It is widely believed that most or all Y-chromosomal genes were once shared with the X chromosome. The DAZ gene, so named for 'deleted in azoospermia,' is a candidate for AZF, the human Y-chromosomal azoospermia factor. Reijo et al. (1995) found that Y-chromosome deletions in 12 men with azoospermia overlapped, thus defining the locations of gene(s) required for spermatogenesis, the azoospermia factor. The region contained a single-copy gene they referred to as DAZ (for 'deleted in azoospermia') which is transcribed in the adult testis and appears to encode an RNA-binding protein. Daz is found on the Y chromosome in Old World primates and apes, but in other mammals, they are represented only by an autosomal gene, DAZLA.
NCBI Summary:
The DAZ (Deleted in AZoospermia) gene family encodes potential RNA binding proteins that are expressed in prenatal and postnatal germ cells of males and females. The protein encoded by this gene is localized to the nucleus and cytoplasm of fetal germ cells and to the cytoplasm of developing oocytes. In the testis, this protein is localized to the nucleus of spermatogonia but relocates to the cytoplasm during meiosis where it persists in spermatids and spermatozoa. Transposition and amplification of this autosomal gene during primate evolution gave rise to the DAZ gene cluster on the Y chromosome. Mutations in this gene have been linked to severe spermatogenic failure and infertility in males. Two transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Jun 2010]
Kinked {beta}-strands mediate high-affinity recognition of mRNA targets by the germ-cell regulator DAZL. Jenkins HT et al. A defect in germ-cell (sperm and oocyte) development is the leading cause of male and female infertility. Control of translation through the binding of deleted in azoospermia (DAZ)-like (DAZL) to the 3'-UTRs of mRNAs, via a highly conserved RNA recognition motif (RRM), has been shown to be essential in germ-cell development. Crystal structures of the RRM from murine DAZL (Dazl), both alone and in complex with RNA sequences from the 3'-UTRs of mRNAs regulated by Dazl, reveal high-affinity sequence-specific recognition of a GUU triplet involving an extended, kinked, pair of -strands. Recognition of the GUU triplet is maintained, whereas the identity and position of bases flanking this triplet varies. The Dazl RRM is thus able to recognize GUU triplets in different sequence contexts. Mutation of bases within the GUU triplet reduces the affinity of binding. Together with the demonstration that multiple Dazl RRMs can bind to a single RNA containing multiple GUU triplets, these structures suggest that the number of DAZL molecules bound to GUU triplets in the 3'-UTR provides a method for modulating the translation of a target RNA. The conservation of RNA binding and structurally important residues between members of the DAZ family, together with the demonstration that mutation of these residues severely impairs RNA binding, indicate that the mode of RNA binding revealed by these structures is conserved in proteins essential for gamete development from flies to humans.
Cellular localization
Cytoplasmic
Comment
RNA immunoprecipitation identifies novel targets of DAZL in human foetal ovary. Rosario R et al. (2017) Can novel meiotic RNA targets of DAZL (deleted in azoospermia-like) be identified in the human foetal ovary? SYCP1 (synaptonemal complex protein-1), TEX11 (testis expressed 11) and SMC1B (structural maintenance of chromosomes 1B) are novel DAZL targets in the human foetal ovary, thus DAZL may have previously unrecognised roles in the translational regulation of RNAs involved in chromosome cohesion and DNA recombination in the oocyte from the time of initiation of meiosis. The phenotype of Dazl deficiency in mouse is infertility in both sexes and DAZL has also been linked to infertility in humans. Few studies have explored targets of this RNA-binding protein. The majority of these investigations have been carried out in mouse, and have focussed on the male thus the basis for its central function in regulating female fertility is largely unknown. We carried out RNA sequencing after immunoprecipitation of endogenous DAZL from human foetal ovarian tissue (17 weeks of gestation, obtained after elective termination of pregnancy) to identify novel DAZL targets involved in meiosis (n = 3 biological replicates). Using quantitative RT-PCR, we examined the expression of selected RNAs identified by our immunoprecipitation across gestation, and visualised the expression of potential target SMC1B in relation to DAZL, with a combination of in situ hybridisation and immunohistochemistry. 3' untranslated region (3'UTR)-luciferase reporter assays and polysome profile analysis were used to investigate the regulation of three RNA targets by DAZL, representing key functionalities: SYCP1, TEX11 and SMC1B. We identified 764 potential RNA targets of DAZL in the human foetal ovary (false discovery rate 0.05 and log-fold change ≥ 2), with functions in synaptonemal complex formation (SYCP1, SYCP3), cohesin formation (SMC1B, RAD21), spindle assembly checkpoint (MAD2L1, TRIP13) and recombination and DNA repair (HORMAD1, TRIP13, TEX11, RAD18, RAD51). We demonstrated that the translation of novel targets SYCP1 (P = 0.004), TEX11 (P = 0.004) and SMC1B (P = 0.002) is stimulated by the presence of DAZL but not by a mutant DAZL with impaired RNA-binding activity. The raw data are available at GEO using the study ID: GSE81524. This analysis is based on identification of DAZL targets at the time when meiosis starts in the ovary: it may have other targets at other stages of oocyte development, and in the testis. Representative targets were validated, but detailed analysis was not performed on the majority of putative targets. These data indicate roles for DAZL in the regulation of several key functions in human oocytes. Through the translational regulation of novel RNA targets SMC1B and TEX11, DAZL may have a key role in regulating chromosome cohesion and DNA recombination; two processes fundamental in determining oocyte quality and whose establishment in foetal life may support lifelong fertility. This study was supported by the UK Medical Research Council (grant no G1100357 to R.A.A. and an intramural MRC programme grant to I.R.A.). The authors declare no competing interests.//////////////////
Ovarian function
Germ cell development, Oogenesis, Oocyte maturation, Early embryo development
Comment
The RNA-binding protein DAZL functions as repressor and activator of mRNA translation during oocyte maturation. Yang CR et al. (2020) Deleted in azoospermia-like (DAZL) is an RNA-binding protein critical for gamete development. In full-grown oocytes, the DAZL protein increases 4-fold during reentry into the meiotic cell cycle. Here, we have investigated the functional significance of this accumulation at a genome-wide level. Depletion of DAZL causes a block in maturation and widespread disruption in the pattern of ribosome loading on maternal transcripts. In addition to decreased translation, DAZL depletion also causes translational activation of a distinct subset of mRNAs both in quiescent and maturing oocytes, a function recapitulated with YFP-3'UTR reporters. DAZL binds to mRNAs whose translation is both repressed and activated during maturation. Injection of recombinant DAZL protein in DAZL-depleted oocytes rescues the translation and maturation to MII. Mutagenesis of putative DAZL-binding sites in these mRNAs mimics the effect of DAZL depletion. These findings demonstrate that DAZL regulates translation of maternal mRNAs, functioning both as the translational repressor and activator during oocyte maturation.//////////////////
Requirement of the 3'-UTR-dependent suppression of DAZL in oocytes for pre-implantation mouse development. Fukuda K et al. (2018) Functional oocytes are produced through complex molecular and cellular processes. In particular, the contribution of post-transcriptional gene regulation mediated by RNA-binding proteins (RBPs) is crucial for controlling proper gene expression during this process. DAZL (deleted in azoospermia-like) is one of the RBPs required for the sexual differentiation of primordial germ cells and for the progression of meiosis in ovulated oocytes. However, the involvement of DAZL in the development of follicular oocytes is still unknown. Here, we show that Dazl is translationally suppressed in a 3'-UTR-dependent manner in follicular oocytes, and this suppression is required for normal pre-implantation development. We found that suppression of DAZL occurred in postnatal oocytes concomitant with the formation of primordial follicles, whereas Dazl mRNA was continuously expressed throughout oocyte development, raising the possibility that DAZL is dispensable for the survival and growth of follicular oocytes. Indeed, follicular oocyte-specific knockout of Dazl resulted in the production of normal number of pups. On the other hand, genetically modified female mice that overexpress DAZL produced fewer numbers of pups than the control due to defective pre-implantation development. Our data suggest that post-transcriptional suppression of DAZL in oocytes is an important mechanism controlling gene expression in the development of functional oocytes.//////////////////
DAZL and CPEB1 regulate mRNA translation synergistically during oocyte maturation. Martins JP et al. (2016) Meiotic progression requires exquisitely coordinated translation of maternal mRNA accumulated during oocyte growth. A major regulator of this program is the cytoplasmic polyadenylation element binding protein 1 (CPEB1). However, the temporal pattern of translation at different meiotic stages implies the function of additional RNA binding proteins (RBPs). Here we report that deleted in azoospermia-like (DAZL) cooperates with CPEB1 to regulate maternal mRNA translation. Using a strategy that monitors ribosome loading onto endogenous mRNAs and a prototypic translation target, we show that ribosome loading is induced in a DAZL- and CPEB1-dependent manner, as the oocyte reenters meiosis. Depletion of the two RBPs from oocytes and 3' UTR mutagenesis demonstrate that both RBPs interact with Tex19.1 3' UTR and cooperate in translation activation of this mRNA. We observed a synergism between DAZL and cytoplasmic polyadenylation elements (CPE) in the translation pattern of maternal mRNAs when using a genome-wide analysis. Mechanistically, the number of DAZL proteins loaded on to the mRNA and the characteristics of the CPE may define the degree of cooperation between the two RBPs in activating translation and meiotic progression.//////////////////
Licensing of gametogenesis, dependent on RNA binding protein DAZL, as a gateway to sexual differentiation of fetal germ cells. Gill ME et al. Mammalian oocytes and spermatozoa derive from fetal cells shared by the sexes. These primordial germ cells (PGCs) migrate to the developing somatic gonad, giving rise to oocytes or spermatozoa. These opposing sexual fates are determined not by the PGCs' own sex chromosome constitution (XX or XY), but by the sexual identity of the fetal gonad that they enter. We asked whether PGCs undergo a developmental transition that enables them to respond to feminizing or masculinizing cues from fetal ovary or testis. We conducted in vivo genetic studies of DAZL, an RNA-binding protein expressed in both ovarian and testicular germ cells. We found that germ cells in C57BL/6 Dazl-deficient fetuses-whether XX or XY-migrate to the gonad but do not develop either male or female features. Instead, they remain in a sexually undifferentiated state similar to that of migrating PGCs. Thus, germ cells in C57BL/6 Dazl-deficient fetuses do not respond to sexual cues from ovary or testis, whereas the earlier processes of germ cell specification and migration are unaffected. We propose that PGCs of both XX and XY fetuses undergo licensing, an active developmental transition that enables the resultant gametogenesis-competent cells to respond to feminizing or masculinizing cues produced by the fetal ovary or testis and hence to embark on oogenesis or spermatogenesis. In C57BL/6 mice, Dazl is required for licensing. Licensing serves as a gateway from the embryonic processes shared between the sexes-germ cell specification and migration-to the sex-specific pathways of oogenesis and spermatogenesis.
Genome-wide analysis of translation reveals a critical role for deleted in azoospermia-like (Dazl) at the oocyte-to-zygote transition. Chen J et al. Oocyte maturation, fertilization, and early embryonic development occur in the absence of gene transcription. Therefore, it is critical to understand at a global level the post-transcriptional events that are driving these transitions. Here we used a systems approach by combining polysome mRNA profiling and bioinformatics to identify RNA-binding motifs in mRNAs that either enter or exit the polysome pool during mouse oocyte maturation. Association of mRNA with the polysomes correlates with active translation. Using this strategy, we identified highly specific patterns of mRNA recruitment to the polysomes that are synchronized with the cell cycle. A large number of the mRNAs recovered with translating ribosomes contain motifs for the RNA-binding proteins DAZL (deleted in azoospermia-like) and CPEB (cytoplasmic polyadenylation element-binding protein). Although a Dazl role in early germ cell development is well established, no function has been described during oocyte-to-embryo transition. We demonstrate that CPEB1 regulates Dazl post-transcriptionally, and that DAZL is essential for meiotic maturation and embryonic cleavage. In the absence of DAZL synthesis, the meiotic spindle fails to form due to disorganization of meiotic microtubules. Therefore, Cpeb1 and Dazl function in a progressive, self-reinforcing pathway to promote oocyte maturation and early embryonic development.
Human DAZL, DAZ and BOULE genes modulate primordial germ-cell and haploid gamete formation. Kee K et al. The leading cause of infertility in men and women is quantitative and qualitative defects in human germ-cell (oocyte and sperm) development. Yet, it has not been possible to examine the unique developmental genetics of human germ-cell formation and differentiation owing to inaccessibility of germ cells during fetal development. Although several studies have shown that germ cells can be differentiated from mouse and human embryonic stem cells, human germ cells differentiated in these studies generally did not develop beyond the earliest stages. Here we used a germ-cell reporter to quantify and isolate primordial germ cells derived from both male and female human embryonic stem cells. By silencing and overexpressing genes that encode germ-cell-specific cytoplasmic RNA-binding proteins (not transcription factors), we modulated human germ-cell formation and developmental progression. We observed that human DAZL (deleted in azoospermia-like) functions in primordial germ-cell formation, whereas closely related genes DAZ and BOULE (also called BOLL) promote later stages of meiosis and development of haploid gametes. These results are significant to the generation of gametes for future basic science and potential clinical applications.
DAZL expression in human oocytes, preimplantation embryos and embryonic stem cells Cauffman G, et al .
In humans, the Deleted in Azoospermia Like (DAZL) gene is believed to function in the development of primordial germ cells and in germ cell differentiation and maturation because the expression of DAZL is only found in the germ and non-germ lineage of the reproductive system and in embryonic stem (ES) cells. The present study examined the presence of DAZL transcripts in the last stages of oocyte maturation, in ES cells, and throughout the preimplantation development; the link between gametes and ES cells. The finding of DAZL transcripts in the last stages of oogenesis and during the first two cell cycles of the preimplantation development was expected, because DAZL is a germ cell marker and the transcripts present at that time are generally encoded by the maternal genome. During the third cell cycle, DAZL showed a variable expression pattern, which may point to the maternal to embryonic transition. After the third cell cycle, transcripts were again consistently detected, suggesting embryonic DAZL transcription. In blastocysts, DAZL transcripts were only detected in those of good quality and this as well in the inner cell mass (ICM) as in the trophectoderm (TE). The presence of DAZL transcripts in the ICM and in ES cells was not surprising since both can lead to the formation of germ cells, but TE cells cannot. The quality-related expression of DAZL in blastocysts, and especially its trophectodermal expression, might imply other functions for DAZL beyond germ cell development.
Dazl Promotes Germ Cell Differentiation from Embryonic Stem Cells.
Yu Z, Ji P, Cao J, Zhu S, Li Y, Zheng L, Chen X, Feng L.
Laboratory for Germ Cell Research, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China.
It has been demonstrated that through the formation of embryoid bodies (EBs) germ cells can be derived from embryonic stem (ES) cells. Here, we describe a transgene expression approach to derive germ cells directly from ES cells in vitro without EB formation. Through the ectopic expression of Deleted in Azoospermia-Like (Dazl), a germ cell-specific RNA-binding protein, both motile tailed-sperm and oocytes were induced from mouse ES (mES) cells in culture. Furthermore, transient overexpression of Dazl led to suppression of Nanog but induced germ cell nuclear antigen in mES cells. Dazl knockdown resulted in reduction in the expression of germ cell markers including Stella, MVH and Prdm1. Our study indicates that Dazl is a master gene controlling germ cell differentiation and that ectopic expression of Dazl promotes the dynamic differentiation of mouse ES cells into gametes in vitro.
Dazl Promotes Germ Cell Differentiation from Embryonic Stem Cells. Yu Z et al. It has been demonstrated that through the formation of embryoid bodies (EBs) germ cells can be derived from embryonic stem (ES) cells. Here, we describe a transgene expression approach to derive germ cells directly from ES cells in vitro without EB formation. Through the ectopic expression of Deleted in Azoospermia-Like (Dazl), a germ cell-specific RNA-binding protein, both motile tailed-sperm and oocytes were induced from mouse ES (mES) cells in culture. Furthermore, transient overexpression of Dazl led to suppression of Nanog but induced germ cell nuclear antigen in mES cells. Dazl knockdown resulted in reduction in the expression of germ cell markers including Stella, MVH and Prdm1. Our study indicates that Dazl is a master gene controlling germ cell differentiation and that ectopic expression of Dazl promotes the dynamic differentiation of mouse ES cells into gametes in vitro.
Expression regulated by
Growth Factors/ cytokines
Comment
Porcine DAZL messenger RNA: its expression and regulation during oocyte maturation. Liu J et al. The Deleted in Azoospermia-Like (DAZL) is known to play an important role during both spermatogenesis and oogenesis, as mutations in this gene may result in male and female sterility. In order to study the expression of DAZL in the pig, we cloned the full-length coding sequence and determined its mRNA and protein expression profile in the ovary and in oocytes undergoing in vitro maturation (IVM). Immunohistochemisty revealed that DAZL protein localizes to oocytes of both preantral and antral follicles. The expression in the oocytes was also confirmed by Western blot. Immunocytochemistry and real time RT-PCR showed that the DAZL transcript and protein accumulate during oocyte maturation. In addition, glial cell line-derived neurotrophic factor (GDNF), epidermal growth factor (EGF), and follicle-stimulating hormone (FSH) significantly stimulate DAZL expression in oocytes derived from antral follicles during IVM. Our results suggest that the porcine DAZL coding sequence is highly homologous to those reported for the human and mouse cDNAs, and that DAZL expression increases during oocyte maturation.
Ovarian localization
Oocyte, Luteal cells
Comment
Immunohistochemical analyses by Nishi et al. (1999) with the human DAZLA antiserum showed that the DAZLA protein is expressed at a cytoplasmic location in female germ cells. Available evidence suggests that the
DAZLA gene is a participant in human oogenesis.
The DAZL and PABP families: RNA-binding proteins with interrelated roles in translational control in oocytes. Brook M et al. Gametogenesis is a highly complex process that requires the exquisite temporal, spatial and amplitudinal regulation of gene expression at multiple levels. Translational regulation is important in a wide variety of cell-types but may be even more prevalent in germ cells, where periods of transcriptional quiescence necessitate the use of post-transcriptional mechanisms to effect changes in gene expression. Consistent with this, studies in multiple animal models have revealed an essential role for mRNA translation in the establishment and maintenance of reproductive competence. Whilst studies in humans are less advanced, emerging evidence suggests that translational regulation plays a similarly important role in human germ cells and fertility. This review highlights specific mechanisms of translational regulation that play critical roles in oogenesis by activating subsets of mRNAs. These mRNAs are activated in a strictly determined temporal manner via elements located within their 3-untranslated region (UTR), which serve as binding sites for trans-acting factors. Whilst we concentrate on oogenesis, these regulatory events also play important roles during spermatogenesis. In particular we focus on the Deleted in Azoospermia-like (DAZL) family of proteins, recently implicated in the translational control of specific mRNAs in germ cells; their relationship with the general translation initiation factor poly(A)-binding protein (PABP) and the process of cytoplasmic mRNA polyadenylation.
Follicle stages
Primordial, Primary, Secondary, Corpus luteum
Comment
Using reverse transcription PCR, Cooke et al. (19960 shows that the Dazla transcript is only detectable in male and female gonads Using immunoblot, Ruggiu et al. (1997) suggested that Dazla is expressed in the oocyte of ovarian follicles.
Pan HA, et al 2002 reported the expression of DAZL protein in the human corpus luteum.
The DAZL gene and its homologues are required for the development of male and
female germ cells in different species. However, their role in other aspects
of human reproduction is not known. The authors have generated a polyclonal antibody to
the DAZL protein and developed a sensitive standard curve
quantitative-competitive-RT-PCR assay to characterize the expression of DAZL
in the human corpus luteum (CL). DAZL transcripts are expressed in the CL, but
the concentrations decreased with advancing luteal phase. In accordance with
the mRNA data, DAZL protein was most abundant in the early phase CL.
Immunohistochemical staining showed DAZL protein in the cytoplasm of
granulosa-luteal cells. The distinct expression pattern of DAZL protein in the
Phenotypes
Mutations
3 mutations
Species: mouse
Mutation name: None
type: null mutation fertility: infertile - ovarian defect Comment:Ruggiu et al.(1997) showed that disruption of the Dazla gene leads to loss of germ cells and complete absence of gamete production, demonstrating that Dazla is essential for the differentiation of germ cells. McNeilly JR, et al 2000 reported that loss of oocytes in Dazl knockout mice results in maintained ovarian steroidogenic function but altered gonadotropin
secretion in adult animals.
Ovaries from -/- females lack any follicular structure
and have no cells positive for either Mullerian inhibiting factor or sulfated glycoprotein-l, indicating a lack of small follicles or corpora lutea. However, by immunocytochemistry, there are cells positive for 3 beta -hydroxysteroid dehydrogenase, 17 alpha -hydroxylase, and aromatase, indicating the presence of steroidogenically active cells capable of producing
estrogen. In addition, these
steroidogenically active cells contain ER beta, inhibin alpha, and
betaB-subunits, and -/- mice have low measurable plasma inhibin A and B
levels. The ovarian steroids and inhibins had no significant effect on either
plasma or pituitary gonadotropin levels, with lower
LH and FSH in intact +/+ and +/- females. However, significantly increased plasma inhibin B together with significantly (P < 0.05) lower FSH
were observed in the +/- females.
Species: mouse
Mutation name: None
type: null mutation fertility: fertile Comment: Decreased Oocyte DAZL Expression in Mice Results in Increased Litter Size by Modulating FSH-Induced Follicular Growth. McNeilly JR et al. While the germ cell specific RNA binding protein, DAZL, is essential for oocytes to survive meiotic arrest, DAZL heterozygous (het) mice have an increased ovulation rate which is associated with elevated inhibin B and decreased plasma FSH. The relationship between decreased oocyte DAZL expression and enhanced follicular development in het mice was investigated using in vitro follicle cultures and in vivo modulation of endogenous FSH by treating mice with inhibin and exogenous FSH. In vitro, follicles from het mice are more sensitive to FSH than wild-type (wt) and can grow in FSH concentrations which are deleterious to wt follicles. In vivo, despite no differences between genotypes in follicle population profiles, analysis of granulosa cell areas in antral follicles identified a significantly greater number of antral follicles with increased granulosa cell area in het ovaries. Modulation of FSH in vivo using decreasing doses of FSH or ovine follicular fluid (oFF) as a source of inhibin confirmed the increased responsiveness of het antral follicles to FSH. Significantly more follicles expressing aromatase protein confirmed the earlier maturation of granulosa cells in het mice. In conclusion, it is suggested that DAZL represses specific unknown genes which regulate the response of granulosa cells to FSH. If this repression is reduced as in DAZL het mice, then follicles can grow to the late follicular stage despite declining levels of circulating FSH, thus leading to more follicles ovulating and increased litter size.
Species: mouse
Mutation name: type: null mutation fertility: fertile Comment: Requirement of the 3'-UTR-dependent suppression of Dazl in oocytes for pre-implantation mouse development. Fukuda K et al. (2018) Functional oocytes are produced through complex molecular and cellular processes. In particular, the contribution of post-transcriptional gene regulation mediated by RNA-binding proteins (RBPs) is crucial for controlling proper gene expression during this process. DAZL (deleted in azoospermia-like) is one of the RBPs required for the sexual differentiation of primordial germ cells and for the progression of meiosis in ovulated oocytes. However, the involvement of DAZL in the development of follicular oocytes is still unknown. Here, we show that Dazl is translationally suppressed in a 3'-UTR-dependent manner in follicular oocytes, and this suppression is required for normal pre-implantation development. We found that suppression of DAZL occurred in postnatal oocytes concomitant with the formation of primordial follicles, whereas Dazl mRNA was continuously expressed throughout oocyte development, raising the possibility that DAZL is dispensable for the survival and growth of follicular oocytes. Indeed, follicular oocyte-specific knockout of Dazl resulted in the production of normal number of pups. On the other hand, genetically modified female mice that overexpress DAZL produced fewer numbers of pups than the control due to defective pre-implantation development. Our data suggest that post-transcriptional suppression of DAZL in oocytes is an important mechanism controlling gene expression in the development of functional oocytes.//////////////////