Development in Drosophila

Ruth Lehmann New York University/Howard Hughes Medical Institute

lehmann@saturn.med.nyu.edu

Model Organisms and InnovativeApproaches in Developmental

BiologyJuquehy, Brazil-2005

Practical session:Ruth Lehmann

Stained Chromatin ShowingSuperficial Cleavage in a Drosophila Embryo

Gastrulation

aa

5

6

7

8

9

10

11

12

14

15

16

17

Overview of the Stages of Development

Yellow: germ cells; green mesoderm,VF ventral furrow, redmidgut (PMG and AMG anterior and posterior midgut),light blue foregut and hindgut, dark blue neuroblast, purplenervous system, pv proventriculus, go, gonad, vnc: ventralnerve cord, sg salivary gland, br brain

From V. Hartenstein Atlas of DrosophilaCSH press

Maternal effect genes:• Bicoid transcription factor

localized to anterior • Nanos translational repressor

localized to posterior• Torso receptor tyrosine kinase

activated at anterior and posterior termini• Dorsal transcription factor

localized to ventral nuclei

Three maternal gene systems control AP patterning

Anterior Posterior TerminalHead/acronthorax

abdomen

telson

abdomen

telson

telson

thorax

abdomen

head

bicoid nanos torso

Head/acron

thorax

telson

Head/acron

thorax

abdomen

telson

Maternal effect genes:

•Observe bicoid and nanos RNA localizationMethod: RNA in situ hybridization, DIC optics

•Analyze gastrulation patterns of embryos from:•wildtype mutant mothers•bicoid mutant mothers•nanos mutant mothers•torso mutant mothers•“dorsal” mutant mothers•Method: Methanol/Formaldehyde fixed embryos (2 + 0-2hrs AEL) DIC optics

Germ cell formation1) Reduction in germ cell number in embryos from tudor mutantmothers germ cells are visualized by Vasa antibody staining

2) Transcriptional derpression of tll and slam in embryos from pgcmutant mothers tll and slam RNA in situ hybridization

Method: RNA in situ hybridization, DIC optics

Oskar organizes germ plasm

Osk-/-

No germplasm/No germ cells

4X 0sk+

More germ plasm/ More germ cells

Osk-bcd3’UTR

Wild type

Drosophilagerm plasm pathway

Reviewed in Starz-Gaiano and Lehmann (2001) Mech Dev. 105, 5-18

germ cellsposterior midgutsomatic gonadal precursors

Germ cell migration in Drosophila

Migration on posterior midgut

Attachment to gonadal mesoderm

Migration through posterior midgut

Gastrulation Germband retraction

Line formation

Formation

Gonad coalescence

aVasa

St 5

St 8 St 12

St 10

St 11

St 10/11

St 13

St 14