Figure 1: Excitatory postsynaptic structure and function of layer II/III pyramidal neurons from the primary somatosensory cortex of postnatal MPS IIIA mice is abnormal.

(A) Representative confocal images show an increase in PSD-95 puncta (red) in layer II/III of the primary somatosensory cortex in 21d (day-old) hypomorphic MPS IIIA (Sgsh^h/h) mice. Scale, 50 μm. Nuclei are stained with DAPI (blue). (B) Quantification of PSD-95 puncta in cortical layers I, II/III, and V of the primary somatosensory cortex of 21d unaffected Sgsh^+/h and Sgsh^h/h mice. Mean ± SEM. N = 5–6 animals per genotype. (C) Western blot for PSD-95 levels in cortical homogenate and synaptosome preparations from 21d unaffected and hypomorphic MPS IIIA mice. Band pixel intensities were measured in ImageJ and normalized to β-actin. Mean ± SEM. N = 3 animals per genotype, spanning 2 litters. (D) Representative maximum intensity projection z-stacks of dendritic segments from pyramidal neurons in layer II/III of the somatosensory cortex of 21d unaffected and hypomorphic MPS IIIA mice. (E) Quantification of dendritic spine head width and shaft length of pyramidal neurons in layer II/III of the somatosensory cortex of 21d unaffected and hypomorphic MPS IIIA mice. Mean ± SEM. N = 3 animals per genotype. (F) Quantification of dendritic spine type. Mean ± SEM. (G) Representative mEPSC recordings from pyramidal neurons in layer II/III of the somatosensory cortex of 21–22d unaffected and hypomorphic MPS IIIA mice. Scale bar depicts 20 pA, 200 msec. (H) Cumulative probability distributions of all mEPSC event amplitudes recorded from pyramidal neurons in layer II/III of the somatosensory cortex of 21–22d unaffected and hypomorphic MPS IIIA (mice, depicting reduced amplitude in mutant animals. N = 1883, 2362 events. p < 0.001, Kolmogorov-Smirnov test. (I) Mean mEPSC amplitude. Mean ± SEM. (J) Mean mEPSC inter-event interval. N = 5 mice per genotype, 16–19 cells total. p = 0.015, Student’s t test.