We sought to determine whether differentiation agents such as retinoids and butyrate regulate transcript levels of interphotoreceptor retinoid binding protein (IRBP) and cone rod homeobox (CRX), a homeodomain transcription factor that regulates IRBP promoter activity. WERI-Rb1 retinoblastoma cells were treated with all-trans retinol, all-trans retinoic acid, or butyrate. IRBP and CRX mRNA levels were determined by quantitative RT-PCR. Butyrate at low concentrations increased both mRNA levels but suppressed them at higher concentrations. Retinoic acid had minimal effects. Retinol increased CRX mRNA over four fold. IRBP and CRX transcript levels are sensitive to butyrate and CRX expression is sensitive to retinol.

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In aging males, androgen production by testicular Leydig cells decreases at a rate of approximately 1% per year. Phenolic compounds may enhance testosterone biosynthesis and delay the onset of male hypogonadism. Gigantol is a bibenzyl compound isolated from several types of orchids of the genus Dendrobium. This compound has various biological activities, including antioxidant activity. However, its capacity to regulate gene expression and steroid production in testicular Leydig cells has never been evaluated. We investigated the effect of gigantol on MA-10 Leydig cells’ gene expression using an RNA-Seq approach. To further investigate the structure-function relationship of the hydroxy-methoxyphenyl moiety of gigantol, experiments were also performed with ferulic acid and isoferulic acid. According to transcriptomic analysis, all genes coding for cholesterol biosynthesis-related enzymes are increased in response to gigantol treatment, resulting in increased lipid droplets accumulation. Moreover, treatments with 10 μM gigantol increased StAR protein levels and progesterone production from MA-10 Leydig cells. However, neither ferulic acid nor isoferulic acid influenced StAR protein synthesis and progesterone production in MA-10 Leydig cells. Thus, our findings indicate that gigantol improves cholesterol and steroid biosynthesis within testicular Leydig cells.

The expression of interphotoreceptor retinoid binding protein (IRBP) is limited to photoreceptor cells of the retina and pinealocytes of the pineal gland. We sought to define cis-elements of the mouse IRBP 5P P flanking region that are required for this restricted activity. In vitro transient transfections of retinoblastoma and neuroblastoma cells and in vivo experiments with transgenic Xenopus laevis indicate that 3 31783/+101 and 3 3156/ +101 IRBP gene fragments directed expression predominantly to the retina and pineal, with minor neuronal expression elsewhere. In contrast, a 3 370/+101 fragment was less restrictive in controlling expression, exhibiting activity not only in retina, but also in forebrain, hindbrain, spinal cord, and motor neurons innervating gills. ß

Testis tumours, including germ cell and stromal cell tumours, are the most common types of cancer in men between the ages of 15 and 35. The incidence of testis tumours is approximately four new cases per 100,000 men per year in Canada (CCS, 2017). Importantly, this prevalence has increased by a factor of three over the past four decades. Several risk factors have been identified, including cryptorchidism (undescended testis), carcinoma in situ, contralateral tumour history and infertility. Very rare in the general population, Leydig cell tumours represent only 1%-3% of all cases of testicular tumours in men (Al-Agha & Axiotis, 2007). In rats, the prevalence of Leydig cell tumours is more common and ranges from 5.3% for the Sprague-Dawley to 76.8% for the F344 strain. However, there is a detection bias in favour of rats where the diagnosis of Leydig cell tumours is based on histological evaluation. In humans, such diagnosis is generally based on palpation and development of symptoms such as gynaecomastia or fertility problems (Cook et al., 1999). In addition, others have questioned the rarity of Leydig cell tumours and suggest that they are more common with an incidence of 18% of all surgically removed testicular cancers (Leonhartsberger et al., 2011). Indeed,

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Serum albumin protein and mRNA were found in mouse IPS and retina, suggesting that the protein is synthesized in the retina. The previously demonstrated ability of serum albumin to bind fatty acids and retinoids and its presence in the mouse IPS suggest a role for serum albumin in transporting retinoids in the retina or IPS, especially at young ages when concentrations appear greatest.

Gap junctions, mainly formed by Gja1 (Connexin43), play an essential role in the regulation of proliferation and differentiation of spermatogonia in the testis. Regulation of the abundance of Gja1 in spermatogonia involves various processes, including gene transcription, mRNA maturation, protein synthesis, post-translational modifications, plasma membrane integration and protein degradation. However, gene expression of Gja1 is abnormally decreased in most testicular germ cell tumors. Hence, a better understanding of the mechanisms of transcriptional regulation of Gja1 in spermatogonia is essential to understand how the loss of its expression occurs during the development of testicular cancer. As in other cell types, activator protein-1 (AP-1) transcription factors may be involved in such regulatory process. Thus, AP-1 members were overexpressed in GC-1 cells to assess their impact on Gja1 expression. We showed that Jun and Fosl2 cooperate to activate the Gja1 promoter in GC-1 cells. Furthermore, the recruitment of Jun to the proximal region (−153 to +46 bp) of the Gja1 promoter has been confirmed via chromatin immunoprecipitation. Protein kinase A and calcium-calmodulin protein kinase I also contribute to the activation of Gja1 expression by improving the cooperation between AP-1 factors. Therefore, the reduction in Gja1 expression in testicular germ cell tumors may involve a loss of cooperation between AP-1 factors.