Novel animal pole-enriched maternal mRNAs are preferentially expressed in neural ectoderm

Many animals utilize maternal mRNAs to pre-pattern the embryo before the onset of zygotic transcription. In Xenopus laevis, vegetal factors 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 8-cell-stage animal blastomeres.

We identified 39 mRNAs isolated from 8-cell animal blastomeres that are >4-fold enriched compared to vegetal pole mRNAs. We characterized 14 of these that are of unknown function. We validated the microarray results for 8/14 genes 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 animal hemisphere of unfertilized eggs, 8-cell animal blastomeres, and diffusely in blastula animal cap ectoderm, gastrula ectoderm and neural ectoderm, neural crest (and derivatives) and cranial placodes (and derivatives). They have varying later expression in some mesodermal and endodermal tissues in tail bud through larval stages.

Novel animal-enriched maternal mRNAs are preferentially expressed in ectodermal derivatives, particularly neural ectoderm. However, they are later expressed in derivatives of other germ layers.