New resources for the Drosophila 4th chromosome: FRT101F enabled mitotic clones and Bloom syndrome helicase enabled meiotic recombination

Abstract

Genes on the long arm of the Drosophila melanogaster 4th chromosome are difficult to study because the chromosome lacks mitotic and meiotic recombination. Without recombination numerous standard methods of genetic analysis are impossible. Here we report new resources for the 4th. For mitotic recombination we generated a chromosome with an FRT very near the centromere in 101F and a derivative that carries FRT101F with a distal ubiquitously expressed GAL80 transgene. This pair of chromosomes enables both unmarked and MARCM clones. For meiotic recombination we demonstrate that a Bloom syndrome helicase and recombination defective double mutant genotype can create recombinant 4th chromosomes via female meiosis. All strains will be available to the community via the Bloomington Drosophila Stock Center. Additional resources for studies of the 4th are in preparation and will also be made available. The goal of the 4th Chromosome Resource Project is to accelerate the genetic analysis of protein coding genes on the 4th, including the 44 genes with no demonstrated function. Studies of these previously inaccessible but largely conserved genes will close longstanding gaps in our knowledge of metazoan development and physiology.

dSmad2 differentially regulates dILP2 and dILP5 in insulin producing and circadian pacemaker cells in unmated adult females

“…dCORL.GAL4 was shown to be expressed in a subset of IPCs, the mushroom body and four pairs of neurons in a ventral lateral region of the central brain that also express dILP5 ( Fig 1A ; [ 13 ]). We previously thought the lateral cells were located in the lobula plate and thus formed part of the visual system.…”

“…The absence of haploinsufficiency for dSmad2 is attested to by its location on the X chromosome where it is hemizygous in all males. The fact that dCORL.GAL4 is expressed in a subset of IPCs [ 13 ] and dILP2 is expressed in all IPCs [ 5 ] ensures that mutant and wild type cells are present in the same brain, providing a highly rigorous experiment.…”

“…One day old unmated female adult brains were dissected, fixed, stained for GFP, FasII, and either dILP2 or dILP5 then mounted and imaged as described [ 13 ]. Primary antibodies: DSHB mouse α-FasII 1D4 (RRID: AB_528235), Abcam rabbit α-GFP ab6556 (RRID: AB_305564), Abcam chicken α-GFP ab13970 (RRID: AB_300798), mouse α-dILP2 and rabbit α-dILP5 (Pierre Leopold, Institute Curie, Paris).…”

“…[11] (BDSC #44384), w P{ry [+t7.2] = hs.FLP}1 P{w[+mC] = tubulinP.GAL80}LL1 P{ry[+t7.2] = neoFRT}19A referred to as Tub.GAL80 [12] (BDSC #5132) and w; P{w[+mC] = dCORL.GAL4(-).PT} P{w[+mC] = UAS. GFP.S65T} / SM6A referred to as dCORL.GAL4 [13]. Rescue of dSmad2 mutant MARCM clones with UAS.dSmad2: dSmad2 mutant, Tub.GAL80, dCORL.GAL4, and yw; P{w[+mC] = UAS.dSmad2} referred to as UAS.dSmad2 [11].…”

Fourth Chromosome Resource Project: a comprehensive resource for genetic analysis in Drosophila that includes humanized stocks

“…The insertion site of FRT101F for mitotic clones is indicated with a green arrow at 46,995 bp. See Goldsmith et al . (2022) for details regarding FRT101F.…”