A putative Xenopus Rho-GTPase activating protein (XrGAP) gene is expressed in the notochord and brain during the early embryogenesis.

The GTPase activating proteins (GAPs) specific for Rho family GTPases serve as either negative regulators or downstream effectors of Rho-GTPases through their ability to interact with specific Rho proteins and additional cytosolic factors. Here we report cloning and expression of a novel Xenopus Rho-GTPase activating protein cDNA designated as XrGAP. It encodes a protein of 1902 amino acids that contains a PDZ domain, a PH motif and a Rho-GAP domain. Sequence analysis shows that XrGAP protein shares 60% overall amino acids identity with a human Rho-GTPase activating protein (ARHGAP10) that is highly expressed in the brain. Northern blot and RT-PCR analysis show that a single XrGAP transcript is maternally expressed and gradually decreases afterwards. Whole-mount in situ hybridization shows that maternal XrGAP transcripts are specifically expressed in the animal hemisphere of the eggs and blastula stage embryos. During gastrulation, XrGAP is detected in the prospective neuroectoderm and the mesoderm. At neurula stages, the expression is in the neural regions including the neural folds, eye analgen and neural crest cells, and subsequently restricted to notochord, developing brain, spinal cord, eye, branchial arches, and otic vesicle at tailbud stages.