Heading towards a dead end: the role of DND1 in germ line differentiation of human iPSCs

The DND microRNA-mediated repression inhibitor 1 (DND1) is a conserved RNA binding protein (RBP) and plays an important role in survival and maintenance of primordial germ cells (PGCs) and the development of the male germline in zebrafish and mice. It was shown to be expressed in human pluripotent stem cells (PSCs), PGCs, and spermatogonia, but little is known about its specific role in pluripotency and human germline development. Here we use CRISPR/Cas mediated knockout and PGC-like cell (PGCLC) differentiation in human iPSCs to analyse if DND1 (1) plays a role in maintaining pluripotency and (2) in specification of PGCLCs. We generated several clonal lines with biallelic loss of function mutations and analysed their potential to differentiate towards PGCLCs and their gene expression on RNA and protein level via bulk RNA sequencing and mass spectrometry. The generated knockout iPSCs showed no differences in pluripotency gene expression, proliferation nor trilineage differentiation potential, but yielded reduced numbers o PGCLCs compared to their parental iPSCs. RNAseq analysis in PGCLCs showed significantly reduced expression of genes associated with cellular developmental processes and cell differentiation in knockout cells, including known markers for PGCs (NANOS3, SOX17, PRDM1, EPCAM) and naïve pluripotency (TFCP2L, DNMT3L).