Homeotic gene

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Homeotic genes are genes which regulate the development of anatomical structures in various organisms such as insects, mammals, and plants. This regulation is done via the programming of various transcription factors by the homeotic genes, and these factors affect genes through regulatory genetic pathways.[1] They include many of the Hox and ParaHox genes which are important for segmentation,[2] They also include the MADS-box-containing genes involved the ABC model of flower development.[3] Not all homeotic genes are Hox genes; the MADS- box genes are homeotic but not Hox genes. Thus, the Hox genes are a proper subset of homeotic genes.

Mutations in the homeotic genes can occur, leading to what are known as homeotic mutants. These mutants display ectopic placement of body parts (such as antennae growing at the posterior of the fly instead of at the head) or abnormal expression of the homeotic gene. Many times, mutation that lead to these ectopic placements are lethal to the organism.[4]

One of the most commonly studied model organisms in regards to homeotic genes is the Drosophila, specifically Drosophila melanogaster. The homeotic genes of this organism occur in either the Antennapedia complex (ANT-C) or the Bithorax complex (BX-C).[5] During development (starting at the blastoderm stage of the embryo), these genes are constantly expressed in order give the different segments of the fly body specific structures and roles.[6] For Drosophila, these genes can be analyzed using the Flybase database

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  1. ^ Hirth F, Hartmann B, Reichert H (May 1998). "Homeotic gene action in embryonic brain development of Drosophila". Development 125: 1579–89. PMID 9521896. 
  2. ^ Young T, Rowland JE, van de Ven C, et al. (October 2009). "Cdx and Hox genes differentially regulate posterior axial growth in mammalian embryos". Dev. Cell 17 (4): 516–26. doi:10.1016/j.devcel.2009.08.010. PMID 19853565. 
  3. ^ Theissen G (2001). "Development of floral organ identity: stories from the MADS house". Curr. Opin. Plant Biol. 4 (1): 75–85. doi:10.1016/S1369-5266(00)00139-4. PMID 11163172. 
  4. ^ Andrew DJ, Horner MA, Petitt MG, et al. (March 1, 1994). "Setting limits on homeotic gene function: restraint of Sex combs reduced activity by teashirt and other homeotic genes". EMBO Journal 13 (5): 1132–44. PMID 7907545. 
  5. ^ Heuer JG, Kaufman TC (May 1992). "Homeotic genes have specific functional roles in the establishment of the Drosophila embryonic peripheral nervous system". Development 115: 35–47. PMID 1353440. 
  6. ^ Breen TR, Harte PJ (January 1993). "trithorax regulates multiple homeotic genes in the bithorax and Antennapedia complexes and exerts different tissue-specific, parasegment-specific and promoter-specific effects on each". Development 117: 119–34. PMID 7900984.