Endocrine Abstracts

JOINT528

Introduction: Emerging evidence suggests that pathogenic variants in genes (like MYBL, PIWIL1, TDRDs) that are involved in the processing of PIWI-interacting RNAs (piRNAs) are a major genetic contributor to spermatogenic arrest. Studies suggest that the entire piRNA processing pathway is affected if one component of the piRNA biogenesis is missing.

Hypothesis: We hypothesize that the lack of single piRNA components may be indicative of a faulty piRNA biogenesis and cause spermatogenic impairment.

Methods: Testicular expression of piRNA-associated proteins were analyzed in 117 biopsies from 115 patients with impaired (n = 87) or complete (n = 30) spermatogenesis. Immunohistochemical (IHC) and in situ hybridization (ISH) stainings identified MYBL and PIWIL1 protein and transcript. Image segmentation was used for quantitative analysis. Statistical significance was determined using Mann-Whitney U and Fisher’s exact tests.

Results: Biopsies from patients with complete spermatogenesis consistently expressed MYBL and PIWIL1 proteins in spermatocytes and round spermatids while 32% (37/117) of biopsies with impaired spermatogenesis showed absence of one or both of these proteins. Quantitative image analysis of a subset of the samples revealed a significantly reduced expression of MYBL and PIWIL1 proteins (P<0.001 and P<0.001, respectively) and transcripts (P=0.002 and P<0.001, respectively) in the biopsies with impaired spermatogenesis.

Conclusion: The observed lack of MYBL and PIWIL1 expression in 32% of biopsies with impaired spermatogenesis substantiates the critical role of piRNA-associated proteins for spermatogenesis. Whether the observed lack of PIWIL1 has an effect on the expression of piRNAs during spermatogenesis remains to be established.