Figure 1. SYNGAP1 is expressed in human radial glia progenitors and colocalizes with the tight junction protein TJP1.

A. SynGO analysis results from D.I.V. 7 corrected organoids proteomic data set. 21 organoids from 3 independent experiments were analyzed.

B. Two-month-old control organoid stained for the neural progenitor marker SOX2, the tight junction protein TJP1 and SYNGAP1. SYNGAP1 is highly expressed at the ventricular wall. White box indicates the region of interest selected for the merged images showing colocalization of the nuclear marker DAPI, TJP1, and SYNGAP1.

C. Schematic for the protein interaction network of SYNGAP1 protein. Analysis performed on 21 organoids from 3 independent experiments at D.I.V. 7. The tight junction protein TJP1 is highlighted in pink.

D. Two-month-old Patient^Corrected organoid stained for the radial glial marker NESTIN, the neuronal marker MAP2, and SYNGAP1. SYNGAP1 is highly expressed within mature MAP2 positive neuronal populations outside of the VZ, as well as in NESTIN positive cells at the ventricle wall. White box indicates the region of interest selected for the merged images showing colocalization of DAPI, SYNGAP1, and NESTIN positive cells.

E. Schematic of key functional domains within the SYNGAP1 alpha 1 isoform and TJP1 proteins including representative spectra of the two identified peptides for the alpha1 isoform.

F. Immunohistochemical staining of the human brain at gestational week 17. Tissue section is from the prefrontal cortex at the level of the lateral ventricle and medial ganglionic eminence. White box indicates the region of interest selected for the merged images showing colocalization of DAPI, TJP1, and SYNGAP1.