Fine tuning of the WNT signalling pathway during zebrafish craniofacial development.

EZEQUIEL MARGARIT; PABLO ARMAS; NICOLAS GARCÍA SIBURU; NORA B CALCATERRA

Valparaíso

Simposio; Latin American zebrafish network Symposium; 2014

LAZEN-Latin American Zebrafish Network

Cellular nucleic acid binding protein (CNBP) is a small and highly conserved protein that binds single-stranded nucleic acids and may act as a nucleic acid chaperone. Data collected so far suggests that CNBP participates in the control of cell proliferation and threshold levels of the protein are necessary for proper craniofacial development. CNBP seems to control the balance between cell proliferation and cell death of craneal neural crest cells; however the molecular targets and celular processes that involve CNBP remain elusive. Monohybrid assays in yeast using mouse and zebrafish genomic libraries allowed us to identify and validate tbx2, smarca5 and wnt5 as in vivo molecular targets of CNBP during zebrafish embryonic development. It was also posible to identify the DNA-consensus binding sequence of CNBP, which was then employed to search for putative CNBP target genes present in the human, mouse, chicken, Xenopus laevis and zebrafish genomes. Apart from being related to embryonic development, no particular functional relationship was observed amongst the 16 identified genes, except for cdk14, ptk7 and tcf7l2, which are members of the ancient Wnt signalling pathway. Thereby, we wondered if CNBP plays a role on the expression of WNT signalling players and pathway regulation. Over-expression and depletion of CNBP in zebrafish developing embryos showed that CNBP up-regulates the transcriptional expression of cdk14, ptk7 and tcf7l2, which is in turn reflected in c-myc and axin2 expression control. Besides, abundance of CNBP affected the expression of its targets in dose-dependent fashion. A recent work reported that cnbp is one of the cis-distant enhancers participating in the fine-tuning of craniofacial morphology. Thus, it is tempting to speculate that polymorphisms in cis-elements controlling the expression of cnbp may lead to subtle changes in the dose or gradient of the protein with biological or even pathological consequences in craniofacial development.