Role Of Fs(2)Ket In The Development Of Optic Lobes In Drosophila

Female sterile?2?Ketel gene-encoded nuclear pore transport protein?subunit is highly conserved and plays an important role in nuclear pore transport,spindle formation and nuclear membrane assembly,and mitochondrial biogenesis in Drosophila.The loss of Fs?2?Ket function affects protein transport into the nucleus,mitotic cycle,embryonic egg shell formation,and mitochondrial function,and photoreceptor axon guidance and cell adhesion in the eye.We speculate that Fs?2?Ket likely affects the development of the optic lobe,although there has been no report on the effects of loss of Fs?2?Ket function on the development of the optic lobes of Drosophila.To explore the effects of loss of Fs?2?Ket function on Drosophila brain development,we knocked down Fs?2?Ket expression using the Gal4-UAS expression system.We used c855a-GAL4 and NP7340-GAL4 to drive Fs?2?Ket RNAi expression in the neuroepithelial cells of the optic lobes.We found that of the four Fs?2?Ket RNAi strains tested,only one RNAi strain,THU2731,has a significant effect on Drosophila brain development.When Fs?2?Ket RNAi2731 is driven by c855a-GAL4 or NP7340-GAL4 at 25^oC,the mutant larvae can grow to the late-third instar stage but will die during pupal stages,and the mutant larvae reach the late-third instar 1 to 3days later than wild type larvae.Due to the different GAL4 activities at different temperatures,the specific time of lethality varied.The lethality occurred at 31^oC at early pupal stages,whereas at 18^oC,the lethality occurs at hatching from the pupal case.For most of our experiments,we expressed Fs?2?Ket RNAi at 25^oC and used w¹¹¹⁸as the control.I conducted a time-course study?48h ALH,60h ALH,72h ALH,96h ALH?to examine the effects of loss of Fs?2?Ket on optic lobe development.At 48h ALH,there was no significant difference between Fs?2?Ket RNAi brains and wild-type brains.At 60h ALH,Fs?2?Ket RNAi brains had fewer neuroepithelial cells,thinner medulla and a smaller brain size,as compared with wild type.At 72h ALH,the neuroepithelial cells in Fs?2?Ket RNAi brains began to change their morphology into rounded cells,and there were fewer neuroepithelial cells,thinner medulla and significantly smaller brain size as compared with wild type.At 96h ALH,most of the neuroepithelial cells in Fs?2?Ket RNAi brains disintegrated and transformed into rounded cells,and the brain was significantly smaller than the control group,the medulla was thin and had holes in it,and the lamina did not form crescent shape,but was diffuse.Fs?2?Ket RNAi larvae reached the late-third instar stage 1-3 days later than wild type.At late third instar,most of the neuroepithelial cells in the Fs?2?Ket RNAi brains were lost and probably transformed into rounded cells;the lamina was not crescent shaped,but became diffuse,the medulla is thin and has cavity,and the brain is smaller.These results indicate that Fs?2?Ket is required for the maintenance of neuroepithelial cells in the OPC,the loss of Fs?2?Ket function leads to defects in lamina and medulla development.