Pair-rule gene

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] 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 on direct regulation by the gap genes.

See also

Drosophila embryogenesis

References

  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. http://linkinghub.elsevier.com/retrieve/pii/0012-1606(81)90347-X. 
  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. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=395283. 
  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. http://linkinghub.elsevier.com/retrieve/pii/0092-8674(84)90418-5. 
  5. ^ 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. http://linkinghub.elsevier.com/retrieve/pii/0092-8674(86)90515-5. 
  6. ^ 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. 

External links