The chicken retrovirus-like gene ENS-1/ERNI and its LTR Soprano are involved in primordial germ cell development

Cultured chicken primordial germ cells (PGCs) are attractive tools for reproductive biology and for preserving and modifying genetic resources. However, it remains difficult to establish cell lines from some breeds or females. In the present study, we performed transcriptome analyses of cultured PGCs from different breeds and found that the expression of the Galliformes -specific endogenous retrovirus-like gene ENS-1/ERNI correlated with the establishment efficiency of PGC lines. CRISPRi targeting the ENS-1/ERNI long terminal repeat (LTR) sequence ( Soprano ) broadly reduced homeostasis-related genes including ribosome, endoplasmic reticulum, and oxidative phosphorylation. These PGCs exhibited abnormal cell cycle arrest under DNA-damaged conditions, suggesting involvement in the quality control mechanisms of chicken PGCs. Furthermore, when transplanted into blastoderms, these PGCs showed a reduction in colonization of the genital ridges. These results indicate the involvement of Soprano LTR and ENS-1/ERNI in the development of chicken PGCs and their adaptation to the in vitro environment.