BmVMP90, a large vitelline membrane protein of the domesticated silkmoth Bombyx mori, is an essential component of the developing ovarian follicle

We present the characterization of BmVMP90, a vitelline membrane protein (VMP) of the silkmoth Bombyx mori bearing similarities with dipteran VMPs whose existence had recently been suggested by an in silico analysis of the silkmoth genome and follicular cell RNA expression analyses. Using a specific antibody, we determine the presence of BmVMP90 protein in ovarian follicular cell extracts at the end of vitellogenesis and in vitelline membrane extracts but not in the chorion of fractionated eggshells isolated from ovulated follicles. Whole mount follicle immunofluorescence studies reveal a pattern of BmVMP90 deposition matching the «imprinted» pattern of follicular cells on the vitelline membrane surface. Antisense DNA-directed inhibition BmVMP90 expression in ex vivo cultures of early vitellogenic follicles produced a phenotype of kidney- or bean-shaped follicles with detached follicular epithelia, suggestive of the importance of BmVMP90 for the integrity of developing follicles and normal deposition of the chorion structure that follows vitelline membrane formation but no adverse effects on the execution of the follicular cell-imprinted program of choriogenesis per se.

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► BmVMP90 is an ovarian protein, expressed at the end of vitellogenesis.
► Specific antibody localizes it in the vitelline membrane of the silkmoth eggshell.
► It possesses a region similar to the dipteran VM domain.
► BmVMP90 knockdown compromises follicle integrity but does not disrupt choriogenesis.