Cadherin-19 expression is restricted to myelin-forming cells in the chicken embryo

We cloned chicken cadherin-19 that demonstrates high similarity to human and rat cadherin-19. Chicken cadherin-19 is a type II classic cadherin that is located on the long arm of chicken chromosome 2 and is composed of 13 exons and 12 introns. The expression profile of cadherin-19 was analyzed by semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ hybridization during chicken embryonic development. Its expression starts at E2.5, then gradually increases to reach a peak at E20. In contrast to previous results obtained in rat, chicken cadherin-19 is expressed both in Schwann cells and oligodendrocytes, also at late stages of development. We found no other cell type positive for cadherin-19 in the chicken embryo throughout development, suggesting that cadherin-19 is selectively expressed by myelin-forming cells and might play a role in myelin formation. The sequence of cadherin-19 shares high similarity with that of cadherin-7 and cadherin-20, and the three genes form a cluster on chromosome 2. Their expression patterns, however, are rather distinct although partial overlap is observed. For example, cadherin-19 and cadherin-7 are co-expressed by Schwann cells but not by oligodendrocytes. Moreover, a subset of interneurons express cadherin-7 but not cadherin-19 or cadherin-20. Despite their close genetic relation, the three cadherins have acquired functions in rather different cell types during nervous system development.