The completely identical HMG-box motif of CaSox4 gene from both male and female genomic DNA of the Chinese alligator (Alligator sinensis) was cloned and sequenced by degenerate primer PCR. Compared with the human and mouse SRY, CaSox4 revealed 51% and 57% nucleotide homology respectively and 49% and 55% amino acid identity respectively. CaSox4 belongs to subgroup C of the Sox gene family. The GC content is 86% in the HMG-box region of the CaSox4 gene. Blast analysis showed that the CaSox4 gene shares 100% amino acid identity with human Sox4, bird SoxLF4, turtle Sra4 and lizard CvSox4 genes. CaSox4 may be orthologous with the human Sox4 gene. This indicates that CaSox4 gene shows the remarkable evolutionary conservation during the evolution of Alligator sinensis. The extensive sequence conservation of the Sox4 gene between reptiles, mammals and birds suggests major functional constraints.
