Male infertility, genetic analysis of the DAZ genes on the human Y chromosome and genetic analysis of DNA repair

Chromosomal abnormalities in men with pregestational and gestational infertility in northeast China

PURPOSE

To detect incidences and the types of chromosomal abnormalities in Chinese men with infertility and determine chromosomal factors association with various phenotypes.

METHODS

Semen analysis and karyotype analysis by G-banding were carried out in 4,659 idiopathic infertile males; additionally, multiplex PCR using nine specific sequence-tagged sites (STSs) was used to detect azoospermia factor (AZF) microdeletions in 412 patients with Y chromosomal abnormalities.

RESULTS

Male infertility was divided into pregestational infertility, characterized by failure to produce a fertilized ovum, and gestational infertility, characterized by embryo loss after fertilization. The former can result from azoospermia, oligozoospermia or oligoasthenozoospermia syndrome, while the latter is associated with developmental early pregnancy loss, habitual miscarriage and stillbirth. Among 4,659 male patients, 412 (8.84 %) showed abnormal chromosomal karyotypes, including 314 (6.74 %) with sex chromosomal abnormalities and 98 (2.10 %) with autosomal abnormalities. The prevalences of numerical and structural abnormalities among patients with chromosomal abnormalities were 259/412 (62.86 %) and 153/412 (37.14 %), respectively. Furthermore, structural sex chromosomal abnormalities were represented by various phenotypic profiles (46,XX, 47,XYY and 45,X/46,XY), and a prevalence of AZF microdeletions of 19/79 (24.05 %). AZF microdeletions were highly associated with Y chromosomal abnormalities (P = 0.018).

CONCLUSION

Various chromosomal abnormalities that result in male infertility could affect spermatogenesis or embryonic development at different levels. Sex chromosomal and autosomal abnormalities were highly associated with pregestational and gestational infertility, respectively. AZF microdeletions may play an important role in lowering the stability of the Y chromosome.

A conserved PUF-Ago-eEF1A complex attenuates translation elongation

PUF (Pumilio/FBF) RNA-binding proteins and Argonaute (Ago) miRNA-binding proteins regulate mRNAs post-transcriptionally, each acting through similar yet distinct mechanisms. Here, we report that PUF and Ago proteins can also function together in a complex with a core translation elongation factor, eEF1A, to repress translation elongation. Both nematode and mammalian PUF/Ago/eEF1A complexes were identified, using co-immunoprecipitation and recombinant protein assays. Nematode CSR-1 (Ago) promotes repression of FBF (PUF) target mRNAs in in vivo assays, and the FBF-1/CSR-1 heterodimer inhibits EFT-3 (eEF1A) GTPase activity in vitro. Mammalian PUM2/Ago/eEF1A inhibits translation of nonadenylated and polyadenylated reporter mRNAs in vitro. This repression occurs after translation initiation and leads to ribosome accumulation within the open reading frame, roughly at the site where the nascent polypeptide emerges from the ribosomal exit tunnel. Together, these data suggest that a conserved PUF/Ago/eEF1A complex attenuates translation elongation.

Genome instability in AZFc region on Y chromosome in leukocytes of fertile and infertile individuals following exposure to gamma radiation

PURPOSE

Men are exposed to various doses of ionizing radiation due to living in regions with high natural background radiation, accidentally, occupationally or for cancer treatment. To study genomic instability of AZFc region to gamma radiation, blood samples from normal, oligozoospermia, and azoospermia individuals were irradiated by a Co-60 source.

METHODS

Irradiated cells were kept for 48 h in order to repair initial DNA damages. Real time PCR was performed for three markers (SY 1206, SY 1197, SY 579) for testing copy number variation before and after irradiation. Copy number variations were compared by calculation of cycle threshold comparative method.

RESULTS

Copy number variations of studied markers in AZFc region (microdeletion and duplication) in all samples after exposure to radiation increased with a dose dependent fashion. The frequency of instability was significantly higher in samples from infertile men in comparison with fertile ones (p < 0.001).

CONCLUSION

No significant difference was seen between the two infertile groups (p > 0.05). This observation might be a possible explanation for induction of azoospermia and oligozoospermia after radiotherapy. Increased frequency of induced microdeletion and duplication in infertile men compared with normal might be attributed to the deficiency in repair systems and the genetic factors involved in incomplete spermatogenesis of infertile men.

KHDC1B is a novel CPEB binding partner specifically expressed in mouse oocytes and early embryos

mRNAs required for meiotic maturation and early embryonic development are stored in growing oocytes. These transcripts are translationally repressed until hormonal cues trigger ovulation. Errors in translation underlie some cases of human infertility and are associated with ovarian germ cell tumors. However, it remains unclear how maternal transcripts are kept quiescent in mammals. This study describes a potential translational regulator, KHDC1B. KHDC1B is a member of a small family of KH-domain containing proteins specific to eutherian mammals. Two family members, KHDC1A and 1B, are highly expressed in oocytes. KHDC1A and 1B bind polyU agarose and form oligomers like other KH-domain proteins. The functions of these proteins were tested by expression in Xenopus embryos. KHDC1A caused cell death, whereas KHDC1B caused cleavage arrest. This arrest phenotype was rescued by coexpression of the mouse translational regulator cytoplasmic polyadenylation binding protein 1 (mCPEB1). Coimmunoprecipitation and coimmunostaining experiments confirmed the functional interaction between KHDC1B and mCPEB1. Finally, KHDC1B levels and binding partners were shown to fluctuate with the cell cycle. KHDC1B, via its interaction with mCEPB1, may regulate translation of mRNA targets required for oocyte maturation.

GLD-3 and control of the mitosis/meiosis decision in the germline of Caenorhabditis elegans

Germ cells can divide mitotically to replenish germline tissue or meiotically to produce gametes. In this article, we report that GLD-3, a Caenorhabditis elegans Bicaudal-C homolog, promotes the transition from mitosis to meiosis together with the GLD-2 poly(A) polymerase. GLD-3 binds GLD-2 via a small N-terminal region present in both GLD-3S and GLD-3L isoforms, and GLD-2 and GLD-3 can be co-immunoprecipitated from worm extracts. The FBF repressor binds specifically to elements in the gld-3S 3'-UTR, and FBF regulates gld-3 expression. Furthermore, FBF acts largely upstream of gld-3 in the mitosis/meiosis decision. By contrast, GLD-3 acts upstream of FBF in the sperm/oocyte decision, and GLD-3 protein can antagonize FBF binding to RNA regulatory elements. To address the relative importance of these two regulatory mechanisms in the mitosis/meiosis and sperm/oocyte decisions, we isolated a deletion mutant, gld-3(q741), that removes the FBF-binding site from GLD-3L, but leaves the GLD-2-binding site intact. Animals homozygous for gld-3(q741) enter meiosis, but are feminized. Therefore, GLD-3 promotes meiosis primarily via its interaction with GLD-2, and it promotes spermatogenesis primarily via its interaction with FBF.