| Summary: | <p>Abstract</p> <p>Background</p> <p>Vertebrate classic cadherins are divided into type I and type II subtypes, which are individually expressed in brain subdivisions (e.g., prosomeres, rhombomeres, and progenitor domains) and in specific neuronal circuits in region-specific manners. We reported previously the expression of <it>cadherin19 </it>(<it>cad19</it>) in Schwann cell precursors. <it>Cad19 </it>is a type II classic cadherin closely clustered on a chromosome with <it>cad7 </it>and <it>cad20</it>. The expression patterns of <it>cad7 </it>and <it>cad20 </it>have been reported previously in chick embryo but not in the developing and adult central nervous system of mammals. In this study, we identified rat <it>cad7 </it>and <it>cad20 </it>and analyzed their expression patterns in embryonic and adult rat brains.</p> <p>Results</p> <p>Rat cad7 protein showed 92% similarity to chick cad7, while rat cad20 protein had 76% similarity to <it>Xenopus </it>F-cadherin. Rat <it>cad7 </it>mRNA was initially expressed in the anterior neural plate including presumptive forebrain and midbrain regions, and then accumulated in cells of the dorsal neural tube and in rhombomere boundary cells of the hindbrain. Expression of rat <it>cad20 </it>mRNA was specifically localized in the anterior neural region and rhombomere 2 in the early neural plate, and later in longitudinally defined ventral cells of the hindbrain. The expression boundaries of <it>cad7 </it>and <it>cad20 </it>corresponded to those of region-specific transcription factors such as <it>Six3</it>, <it>Irx3 </it>and <it>Otx2 </it>in the neural plate, and <it>Dbx2 </it>and <it>Gsh1 </it>in the hindbrain. At later stages, the expression of <it>cad7 </it>and <it>cad20 </it>disappeared from neuroepithelial cells in the hindbrain, and was almost restricted to postmitotic cells, e.g. somatic motor neurons and precerebellar neurons. These results emphasized the diversity of <it>cad7 </it>and <it>cad20 </it>expression patterns in different vertebrate species, i.e. birds and rodents.</p> <p>Conclusion</p> <p>Taken together, our findings suggest that the expression of <it>cad7 </it>and <it>cad20 </it>demarcates the compartments, boundaries, progenitor domains, specific nuclei and specific neural circuits during mammalian brain development.</p>
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