Functional Study Of Dmrt5 During Xenopus Tropicalis Early Embryogenesis

DMRT/Dmrt (Doublesex and Mab-3 Related Transcription factor) genes encode a large family of transcription factors related to Drosophila melanogaster doublesex (Dsx) and Caenorhabditis elegans Mab3, which is characterized by a unique zinc finger like DNA-binding motif known as the DM domain. So far, eight Dmrt genes have been identified in vertebrate and most of the members have been implicated in sexual differentiation and determination since their specially expresion in gonads. However, some Dmrt genes also involve in other developmental processes such as the development of somites, neurogenesis. Our previous study has found that Xenopus laevis Dmrt4 is initially expressed in the anterior neural ridge and then becomes progressively restricted to part of the telencephalon and the olfactory placode epithelium. Functional studies by overexpression and knockdown through antisense morpholino oligonucleotide or inhibitory mutant reveal that Dmrt4 is an important regulator of neurogenesis in the olfactory system upstream of neurogenin and Xetf2. Nevertheless, the efficiency of Dmrt4 gene knockdown keeps low, which leads us to assume that there might be some other Dmrt homologous playing redundant roles during the process of the olfactory neurogenesis.In this study, we report the cloning, temproal-spatial expression pattern and functional analysis of Xenopus tropicalis Dmrt5, to illustrate whether Dmrt5 also has important functions that similar to Dmrt4 during olfactory neurogenesis:Firstly, the full length cDNA of Dmrt5 was cloned by RT-PCR from X.tropicalis embryos. Sequence and phylogenetic analysis were perform to ensure that we get the right clone.Secondly, RT-PCR and whole mount in situ hybridization were performed to establish the temproal-spatial expression pattern of Dmrt5 during early embryogenesis. And data shows that Dmrt5 might be a maternal factor and the zygotic expression of Dmrt5 is initiated around midblastu stage. During neurula stage, the expression of Dmrt5 is restrict to the head area especially to the anterior neural ridge (the later olfactory primordium and telencephalon) and the ventral midbrain.Thirdly, caudalizing factors, such as Fgf, Wnt, RA can inhibit the expression of Dmrt5,which make its anterior expression, is corresponding to the hypothesis of neural induction. At last, Interference with Dmrt5 function by injection of a morpholino oligonucleotide or an inhibitory mutant resulted in the loss of the olfactory expression of Neurogenin and Xebf2, which is similar to Dmrt4. And even more, we found that loss of Dmrt5 function can also repress the expression of Dmrt4.From all above data we speculate that Dmrt5 could regulate olfactory neurogenesis similar to Dmrt4 and this kind of regulation could be achieved via Dmrt4.