Establishing pair rule gene expression
Primary
pair rule genes are regulated by the gap genes. The broad domains of
gap gene expression are translated into a striped pattern. This process
requires a complex regulation of the pair rule genes. Principally, the
different stripes of pair rule expression are regulated independently.
The cis regulatory regions of primary pair rule genes are composed of
modular elements, each regulating one or two individual stripes in response
to specific concentrations of maternal and gap genes. The striped pattern
of even skipped has been analyzed in detail. Krüppel and
giant repress stripe 2 and 5, whereas stripes 3,4,6 and 7 respond
to different concentrations of knirps and hunchback. Gap
genes have predominantly inhibitory effects on pair rule stripes. 
Pair
rule gene expression is initiated in broad domains. During cell cycle
14, the expression domains of gap genes and pair rule genes co-evolve.
While
gap genes like Krüppel and giant are successively refined,
they repress the expression of even skipped stripes 2 and 5 such
that these stripes appear where the combined activity of giant and
Krüppel is lowest: between their expression domains. Three primary pair rule genes are known today: even skipped, runt and hairy. Different primary pair rule genes are expressed at slightly different positions. For example every hairy stripe is expressed slightly posterior to the corresponding even skipped stripe. Accordingly, different concentrations and combinations of gap genes regulate the hairy stripes.
Media list
eve regulation............additional
information
eve gt Kr movie..........additional
information
establishing eve expression..........additional
informationGenes discussed
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Gene
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Gene product
- Domains
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Function
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Links
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D-STAT (STAT92E; common alternative name:
marelle (mrl))
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transcription factor - cytoplasmic signal transducing
protein
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functions during segmentation and establishment of
planar polarity during eye development
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even-skipped (eve)
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transcription factor - homeodomain
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pair rule gene establishing epidermal cell fate
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fish-hook (preferred name: Sox box protein
70D, common alternative name: Dichaete (D))
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HMG-domain protein - SOX-domain protein
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implicated in the regulation of pair-rule genes
and later functions in wing morphogenesis
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giant (gt)
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transcription factor - basic leucine zipper
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gap gene
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hairy (h)
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transcription factor - bHLH - Hairy/E(spl) class
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pair-rule gene, later it antagonizes sensory bristle
formation
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hunchback
(hb)
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transcription factor - zinc finger |
gap gene, later required for proper temporal generation
of NB sublineages
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knirps (kni)
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transcription factor - steroid receptor - zinc
finger
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gap gene, later organizes the development of the second
wing vein
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Krüppel (Kr)
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transcription factor - zinc finger transcriptional
repressor
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gap gene, later required for proper temporal generation
of NB sublineages
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runt (run)
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transcription factor - novel
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pair rule gene, also contributes to neuroblast cell
identity
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