POMGNT2 and neuromuscular disease caused by qualitative or quantitative defects of alpha-dystroglycan: Using the Pomgnt2-knockout (KO) mouse as a dystroglycanopathy model, we show that breaches of the pial basement membrane appeared at embryonic day 11.5, coinciding with the ectopic clustering of Cajal–Retzius cells and subplate neurons and prior to the migration onset of pyramidal neurons.