Phylogenetic analysis and developmental expression of brp-like genes in amphioxus and zebrafish

Characterization and expression of AmphiBMP3 /3b gene in amphioxus Branchiostoma japonicum

Bone morphogenetic proteins (BMPs) are responsible for regulating embryo development and tissue homeostasis beyond osteogenesis. However, the precise biological roles of BMP3 and BMP3b remain obscure to a certain extent. In the present study, we cloned an orthologous gene (AmphiBMP3/3b) from amphioxus (Branchiostoma japonicum) and found its exon/intron organization is highly conserved. Further, in situ hybridization revealed that the gene was strongly expressed in the dorsal neural plate of the embryos. The gene also appeared in Hatschek's left diverticulum, neural tube, preoral ciliated pit and gill slit of larvae, and adult tissues including ovary, neural tube and notochordal sheath. Additionally, real-time quantitative polymerase chain reaction (RTqPCR) analysis revealed that the expression displayed two peaks at gastrula and juvenile stages. These results indicated that AmphiBMP3/3b, a sole orthologue of vertebrate BMP3 and BMP3b, might antagonize ventralizing BMP2 orthologous signaling in embryonic development, play a role in the evolutionary precursors of adenohypophysis, as well as act in female ovary physiology in adult.

Characterization of an evolutionarily conserved metallophosphoesterase that is expressed in the fetal brain and associated with the WAGR syndrome

Among the human diseases that result from chromosomal aberrations, a de novo deletion in chromosome 11p13 is clinically associated with a syndrome characterized by Wilms' tumor, aniridia, genitourinary anomalies, and mental retardation (WAGR). Not all genes in the deleted region have been characterized biochemically or functionally. We have recently identified the first Class III cyclic nucleotide phosphodiesterase, Rv0805, from Mycobacterium tuberculosis, which biochemically and structurally belongs to the superfamily of metallophosphoesterases. We performed a large scale bioinformatic analysis to identify orthologs of the Rv0805 protein and identified many eukaryotic genes that included the human 239FB gene present in the region deleted in the WAGR syndrome. We report here the first detailed biochemical characterization of the rat 239FB protein and show that it possesses metallophosphodiesterase activity. Extensive mutational analysis identified residues that are involved in metal interaction at the binuclear metal center. Generation of a rat 239FB protein with a mutation corresponding to a single nucleotide polymorphism seen in human 239FB led to complete inactivation of the protein. A close ortholog of 239FB is found in adult tissues, and biochemical characterization of the 239AB protein demonstrated significant hydrolytic activity against 2',3'-cAMP, thus representing the first evidence for a Class III cyclic nucleotide phosphodiesterase in mammals. Highly conserved orthologs of the 239FB protein are found in Caenorhabditis elegans and Drosophila and, coupled with available evidence suggesting that 239FB is a tumor suppressor, indicate the important role this protein must play in diverse cellular events.

Characterization and expression of two amphioxus DDAH genes originating from an amphioxus-specific gene duplication

Two dimethylarginine dimethylaminohydrolase (DDAH) homologous genes in amphioxus are identified and cloned. The phylogenetic analysis indicates two DDAHs in amphioxus originated by independent duplication specific in cephalochordate lineage. Analysis of AmphiDDAHa and AmphiDDAHb genomic structure shows their comparability with the DDAH in vertebrate and aboriginality which is consistent with animal classification. To explore the function relationship of AmphiDDAHa and AmphiDDAHb with AmphiNOS, the nitric oxide synthase homologue in amphioxus, we investigate the three genes expression patterns in embryos and adult tissues. The results indicate that these three genes possess different spatial and temporal expression patterns during embryogenesis. AmphiDDAHa transcripts are detected extensively in the differentiating ectoderm, mesendoderm in gastrula/early neurula, the developing and newly formed neural tube, somites, notochord, alimentary canal and epidermis at neurula stage, as well as in the differentiating pharynx and tailbud at early larval stage. While AmphiDDAHb is expressed in the differentiating non-neural ectoderm at the gastrla/early neurula stage, then locates abroad in the developing and formed neural tube, notochord, somites and alimentary canal. AmphiNOS is expressed weakly but widely from early neurula stage to at least 72-h larva stage. In adult, AmphiDDAHa and AmphiNOS share similar expression patterns in diverse adult tissues and cells such as the neural cord, gut, midgut diverticulum, wheel organ, gill, blood vessels, endostyle, oocytes and macrophages. But no expression of AmphiDDAHb is detected in tissues mentioned above. The results suggest that AmphiDDAHa and AmphiDDAHb should be two homologous genes with different functions in amphioxus. AmphiDDAHa may play a conserved role in the regulation of NO synthesis and immune defense, whereas AmphiDDAHb may mainly play the roles in the cell movement or differentiation of embryonic non-neural ectoderm cells during gastrulation and early neurulation.

The expression of AmphiTCTP, a TCTP orthologous gene in amphioxus related to the development of notochord and somites

The translationally controlled tumor protein (TCTP) is highly conserved and has been widely found in eukaryotic organisms. Here, we report the phylogenetic analysis and developmental expression of AmphiTCTP, a TCTP homologous gene in cephalochordate amphioxus. Phylogenetic analysis indicates that the putative protein of AmphiTCTP is close to its vertebrate orthologs. The mRNA of AmphiTCTP is found in fertilized eggs, early cleavage embryo and most of the early developmental stages by in situ hybridization and RT-PCR, but its expression is not detectable from late cleavage stage to mid-gastrula. The expression of AmphiTCTP in zygotes and early cleavage stages shows that AmphiTCTP may be a maternal gene. From the early neurula stage onward, AmphiTCTP transcript is localized in the presumptive notochord, presomitic mesoderm, and nascent somites. However, its expression is gradually down-regulated after the notochord and somites have been formed. The expression pattern of AmphiTCTP thus coincides with the differentiation of the notochord and somites, this suggests that AmphiTCTP may not be a housekeeping gene and may play an important role in mesoderm development.