Loss of Kr from the progenitor resulted in a simple omission of the Kr-dependent fate without duplicating its subsequent fate. This is in contrast with the chinmo-required neurons unanimously adopting the next Chinmo-independent fate in the chinmo mutant NB clones. These observations suggest that Kr regulates temporal

fate in the progenitor, whereas Chinmo acts in the offspring to allow subpatterning of temporal fates. Multiple time-dependent mechanisms may operate in hierarchy to refine the temporal identity from the progenitor to the individual postmitotic neurons. To detect temporal cell-fate transformation (acquisition of a chronologically inappropriate fate) in a neuronal lineage requires birth dating of each offspring to faithfully determine individuals’ prospective cell fates. This is extremely challenging in a protracted neuronal lineage that rapidly alters temporal identity. selleck compound Due to twin-spot mosaic analysis with a repressible cell marker (MARCM), we can create homozygous mutant cells in an otherwise heterozygous organism and mark them and their accompanying wild-type sister clones simultaneously in different colors,

which directly reveals when the mutant GSK1210151A molecular weight clones were born and allows one to deduce their prospective cell fates (Figure 1A, right) (Yu et al., 2009 and Yu et al., 2010). To determine the roles of Chinmo in the orderly derivation of 40 PN types from adPN progenitor, we introduced a protein null allele of chinmo into twin-spot MARCM for knocking out chinmo in various mosaic patterns. chinmo mutant clones were consistently labeled with mCD8::GFP, whereas their wild-type sister clones expressed rCD2::RFP ( Figure 1A). We first determined whether any adPN temporal fates are missing in chinmo mutant clones generated at the beginning of the

lineage. Full-size NB clones exist unpaired when labeled with a neuronal driver ( Figure 1B, wild-type clone) ( Yu et al., 2010). Examining the largest adPN NB clones, labeled with GAL4-GH146, why consistently revealed that seven out of 27 GH146-positive glomerular targets were not innervated by chinmo mutant adPNs ( Figure 1C, orange arrowheads indicate the missing glomerular targets). Normal cell counts were obtained in chinmo mutant aPN NB clones (wild-type: 48.4 ± 7.7, n = 12 versus chinmo: 45.2 ± 8.7, n = 10), and we did not detect any ectopic glomerular targets. These observations argue that the missing PN types had been made but sent their dendrites to chronologically inappropriate targets. The seven unlabeled glomerular targets are normally innervated by adPNs born in two blocks separated by a DM3-targeting adPN (Figure 1E). Three adPN temporal fates, DM4, DL5, and VM3 (VM3a) adPN, exist in the first Chinmo-required window. And five adPN temporal fates, including the second VM3 (VM3b), DL4, DL1, DA3, and DC2 fate, are normally encoded within the second Chinmo-dependent window, followed by the Chinmo-independent D-targeting temporal fate.