Expression analysis of Runx3 and other Runx family members during Xenopus development

Runx genes encode a family of proteins defined by the highly conserved runt DNA-binding domain. Studies in several organisms have shown that these transcription factors regulate multiple aspects of embryonic development and are responsible for the pathogenesis of several human diseases. Here we report the cloning and expression of Runx3 during Xenopus development and compare its expression pattern to other Runx family members, Runx1 and Runx2, and to Cbfb, the obligatory binding partner of Runx proteins. Using in situ hybridization in the whole embryo and on sections we show that Runx3 is coexpressed with Runx1 in the hematopoietic lineage and in Rohon-Beard sensory neurons. In contrast Runx3 and Runx2 are co-expressed in craniofacial cartilage elements. Runx3 shows also unique expression domains in a number of derivatives of the neurogenic placodes, including the ganglia of the anteroposterior and middle lateral line nerves, and ganglia of the trigeminal, glossopharyngeal, facial and vagal nerves. These observations suggest a critical role for Runx3 in the development of cranial sensory neurons, while in other tissues its co-expression with Runx1 or Runx2 may signify functional redundancy between these family members.