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-a γ-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, given reports that it might not independently engage in 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.

中文翻译：

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小鼠Pcdhg基因簇的CRISPR / Cas9审讯揭示了Pcdhgc4的关键同工型特异性作用。

哺乳动物的Pcdhg基因簇编码22个细胞粘附分子家族，即γ-原钙粘蛋白（γ-Pcdhs），对神经元存活和神经回路形成至关重要。其功能所需的同工型多样性（γ-Pcdh标志）的程度尚不清楚。我们使用了CRISPR / Cas9方法来减少同工型多样性，将每个Pcdhg可变外显子与合并的sgRNA靶向，以产生等位基因序列的26个小鼠品系，其中1至21个同工型通过引导位点处的离散indel破坏和/或较大的缺失/重排。对5个突变体系的分析表明，产后生存力和神经元存活率不需要同工型多样性。出人意料的是，鉴于有报道称它可能不独立参与反式相互作用，我们发现由Pcdhgc4编码的γC4是唯一的关键同工型。