Identification and Characterization of Maternally Localized Genes Involved in Neural Development of Xenopus laevis
Open AccessMany animals utilize maternal mRNAs to pre-pattern the embryo before the onset of zygotic transcription. In Xenopus laevis, numerous studies identified vegetal factors that specify the germ line, endoderm and dorsal axis, but there are few studies demonstrating roles for animal-enriched maternal mRNAs. Therefore, we carried out a microarray analysis to identify novel maternal transcripts enriched in animal blastomeres. We chose two of the identified transcripts for further study in gain-of-function and loss-of-function experiments. We identified 39 mRNAs isolated from animal blastomeres that are >4-fold enriched compared to vegetal pole mRNAs. We characterized the expression patterns for 14 of these that are of unknown function. We validated the microarray results for 8/14 genes of unknown function by qRT-PCR and for 14/14 genes by in situ hybridization assays. Because no developmental functions are reported yet, we provide the expression patterns for each of the 14 genes. Each is expressed in the blastula animal cap ectoderm, gastrula ectoderm and enriched in the neural ectoderm, neural crest (and derivatives) and cranial placodes (and derivatives). They have varying levels of later expression in some mesodermal tissues and rarely in endodermal tissues in tail bud through larval stages. We performed an initial functional characterization of two of these genes, WBP2NL and SMCR7L, and determined that both proteins are necessary for proper neural development. In the absence of WBP2NL, the neural plate expands at the expense of the neural crest and epidermis, whereas increased levels of WBP2NL cause the neural crest and epidermal domains of the embryonic ectoderm to expand at the expense of the neural plate. In the absence of SMCR7L, cells fail to express tissue-specific genes. Increased levels of SMCR7L cause embryonic ectoderm cells to express neural plate and border zone/neural crest fates instead of epidermal fates.Our studies demonstrate that novel animal-enriched maternal mRNAs are preferentially expressed in ectodermal derivatives, particularly neural ectoderm. However, they are later expressed in other germ layers. WBP2NL likely plays a role in maintaining the appropriate size of the neural ectoderm. SMCR7L may be required for progression from pluripotency to germ layer differentiation and may also play a role in maintenance of the appropriate size of the neural ectoderm. We hypothesize that study of the molecules involved in the earliest stages of neural specification in Xenopus will expand the list of known genes involved in these processes and serve as the basis for further inquiry. Understanding the molecular basis of neural development may also prove beneficial in improved diagnosis and treatment of a wide range of neural developmental disorders and neurodegenerative diseases. Furthermore, improving our understanding of the earliest factors that specify neural versus non-neural tissue will allow greater fidelity in manipulating stem cells or induced pluripotent stem cells to differentiate into neural tissue, ultimately improving yields of the desired cell type and improving the chances of clinical application of these cells.
- All rights reserved
Notice to Authors
If you are the author of this work and you have any questions about the information on this page, please use the Contact form to get in touch with us.