Cloning and developmental expression of zebrafish GTP cyclohydrolase I

GTP cyclohydrolase I (GCH) catalyses the conversion of GTP to dihydroneopte rin triphosphate, initiating the pteridine pathway. The final product tetra hydrobiopterin (H(4)biopterin) is the cofactor for neurotransmitter synthes is and for tyrosine supply during melanogenesis. Sepiapterin accumulates as a pigment. We cloned the zebrafish gch cDNA, which encodes a protein highl y homologous to other vertebrate sequences and characterised the recombinan t enzyme. By in situ hybridisation, we found that gch is expressed in both the melanophore and xanthophore lineages during early development. gch-expr ession almost disappears after 3 days post-fertilisation (dpf), despite fur ther sepiapterin synthesis. gch-transcripts are also located in catecholami nergic neurons, within the central nervous system and in the arch-associate d neurons. (C) 2001 Published by Elsevier Science Ireland Ltd.