Conservation and divergence of bHLH genes in the calcisponge Sycon ciliatum

Fortunato, Sofia A.V., Vervoort, Michel, Adamski, Marcin, and Adamska, Maja (2016) Conservation and divergence of bHLH genes in the calcisponge Sycon ciliatum. EvoDevo, 7 (23). pp. 1-12.

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Background: Basic Helix-Loop-Helix (bHLH) genes encode a large family of eukaryotic transcription factors, categorized into six high-order groups: pan-eukaryotic group B involved in regulation of cell cycle, metabolism, and development; holozoan-specific groups C and F involved in development and maintenance of homeostasis; and metazoan-specific groups A, D and E including well-studied genes, such as Atonal, Twist and Hairy, with diverse developmental roles including control of morphogenesis and specification of neurons. Current scenarios of bHLH evolution in animals are mainly based on the bHLH gene set found in the genome of demosponge Amphimedon queenslandica. In this species, the majority of the 21 identified bHLH genes belong to group B, and the single group A gene is orthologous to several neurogenic bilaterian subfamilies, including atonal and neurogenin.

Results: Given recently discovered differences in developmental toolkit components between siliceous and calcareous sponges, we have carried out genome-wide analysis of bHLH genes in Sycon ciliatum, an emerging calcisponge model. We identified 30 bHLH genes in this species, representing 12 individual families, including four group A families not found in Amphimedon, and two larger family groupings. Notably, the families represented in Sycon are only partially overlapping with those represented in Amphimedon. Developmental expression analysis of a subset of the identified genes revealed patterns consistent with deeply conserved roles, such as specification of sensory cells by Atona-related and stem cells by Myc genes.

Conclusions: Our results demonstrate independent gene loss events in demosponges and calcisponges, implying a complex bHLH toolkit in the last common metazoan ancestor.

Item ID: 46160
Item Type: Article (Research - C1)
ISSN: 2041-9139
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© 2016 The Author(s). This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Funders: Sars International Centre for Marine Molecular Biology, Norway, Universitaire de France, Laboratory of Excellence (LABEX)
Projects and Grants: LABEX ANR-11-LABX-0071
Date Deposited: 24 Oct 2016 01:54
FoR Codes: 31 BIOLOGICAL SCIENCES > 3104 Evolutionary biology > 310404 Evolution of developmental systems @ 50%
31 BIOLOGICAL SCIENCES > 3105 Genetics > 310503 Developmental genetics (incl. sex determination) @ 50%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 100%
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