Expression of genome defence protein members in proliferating and quiescent rat male germ cells and the Nuage dynamics

Transcriptomic dynamics and cell-to-cell communication during the transition of prospermatogonia to spermatogonia revealed at single-cell resolution

BACKGROUND

Spermatogonia are essential for the continual production of sperm and regeneration of the entire spermatogenic lineage after injury. In mammals, spermatogonia are formed in the neonatal testis from prospermatogonia (also termed gonocytes), which are established from primordial germ cells during fetal development. Currently, the molecular regulation of the prospermatogonial to spermatogonia transition is not fully understood.

RESULTS

In this study, we examined the gene expression patterns of prospermatogonia, spermatogonia and testicular somatic cells at 4 different stages, including embryonic day (E) 12.5, E17.5 and postnatal days (P) 1 and 6, using single-cell RNA sequencing (scRNA-seq). We identified 5 different molecular states in the prospermogonial population and revealed gene expression dynamics in corresponding testicular somatic cells. Specifically, we found that prospermatogonia mainly receive signals, while Leydig cells and peritubular myoid cells are the mediators for transmitting signals, indicating their potential roles in regulating the development and differentiation of prospermatogonia. Transcription regulon analyses revealed the involvement of basic helix-loop-helix (bHLH) transcription factors in directing prospermogonial fate decisions. We then disrupted this transcription network by ectopic expression of inhibitor of differentiation 2 (Id2), which is a negative regulator of bHLH transcription factors. The overexpression of Id2 in prospermatogonia caused severe defects in the progression of prospermatogonia to spermatogonia.

CONCLUSION

Together, these findings provide a crucial dataset for dissecting key genes that direct the establishment of the foundational spermatogonial pool and the fate transitions of different somatic cell lineages in the testis during fetal and neonatal periods of development.

The functions and mechanisms of piRNAs in mediating mammalian spermatogenesis and their applications in reproductive medicine

As the most abundant small RNAs, piwi-interacting RNAs (piRNAs) have been identified as a new class of non-coding RNAs with 24-32 nucleotides in length, and they are expressed at high levels in male germ cells. PiRNAs have been implicated in the regulation of several biological processes, including cell differentiation, development, and male reproduction. In this review, we focused on the functions and molecular mechanisms of piRNAs in controlling spermatogenesis, including genome stability, regulation of gene expression, and male germ cell development. The piRNA pathways include two major pathways, namely the pre-pachytene piRNA pathway and the pachytene piRNA pathway. In the pre-pachytene stage, piRNAs are involved in chromosome remodeling and gene expression regulation to maintain genome stability by inhibiting transposon activity. In the pachytene stage, piRNAs mediate the development of male germ cells via regulating gene expression by binding to mRNA and RNA cleavage. We further discussed the correlations between the abnormalities of piRNAs and male infertility and the prospective of piRNAs' applications in reproductive medicine and future studies. This review provides novel insights into mechanisms underlying mammalian spermatogenesis and offers new targets for diagnosing and treating male infertility.

Development of a Bioinformatics Framework for Identification and Validation of Genomic Biomarkers and Key Immunopathology Processes and Controllers in Infectious and Non-infectious Severe Inflammatory Response Syndrome

Sepsis is defined as dysregulated host response caused by systemic infection, leading to organ failure. It is a life-threatening condition, often requiring admission to an intensive care unit (ICU). The causative agents and processes involved are multifactorial but are characterized by an overarching inflammatory response, sharing elements in common with severe inflammatory response syndrome (SIRS) of non-infectious origin. Sepsis presents with a range of pathophysiological and genetic features which make clinical differentiation from SIRS very challenging. This may reflect a poor understanding of the key gene inter-activities and/or pathway associations underlying these disease processes. Improved understanding is critical for early differential recognition of sepsis and SIRS and to improve patient management and clinical outcomes. Judicious selection of gene biomarkers suitable for development of diagnostic tests/testing could make differentiation of sepsis and SIRS feasible. Here we describe a methodologic framework for the identification and validation of biomarkers in SIRS, sepsis and septic shock patients, using a 2-tier gene screening, artificial neural network (ANN) data mining technique, using previously published gene expression datasets. Eight key hub markers have been identified which may delineate distinct, core disease processes and which show potential for informing underlying immunological and pathological processes and thus patient stratification and treatment. These do not show sufficient fold change differences between the different disease states to be useful as primary diagnostic biomarkers, but are instrumental in identifying candidate pathways and other associated biomarkers for further exploration.

Evolving Role of RING1 and YY1 Binding Protein in the Regulation of Germ-Cell-Specific Transcription

Separation of germline cells from somatic lineages is one of the earliest decisions of embryogenesis. Genes expressed in germline cells include apoptotic and meiotic factors, which are not transcribed in the soma normally, but a number of testis-specific genes are active in numerous cancer types. During germ cell development, germ-cell-specific genes can be regulated by specific transcription factors, retinoic acid signaling and multimeric protein complexes. Non-canonical polycomb repressive complexes, like ncPRC1.6, play a critical role in the regulation of the activity of germ-cell-specific genes. RING1 and YY1 binding protein (RYBP) is one of the core members of the ncPRC1.6. Surprisingly, the role of Rybp in germ cell differentiation has not been defined yet. This review is focusing on the possible role of Rybp in this process. By analyzing whole-genome transcriptome alterations of the Rybp^-/- embryonic stem (ES) cells and correlating this data with experimentally identified binding sites of ncPRC1.6 subunits and retinoic acid receptors in ES cells, we propose a model how germ-cell-specific transcription can be governed by an RYBP centered regulatory network, underlining the possible role of RYBP in germ cell differentiation and tumorigenesis.