Comparative analysis of type II classic cadherin mRNA distribution patterns in the developing and adult mouse somatosensory cortex and hippocampus suggests significant functional redundancy

The type II classic cadherin subfamily contains a number of extensively studied genes (cdh6, cdh8, cdh11); however, the expression and function of the other members have only been partially described. Here we employed reverse-transcription polymerase chain reaction (RT-PCR) and in situ hybridization to characterize cortical and hippocampal expression of all type II cadherins (with the exception of the nonneural Cdh5) in the developing and adult mouse brain. Many of these genes have ubiquitous mRNA distribution patterns throughout development, indicating high functional redundancy, which might be necessary for safe production of the strictly laminated structure of these regions. A few of the genes examined, however, exhibit a unique spatiotemporal pattern of expression, particularly during cortical development, indicating a potentially specific function. In the developing and adult hippocampus, almost all of these genes are strongly expressed in glutamatergic neurons of the CA1-CA3 pyramidal cell layer and the granular layer of the dentate gyrus. In contrast, there are significant expression differences within the GABAergic cells of the adult hippocampus. Our results indicate that selective expression of type II cadherins may generate a flexible cell-adhesion machinery for developing neurons to selectively bind to each other, but can also provide a high level of security due to the multiple overlaps in the expression domains. J. Comp. Neurol. 520:13871405, 2012. (c) 2011 Wiley Periodicals, Inc.