Abstract
Leydig cells (LC) are the main testicular androgen-producing cells. In eutherian mammals, two types of LCs emerge successively during testicular development, fetal Leydig cells (FLCs) and adult Leydig cells (ALCs). Both display significant differences in androgen production and regulation. Using bulk RNA sequencing, we compared the transcriptomes of both LC populations to characterize their specific transcriptional and functional features. Despite similar transcriptomic profiles, a quarter of the genes show significant variations in expression between FLCs and ALCs. Non-transcriptional events, such as alternative splicing was also observed, including a high rate of intron retention in FLCs compared to ALCs. The use of single-cell RNA sequencing data also allowed the identification of nine FLC-specific genes and 50 ALC-specific genes. Expression of the corticotropin-releasing hormone 1 (Crhr1) receptor and the ACTH receptor melanocortin type 2 receptor (Mc2r) specifically in FLCs suggests a dual regulation of steroidogenesis. The androstenedione synthesis by FLCs is stimulated by luteinizing hormone (LH), corticotrophin-releasing hormone (CRH), and adrenocorticotropic hormone (ACTH) whereas the testosterone synthesis by ALCs is dependent exclusively on LH. Overall, our study provides a useful database to explore LC development and functions.
Highlights
Leydig cells (LC) are the main steroidogenic cells of the testes
We evaluated the purity of our fetal Leydig cells (FLCs) and adult Leydig cells (ALCs) samples by measuring the expression level of several genes specific to different testicular cells (Supplementary Figure 1B)
We found that Betaine-Homocysteine S-Methyltransferase (Bhmt) and Sulfotransferase Family 1E Member 1 (Sult1e1) are co-expressed with Star in adult P100 testis but not in fetal E16.5 testis confirming that these genes are expressed in ALCs and not in FLCs or any other testicular cells
Summary
Leydig cells (LC) are the main steroidogenic cells of the testes. They synthesize androgens that are essential for both masculinisation of the organism and spermatogenesis. The FLC population expands considerably during fetal testis development through the recruitment and differentiation of Leydig progenitor cells rather than by mitotic division of differentiated FLCs. Comparing FLCs and ALCs (Byskov, 1986; Kerr et al, 1988; Migrenne et al, 2001; Brennan et al, 2003; Barsoum and Yao, 2010; Ademi et al, 2020). The ALCs appear around one week after birth and increase in number during puberty They arise from LC progenitors located in the testicular interstitium (Davidoff et al, 2004; Barsoum et al, 2013; Shima et al, 2013; Kilcoyne et al, 2014; Ademi et al, 2020). Evidence shows that a subset of FLCs dedifferentiates at fetal stages to serve as potential ALC stem cells (Shima et al, 2018)
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