VPA mice showed increased dendritic spine density.

<p>Cortical neuron cultures were obtained on E18 from fetuses prenatally exposed to SAL or VPA on E13, and the cells were maintained until DIV 19–20. (<i>n</i> = 3 mice for each group, <i>n</i> = 3–6 cells for each mouse, 3–6 branches were analyzed per cell.) <b>(A)</b> Representative fluorescence images of dendritic spines in primary neuron cultures. <b>(B)</b> Quantification of spine density of spine density on secondary dendrites 50–100 μm away from the center of the soma. VPA mice exhibited a significant increase in spine density. (* significantly different among groups, *** <i>p</i> < 0.001, <i>n</i> = 18 for SAL, <i>n</i> = 13 for VPA).</p

VPA mice showed physical and anatomical changes.

<p><b>(A-D)</b> Body and brain weight was decreased in VPA mice on E18 and P13. <b>(E)</b> Representative pictomicrographs of Nissl staining and H&E staining of the hippocampus. Arrows indicate hypocellularity in the CA1-subiculum region of the hippocampus. Scale bar indicates 500 μm. (<b>A-D</b> * Significantly different among groups, ** <i>p</i> < 0.01, *** <i>p</i> < 0.001, <i>n</i> = 9 for SAL, n = 10 VPA for behavioral tests.)</p

VPA mice showed decreased PTEN expression in multiple brain areas.

<p>Representative immunofluorescence images of CA1, CA3, DG of the hippocampus, and cortex stained with PTEN (red), MAP2 (green), DAPI (blue). Scale bar indicates 50 μm.</p

VPA mice showed altered PTEN and p-AKT/AKT ratio in the brain.

<p>The protein level of PTEN and p-AKT in the hippocampus and cerebral cortex was examined by western blotting. <b>(A-D)</b> Representative blots of p-AKT, AKT, PTEN, and β-actin in the hippocampus and cortex at E18 and P13. <b>(E-F)</b> Densitometric analysis of western blots. Phosphorylated-AKT expression was normalized by AKT and PTEN expression was normalized by β-actin. (* significantly different from SAL, * <i>p</i> < 0.05, ** <i>p</i> < 0.01, *** <i>p</i> < 0.001, <i>n</i> = 4 for E18 SAL, E18 VPA, and P13 SAL, <i>n</i> = 8 for P13 VPA).</p

SLC38A8 mutations result in arrested retinal development with loss of cone photoreceptor specialisation.

Foveal hypoplasia, optic nerve decussation defects and anterior segment dysgenesis is an autosomal recessive disorder arising from SLC38A8 mutations. SLC38A8 is a putative glutamine transporter with strong expression within the photoreceptor layer in the retina. Previous studies have been limited due to lack of quantitative data on retinal development and nystagmus characteristics. In this multi-centre study, a custom-targeted next generation sequencing (NGS) gene panel was used to identify SLC38A8 mutations from a cohort of 511 nystagmus patients. We report 16 novel SLC38A8 mutations. The sixth transmembrane domain is most frequently disrupted by missense SLC38A8 mutations. Ninety percent of our cases were initially misdiagnosed as PAX6-related phenotype or ocular albinism prior to NGS. We characterized the retinal development in vivo in patients with SLC38A8 mutations using high-resolution optical coherence tomography. All patients had severe grades of arrested retinal development with lack of a foveal pit and no cone photoreceptor outer segment lengthening. Loss of foveal specialization features such as outer segment lengthening implies reduced foveal cone density, which contributes to reduced visual acuity. Unlike other disorders (such as albinism or PAX6 mutations) which exhibit a spectrum of foveal hypoplasia, SLC38A8 mutations have arrest of retinal development at an earlier stage resulting in a more under-developed retina and severe phenotype