RT Journal Article SR Electronic T1 CRISPR/Cas9 interrogation of the mouse Pcdhg gene cluster reveals a crucial isoform-specific role for Pcdhgc4 JF bioRxiv FD Cold Spring Harbor Laboratory SP 739508 DO 10.1101/739508 A1 Andrew M. Garrett A1 Peter J. Bosch A1 David M. Steffen A1 Leah C. Fuller A1 Charles G. Marcucci A1 Alexis A. Koch A1 Preeti Bais A1 Joshua A. Weiner A1 Robert W. Burgess YR 2019 UL http://biorxiv.org/content/early/2019/08/19/739508.abstract AB The mammalian Pcdhg gene cluster encodes a family of 22 cell adhesion molecules, the gamma-Protocadherins (γ-Pcdhs), critical for neuronal survival and neural circuit formation. The extent to which isoform diversity–aγ-Pcdh hallmark–is required for their functions remains unclear. We used a CRISPR/Cas9 approach to reduce isoform diversity, targeting each Pcdhg variable exon with pooled sgRNAs to generate an allelic series of 26 mouse lines with 1 to 21 isoforms disrupted via discrete indels at guide sites and/or larger deletions/rearrangements. Analysis of 5 mutant lines indicates that postnatal viability and neuronal survival do not require isoform diversity. Surprisingly, as it is the only γ-Pcdh that cannot independently engage in homophilic trans-interactions, we find that γC4, encoded by Pcdhgc4, is the only critical isoform. Because the human orthologue is the only PCDHG gene constrained in humans, our results indicate a conserved γC4 function that likely involves distinct molecular mechanisms.