The roles of DAZL in RNA biology and development

Translation machinery: the basis of translational control

Messenger RNA (mRNA) translation consists of initiation, elongation, termination, and ribosome recycling, carried out by the translation machinery, primarily including tRNAs, ribosomes, and translation factors (TrFs). Translational regulators transduce signals of growth and development, as well as biotic and abiotic stresses, to the translation machinery, where global or selective translational control occurs to modulate mRNA translation efficiency (TrE). As the basis of translational control, the translation machinery directly determines the quality and quantity of newly synthesized peptides and, ultimately, the cellular adaption. Thus, regulating the availability of diverse machinery components is reviewed as the central strategy of translational control. We provide classical signaling pathways (e.g., integrated stress responses) and cellular behaviors (e.g., liquid-liquid phase separation) to exemplify this strategy within different physiological contexts, particularly during host-microbe interactions. With new technologies developed, further understanding this strategy will speed up translational medicine and translational agriculture.

Cloning, expression analysis and localization of DAZL gene implicated in germ cell development of male Hezuo pig

Deleted in azoospermia-like (DAZL) is essential for mammalian testicular function and spermatogenesis. To explore the molecular characterization, expression patterns, and cellular localization of the DAZL in Hezuo pig testes, testicular tissue was isolated from Hezuo pig at five development stages including 30 days old (30 d), 90 days old (90 d), 120 days old (120 d), 180 days old (180 d), and 240 days old (240 d). DAZL cDNA was first cloned using the RT-PCR method, and its molecular characterization was analyzed using relevant bioinformatics software. Subsequently, the expression patterns and cellular localization of DAZL were evaluated using quantitative real-time PCR (qRT-PCR), Western blot, and immunohistochemistry. The cloning and sequence analysis showed that the Hezuo pig DAZL cDNA fragment contained 888 bp open reading frame (ORF) capable of encoding 295 amino acid residues and exhibited high identities with some other mammals. The qRT-PCR and Western blot results indicated that DAZL was specifically expressed in Hezuo pig testes, and DAZL levels of both mRNA and protein were expressed at all five reproductive stages of Hezuo pig testes, with extremely significant higher expression levels in 90 d, 120 d, 180 d, and 240 d than those in 30 d (p < 0.01). Additionally, immunohistochemistry results revealed that DAZL protein was mainly localized in gonocytes at 30 d testes, primary spermatocytes, and spermatozoon at other developmental stages, and Leydig cells throughout five development stages. Together, these results suggested that DAZL may play an important role by regulating the proliferation or differentiation of gonocytes, development of primary spermatocytes and spermatozoon, and functional maintenance of Leydig cells in testicular development and spermatogenesis of Hezuo pig. Nevertheless, the specific regulatory mechanisms underlying these phenomena still requires further investigated and verified.

Seasonal changes in the expression of molecular markers of stallion germ cells

The economic impacts of infertility and subfertility of stallions greatly influence the horse breeding industry. Self-renewal and differentiation of spermatogonial stem cells are the initial processes to maintain an adequate sperm population. Thus, understanding these processes may provide useful information to reveal the causes and remedies of subfertile and infertile stallions. Stallions are seasonal breeders. About 50% of the sperm population is reduced during the non-breeding season (NBS) in stallions. The seasonal regulation of spermatogenesis renders stallions as ideal models to understand the process of sperm production. Furthermore, comparing internal and external factors related to spermatogenesis during the breeding season (BS) and NBS may provide a solution for subfertile/infertile stallions. It is especially pertinent to study the expression pattern of different protein markers during undifferentiated, differentiating, and differentiated spermatogonia. Deleted in azoospermia-like (DAZL), undifferentiated cell transcription factor 1 (UTF-1), and protein gene product 9.5 (PGP9.5) are the molecular markers expressed at different stages of spermatogenesis. However, whether the expression pattern of these molecular markers is similar throughout the year in stallion remains undetermined. The objectives of this study were to (1) investigate the expression pattern and localization of DAZL, UTF-1, and PGP9.5 within seminiferous tubules and (2) evaluate the relative mRNA levels of these three germ cell markers in stallion testes during BS and NBS. Immunohistochemistry was performed to check and compare the expression pattern and localization of DAZL, UTF-1, and PGP9.5 antibodies. Reverse transcription-quantitative PCR analysis was performed to calculate the relative mRNA expression levels in the testes. Testicular tissues from thoroughbred stallions were collected during routine castration that was carried out in field conditions. Immunostaining of germ cells with DAZL and UTF-1 in BS and NBS were not significantly different. However, the relative mRNA expression levels of DAZL and UTF-1 were significantly different in both groups. Interestingly, the immunolabeling and the relative mRNA expression of PGP9.5 were significantly different between BS and NBS. From these results, it is hypothesized that the expression level of these putative molecular markers might be gonadotropin-dependent in stallion testes.

Single-Cell Atlas of Adult Testis in Protogynous Hermaphroditic Orange-Spotted Grouper, Epinephelus coioides

Spermatogenesis is a process of self-renewal and differentiation in spermatogonial stem cells. During this process, germ cells and somatic cells interact intricately to ensure long-term fertility and accurate genome propagation. Spermatogenesis has been intensely investigated in mammals but remains poorly understood with regard to teleosts. Here, we performed single-cell RNA sequencing of ~9500 testicular cells from the male, orange-spotted grouper. In the adult testis, we divided the cells into nine clusters and defined ten cell types, as compared with human testis data, including cell populations with characteristics of male germ cells and somatic cells, each of which expressed specific marker genes. We also identified and profiled the expression patterns of four marker genes (calr, eef1a, s100a1, vasa) in both the ovary and adult testis. Our data provide a blueprint of male germ cells and supporting somatic cells. Moreover, the cell markers are candidates that could be used for further cell identification.

Primordial Germ Cell Specification in Vertebrate Embryos: Phylogenetic Distribution and Conserved Molecular Features of Preformation and Induction

The differentiation of primordial germ cells (PGCs) occurs during early embryonic development and is critical for the survival and fitness of sexually reproducing species. Here, we review the two main mechanisms of PGC specification, induction, and preformation, in the context of four model vertebrate species: mouse, axolotl, Xenopus frogs, and zebrafish. We additionally discuss some notable molecular characteristics shared across PGC specification pathways, including the shared expression of products from three conserved germline gene families, DAZ (Deleted in Azoospermia) genes, nanos-related genes, and DEAD-box RNA helicases. Then, we summarize the current state of knowledge of the distribution of germ cell determination systems across kingdom Animalia, with particular attention to vertebrate species, but include several categories of invertebrates - ranging from the "proto-vertebrate" cephalochordates to arthropods, cnidarians, and ctenophores. We also briefly highlight ongoing investigations and potential lines of inquiry that aim to understand the evolutionary relationships between these modes of specification.

Expressional Profiling of TEX11, ESRα and BOLL Genes in Yak under Different Feeding Conditions

Simple Summary

The yak (Bos grunniens) is regarded as one of the most magnificent domestic animals in the mountains of Asia, and it is well-adapted to the harsh environment of the Qinghai–Tibetan Plateau. Slow growth rate and low production and reproductive potential are the main limitations of yaks. It has been suggested that enhanced nutrition can improve reproductive efficiency in animals; however, this is still unclear for yaks. Hence, this study was designed to observe the effect of supplementary feeding on transcription and expression profiles of different genes related to reproduction. Such characterization under different feeding conditions can provide potential guidance for enhancement of the reproductive efficacy of yaks.

Abstract

Previous studies have demonstrated that nutrition plays a crucial part in improving the reproductive potential of farm animals; however, there is currently no research on the transcription and expression profiling of genes in yaks under different feeding conditions. Therefore, this research was planned to compare the transcription and expression profiles of TEX11, ESRα, and BOLL in yaks under natural grazing with concentrate supplementation (NG + CS) and NG without concentrate supplementation. The transcription and expressional levels of TEX11, ESRα, and BOLL mRNA were explored from the testes of yaks using qPCR, Western blotting, immunofluorescence, and immunochemistry. The results of the qPCR illustrated that the transcription levels of TEX11, ESRα, and BOLL were upregulated in the NG + CS group compared to those in the NG group. Moreover, the results of the immunochemistry and immunofluorescence showed that the expression of TEX11, ESRα, and BOLL proteins increased after concentrate supplementation. Meanwhile, ESRα protein levels were lower in the testes and epididymides of yaks in the NG group than in those in the NG + CS group. Similarly, BOLL protein expression was higher in the testes and epididymides of the NG + CS group, but its expression was lower in the epididymides of the NG group. Furthermore, Western blotting showed that the molecular weights of ESRα and BOLL proteins were 64 kDa and 31 kDa, respectively. Finally, in the conclusion we summarize how a proper level of dietary energy supplementation can improve the reproductive potential of yaks by upregulating genes related to reproduction.

Transcriptome analysis provides insights into long noncoding RNAs in medaka gonads

Long non-coding RNAs (lncRNAs) are gradually regarded as regulators in sex determination and gonad development of various animals. Medaka (Oryzias latipes) is an excellent reproductive research model with sex-determining genes. However, the regulation of gonadal lncRNAs on medaka reproductive development remains unknown. Here, 5317 lncRNAs were obtained from medaka ovary and testis by Illumina HiSeq4000, among which 177 lncRNAs were up-regulated and 120 lncRNAs were down-regulated in the testis compared to the ovary. In addition, 6904 cis-regulated target genes were predicted from 3099 lncRNAs. GO and KEGG enrichment analysis showed that these target genes were mainly involved in phosphorylation, metabolic, metabolism of xenobiotics by cytochrome P450, insulin secretion, and GnRH signaling pathways. Furthermore, six highly expressed lncRNAs were randomly selected to verify the sequencing data by quantitative real time PCR (qRT-PCR). Next, in situ hybridization revealed that one of the sex-biased lncRNA MSTRG.14827.1 was highly expressed in immature germ cells, indicating MSTRG.14827.1 may play a key role in gametogenesis. Taken together, this study provides emerging lncRNA libraries and opens new avenues for future investigation of lncRNAs in medaka.

Expression of DAZL Gene in Selected Tissues and Association of Its Polymorphisms with Testicular Size in Hu Sheep

Simple Summary

The deleted in azoospermia-like (DAZL) is an RNA binding protein coding gene in autosomal, playing important roles in testicular development and gametogenesis. In this paper, we found that DAZL is extremely highly expressed in testis compared with other organs and reaches to a peak at sex maturity (6-month old) in testis. Two single nucleotide polymorphisms (SNPs) within DAZL were found to have significant effect on the variation coefficient between left and right epididymis weight.

Abstract

The deleted in azoospermia-like (DAZL) gene encoding an RNA binding protein is pivotal in gametogenesis in lots of species and also acts as a pre-meiosis marker. The current study was conducted to detect expression profiles and single nucleotide polymorphisms (SNPs) of DAZL in sheep using qPCR, DNA-pooled sequencing, improved multiplex ligase detection reaction (iMLDR^®) and restriction fragment length polymorphism (RFLP) methods. The results confirmed that ovine DAZL showed the highest expression level at six-months of age across five developmental stage. At six-month stage, DAZL expressed primarily in testis across seven tissues analyzed. The abundance of DAZL in the large-testis group is higher than that in the small-testis group although it is not significant. In addition, six SNPs (SNP1-SNP6) were identified in DAZL. Of those, SNP1 (p < 0.05) and SNP6 (p < 0.01) were significantly correlated with the variation coefficient between left and right epididymis weight (VCTW). The current study implies DAZL may play important roles in testicular development and its SNPs are associated with testicular parameters, which supply important indicators for ram selection at early stage.

Single-cell analysis of human ovarian cortex identifies distinct cell populations but no oogonial stem cells

The human ovary orchestrates sex hormone production and undergoes monthly structural changes to release mature oocytes. The outer lining of the ovary (cortex) has a key role in defining fertility in women as it harbors the ovarian reserve. It has been postulated that putative oogonial stem cells exist in the ovarian cortex and that these can be captured by DDX4 antibody isolation. Here, we report single-cell transcriptomes and cell surface antigen profiles of over 24,000 cells from high quality ovarian cortex samples from 21 patients. Our data identify transcriptional profiles of six main cell types; oocytes, granulosa cells, immune cells, endothelial cells, perivascular cells, and stromal cells. Cells captured by DDX4 antibody are perivascular cells, not oogonial stem cells. Our data do not support the existence of germline stem cells in adult human ovaries, thereby reinforcing the dogma of a limited ovarian reserve.

Gene expression patterns and protein cellular localization suggest a novel role for DAZL in developing Tibetan sheep testes

Deleted in azoospermia-like (DAZL) is essential for mammalian spermatogenesis as it regulates proliferation, development, maturation and functional maintenance of male germ cells. Its expression and regulation vary with different species or in the same animal at different developmental stages, and despite its importance, very little is known about its roles in sheep, especially Tibetan sheep. To investigate the expression patterns and regulatory roles of DZAL in Tibetan sheep testis, testicular tissue was isolated from sheep at three crucial development stages: 3 months old, 1 year old and 3 years old. Using quantitative real-time PCR and Western blot, we found that DAZL mRNA first decreased and then increased with advancing age, while DAZL protein exhibited an opposite expression pattern, with first increased and subsequently decreased levels. Immunohistochemistry and immunofluorescence revealed that DAZL protein was located predominantly in the cytoplasm of Leydig cells and in both the cytoplasm and nucleus of spermatids. ELISA indicated that testosterone content within developing testes was first enhanced and then declined. Our results, taken together, demonstrate, for the first time, that DAZL gene is involved in Tibetan sheep spermatogenesis by regulating the development of spermatids in post-pubertal rams, along with a novel role in functional maintenance of Leydig cells in postnatal rams.

Histomorphological Comparisons and Expression Patterns of BOLL Gene in Sheep Testes at Different Development Stages

BOLL is implicated in mammalian testicular function maintenance and spermatogenesis. To understand the expression patterns and biological functions of sheep BOLL, we examined the expression and immunolocalization of BOLL in the developing testes of Small-Tail Han sheep aged 0 days (D0), 2 months (2M), 5 months (5M), 1 year (1Y), and 2 years (2Y), by qPCR, Western blot, and immunohistochemistry methods. Firstly, morphological studies revealed that, in addition to spermatogonia, ordered and clear spermatocytes, as well as round and elongated spermatids and sperm, were found in the 1Y and 2Y testicular seminiferous tubules of the sheep testes, compared with the D0, 2M, and 5M testes, as analyzed by hematoxylin and eosin (H&amp;E) staining. The diameter and area of the seminiferous tubules, epithelial thickness, and the area and perimeter of the tubule lumens gradually increased with age. BOLL was specifically expressed in testes and upregulation of BOLL transcript expression was higher in the testes of the 1Y and 2Y groups than in those of the D0, 2M, and 5M groups. Similarly, BOLL protein was expressed mainly in the 1Y and 2Y testes, ranging from primary spermatocytes to round spermatids, as well as in the spermatozoa. This study is the first demonstration that sheep BOLL might serve as a key regulator of the spermiogenesis involved in sperm maturity, in addition to its role as a crucial meiotic regulator.

Age-related and photoperiodic variation of the DAZ gene family in the testis of the Syrian hamster (Mesocricetus auratus)

SummaryThe Deleted in AZoospermia (DAZ) gene family regulates the development, maturation and maintenance of germ cells and spermatogenesis in mammals. The DAZ family consists of two autosomal genes, Boule and Dazl (Daz-like), and the Daz gene on chromosome Y. The aim of this study was to analyze the localization of DAZL and BOULE during testicular ontogeny of the seasonal-breeding Syrian hamster, Mesocricetus auratus. We also evaluated the testicular expression of DAZ family genes under short- or long-photoperiod conditions. In the pre-pubertal and adult testis, DAZL protein was found mainly in spermatogonia. BOULE was found in the spermatogonia from 20 days of age and during the pre-pubertal and adult period it was also detected in spermatocytes and round spermatids. DAZL and BOULE expression in spermatogonia was strictly nuclear only in 20-day-old hamsters. We also detected the novel mRNA and protein expression of BOULE in Leydig cells. In adult hamsters, Dazl expression was increased in regressed testis compared with non-regressed testis and DAZL protein expression was restricted to primary spermatocytes in regressed testis. These results show that DAZL and BOULE are expressed in spermatogonia at early stages in the Syrian hamster, then both proteins translocate to the cytoplasm when meiosis starts. In the adult regressed testis, the absence of DAZL in spermatogonia might be related to the decrease in germ cell number, suggesting that DAZ gene family expression is involved in changes in seminiferous epithelium during photoregression.

Over Expression of NANOS3 and DAZL in Human Embryonic Stem Cells

The mechanisms underlying human germ cell development are largely unknown, partly due to the scarcity of primordial germ cells and the inaccessibility of the human germline to genetic analysis. Human embryonic stem cells can differentiate to germ cells in vitro and can be genetically modified to study the genetic requirements for germ cell development. Here, we studied NANOS3 and DAZL, which have critical roles in germ cell development in several species, via their over expression in human embryonic stem cells using global transcriptional analysis, in vitro germ cell differentiation, and in vivo germ cell formation assay by xenotransplantation. We found that NANOS3 over expression prolonged pluripotency and delayed differentiation. In addition, we observed a possible connection of NANOS3 with inhibition of apoptosis. For DAZL, our results suggest a post-transcriptional regulation mechanism in hES cells. In addition, we found that DAZL suppressed the translation of OCT4, and affected the transcription of several genes associated with germ cells, cell cycle arrest, and cell migration. Furthermore, DAZL over expressed cells formed spermatogonia-like colonies in a rare instance upon xenotransplantation. These data can be used to further elucidate the role of NANOS3 and DAZL in germ cell development both in vitro and in vivo.

Spermatogenesis: The Commitment to Meiosis

Mammalian spermatogenesis requires a stem cell pool, a period of amplification of cell numbers, the completion of reduction division to haploid cells (meiosis), and the morphological transformation of the haploid cells into spermatozoa (spermiogenesis). The net result of these processes is the production of massive numbers of spermatozoa over the reproductive lifetime of the animal. One study that utilized homogenization-resistant spermatids as the standard determined that human daily sperm production (dsp) was at 45 million per day per testis (60). For each human that means ∼1,000 sperm are produced per second. A key to this level of gamete production is the organization and architecture of the mammalian testes that results in continuous sperm production. The seemingly complex repetitious relationship of cells termed the "cycle of the seminiferous epithelium" is driven by the continuous commitment of undifferentiated spermatogonia to meiosis and the period of time required to form spermatozoa. This commitment termed the A to A1 transition requires the action of retinoic acid (RA) on the undifferentiated spermatogonia or prospermatogonia. In stages VII to IX of the cycle of the seminiferous epithelium, Sertoli cells and germ cells are influenced by pulses of RA. These pulses of RA move along the seminiferous tubules coincident with the spermatogenic wave, presumably undergoing constant synthesis and degradation. The RA pulse then serves as a trigger to commit undifferentiated progenitor cells to the rigidly timed pathway into meiosis and spermatid differentiation.

Long non-coding RNA regulation of reproduction and development

Noncoding RNAs (ncRNAs) have long been known to play vital roles in eukaryotic gene regulation. Studies conducted over a decade ago revealed that maturation of spliced, polyadenylated coding mRNA occurs by reactions involving small nuclear RNAs and small nucleolar RNAs; mRNA translation depends on activities mediated by transfer RNAs and ribosomal RNAs, subject to negative regulation by micro RNAs; transcriptional competence of sex chromosomes and some imprinted genes is regulated in cis by ncRNAs that vary by species; and both small-interfering RNAs and piwi-interacting RNAs bound to Argonaute-family proteins regulate post-translational modifications on chromatin and local gene expression states. More recently, gene-regulating noncoding RNAs have been identified, such as long intergenic and long noncoding RNAs (collectively referred to as lncRNAs)--a class totaling more than 100,000 transcripts in humans, which include some of the previously mentioned RNAs that regulate dosage compensation and imprinted gene expression. Here, we provide an overview of lncRNA activities, and then review the role of lncRNAs in processes vital to reproduction, such as germ cell specification, sex determination and gonadogenesis, sex hormone responses, meiosis, gametogenesis, placentation, non-genetic inheritance, and pathologies affecting reproductive tissues. Results from many species are presented to illustrate the evolutionarily conserved processes lncRNAs are involved in.

Gonad specific genes in Atlantic salmon (Salmon salar L.): characterization of tdrd7-2, dazl-2, piwil1 and tdrd1 genes

Atlantic salmon is a commercially important species. Understanding key processes in their life history, such as germ cell development is essential for further improvements within salmon farming. Since salmonids have undergone an additional whole genome duplication compared to many other fish species, they possess more gene paralogues. Therefore, data on gene expression and function from other species may not apply for salmon. Our aim was to study the spatial and tissue specific expression of genes known from model species to be essential for germ cell development, to identify germ cell specific factors in salmon. Based on homology with other species, selected genes were predicted in the salmon genome assembly. Gene expression was measured by PCR in a variety of juvenile salmon tissues. For genes expressed exclusively in gonads we measured the expression in the same tissues as well as in eggs, embryos and larvae by qPCR. Finally, we revealed the cellular localization of the gonad specific mRNAs by in situ hybridization (ISH). Several of the selected genes (tdrd7, cxcr4b and dazl), were found in more than one copy (indicated by a number following the gene name) in the salmon genome. Expression of tdrd7-2, dazl-2, piwil1 and tdrd1 was detected exclusively in the testis and ovary of juvenile salmon, and transcripts of tdrd7-2, dazl-2 and piwil1 were localized within male and female germ cells. While tdrd7-2, piwil1 and tdrd1 were expressed in unfertilized eggs and all embryo and larval stages measured, dazl-2 was expressed in unfertilized eggs and embryos until the onset of gastrulation. This study shows that several of the genes known from model species to be essential for germ cell development, display paralogues in salmon with dissimilar and similar expression patterns in comparison to other species. Transcripts of tdrd7-2, dazl-2, piwil1 and tdrd1 are detected exclusively in gonads of juveniles and are found among maternal RNA of eggs and subsequent embryos. This information is valuable for further studies aiming at understanding salmon germ cell development.