Studies On Cloning And Expression Of Dax1Gene In Branchiostoma Belcheri Tsingtauense

Branchiostoma is a representative of cephalochordate. It has a uniqueclassification status that lies between invertebrate and vertebrate. Branchiostoma playsan important role in evolutionary origins of vertebrate. The genome of Branchiostomadoes not undergo duplication. Therefore, it has caught great attention of biologists, andrecently seems to be a model to study evolution of vertebrate.Dax1is also called nr0b1，which is a member of the nuclear receptor superfamily.It was initially isolated from human. Abnormal duplication of human dax1causesmale-to-female dosage-sensitive sex reversal, while mutations in the gene areresponsible for X-linked adrenal hypoplasia congenita. Dax1also exists in theLamellibranchia, Pisces, Amphibia, Reptilia, Aves and Mammalia.Branchiostoma was firstly found by a zoologist in1774. However, dax1inBranchiostoma has not been reported. Branchiostoma belcheri tsingtauense was usedfor all experiments. Specific primers were designed from the conserved regions ofdax1sequences. The dax1cDNA was synthesized from total RNA using RACE. It is1536bp long, with a predicted ORF encoding a protein of292amino acids. The5’UTR and3’ UTR are216bp and441bp，respectively. The dax1DNA was amplifiedfrom genomic DNA using genome walking. DIG labeled cDNA probe was synthesizedby PCR. The probe is approximately250bp. In situ hybridization showed that dax1isexpressed in the gonad and gill, but not in the muscle. Dax1did not show an apparentsexually dimorphic pattern in our study.