THE ROLE OF CYYR1 GENE DURING ZEBRAFISH DEVELOPMENT IN HH-MEDIATED MYOGENESIS AND NEUROMASTS DIFFERENTIATION

CYYR1 (Cysteine/tyrosine-rich 1) cloned on human chromosome 21 defines a new family of highly conserved vertebrate-specific genes1,2. The analysis of the human locus revealed the presence of a multitranscript-system that includes alternative spliced isoforms and one ncRNA gene overlapping CYYR1 in antisense orientation3. Original results suggest the need of further investigations in order to verify a putative role of CYYR1 in the tumorigenic process, caused by dysfunction of cell differentiation and possibly related to the Hh pathway4; to date, the specific function of the CYYR1 product is still unknown. The zebrafish cyyr1 is present in single copy and maintains almost 58% of identity with human protein therefore, we decided to perform a full characterization of cyyr1 expression and function using zebrafish as model system. WISH approach defined a broad expression in central nervous system (CNS), somites and muscles during somitogenesis and at 24-48 hpf. The cyyr1 knock-down with two different MOs targetting the ATG and the first splice-site of the transcript, affected both CNS and muscle development with a significant rescue in embryo co-injected with cyyr1 mRNA. Defects were also evident in ciliated cells of neuromast of the lateral line. Morphologically, the cyyr1-MOs injected embryos display some features of embryos inhibited for the Hh pathway through injection of the lefty mRNA and cyyr1 expression was significantly inhibited following Hh inhibition. Interestingly, the injection of cyyr1 mRNA was able to partially rescue Hh-defective phenotype in embryos at 24 hpf. Results obtained through immunofluorescent staining, qPCR and western blotting, support a role for cyyr1 in primary myogenesis probably downstream of Hh pathway. 1. Vitale L et al. Gene 2002, 290:141-51. 2. Casadei R et al. Gene Expr Patterns 2011, 11: 271-6. 3. Casadei R et al. Mol Biol Rep 2014, 41:6025-38. 4. Xu J et al. Genetics 2006, 174:735-52.