Down-regulation of coasy, the gene associated with NBIA-VI, reduces Bmp signaling, perturbs dorso-ventral patterning and alters neuronal development in zebrafish.

Deepak Khatri,Eugenio Monti,Dario Finazzi,Natascia Tiso,Nicola Facchinello,Daniela Zizioli,Maurizio Memo,Sara Vezzoli,Giuseppe Borsani,Alessandra Gianoncelli

doi:10.1038/srep37660

Abstract

Mutations in Pantothenate kinase 2 and Coenzyme A (CoA) synthase (COASY), genes involved in CoA biosynthesis, are associated with rare neurodegenerative disorders with brain iron accumulation. We showed that zebrafish pank2 gene plays an essential role in brain and vasculature development. Now we extended our study to coasy. The gene has high level of sequence identity with the human ortholog and is ubiquitously expressed from the earliest stages of development. The abrogation of its expression led to strong reduction of CoA content, high lethality and a phenotype resembling to that of dorsalized mutants. Lower doses of morpholino resulted in a milder phenotype, with evident perturbation in neurogenesis and formation of vascular arborization; the dorso-ventral patterning was severely affected, the expression of bone morphogenetic protein (Bmp) receptors and activity were decreased, while cell death increased. These features specifically correlated with the block in CoA biosynthesis and were rescued by the addition of CoA to fish water and the overexpression of the human wild-type, but not mutant gene. These results confirm the absolute requirement for adequate levels of CoA for proper neural and vascular development in zebrafish and point to the Bmp pathway as a possible molecular connection underlining the observed phenotype.

Highlights

Mutations in Coenzyme A (CoA) synthase (COASY) were found in patients with clinical manifestation and magnetic resonance imaging (MRI) signs typical of Neurodegeneration with Brain Iron Accumulation (NBIA) (MIM 615643)[8,9]
Analysis of the UniGene database allowed the retrieval of 25 Expressed Sequence Tag (EST) derived from coasy zebrafish transcripts, indicating that the gene is expressed in different tissues and developmental stages
Since our previous findings revealed that pank[2] down-regulation affected the formation of the normal vasculature, we extended our analysis by investigating the requirement for coasy during vascular system development

Summary

Introduction

Mutations in COASY were found in patients with clinical manifestation and magnetic resonance imaging (MRI) signs typical of NBIA (MIM 615643)[8,9]. The use of a transgenic bone morphogenetic protein (Bmp)-reporter line evidenced a relevant reduction of bmp activation, associated with lower levels of different Bmp-receptor isoforms, a severe perturbation in antero-posterior patterning, somitogenesis, and neurogenesis, as evidenced by in situ hybridization with a variety of markers This complex phenotype was rescued by treatment of embryos with CoA in fish water or by injection of the human COASY mRNA. The study demonstrates the essential role of coasy and CoA biosynthesis in normal zebrafish development and indicates that neurogenesis and Bmp signaling are sensitive to partial CoA depletion This piece of information could be of relevance for the understanding of the specific phenotype and pathogenic process associated with mutations of the human COASY gene

Methods

Results

Conclusion