Efficient genome editing in erythroid cells unveils novel MYB target genes and regulatory functions

Summary: Targeted genome editing holds great promise in biology. However, efficient genome modification, including gene knock-in (KI), remains an unattained goal in multiple cell types and loci due to poor transfection efficiencies and low target genes expression, impeding the positive selection of recombined cells. Here, we describe a genome editing approach to achieve efficient gene targeting using hard to transfect erythroid cell lines. We demonstrate robust fluorescent protein KI efficiency in low expressed transcription factor (TF) genes (e.g., Myb or Zeb1). We further show the ability to target two independent loci in individual cells, exemplified by MYB-GFP and NuMA-Cherry double KI, allowing multicolor labeling of regulatory factors at physiological endogenous levels. Our KI tagging approach allowed us to perform genome-wide TF analysis at increased signal-to-noise ratios, and highlighted previously unidentified MYB target genes and pathways. Overall, we establish a versatile CRISPR-Cas9-based platform, offering attractive opportunities for the dissection of the erythroid differentiation process

Multigenerational impacts of bile exposure are mediated by TGR5 signaling pathways

Abstract Besides their well-known roles in digestion and fat solubilization, bile acids (BAs) have been described as signaling molecules activating the nuclear receptor Farnesoid-X-receptor (FXRα) or the G-protein-coupled bile acid receptor-1 (GPBAR-1 or TGR5). In previous reports, we showed that BAs decrease male fertility due to abnormalities of the germ cell lineage dependent on Tgr5 signaling pathways. In the presentstudy, we tested whether BA exposure could impact germ cell DNA integrity leading to potential implications for progeny. For that purpose, adult F0 male mice were fed a diet supplemented with cholic acid (CA) or the corresponding control diet during 3.5 months prior mating. F1 progeny from CA exposed founders showed higher perinatal lethality, impaired BA homeostasis and reduced postnatal growth, as well as altered glucose metabolism in later life. The majority of these phenotypic traits were maintained up to the F2 generation. In F0 sperm cells, differential DNA methylation associated with CA exposure may contribute to the initial programming of developmental and metabolic defects observed in F1 and F2 offspring. Tgr5 knock-out mice combined with in vitro strategies defined the critical role of paternal Tgr5 dependent pathways in the multigenerational impacts of ancestral CA exposure

Bile acid-FXRalpha pathways regulate male sexual maturation in mice.

International audienceThe bile acid receptor Farnesol-X-Receptor alpha (FRXalpha) is a member of the nuclear receptor superfamily. FRXalpha is expressed in the interstitial compartment of the adult testes, which contain the Leydig cells. In adult, short term treatment (12 hours) with FRXalpha agonist inhibits the expression of steroidogenic genes via the induction of the Small heterodimer partner (SHP). However the consequences of FRXalpha activation on testicular pathophysiology have never been evaluated. We demonstrate here that mice fed a diet supplemented with bile acid during pubertal age show increased incidence of infertility. This is associated with altered differentiation and increase apoptosis of germ cells due to lower testosterone levels. At the molecular level, next to the repression of basal steroidogenesis via the induction expression of Shp and Dax-1, two repressors of steroidogenesis, the main action of the BA-FRXalpha signaling is through lowering the Leydig cell sensitivity to the hypothalamo-pituitary axis, the main regulator of testicular endocrine function. In conclusion, BA-FRXalpha signaling is a critical actor during sexual maturation

Bile acid homeostasis controls CAR signaling pathways in mouse testis through FXRalpha

Bile acids (BAs) are molecules with endocrine activities controlling several physiological functions such as immunity, glucose homeostasis, testicular physiology and male fertility. The role of the nuclear BA receptor FXR alpha in the control of BA homeostasis has been well characterized. The present study shows that testis synthetize BAs. We demonstrate that mice invalidated for the gene encoding FXR alpha have altered BA homeostasis in both liver and testis. In the absence of FXR alpha, BA exposure differently alters hepatic and testicular expression of genes involved in BA synthesis. Interestingly, Fxr alpha-/- males fed a diet supplemented with BAs show alterations of testicular physiology and sperm production. This phenotype was correlated with the altered testicular BA homeostasis and the production of intermediate metabolites of BAs which led to the modulation of CAR signaling pathways within the testis. The role of the CAR signaling pathways within testis was validated using specific CAR agonist (TCPOBOP) and inverse agonist (androstanol) that respectively inhibited or reproduced the phenotype observed in Fxr alpha-/- males fed BA-diet. These data open interesting perspectives to better define how BA homeostasis contributes to physiological or pathophysiological conditions via the modulation of CAR activit

Bile acid homeostasis controls CAR signaling pathways in mouse testis through FXRalpha.

International audienceBile acids (BAs) are molecules with endocrine activities controlling several physiological functions such as immunity, glucose homeostasis, testicular physiology and male fertility. The role of the nuclear BA receptor FXRalpha in the control of BA homeostasis has been well characterized. The present study shows that testis synthetize BAs. We demonstrate that mice invalidated for the gene encoding FXRalpha have altered BA homeostasis in both liver and testis. In the absence of FXRalpha, BA exposure differently alters hepatic and testicular expression of genes involved in BA synthesis. Interestingly, Fxralpha-/- males fed a diet supplemented with BAs show alterations of testicular physiology and sperm production. This phenotype was correlated with the altered testicular BA homeostasis and the production of intermediate metabolites of BAs which led to the modulation of CAR signaling pathways within the testis. The role of the CAR signaling pathways within testis was validated using specific CAR agonist (TCPOBOP) and inverse agonist (androstanol) that respectively inhibited or reproduced the phenotype observed in Fxralpha-/- males fed BA-diet. These data open interesting perspectives to better define how BA homeostasis contributes to physiological or pathophysiological conditions via the modulation of CAR activity

Crosstalk between BPA and FXRα Signaling Pathways Lead to Alterations of Undifferentiated Germ Cell Homeostasis and Male Fertility Disorders

International audienceSeveral studies have reported an association between the farnesoid X receptor alpha (FXRα) and estrogenic signaling pathways. Fxrα could thus be involved in the reprotoxic effects of endocrine disruptors such as bisphenol-A (BPA). To test this hypothesis, mice were exposed to BPA and/or stigmasterol (S), an FXRα antagonist. Following the exposure to both molecules, wild-type animals showed impaired fertility and lower sperm cell production associated with the alteration of the establishment and maintenance of the undifferentiated germ cell pool. The crosstalk between BPA and FXRα is further supported by the lower impact of BPA in mice genetically ablated for Fxrα and the fact that BPA counteracted the effects of FXRα agonists. These effects might result from the downregulation of Fxrα expression following BPA exposure. BPA and S act additively in human testis. Our data demonstrate that FXRα activity modulates the impact of BPA on male gonads and on undifferentiated germ cell population

The Bile Acid Nuclear Receptor FXRα Is a Critical Regulator of Mouse Germ Cell Fate

International audienceSpermatogenesis is the process by which spermatozoa are generated from spermatogonia. This cell population is heterogeneous, with self-renewing spermatogonial stem cells (SSCs) and progenitor spermatogonia that will continue on a path of differentiation. Only SSCs have the ability to regenerate and sustain spermatogenesis. This makes the testis a good model to investigate stem cell biology. The Farnesoid X Receptor alpha (FXRα) was recently shown to be expressed in the testis. However, its global impact on germ cell homeostasis has not yet been studied. Here, using a phenotyping approach in Fxrα-/- mice, we describe unexpected roles of FXRα on germ cell physiology independent of its effects on somatic cells. FXRα helps establish and maintain an undifferentiated germ cell pool and in turn influences male fertility. FXRα regulates the expression of several pluripotency factors. Among these, in vitro approaches show that FXRα controls the expression of the pluripotency marker Lin28 in the germ cells