Molecular cloning, expression and regulation of the avian tubby-like protein 1 (tulp1) gene.

The tubby-like protein 1 (tulp1) gene is a member of the tubby multigene family which includes tub, tulp1, tulp2 and tulp3. Human and mouse tulp1 genes were cloned and mutations in tulp1 have been implicated in retinitis pigmentosa in man. Here we report on the cDNA cloning of the chicken tulp1 homologue and its protein product deduced from the nucleotide sequence. The chicken Tulp1 protein comprises 358 amino acids with a calculated molecular mass of 40 kDa. The overall structure of Tub and Tulp proteins, exemplified by the highly conserved C-terminal domain of 255 amino acids and the signature motif KLACE, is also preserved in chicken Tulp1. Phylogenetic analysis demonstrates that chicken tulp1 cDNA and protein are closely related to human and mouse tulp1. In addition, chicken tulp1 mRNA is abundantly expressed in retina similar to tulp1 expression in human and mouse. Two tulp1-specific transcripts of 2 and 3 kb in size were identified that showed differential regulation during embryonic and postnatal development. Finally, tulp1 mRNA was found to be expressed in chicken erythroid cells and upregulated by ligand-activated thyroid hormone receptor (TR alpha/c-erbA).