Functional significance of isoform diversification in the protocadherin gamma gene cluster |
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Authors: | Weisheng V Chen Francisco J Alvarez Julie L Lefebvre Brad Friedman Chiamaka Nwakeze Eric Geiman Courtney Smith Chan Aye Thu Juan Carlos Tapia Bosiljka Tasic Joshua R Sanes Tom Maniatis |
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Institution: | Department of Biochemistry and Molecular Biophysics, Columbia University Medical Center, 701 W. 168 Street, New York, NY 10032, USA. |
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Abstract: | The mammalian Protocadherin (Pcdh) alpha, beta, and gamma gene clusters encode a large family of cadherin-like transmembrane proteins that are differentially expressed in individual neurons. The 22 isoforms of the Pcdhg gene cluster are diversified into A-, B-, and C-types, and the C-type isoforms differ from all other clustered Pcdhs in sequence and expression. Here, we show that mice lacking the three C-type isoforms are phenotypically indistinguishable from the Pcdhg null mutants, displaying virtually identical cellular and synaptic alterations resulting from neuronal apoptosis. By contrast, mice lacking three A-type isoforms exhibit no detectable phenotypes. Remarkably, however, genetically blocking apoptosis rescues the neonatal lethality of the C-type isoform knockouts, but not that of the Pcdhg null mutants. We conclude that the role of the Pcdhg gene cluster in neuronal survival is primarily, if not specifically, mediated by its C-type isoforms, whereas a separate role essential for postnatal development, likely in neuronal wiring, requires isoform diversity. |
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