Molecular mechanisms underlying nuchal hump formation in dolphin cichlid, Cyrtocara moorii

Abstract

East African cichlid fishes represent a model to tackle adaptive changes and their connection to rapid speciation and ecological distinction. In comparison to bony craniofacial tissues, adaptive morphogenesis of soft tissues has been rarely addressed, particularly at the molecular level. The nuchal hump in cichlids fishes is one such soft-tissue and exaggerated trait that is hypothesized to play an innovative role in the adaptive radiation of cichlids fishes. It has also evolved in parallel across lakes in East Africa and Central America. Using gene expression profiling, we identified and validated a set of genes involved in nuchal hump formation in the Lake Malawi dolphin cichlid, Cyrtocara moorii. In particular, we found genes differentially expressed in the nuchal hump, which are involved in controlling cell proliferation (btg3, fosl1a and pdgfrb), cell growth (dlk1), craniofacial morphogenesis (dlx5a, mycn and tcf12), as well as regulators of growth-related signals (dpt, pappa and socs2). This is the first study to identify the set of genes associated with nuchal hump formation in cichlids. Given that the hump is a trait that evolved repeatedly in several African and American cichlid lineages, it would be interesting to see if the molecular pathways and genes triggering hump formation follow a common genetic track or if the trait evolved in parallel, with distinct mechanisms, in other cichlid adaptive radiations and even in other teleost fishes.

Characterization of antimicrobial susceptibility, extended-spectrum β-lactamase genes and phylogenetic groups of Shigatoxin producing Escherichia coli isolated from patients with diarrhea in Iran

“…The blaTEM was more common, followed by blaCTX-M9 , blaSHV and blaOXA. In respect to higher prevalence of blaTEM, our findings are similar with a study from India [ 33 ], whereas in other studies blaCTX-M was more common [ 30 , 31 ].…”

Transcriptomics Unravels Molecular Players Shaping Dorsal Lip Hypertrophy in the Vacuum Cleaner Cichlid, Gnathochromis Permaxillaris

“…The role of foxp1 in lip hypertophy might be linked to its function in inhibition of cell proliferation by repressing the transcription of growth/cell cycle stimulating factors [83][84][85]. The second predicted TF, tcf12, has been recently shown to be involved in hypertophy of frontal head soft tissues (nuchal hump) in another East African cichlid species [10], however, we did not nd its consistent expression difference between the lip regions by neither the RNA-seq nor the qPCR method in this study.…”

“…In order to select candidate reference genes, we used the transcriptome data and followed an approach that we have already used in our previous studies [10,102]. In brief, we rst identi ed the genes showing no expression difference (FDR = 1) between the lip regions for each species and ranked them according to their level of expression to attain those with highest expression.…”

“…Much less is known about the morphogenic molecular players and underlying signals of craniofacial soft tissues, that also exhibit varied adaptive peculiarities. In cichlid shes, the molecular mechanisms underlying exaggerated softtissue morphologies in lip, nose and nuchal hump phenotypes have been addressed only recently [5][6][7][8][9][10].…”

Expression variations in Ectodysplasin-A gene (eda) may contribute to morphological divergence of scales in Haplochromine cichlids

“…The primers were designed at conserved sequence of coding regions using the transcriptome data of several East African haplochromine species (Astatotilapia burtoni, Aulonocara baenschi, Cyrtocara moorii, Pundamilia nyererei, Metriaclima zebra, Simochromis diagramma, Tropheus duboisi, and Gnathochromis pfefferi) as well as two more distant species from different African cichlid tribes (Oreochromis niloticus and Neolamprologus brichardi) [7,[36][37][38][39]. The sequences from all the species were imported to CLC Genomic Workbench, version 7.5 (CLC Bio, Aarhus, Denmark), and after alignment, the exon/exon junctions were specified using the Astatotilapia burtoni annotated genome in the Ensembl database (http://www.ensembl.org) [40].…”