Cell‐specific Glycomic and Signaling Alterations Associated with Human Ganglioside Deficiency

Salt & Pepper Syndrome (S&PS) is an autosomal recessive neurological disorder characterized by seizures, severe intellectual disability, choreoathetosis, dysmorphic facial features, and altered skin pigmentation. S&PS is caused by a mutation in the ST3GAL5 gene that encodes GM3 synthase, a glycosphingolipid‐specific sialyltransferase. ST3GAL5 synthesizes GM3 ganglioside by adding sialic acid to lactosylceramide. Both GM3 and ST3GAL5 are highly enriched in neural tissues. S&PS fibroblasts completely lack GM3 and comprehensive glycomic analysis revealed collateral alterations in N‐linked, O‐linked, and GSL glycans in comparison to normal fibroblasts. S&PS and normal fibroblasts were reverted to pluripotency and the resulting induced pluripotent stem cells (iPS cells) were subsequently differentiated to neural crest cells (NC cells) to investigate neural specific glycosylation and signaling alterations associated with loss of GM3. Complete loss of GM3 was recapitulated in the S&PS iPS and NC cells. N‐linked glycosylation was uniquely altered in S&PS NC cells, resulting in greatly increased abundance of high‐mannose glycans. Since glycosphingolipid abundance and glycoprotein glycosylation both modulate receptor signaling in numerous contexts, we assessed the activity of a spectrum of receptor tyrosine kinase pathways by antibody array. A decrease in ErbB3 phosphorylation was detected in the S&PS NC cells in comparison to normal cells. Western blot analysis also showed a sharp decrease in ErbB3 receptor expression as well as an increase in EGFR expression during the course of differentiation of S&PS iPS to NC cells. S&PS iPS cells provide a novel platform to investigate the influence of glycosphingolipids on cell signaling in specific cell types. Support or Funding Information NIGMS/NIH