The clustered protocadherin genes show altered expression levels in Smchd1 mutants. ( A ) The clustered protocadherin genes (Pcdhα, Pcdhβ, and Pcdhγ) lie in a cluster on mouse Chr:18 and are expressed in a unique manner. Transcripts from the Pcdhα and Pcdhγ genes show alternative first exons that are monoallelically expressed in a random combinatorial manner and spliced to downstream exons that are biallelically expressed. The Pcdhβ genes exist as individual genes. ( B ) The expression levels of the protocadherin genes (Pcdhα, Pcdhβ, and Pcdhγ) were quantified by qRT-PCR using RNA derived from whole adult male mouse brains. The synthesis of first-strand cDNA was primed with a cocktail of the reverse primers used for qRT-PCR. In each case, the qRT-PCR signal was normalized relative to that of Rala and plotted relative to the corresponding Smchd1+/+ sample. Statistical analysis was performed using the t test. ** P < 0.01 and * P < 0.05 compared with wildtype. Error bars indicate standard error.