Loss of function of Sphingosine-1-phosphate lyase (SGPL1) is associated with a multi-systemic disorder consisting of primary adrenal insufficiency and steroid-resistant nephrotic syndrome, with a third of patients manifesting ichthyosis. S1P lyase carries out the final degradative step in the sphingolipid pathway, irreversible cleavage of sphingosine-1-phosphate (S1P). Upstream accumulation of sphingolipid intermediates, such as ceramides and sphingosine, which are integral in the formation of the lamellar lipid bilayer, have been identified in multiple SGPL1 KO cell types. Furthermore, high levels of S1P leads to increased intracellular calcium, a prerequisite for keratinocyte differentiation.To elucidate the disease mechanism and the role SGPL1 plays in the skin barrier we established CRISPR-Cas9 SGPL1 knock-out and a lentiviral induced SGPL1 overexpression in nTERT immortalised keratinocytes and then organotypic skin equivalents. RNASeq analysis demonstrated that both loss and overexpression of S1P lyase leads to differential expression of genes involved in keratinisation, calcium signalling and oxidative phosphorylation. Furthermore, in S1P depleted media, loss of S1P lyase significantly reduced keratinocyte proliferation and migration. In a 3D environment both the loss and overexpression of S1P lyase resulted in a thickened stratum corneum with the KO models displaying premature terminal differentiation and irregular calcium-dependent intracellular junctions.These results demonstrate, for the first time, how loss of S1P lyase causes an imbalance of sphingolipids within keratinocytes, leading to defects in differentiation and the ichthyosis seen in patients. The SGPL1-KO organotypic phenocopies the S1P lyase deficiency phenotype providing an ideal model for further studies and testing of therapeutic strategies.

ESDR099 - Ichthyosis associated with sphingosine 1-phosphate lyase deficiency is due to aberrant calcium and sphingolipid regulation.

50th Annual Meeting of the European Society for Dermatological Research. VIRTUAL MEETING