Abnormal migration behavior linked to Rac1 signaling contributes to primordial germ cell exhaustion in Fanconi anemia pathway-deficient Fancg-/- embryos.

Amandine Jarysta,Franck Letourneur,Virginie Firlej,Florent Dumont,Thierry Kortulewski,Isabelle Allemand,Clémentine Lapoujade,Lydia Riou,Pierre Fouchet,Sébastien Jacques,Filippo Rosselli,Vilma Barroca,Anne-Sophie Gille

doi:10.1093/hmg/ddab222

Abstract

Fanconi anemia (FA) is a rare human genetic disorder characterized by bone marrow failure, predisposition to cancer and developmental defects including hypogonadism. Reproductive defects leading to germ cell aplasia are the most consistent phenotypes seen in FA mouse models. We examined the role of the nuclear FA core complex gene Fancg in the development of primordial germ cells (PGCs), the embryonic precursors of adult gametes, during fetal development. PGC maintenance was severely impaired in Fancg−/− embryos. We observed a defect in the number of PGCs starting at E9.5 and a strong attrition at E11.5 and E13.5. Remarkably, we observed a mosaic pattern reflecting a portion of testicular cords devoid of PGCs in E13.5 fetal gonads. Our in vitro and in vivo data highlight a potential role of Fancg in the proliferation and in the intrinsic cell motility abilities of PGCs. The random migratory process is abnormally activated in Fancg−/− PGCs, altering the migration of cells. Increased cell death and PGC attrition observed in E11.5 Fancg−/− embryos are features consistent with delayed migration of PGCs along the migratory pathway to the genital ridges. Moreover, we show that an inhibitor of RAC1 mitigates the abnormal migratory pattern observed in Fancg−/− PGCs.

Highlights

Fanconi anemia (FA) is a recessive disease characterized by congenital defects, progressive bone marrow (BM) failure and predisposition to cancer, including acute myeloid leukemia and squamous cell carcinoma
We found that loss of Fancg resulted in a defect in the number of primordial germ cells (PGCs) starting at E9.5 and a strong attrition at E11.5 and E13.5, along with a mosaic pattern of testicular cords in E13.5 fetal gonads with cords devoid of PGCs
Fancg+/− mice were backcrossed with a transgenic OG2 mouse in which enhanced green fluorescent protein (EGFP) is controlled by the distal enhancer of the Oct3/4 promoter to identify the embryonic stage at which germ cell depletion begins [32]

Summary

Introduction

Fanconi anemia (FA) is a recessive disease characterized by congenital defects, progressive bone marrow (BM) failure and predisposition to cancer, including acute myeloid leukemia and squamous cell carcinoma. 21 genes (FANCA, FANCB, FANCC, FANCD1/BRCA2, FANCD2, FANCE, FANCF, FANCG/XRCC9, FANCI, FANCJ/BRIP1/BACH1, FANCL/PHF9/Pog, FANCM/Hef, FANCN/PALB2, FANCO/Rad51c, FANCP/SLX4, FANCQ/XPF, FANCR/RAD51, FANCS/BRCA1, FANCT/UBE2T, FANCU/XRCC2 and FANCV/REV7) along with FA Associated Proteins FAAP100, FAAP20 and FAAP24 have been identified to participate in the emergence of FA pathology [1]. In response to a stalled replication fork or to DNA damage, a group of eight proteins (FANCA, B, C, E, F, G, M and L) forms a nuclear core complex. Via the E3-ligase activity of FANCL, this complex mediates the mono-ubiquitination of a second group of proteins composed of FANCD2 and FANCI (the ID complex). Once mono-ubiquitinated, the ID complex is recruited to DNA repair foci and interacts with a third group of FANC proteins (FANCD1, FANCJ, FANCN, FANCP and FANCS) and other BRCA1-interacting proteins. FANCG/XRCC9 is a 65 kDa protein with at least seven protein–protein interaction tetratricopeptide repeat motifs [3]

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