PhD Candidate Stanford Institute for Stem Cell Biology and Regenerative Medicine Menlo Park, California, United States
Abstract: Focal Cortical Dysplasia Type Ia (FCD 1a) is a category of drug-resistant epilepsy that is difficult to diagnose and frequently requires surgery for treatment. A common hallmark of FCD 1a is hyper-columnar radial organization of neurons. Interestingly, the X-linked gene SLC35A2, which has been implicated in a variety of rare brain disorders, has been found in over 29% of FCD 1a cases. SLC35A2 encodes for a UDP-galactose translocator, but its specific role in cortical development and epilepsy remains unknown. We seek to model malformations in cortical development caused by SLC35A2 in order to understand the role of the gene in cortical development. Given the importance of proteoglycans which play a critical role in neuronal migration during development, we hypothesize that SLC35A2 is crucial to the proper production of proteoglycans and neuronal migration in the developing brain. Furthermore, we hypothesize that somatic mutations in SLC35A2 must occur in neural stem cells whose progenitors will go on to abnormally migrate and generate the disease phenotype. To test this hypothesis, we generated a human induced pluripotent stem cell (iPSC) line with the SLC35A2 locus knocked out and subsequently generated in vitro cortical organoids. We found that SLC35A2 is required for the generation of neural stem cells, and brain organoids generated from the SLC35A2KO iPSC line exhibited reduced ability to form neural rosette structures when examined using immunofluorescence (IF). We then used lentiviral mediated delivery of SLC35A2 short hairpin RNA (shRNA) to the cortical organoids to accurately model the induction somatic mutation during development. This is a crucial first step to model the cortical malformations that arise due to SLC35A2 mutations. These results will enable further investigation into the specific mechanism of SLC35A2 causing FCD 1a. In a broader context, this study can offer insights into human brain development and the function of SLC35A2, potentially guiding new therapeutic approaches for related glycosylation related disorders.
