Dev. 2015 Aug;137:45-52. doi: 10.1016/j.mod.2015.03.002. Epub 2015 Mar 28.

Functional analysis of sex-determination genes by gene silencing with LNA-DNA gapmers in the silkworm, Bombyx mori.

Author information

1
Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan.
2
Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan. Electronic address: gakyo@k.u-tokyo.ac.jp.

Abstract

The sexual fate of B. mori is determined genetically; ZW, female and ZZ, male. Recently, we successfully identified a strong candidate gene at the top of the sex determination cascade in B. mori. This gene was termed Feminizer (Fem) and revealed to be a source of Fem-piRNA. Further, we found that B. mori doublesex (Bmdsx) splicing was markedly altered to produce the male-type isoform when a Fem-piRNA inhibitor was injected into ZW embryos. Moreover, knockdown of Masculinizer (Masc), a Fem-piRNA target gene, altered to produce the female-type isoform of Bmdsx in male embryos. However, it remains unclear as to whether Masc directly regulates the sex-specific expression of Bmdsx. In previous studies, we determined that the male-specific isoform of the Bombyx homolog of IGF-II mRNA-binding protein (Imp(M)) was involved in the male-specific splicing of Bmdsx. In an attempt to clarify the genetic relationship between Fem, Masc, Imp(M), and Bmdsx, knockdown experiments were performed. Knockdown of Fem shifted into male-type Bmdsx, Imp(M) and Masc in female embryos. Knockdown of Masc led to the production of the female-type Bmdsx and a dramatic reduction in Imp(M) expression in male embryos. Knockdown of Imp(M) shifted Bmdsx splice mode from the male-type into the female-type. Our results suggest that: (1) Fem reduces Masc expression, (2) Masc dramatically induces Imp(M) expression, and (3) Imp(M) shifting Bmdsx splice mode from the female-type into the male-type. Based on these findings, we propose a possible genetic cascade regulating sex determination in B. mori.

KEYWORDS:

Bmdsx; Bombyx mori; Fem; Imp; Masc; Sex determination

PMID:
25828912
DOI:
10.1016/j.mod.2015.03.002
[Indexed for MEDLINE]
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