Homeobox gene Prx3 expression in rodent brain and extraneural tissues

Different cDNA clones encoding a rat homeobox gene and the mouse homologue OG-12 were cloned from adult rat brain and mouse embryo mRNA, respectively. The predicted amino acid sequences of the proteins belong to the paired-related subfamily of homeodomain proteins (Prx homeodomains). Hence, the gene was named Prx3 and the mouse and rat genes are indicated as mPrx3 and rPrx3, respectively. In the mouse as well as in the rat, the predicted Prx3 proteins share the homeodomain but have three different N termini, a 12-aa residue variation in the C terminus, and contain a 14-aa residue motif common to a subset of homeodomain proteins, termed the “aristaless domain.” Genetic mapping of Prx3 in the mouse placed this gene on chromosome 3. In situ hybridization on whole mount 12.5-day-old mouse embryos and sections of rat embryos at 14.5 and 16.5 days postcoitum revealed marked neural expression in discrete regions in the lateral and medial geniculate complex, superior and inferior colliculus, the superficial gray layer of the superior colliculus, pontine reticular formation, and inferior olive. In rat and mouse embryos, nonneuronal structures around the oral cavity and in hip and shoulder regions also expressed the Prx3 gene. In the adult rat brain, Prx3 gene expression was restricted to thalamic, tectal, and brainstem structures that include relay nuclei of the visual and auditory systems as well as other ascending systems conveying somatosensory information. Prx3 may have a role in specifying neural systems involved in processing somatosensory information, as well as in face and body structure formation.