Identification and functional analysis of novel genes expressed in the Anterior Visceral Endoderm

During early development, the correct establishment of the body axes is a critical step. The anterior pole of the mouse embryo is established when Distal Visceral Endoderm (DVE) cells migrate to form the Anterior Visceral Endoderm (AVE). Asymmetrical expression of Lefty1, Cerl and Dkk determines the direction of DVE migration and the future anterior side. Besides being implicated in the establishment of Anterior-Posterior axis the AVE has also been correlated with anterior neural specification. In order to better understand the role of the AVE in these processes, this cell population was isolated using a cerlP-EGFP transgenic mouse line, and a differential screening was performed using Affymetrix GeneChip technology. From this differential screening, 175 genes were found to be upregulated in the AVE, whereas 35 genes were upregulated in the Proximal-posterior sample. Using DAVID, here we characterize the AVE cell population regarding cellular component, molecular function and biological processes. Among the genes that were found to be upregulated in the AVE, several novel genes with expression in the AVE were identified. Four of the identified transcripts displaying high-fold change were further characterized by in situ hybridization in early stages of development in order to validate the screening. From those four selected genes, ADTK1 was chosen to be functionally characterized by targeted inactivation in ES cells. ADTK1 encodes for an unknown serine/threonine kinase. ADTK null mutants present short limbs and defects in the eye and ear. Taken together, these data point to the importance of reporting novel genes present in the AVE.

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Gonçalves L, Filipe M, Marques S, Salgueiro AM, Becker JD, Belo JA