A Fly by Any Other Name

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Drosophila melanogaster

• A Fly by Any Other Name

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Segmentation of Larvae
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Three Classes ofSegmentation Genes
mutant
wild type
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Gradients of Maternal Effect Gene Products Direct
Subsequent Patterning

• Gap gene expression is regulated by bcd, hb,
  cad
• Gap genes in turn regulate pair-rule segment
  polarity genes and autoregulate themselves

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Expression of Gap Genes
Ems, btd, otd expression pattern similar to
hb activated by bcd
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Interaction of Maternal Effect Gap Genes
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Gap Genes as Txn Regulators
Eve txn reg sequences
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Transgenic Analysis of Eve Expression
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Expression of Pair-rule Genes

• Expressed in 7 vertical stripes corresponding to
  parasegments
• Expression is at border of segments

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Refinement ofPair-rule Gene Expression
Ftz expression (brown) in 7 stripes corresponding
to even numbered parasegments co-stained for eve
expression (blue) in odd numbered parasegments
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Segment Polarity Genes

• Pair-rule genes define every other parasegment
• In turn, pair-rule genes regulate segment
  polarity genes

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Segment Polarity Genes

• Expressed in a single column of cells at the
  posterior/anterior border of every parasegment

P
A
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Segment Polarity Genes
wg, hh, en signaling specify individual cell
types within parasegment
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Gradients of Wg Hh
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(No Transcript)
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Homeotic Genes

• Gap genes pair-rule genes initiate homeotic
  gene expression in proper domains
• Segment polarity genes confine homeotic gene
  expression to appropriate parasegments
• Homeotic genes regulate their own expression

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Homeotic Selector Genes
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Autoregulation of Homeotic Genes

• Each homeotic gene is negatively regulated by the
  more posteriorly expressed homeotic genes
• Antp txn is repressed by Ubx
• LOF mutations in homeotic genes causes anterior
  transformation
• GOF mutations in homeotic genes causes posterior
  transformation

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Ultrabithorax LOF Mutation
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Dominant Antennapedia Mutation