Zerknüllt

Zerknüllt (zen, German for "crumpled") is a gene in the Antennapedia complex of Drosophila (fruit flies) and other insects, where it operates very differently from the canonical Hox genes in the same gene cluster. Comparison of Hox genes between species showed that the Zerknüllt gene evolved from one of the standard Hox genes (the 'paralogy group 3' Hox gene) in insects through accumulating many amino acid changes, changing expression pattern, losing ancestral function and gaining a new function.[1][2]

Zerknüllt 1
Identifiers
OrganismDrosophila melanogaster
Symbolzen
UniProtP09089
Zerknüllt 2
Identifiers
OrganismDrosophila melanogaster
Symbolzen2
UniProtP09090

Zerknüllt codes for a homeoprotein regulates aspects of early embryogenesis in insects. Unlike the canonical Hox genes which are expressed in precise zones along the anteroposterior (head to tail) body axis, zerknüllt expression is restricted along the dorsoventral (back to belly) body axis. Expression of Zerknüllt is repressed in the ventral part of the embryo by a protein called Dorsal, and activated in the dorsal part of the embryo by the TGF beta signaling pathway.[3] The cells which activate the Zerknüllt develop into extraembryonic tissues which surround the developing insect embryo.[4]

Zerknüllt has been found to undergo a number of gene duplications in certain insect lineages. For example, in the beetle Tribolium castaneum zen duplicated to yield zen and zen2; in many flies, including Drosophila, zen duplicated to give zen, zen2 and the even more divergent Bicoid gene.[5][6] Large expansions of zen through gene duplication have also been observed within Lepidoptera. In this group, zen has duplicated at least four times resulting in the emergence of the additional divergent 'Special homeobox' (Shx) genes, named ShxA, ShxB, ShxC and ShxD.[7] The original zen gene is still present. In some lepidopteran species, such as the Domesticated Silkmoth Bombyx mori, even greater numbers of duplications of zen occurred, with 12 Shx loci annotated along with zen.[8]

See also

References
  1. Falciani F, Hausdorf B, Schröder R, Akam M, Tautz D, Denell R, Brown S (August 1996). "Class 3 Hox genes in insects and the origin of zen". Proceedings of the National Academy of Sciences of the United States of America. 93 (16): 8479–84. doi:10.1073/pnas.93.16.8479. PMID 8710895.
  2. Panfilio KA, Liu PZ, Akam M, Kaufman TC (April 2006). "Oncopeltus fasciatus zen is essential for serosal tissue function in katatrepsis". Developmental Biology. 292 (1): 226–43. doi:10.1016/j.ydbio.2005.12.028. PMID 16460723.
  3. Rushlow C, Colosimo PF, Lin MC, Xu M, Kirov N (February 2001). "Transcriptional regulation of the Drosophila gene zen by competing Smad and Brinker inputs". Genes & Development. 15 (3): 340–51. doi:10.1101/gad.861401. PMID 11159914.
  4. Rushlow C, Frasch M, Doyle H, Levine M (December 1987). "Maternal regulation of zerknüllt: a homoeobox gene controlling differentiation of dorsal tissues in Drosophila". Nature. 330 (6148): 583–6. doi:10.1038/330583a0. PMID 2891036.
  5. Brown SJ, Fellers JP, Shippy TD, Richardson EA, Maxwell M, Stuart JJ, Denell RE (March 2002). "Sequence of the Tribolium castaneum homeotic complex: the region corresponding to the Drosophila melanogaster antennapedia complex". Genetics. 160 (3): 1067–74. PMID 11901122.
  6. Negre B, Casillas S, Suzanne M, Sánchez-Herrero E, Akam M, Nefedov M, et al. (May 2005). "Conservation of regulatory sequences and gene expression patterns in the disintegrating Drosophila Hox gene complex". Genome Research. 15 (5): 692–700. doi:10.1101/gr.3468605. PMID 15867430.
  7. Ferguson L, Marlétaz F, Carter JM, Taylor WR, Gibbs M, Breuker CJ, Holland PW (October 2014). "Ancient expansion of the hox cluster in lepidoptera generated four homeobox genes implicated in extra-embryonic tissue formation". PLoS Genetics. 10 (10): e1004698. doi:10.1371/journal.pgen.1004698. PMID 25340822.
  8. Chai CL, Zhang Z, Huang FF, Wang XY, Yu QY, Liu BB, et al. (December 2008). "A genomewide survey of homeobox genes and identification of novel structure of the Hox cluster in the silkworm, Bombyx mori". Insect Biochemistry and Molecular Biology. Special Issue on the Silkworm Genome. 38 (12): 1111–20. doi:10.1016/j.ibmb.2008.06.008. PMID 19280701.
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