Altered gene expression signature of early stages of the germ line supports the pre‐meiotic origin of human spermatogenic failure

Abstract

Summary The molecular basis of spermatogenic failure (SpF) is still largely unknown. Accumulating evidence suggests that a series of specific events such as meiosis, are determined at the early stage of spermatogenesis. This study aims to assess the expression profile of pre‐meiotic genes of infertile testicular biopsies that might help to define the molecular phenotype associated with human deficiency of sperm production. An accurate quantification of testicular mRNA levels of genes expressed in spermatogonia was carried out by RT‐qPCR in individuals showing SpF owing to germ cell maturation defects, Sertoli cell‐only syndrome or conserved spermatogenesis. In addition, the gene expression profile of SpF was compared with that of testicular tumour, which is considered to be a severe developmental disease of germ cell differentiation. Protein expression from selected genes was evaluated by immunohistochemistry. Our results indicate that SpF is accompanied by differences in expression of certain genes associated with spermatogonia in the absence of any apparent morphological and/or numerical change in this specific cell type. In SpF testicular samples, we observed down‐regulation of genes involved in cell cycle (CCNE1 and POLD1), transcription and post‐transcription regulation (DAZL, RBM15 and DICER1), protein degradation (FBXO32 and TM9SF2) and homologous recombination in meiosis (MRE11A and RAD50) which suggests that the expression of these genes is critical for a proper germ cell development. Interestingly, a decrease in the CCNE1, DAZL, RBM15 and STRA8 cellular transcript levels was also observed, suggesting that the gene expression capacity of spermatogonia is altered in SpF contributing to an unsuccessful sperm production. Altogether, these data point to the spermatogenic derangement being already determined at, or arising in, the initial stages of the germ line.

Genome-Wide Association Study for Indicator Traits of Sexual Precocity in Nellore Cattle

“…Many of these genes are also directly involved in spermatogenesis, such as the HILS1 gene that remodels chromatin during gamete production [ 50 ], the KAT7 and ICAM2 genes expressed in Sertoli cells [ 51 , 52 ], the TCAM1 gene expressed in spermatocytes [ 53 ], the SLC26A3 gene that is essential for sperm capacitation [ 54 ], and the RAD18 gene that plays a crucial role in genome maintenance during sperm production [ 55 ]. Other important genes are the FBXO32 (Chr14/17.83–18.51Mb) and EBF2 (Chr08/73.91-75Mb) genes related to infertility and hypogonadism in men, respectively [ 56 , 57 ], and the GH1 gene (Chr19/48.69–49.21Mb) associated with seminal characteristics and sexual behavior in cattle [ 58 ].…”

Altered miRNA Signature of Developing Germ-cells in Infertile Patients Relates to the Severity of Spermatogenic Failure and Persists in Spermatozoa

“…Furthermore, Dicer1, a protein necessary for miRNA processing and Dnd1, a protein implicated in the protection of mRNAs from miRNAs, are essential for the completion of spermatogenesis 3 11 22 . We have previously demonstrated that low spermatogenic efficiency in infertile men is accompanied by an altered gene expression capacity of germ-cells, which contributes to unsuccessful sperm production 23 24 , thus, in this context, it is reasonable to study the cellular miRNA expression behavior, as a likely mechanism of gene expression regulation, in spermatogenic disorders.…”

“…To determine the cellular miRNA content of testicular germ-cells, we considered the fact that the miRNA expression levels per tubule are the result of a composite of different cell types, as we have previously described for determining mRNA germ-cell content 23 24 . Therefore, we calculated the miRNA expression levels per germ-cell by adjusting total expression levels to the proportion of germ-cell stages that specifically express the miRNAs in a seminiferous tubule, to correct for the actual amount of expressing germ-cells in each particular sample.…”

Unraveling transcriptome dynamics in human spermatogenesis

“…In humans, knowledge about the molecular processes that control spermatogenesis is still limited. Recent gene expression studies have shown that human spermatogenesis is controlled by a complex network of molecular pathways ( Bonache et al, 2014 ; Feig et al, 2007 ; Shafipour et al, 2014 ). However, these studies investigated expression changes in entire testicular biopsies from healthy and subfertile men.…”