CYYR1 (Cysteine/tyrosine-rich 1) cloned on HC21 defines a family of highly conserved
vertebrate-specific genes. The human locus is characterized by a multitranscript-system
including at least six alternative spliced isoforms. To date, the function of the CYYR1 product
is still unknown even if original results suggest its possible involvement in myogenesis
differentiation with a putative role in the tumorigenic process related to the Hh pathway.
Zebrafish cyyr1 orthologue is present in single copy and the predicted protein maintains
almost 58% of identity with human protein. By WISH approach, we show a cyyr1 broad
expression in central nervous system (CNS), somites and muscles during development. The
protein seems to localize in plasma and even nuclear membranes.
We perform cyyr1 knock-down with two different approaches: microinjection of morpholino
oligos targeting the ATG and the first splice-site of the transcript, and the generation of cyyr1
null fish through CRISPr/Cas9 technique. Defects in heart and muscle development with a
significant rescue in embryo co-injected with cyyr1 mRNA, were observed in morphants,
while cyyr1 mutants analyses confirmed morphological and molecular weakness in heart.
Dysregulation of Nodal and/or Hedgehog (Hh) pathways in zebrafish decreased cyyr1
expression and the injection of cyyr1 mRNA was able to partially rescue Hh-defective
phenotype in embryos. In order to verify a putative role of CYYR1 in the process caused by
dysfunction of cell differentiation we performed experiments in rhabdomyosarcoma cell
lines showing an inverse correlation between CYYR1 expression and the range of
differentiating capabilities of these cells. Interestingly, treatments with inhibitors of Hh allow
us to confirm a correlation between CYYR1 and this pathway
