The ParaHox gene Gsx patterns the apical organ and central nervous system but not the foregut in scaphopod and cephalopod mollusks

Wollesen, Tim, Rodriguez Monje, Sonia Victoria, McDougall, Carmel, Degnan, Bernard M. and Wanninger, Andreas (2015) The ParaHox gene Gsx patterns the apical organ and central nervous system but not the foregut in scaphopod and cephalopod mollusks. EvoDevo, 6 1: . doi:10.1186/s13227-015-0037-z

Author Wollesen, Tim
Rodriguez Monje, Sonia Victoria
McDougall, Carmel
Degnan, Bernard M.
Wanninger, Andreas
Title The ParaHox gene Gsx patterns the apical organ and central nervous system but not the foregut in scaphopod and cephalopod mollusks
Journal name EvoDevo   Check publisher's open access policy
ISSN 2041-9139
Publication date 2015-12-29
Year available 2015
Sub-type Article (original research)
DOI 10.1186/s13227-015-0037-z
Open Access Status DOI
Volume 6
Issue 1
Total pages 18
Place of publication London, United Kingdom
Publisher BioMed Central
Language eng
Formatted abstract
Background: It has been hypothesized that the ParaHox gene Gsx patterned the foregut of the last common bilaterian ancestor. This notion was corroborated by Gsx expression in three out of four lophotrochozoan species, several ecdysozoans, and some deuterostomes. Remarkably, Gsx is also expressed in the bilaterian anterior-most central nervous system (CNS) and the gastropod and annelid apical organ. To infer whether these findings are consistent with other mollusks or even lophotrochozoans, we investigated Gsx expression in developmental stages of representatives of two other molluscan classes, the scaphopod Antalis entalis and the cephalopod Idiosepius notoides.

Results: Gsx is not expressed in the developing digestive tract of Antalis entalis and Idiosepius notoides. Instead, it is expressed in cells of the apical organ in the scaphopod trochophore and in two cells adjacent to this organ. Late-stage trochophores express Aen-Gsx in cells of the developing cerebral and pedal ganglia and in cells close to the pavilion, mantle, and foot. In postmetamorphic specimens, Aen-Gsx is expressed in the cerebral and pedal ganglia, the foot, and the nascent captacula. In early squid embryos, Ino-Gsx is expressed in the cerebral, palliovisceral, and optic ganglia. In late-stage embryos, Ino-Gsx is additionally expressed close to the eyes and in the supraesophageal and posterior subesophageal masses and optic lobes. Developmental stages close to hatching express Ino-Gsx only close to the eyes.

Conclusions: Our results suggest that Gsx expression in the foregut might not be a plesiomorphic trait of the Lophotrochozoa as insinuated previously. Since neither ecdysozoans nor deuterostomes express Gsx in their gut, a role in gut formation in the last common bilaterian ancestor appears unlikely. Gsx is consistently expressed in the bilaterian anterior-most CNS and the apical organ of lophotrochozoan larvae, suggesting a recruitment of Gsx into the formation of this organ in the Lophotrochozoa. The cephalopod posterior subesophageal mass and optic ganglia and the scaphopod pedal ganglia also express Gsx. In summary, Gsx expression only appears to be conserved in the anterior-most brain region during evolution. Accordingly, Gsx appears to have been recruited into the formation of other expression domains, e.g., the apical organ or the foregut, in some lophotrochozoans.
Keyword Brain
Homeobox genes
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2016 Collection
School of Biological Sciences Publications
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