Human SOX8 blocking peptide

Androgens are modulators of skeletal muscle adaptation and regeneration processes. The control of satellite cell activity is a key mechanism during this process. In this study, we analyzed the ability of dihydrotestosterone (DHT) and anabolic steroids to induce and modulate the differentiation of C2C12 myoblastoma cells toward myotubes. C2C12 cells were dose-dependently treated with DHT and anabolic steroids. The time-dependent effects on differentiation were measured and correlated with the expression of genes involved in the regulation of satellite cell activity. The distribution of C2C12 cells within the cell cycle was measured by flow cytometry and differentiation by creatine kinase (CK) activity. Gene expression was analyzed using quantitative real-time PCR and confocal microscopy. The treatment with DHT and anabolic steroids resulted in a stimulation of C2C12 cell proliferation and CK activity. The antiandrogen flutamide was able to antagonize this effect. The expression of the androgen receptor, SOX8, SOX9, Delta, Notch, myostatin, and paired box gene7 (Pax7) was modulated by androgens. The treatment with DHT and anabolic steroids resulted in a strong stimulation of myostatin expression not only in undifferentiated cells but also in myotubes. The stimulation could be antagonized by flutamide. The expression of Pax7 was detectable in C2C12 cells early after treatment with DHT. Our results demonstrate that the key mechanisms of satellite cell differentiation are modulated by androgens. Androgens stimulate the proliferation of C2C12 cells, accelerate the process of differentiation, and increase the expression of myostatin in undifferentiated and differentiated cells. Our findings may have implications not only for the treatment of muscular diseases but also for the improvement of doping analytical methods.

The sex-determining gene Sry and its target gene Sox9 initiate the early steps of testis development in mammals. Of the related Sox genes Sox8, Sox9, and Sox10, all expressed during Sertoli cell differentiation, only inactivation of Sox9 before the sex determination stage at Embryonic Day 11.5 (E11.5) causes XY sex reversal, while Sox9 inactivation after this stage has no effect on testis cord differentiation. We have previously shown that both Sox9 and Sox8 are essential for maintaining testicular function in post-E14.0 Sertoli cells. To gain insight into the molecular and cellular processes underlying the abnormal development of Sox9 and Sox8 mutant testes, we performed a detailed developmental study of embryonic and neonatal stages. We observe a progressive disruption of the basal lamina surrounding the testis cords that starts at E17.5 and already at E15.5 reduced expression levels of collagen IV, collagen IXa3 and testatin, structural components of the basal lamina, and the extracellular matrix transcriptional regulator Scleraxis. Lineage tracing reveals that mutant Sertoli cells delaminate from testis cords and are present as isolated cells between remaining cords. Also, Sox10 expression is strongly reduced in the absence of Sox9 and/or Sox8. Finally, we document increasing expression of the ovarian marker FOXL2 in mutant cords starting at E15.5, indicating progressive transdifferentiation of mutant Sertoli cells. This study shows that Sox9 and Sox8 maintain integrity of the basal lamina to prevent testis cord disintegration and that both factors actively suppress the ovarian program during early testis development.