Pair-rule gene

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Expression of the pair-rule genes even-skipped and fushi tarazu in alternating bands in the Drosophila early embryo. Each band corresponds to one parasegment.

A pair-rule gene is a type of gene involved in the development of the segmented embryos of insects. Pair-rule genes are defined by the effect of a mutation in that gene, which causes the loss of the normal developmental pattern in alternating segments.

Pair-rule genes were first described by Christiane Nüsslein-Volhard and Eric Wieschaus in 1980.[1] They used a genetic screen to identify genes required for embryonic development in the fruit fly Drosophila melanogaster. In normal unmutated Drosophila, each segment produces bristles called denticles in a band arranged on the side of the segment closer to the head (the anterior). They found five genes – even-skipped, hairy, odd-skipped, paired and runt – where mutations caused the deletion of a particular region of every alternate segment. For example, in even-skipped, the denticle bands of alternate segments are missing, which results in an embryo having half the number of denticle bands. Later work identified more pair-rule genes in the Drosophila early embryo – fushi tarazu, odd-paired, sloppy paired, and tenm.[2][3]

Once the pair-rule genes had been identified at the molecular level it was found that each gene is expressed in alternate parasegments – regions in the embryo that are closely related to segments, but are slightly out of register.[4][5][6][7] Each parasegment includes the posterior part of one (future) segment, and an anterior part of the next (more posterior) segment. The bands of expression of the pair-rule genes correspond to the regions missing in the mutant. The expression of the pair-rule genes in bands is dependent both upon direct regulation by the gap genes [8] and on regulatory interactions between the pair-rule genes themselves. [9]

See also[edit]

Drosophila embryogenesis


  1. ^ Nüsslein-Volhard C, Wieschaus E (October 1980). "Mutations affecting segment number and polarity in Drosophila". Nature 287 (5785): 795–801. doi:10.1038/287795a0. PMID 6776413. 
  2. ^ Wakimoto BT, Kaufman TC (January 1981). "Analysis of larval segmentation in lethal genotypes associated with the antennapedia gene complex in Drosophila melanogaster". Dev. Biol. 81 (1): 51–64. doi:10.1016/0012-1606(81)90347-X. PMID 6780397. 
  3. ^ Baumgartner S, Martin D, Hagios C, Chiquet-Ehrismann R (August 1994). "Tenm, a Drosophila gene related to tenascin, is a new pair-rule gene". EMBO J. 13 (16): 3728–40. PMC 395283. PMID 8070401. 
  4. ^ Hafen E, Kuroiwa A, Gehring WJ (July 1984). "Spatial distribution of transcripts from the segmentation gene fushi tarazu during Drosophila embryonic development". Cell 37 (3): 833–41. doi:10.1016/0092-8674(84)90418-5. PMID 6430568. 
  5. ^ Ingham, P. W., K. R. Howard, and D. Ish-Horowicz (1985). "Transcription pattern of the Drosophila segmentation gene hairy". Nature 318: 439–445. doi:10.1038/318439a0. 
  6. ^ Macdonald PM, Ingham P, Struhl G (December 1986). "Isolation, structure, and expression of even-skipped: a second pair-rule gene of Drosophila containing a homeo box". Cell 47 (5): 721–34. doi:10.1016/0092-8674(86)90515-5. PMID 2877745. 
  7. ^ Lawrence PA, Johnston P, Macdonald P, Struhl G (1987). "Borders of parasegments in Drosophila embryos are delimited by the fushi tarazu and even-skipped genes". Nature 328 (6129): 440–2. doi:10.1038/328440a0. PMID 2886916. 
  8. ^ Ingham, P. W., Ish-Horowicz, D., & Howard, KR (1986). "Correlative changes in homoeotic and segmentation gene expression in Krüppel mutant embryos of Drosophila". The EMBO Journal 5 (7): 1659. 
  9. ^ Howard K . and Ingham P. "Regulatory interactions between the segmentation genes fushi tarazu, hairy, and engrailed in the Drosophila blastoderm". Cell 44 (6): 949–957. doi:10.1016/0092-8674(86)90018-8. 

External links[edit]