piRNA-associated proteins and retrotransposons are differentially expressed in murine testis and ovary of aryl hydrocarbon receptor deficient mice

Abstract

Previous studies suggested that the aryl hydrocarbon receptor (AhR) contributes to mice reproduction and fertility. However, the mechanisms involved remain mostly unknown. Retrotransposon silencing by Piwi-interacting RNAs (piRNAs) is essential for germ cell maturation and, remarkably, AhR has been identified as a regulator of murine B1-SINE retrotransposons. Here, using littermate AhR+/+ and AhR−/− mice, we report that AhR regulates the general course of spermatogenesis and oogenesis by a mechanism likely to be associated with piRNA-associated proteins, piRNAs and retrotransposons. piRNA-associated proteins MVH and Miwi are upregulated in leptotene to pachytene spermatocytes with a more precocious timing in AhR−/− than in AhR+/+ testes. piRNAs and transcripts from B1-SINE, LINE-1 and IAP retrotransposons increased at these meiotic stages in AhR-null testes. Moreover, B1-SINE transcripts colocalize with MVH and Miwi in leptonema and pachynema spermatocytes. Unexpectedly, AhR−/− males have increased sperm counts, higher sperm functionality and enhanced fertility than AhR+/+ mice. In contrast, piRNA-associated proteins and B1-SINE and IAP-derived transcripts are reduced in adult AhR−/− ovaries. Accordingly, AhR-null female mice have lower numbers of follicles when compared with AhR+/+ mice. Thus, AhR deficiency differentially affects testis and ovary development possibly by a process involving piRNA-associated proteins, piRNAs and transposable elements.

Dioxin Receptor Adjusts Liver Regeneration After Acute Toxic Injury and Protects Against Liver Carcinogenesis

“…One relevant question that remains to be investigated is to what extent the effects reported here depend on the expansion of liver stem-like cells, on the absence of AhR in those cells or on both phenomena. The first possibility is supported by recent observations from our laboratory showing that AhR deficiency also improves lung regeneration after naphthalene-induced damage through an increase in the pool of basal and Clara stem-like cells (Hernández-Morales, unpublished observations), and that AhR-null testes have increased levels of early progenitor cells 25 . The second would imply that AhR deprivation triggers cell autonomous effects leading to undifferentiation and stemness.…”

“…Reverse transcription was done using random priming and the iScript Reverse Transcription Super Mix (Bio-Rad). Real-time PCR (qPCR) was performed using SYBR® Select Master Mix (Life Technologies) in a Step One Thermal Cycler (Applied Biosystems) as indicated 25 , 33 . Gapdh was used to normalize target gene expression (ΔCt) and 2 −ΔΔCt to calculate changes in mRNA levels with respect to untreated conditions.…”

“…The aryl hydrocarbon/dioxin receptor (AhR) interacts with signalling pathways controlling not only the cell response to toxic and carcinogenic compounds but also relevant physiological functions 19 , 20 . Recent work suggests that AhR may have a causal role in maintaining cell differentiation in the immune system 21 – 24 , gonads 25 , melanoma tumors 26 , 27 and skin epithelium 28 . AhR expression appears also relevant in embryonic stem cells 29 , 30 , osteoblasts 31 , 32 and embryonic teratocarcinoma cells 33 .…”

The Aryl Hydrocarbon Receptor Promotes Differentiation During Mouse Preimplantational Embryo Development

“…We have first found that zygotes from AhR -/- mice have basal overexpression of well-known pluripotency factors Oct4, Nanog and Sox2 , in agreement with our previous studies showing that AhR-null mice have an increased ability to regenerate lung (Morales-Hernandez et al, 2017) and liver (Moreno-Marin et al, 2017) and a higher potential to sustain undifferentiation of human embryionic carcinoma cells (Morales-Hernandez et al, 2016). The apparent global role of AhR in controlling differentiation was also reported by its ability to regulate ovarian follicular development through piRNA-associated proteins, piRNAs and retrotransposons (Rico-Leo et al, 2016).…”

The tryptophan derivative 6-formylindolo[3,2-b]carbazole, FICZ, a dynamic mediator of endogenous aryl hydrocarbon receptor signaling, balances cell growth and differentiation

“…In addition, FICZ (10 nM) regulated the transcription of Alu retrotransposons located in the upstream promoter regions of the pluripotency genes NANOG and OCT4 (Morales-Hern andez et al 2016). When administered by injection into mouse testes, 4 lg FICZ kg À1 also repressed the germ-line specific genes MVH, Mili, and Miwi, effects mediated by the AHR and proposed to control the expression of small non-coding TEs involved in the maturation of germ cells (Rico-Leo et al 2016).…”