Alternative splicing of CADM1 is associated with endothelial progenitor cell dysfunction in preeclampsia

Preeclampsia is a pregnancy specific hypertensive disorder and is associated with an increased postpartum risk of cardiovascular morbidity for both women and their offspring. Previous studies have indicated that cord blood endothelial colony forming cells (ECFCs) are dysfunctional in preeclampsia. The specific mechanisms are not yet fully understood but dysregulation of alternative splicing has been proposed as one of the pathogenic pathways. In order to identify specific targets of alternative splicing in fetal ECFCs, we performed transcriptome-wide differential splicing analyses between cord blood ECFCs from preeclamptic (n=16) and normal pregnancies (n=13). Selected splicing events were validated using fragment length analysis and Sanger sequencing. In silico transcriptome-wide differential splicing analysis identified a significantly increased abundance of the CADM1 isoform ENST00000542447 in the preeclamptic cohort (p=0.002), which was confirmed by wet-lab validation. The deleted exon 8 harbours glycosylation sites known to mediate cell-cell adhesion. To investigate the functional impact of alternative splice variants, we induced an in vitro splice switch using antisense morpholino treatment and followed cellular effects using migration and angiogenesis assays in ECFCs from six normal pregnancies. The CADM1 exon 8 skipping converted the normal ECFCs to a preeclampsia-like state characterised by a decreased migration ability (panova=0.005) and decreased tubule length (panova=0.02). We propose aberrant splicing of CADM1 and the resulting changes in the adherence properties of ECFCs as a potential contributor to cardiovascular sequelae in the offspring of preeclamptic pregnancies.