Identification of Photoperiod-Induced LncRNAs and mRNAs in Pituitary Pars Tuberalis of Sheep

Abstract

The pituitary pars tuberalis (PT) is the regulating center of seasonal reproduction, which can sense the melatonin signal and eventually cause downstream changes of GnRH secretion through TSHβ. Recently, lncRNAs have been identified in animal reproductive-related tissues, and they play important roles in reproductive regulation. Therefore, in this study, we expect to identify photoperiod-induced lncRNAs and genes in pituitary PT of sheep by comparison of expression profiles between short photoperiod (SP) and long photoperiod (LP). Through RNA-Seq, a total of 55,472 lncRNAs were identified in pituitary PT of Sunite ewes. The number of differentially expressed (DE) genes and lncRNAs between SP and LP increased gradually with the extension of LP (from LP7 to LP42). The notable LP-induced candidate genes included EYA3, TSHB, SIX1, DCT, VMO1, AREG, SUV39H2, and EZH2, and SP-induced genes involved ENSOARG00000012585, CHGA, FOS, SOCS3, and TH. In enriched pathways for DE genes and lncRNA target genes between SP and LP, the reproduction- and circadian-related pathways were highlighted. In addition, the interactome analysis of lncRNAs and their targets implied that MSTRG.209166 and its trans-target TSHB, MSTRG.288068 and its cis-target SIX1, and ENSOARG00000026131 and its cis-target TH might participate in regulation of seasonal reproduction. Together, these results will help to determine important photoperiod-induced lncRNAs and genes and give us some new insights into the epigenetic regulation of seasonal reproduction in sheep.

Transcriptomic Changes of Photoperiodic Response in the Hypothalamus Were Identified in Ovariectomized and Estradiol-Treated Sheep

“…All ewes were fed ad libitum and had free access to water. OVX + E 2 sheep and light control rooms were constructed as previously described ( La, et al, 2020 ; He et al, 2021 ; Xia, et al, 2021 ). In brief, estradiol treatment was achieved with an inner diameter of 3.35 mm and an outer diameter of 4.65 mm, packed with 20 mg crystalline 17β-estradiol (Sigma Chemical Co., St. Louis, MO).…”

GnRHand the photoperiodic control of seasonal reproduction: Delegating the task to kisspeptin andRFRP‐3

“…[114][115][116][117][118][119] Furthermore, recent RNA-sequencing analyses in sheep have identified hundreds of genes that display strong photoperiodic and circannual control of expression. 62,66,70,72,120 These inner switches in expression seem to be accounted for by epigenetic changes at the gene promoter level, as shown for Tshb and Eya3. 62 Furthermore, the PT-expressed histone methyltransferases Ezh2 and Suv39H2 display a robust increase in expression under long days compared to short days.…”

“…The PT displays circannual fluctuations in Tshb and Eya3 expression in sheep and hamsters, which are accompanied by changes in Dio2 / Dio3 expression and concomittant modifications of both reproductive and metabolic phenotypes 114–119 . Furthermore, recent RNA‐sequencing analyses in sheep have identified hundreds of genes that display strong photoperiodic and circannual control of expression 62,66,70,72,120 . These inner switches in expression seem to be accounted for by epigenetic changes at the gene promoter level, as shown for Tshb and Eya3 62 .…”

“…68,69 Recent transcriptomics studies in sheep have demonstrated that, beyond clock genes, Tshb and Eya3, there are indeed several hundreds of PT-expressed genes that display large seasonal switches in expression level. 7,66,[70][71][72] To conclude, there is overwhelming evidence that the PT is sensitive to the photoperiodic melatonin signal, which impacts its structure, function, molecular signature and endocrine output.…”

“…By contrast to PD thyrotropes, which are under the control of the thyroid axis, PT thyrotropes lack receptors for thyrotropin‐releasing hormone and triiodothyronine (T3) 67 and are therefore mostly sensitive to melatonin because they express MT1 receptor 68,69 . Recent transcriptomics studies in sheep have demonstrated that, beyond clock genes, Tshb and Eya3 , there are indeed several hundreds of PT‐expressed genes that display large seasonal switches in expression level 7,66,70–72 . To conclude, there is overwhelming evidence that the PT is sensitive to the photoperiodic melatonin signal, which impacts its structure, function, molecular signature and endocrine output.…”