Molecular biology of mosquito oogenesis

1995 Fiscal Year Final Research Report Summary

• Project/Area Number: 06670270
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: 寄生虫学(含医用動物学)
• Research Institution: Juntento University School of Medicine
• Principal Investigator: UCHIDA Keikichi Juntendo University School of Medicine, Dept. of Biology, Assistant Professor, 医学部, 講師 (40053368)
• Co-Investigator(Kenkyū-buntansha): ESHITA Yuki Kurume University, Dept. of Parasitol., Assistant Prof., 医学部, 講師 (10082223) ; OHMORI D Juntendo University School of Medicine, Dept. of Chemistry, Assoc. Prof., 医学部, 助教授 (00124967)
• Project Period (FY): 1994 – 1995
• Keywords: Culex pipiens pallens / Molecular biology / Ovarian development / Fat body / Organ culture / Vitellogenin

Research Abstract

1. A basic organ culture method for investigating the mechanism of mosquito oogenesis at molecular levels was established. Ovarian follicles removed from females 2 days after a blood meal increased in size and a few of them formed a micropile apparatus, which usually accompanies matured eggs, when cultured in a cell culture well with a medium containing amino acids at high concentrations.
2. Fat bodies removed from unfed females did not release any immunologically-detectable vitellogenin molecules into the medium at all when cultured in the above system, suggesting that amino acids alone may not stimulate vitellogenin synthesis in the fat body. In order to examine this aspect further at the transcriptional level, analysis of mRNA in the organ is now underway.
3. In parallel with the study on vitellogenin synthesis in the fat body, the synthesis of ovary-specific proteins during oogenesis was also investigated. High activities of proteinases, which seem to belong to cathepsins, were found in the developing follicles after a blood meal. The activity tended to increase during the follicle growth and the mature eggs preserved the highest enzymatic potentials.
<Prospect> Most of the proteinases found in the developing follicles are supposed to work in embryogenesis after oviposition. However, some of them may certainly be activated in degenerating follicles to break down the vitellogenin already incorporated in the oocyte. Investigation of these enzymes and their gene expression control will certainly help to understand the regulation of the number of mature eggs in blood-fed female mosquitoes---how do they "recognize" the appropriate number of follicles to mature from nutrients available from the ingested blood? . The knowledge will then lead to a effective control of mosquito vectors, not only for filariasis but for many other mosquito-born diseases in the world.