Transcriptional dynamics of a conserved gene expression network associated with craniofacial divergence in Arctic charr

EvoDevo

Sigrídur Rut Franzdóttir¹  Zophonías O Jónsson²  Sigurdur S Snorrason¹  Jóhannes Gudbrandsson¹  Valerie Helene Maier¹  Arnar Pálsson²  Kalina Hristova Kapralova¹  Ehsan Pashay Ahi¹ 

[1] Institute of Life and Environmental Sciences, University of Iceland, Sturlugata 7, 101 Reykjavik, Iceland;Biomedical Center, University of Iceland, Vatnsmýrarvegur 16, 101 Reykjavik, Iceland

关键词: Salvelinus alpinus;    Morphogenesis;    Gene network;    Divergent evolution;    Craniofacial development;    Coexpression;    Arctic charr;   

Others  :  1093218
DOI  :  10.1186/2041-9139-5-40

 received in 2014-07-11, accepted in 2014-09-17,  发布年份 2014

【 摘 要 】

Background

Understanding the molecular basis of craniofacial variation can provide insights into key developmental mechanisms of adaptive changes and their role in trophic divergence and speciation. Arctic charr (Salvelinus alpinus) is a polymorphic fish species, and, in Lake Thingvallavatn in Iceland, four sympatric morphs have evolved distinct craniofacial structures. We conducted a gene expression study on candidates from a conserved gene coexpression network, focusing on the development of craniofacial elements in embryos of two contrasting Arctic charr morphotypes (benthic and limnetic).

Results

Four Arctic charr morphs were studied: one limnetic and two benthic morphs from Lake Thingvallavatn and a limnetic reference aquaculture morph. The presence of morphological differences at developmental stages before the onset of feeding was verified by morphometric analysis. Following up on our previous findings that Mmp2 and Sparc were differentially expressed between morphotypes, we identified a network of genes with conserved coexpression across diverse vertebrate species. A comparative expression study of candidates from this network in developing heads of the four Arctic charr morphs verified the coexpression relationship of these genes and revealed distinct transcriptional dynamics strongly correlated with contrasting craniofacial morphologies (benthic versus limnetic). A literature review and Gene Ontology analysis indicated that a significant proportion of the network genes play a role in extracellular matrix organization and skeletogenesis, and motif enrichment analysis of conserved noncoding regions of network candidates predicted a handful of transcription factors, including Ap1 and Ets2, as potential regulators of the gene network. The expression of Ets2 itself was also found to associate with network gene expression. Genes linked to glucocorticoid signalling were also studied, as both Mmp2 and Sparc are responsive to this pathway. Among those, several transcriptional targets and upstream regulators showed differential expression between the contrasting morphotypes. Interestingly, although selected network genes showed overlapping expression patterns in situ and no morph differences, Timp2 expression patterns differed between morphs.

Conclusion

Our comparative study of transcriptional dynamics in divergent craniofacial morphologies of Arctic charr revealed a conserved network of coexpressed genes sharing functional roles in structural morphogenesis. We also implicate transcriptional regulators of the network as targets for future functional studies.

【 授权许可】

   
2014 Ahi et al.; licensee BioMed Central Ltd.

【 图 表 】

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