Structure and function of a sea urchin orthodenticle-related gene (HpOtx)

Two distinct types of orthodenticle-related proteins (HpOtxE/L) have been implicated as transcription activators of the aboral ectoderm-specific arylsulfatase (Ars) gene. Here, we describe the structure of HpOtx gene and present evidence that mRNAs of HpOtxE/L are transcribed from a single HpOtx gene by altering the transcription start site and by alternative splicing. By transactivation experiments, we have also demonstrated that HpOtxL activates the Ars promoter in the gastrula-stage embryo.