FGFR3 is Expressed by Human Primordial Germ Cells and is Repressed after Meiotic Initiation to Form Primordial Oocytes

Human germ cell development is a highly regulated process beginning soon after embryo implantation with the specification of primordial germ cells (PGCs) and ending in adulthood with the differentiation of gametes. Here, we show that fibroblast growth factor receptor 3 (FGFR3) is expressed by human PGCs during the first and second trimester, becoming repressed as PGCs differentiate into primordial oocytes. Using fluorescence activated cell sorting (FACS) with antibodies that recognize FGFR3 followed by single cell RNA sequencing, we show that isolating FGFR3-positive cells enriches for human PGCs. Taken together, FGFR3 could be used in future studies as a strategy to identify maturing hPGCs. In our work, we performed single cell RNA-sequencing (scRNA-seq) with 10x Genomics on FGFR3 sorted ovarian cells from Week 8 and Week 13 human prenatal ovaries. We have also performed scRNA-seq of Day 4 PGCLC aggregate cells differentiated from UCLA1 human embryonic stem cells