Primate-Specific DAZ Regulates Translation of Cell Proliferation-Related mRNAs and is Essential for Maintenance of Spermatogonia.

Primate-specific DAZ (deleted in azoospermia) has evolved in the azoospermia factor c (AZFc) locus on the Y chromosome. Loss of DAZ is associated with azoospermia in patients with deletion of the AZFc region (AZFc_del). However, the molecular mechanisms of DAZ in spermatogenesis remain uncertain. In this study, the molecular mechanism of DAZ is identified, which is unknown since it is identified 40 years ago because of the lack of a suitable model. Using clinical samples and cell models, it is shown that DAZ plays an important role in spermatogenesis and that loss of DAZ is associated with defective proliferation of c-KIT-positive spermatogonia in patients with AZFc_del. Mechanistically, it is shown that knockdown of DAZ significantly downregulated global translation and subsequently decreased cell proliferation. Furthermore, DAZ interacted with PABPC1 via the DAZ repeat domain to regulate global translation. DAZ targeted mRNAs that are involved in cell proliferation and cell cycle phase transition. These findings indicate that DAZ is a master translational regulator and essential for the maintenance of spermatogonia. Loss of DAZ may result in defective proliferation of c-KIT-positive spermatogonia and spermatogenic failure.

Partial-AZFc deletions in Chilean men with primary spermatogenic impairment: gene dosage and Y-chromosome haplogroups.

PURPOSE: To investigate the association of partial-AZFc deletions in Chilean men with primary spermatogenic failure and their testicular histopathological phenotypes, analyzing the contribution of DAZ dosage, CDY1 copies, and Y-chromosome haplogroups. SUBJECTS AND METHODS: We studied 479 Chilean men: 334 infertile patients with histological examination (233 cases with spermatogenic defects and 101 normal spermatogenesis, obstructive controls, OC), and 145 normozoospermic controls (NC). AZFc subdeletions were detected by single-tagged sequences and single nucleotide variants analysis. DAZ-copy number was quantified by real-time qPCR. Y-chromosome haplogroups (Y-hg) were hierarchically genotyped through 16 biallelic-markers. RESULTS: The prevalence of AZFc-partial deletions was increased in cases (6%) compared with NC (1.4%) (P = 0.035). There was no difference between 143 Sertoli-cell only syndrome, 35 maturation arrest, or 35 mix atrophy patients and controls. However, gr/gr deletions were more frequent in 16 subjects with hypospermatogenesis compared with NC (P = 0.003) and OC (P = 0.013). Y-hg R was the most prevalent (~ 50%), but decreased among gr/gr deletions (21%, P = 0.03). The prevalence of Y-hg M increased in cases versus controls, both in total and non-deleted men (3.9 and 3.7% versus 0.4%, P = 0.009 and P = 0.016, respectively). Among gr/gr deletions, Y-hg H increased compared with non-deleted men (14.3% versus 0.4%, P = 0.0047). CONCLUSION: Partial-AZFc deletions in a Chilean admixed population are associated with secretory azo/oligozoospermia and might have a role in the development of hypospermatogenesis. Low represented haplogroups, Y-hg M and Y-hg H, show an association with the occurrence of spermatogenic failure and gr/gr deletions respectively; however, additional studies are required.

Dynamic and regulated TAF gene expression during mouse embryonic germ cell development.

Germ cells undergo many developmental transitions before ultimately becoming either eggs or sperm, and during embryonic development these transitions include epigenetic reprogramming, quiescence, and meiosis. To begin understanding the transcriptional regulation underlying these complex processes, we examined the spatial and temporal expression of TAF4b, a variant TFIID subunit required for fertility, during embryonic germ cell development. By analyzing published datasets and using our own experimental system to validate these expression studies, we determined that both Taf4b mRNA and protein are highly germ cell-enriched and that Taf4b mRNA levels dramatically increase from embryonic day 12.5-18.5. Surprisingly, additional mRNAs encoding other TFIID subunits are coordinately upregulated through this time course, including Taf7l and Taf9b. The expression of several of these germ cell-enriched TFIID genes is dependent upon Dazl and/or Stra8, known regulators of germ cell development and meiosis. Together, these data suggest that germ cells employ a highly specialized and dynamic form of TFIID to drive the transcriptional programs that underlie mammalian germ cell development.

Evaluation of chromosomal abnormalities and Y chromosome microdeletion in infertile males of 10 families.

This study was designed to investigate the hormonal, seminal changes and chromosomal aberrations in cases of male infertility. A total of ten infertile families from Khyber Pakhtunkhwa of Pakistan were included in the study. The families were clinically evaluated by standard criteria; diagnosis of azoospermic and oligospermic males was confirmed. Seminal, hormonal, ultra sonographic and histopathological examinations were carried out for all the affected participants of the study. Karyotyping was performed on peripheral blood lymphocytes according to standard methods. Hormones were altered in six families. Ultrasonographic abnormal finding was observed in six families. Karyotyping analysis revealed numerical aberration in family G (0X) and family I (XXY). The remainingfamilies had no structural or numerical aberration. Y chromosome microdeletion analysis revealed AZFc deletion in both the affected participants of the family C. The remaining families were found normal for microdeletion. The occurrence of chromosomal anomalies and Y chromosome microdeletions among infertile males strongly suggests the need to include these two tests in routine investigations of male in fertility cases.

Effects of ten-eleven translocation 1 (Tet1) on DNA methylation and gene expression in chicken primordial germ cells.

Ten-eleven translocation 1 (Tet1) is involved in DNA demethylation in primordial germ cells (PGCs); however, the precise regulatory mechanism remains unclear. In the present study the dynamics of 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) in developing PGCs and the role of Tet1 in PGC demethylation were analysed. Results show that 5mC levels dropped significantly after embryonic Day 4 (E4) and 5hmC levels increased reaching a peak at E5-E5.5. Interestingly, TET1 protein was highly expressed during E5 to E5.5, which showed a consistent trend with 5hmC. The expression of pluripotency-associated genes (Nanog, PouV and SRY-box 2 (Sox2)) and germ cell-specific genes (caveolin 1 (Cav1), piwi-like RNA-mediated gene silencing 1 (Piwi1) and deleted in azoospermia-like (Dazl)) was upregulated after E5, whereas the expression of genes from the DNA methyltransferase family was decreased. Moreover, the Dazl gene was highly methylated in early PGCs and then gradually hypomethylated. Knockdown of Tet1 showed impaired survival and proliferation of PGCs, as well as increased 5mC levels and reduced 5hmC levels. Further analysis showed that knockdown of Tet1 led to elevated DNA methylation levels of Dazl and downregulated gene expression including Dazl. Thus, this study reveals the dynamic epigenetic reprogramming of chicken PGCs invivo and the molecular mechanism of Tet1 in regulating genomic DNA demethylation and hypomethylation of Dazl during PGC development.

High frequency of de novo DAZ microdeletion in sperm nuclei of subfertile men: possible involvement of genome instability in idiopathic male infertility.

The occurrence and diagnosis of Y-chromosome microdeletions, specifically deletions of the DAZ (Deleted in Azoospermia) genes are an important issue in male infertility. Screening Y chromosome microdeletion is mainly done using polymerase chain reaction (PCR) on blood leukocytes. However, there is some evidence indicating that presence of DAZ in somatic cells might not be indicative of its presence in the germ cell lineage. Therefore, a total of 130 men with poor semen quality were examined for presence of DAZ microdeletion in their leukocytes. From these, sperm from 40 randomly selected men with no DAZ microdeletions in their leukocytes (n = 10 oligozoospermia; n = 10 asthenozoospermia; n = 10 oligoasthenozoospermia; and n = 10 near-azoospermia) were were compared to sperm from men of normal semen quality (n = 10) using combined primed in situ labelling and fluorescent in situ hybridization (PRINS-FISH) technique as well as screening for sex chromosome aneuploidy. There was an increased frequency of DAZ microdeletion in blood samples from oligozoospermic (5%) (p < 0.05) and near azoospermic patients (14%) (p < 0.01). A high frequency of DAZ microdeletion was observed in the sperm of patients with no DAZ microdeletion in their leukocytes compared to control (p < 0.01). The frequency of sex chromosome aneuploidy also increased, correlating with the severity of infertility in the studied groups. A similar result was observed for sex chromosome aneuploidy. The results might be indicative of DAZ microdeletion induction during spermatogenesis.