Molecular cloning of TSARG6 gene related to apoptosis in human spermatogenic cells

A novel homozygous mutation in DNAJB13-a gene associated with the sperm axoneme-leads to teratozoospermia

PURPOSE

To evaluate the unknown genetic causes of teratozoospermia, and determine the pathogenicity of candidate variants.

METHODS

A primary infertile patient and his family members were recruited in the West China Second University Hospital of Sichuan University. Whole-exome sequencing was performed to identify causative genes in a man with teratozoospermia. Immunofluorescence staining and western blotting were applied to assess the pathogenicity of the identified variant. Intracytoplasmic sperm injection (ICSI) was used to assist fertilization for the patient with teratozoospermia.

RESULTS

We performed whole-exome sequencing (WES) and detected a novel homozygous frameshift mutation of c.335_336del [p.E112Vfs*3] in DNAJB13 on a primary infertile male patient. Intriguingly, we identified abnormal sperm morphology in this patient, with recurrent respiratory infections and chronic cough. Furthermore, we confirmed that this mutation resulted in negative effects on DNAJB13 expression in the spermatozoa of the affected individual, causing ultrastructural defects in his sperm. Remarkably, our staining revealed that DNAJB13 was expressed in the cytoplasm of primary germ cells and in the flagella of spermatids during spermiogenesis in humans and mice. Finally, we are the first group to report a favorable prognosis using ICSI for a patient carrying this DNAJB13 mutation.

CONCLUSION

Our study revealed a novel homozygous frameshift mutation of c.335_336del [p.E112Vfs*3] in DNAJB13 involved in teratozoospermia phenotype. Our study greatly expands the spectrum of limited DNAJB13 mutations, and is expected to provide a better understanding of genetic counseling diagnoses and subsequent treatment of male infertility.

Missense mutation in DNAJB13 gene correlated with male fertility in asthenozoospermia

BACKGROUND

The most common type of male infertility is asthenospermia. We cloned DnaJ heat shock protein family member B13 (Dnajb13/DNAJB13), a type II HSP40 family member that is highly expressed in the testis. DNAJB13 plays a crucial role in sperm flagellar function.

OBJECTIVES

The aim of this study was to investigate whether a correlation exists between DNAJB13 and low sperm motility in infertile men.

MATERIALS AND METHODS

In the present study, we performed a mutation screening of the DNAJB13 gene in 92 idiopathic asthenozoospermia patients and 200 men with normal fertility. Additionally, we used immunoelectron microscopy, co-immunoprecipitation, mass spectrometric detection, indirect immunofluorescence assay, transmission electron microscopy studies, isobaric tags for relative and absolute quantitation, and multiple reaction monitoring studies to analyze changes in DNAJB13 protein.

RESULTS

A novel c.106T>C mutation of DNAJB13 was present in nearly 10% (9/92) of idiopathic asthenozoospermia patients and was absent in 200 fertile men. A computer-assisted sperm analyzer and transmission electron microscopy analysis using samples from 9 patients with DNAJB13 mutations demonstrated that most spermatozoa were immotile due to sperm tail defects. Multiple reaction monitoring results indicated that DNAJB13 protein levels were reduced after gene mutation. We achieved a pregnancy rate of 100% in 8 patients with DNAJB13 mutations using ICSI.

DISCUSSION AND CONCLUSION

The DNAJB13 heterozygous variant may affect fertility. ICSI can help these patients with low fertility to father children.

Mutations in DNAJB13, Encoding an HSP40 Family Member, Cause Primary Ciliary Dyskinesia and Male Infertility

Primary ciliary dyskinesia (PCD) is an autosomal-recessive disease due to functional or ultra-structural defects of motile cilia. Affected individuals display recurrent respiratory-tract infections; most males are infertile as a result of sperm flagellar dysfunction. The great majority of the PCD-associated genes identified so far encode either components of dynein arms (DAs), which are multiprotein-ATPase complexes essential for ciliary motility, or proteins involved in DA assembly. To identify the molecular basis of a PCD phenotype characterized by central complex (CC) defects but normal DA structure, a phenotype found in ∼15% of cases, we performed whole-exome sequencing in a male individual with PCD and unexplained CC defects. This analysis, combined with whole-genome SNP genotyping, identified a homozygous mutation in DNAJB13 (c.833T>G), a gene encoding a HSP40 co-chaperone whose ortholog in the flagellated alga Chlamydomonas localizes to the radial spokes. In vitro studies showed that this missense substitution (p.Met278Arg), which involves a highly conserved residue of several HSP40 family members, leads to protein instability and triggers proteasomal degradation, a result confirmed by the absence of endogenous DNAJB13 in cilia and sperm from this individual. Subsequent DNAJB13 analyses identified another homozygous mutation in a second family; the study of DNAJB13 transcripts obtained from airway cells showed that this mutation (c.68+1G>C) results in a splicing defect consistent with a loss-of-function mutation. Overall, this study, which establishes mutations in DNAJB13 as a cause of PCD, unveils the key role played by DNAJB13 in the proper formation and function of ciliary and flagellar axonemes in humans.

Promoter targeted bisulfite sequencing reveals DNA methylation profiles associated with low sperm motility in asthenozoospermia

STUDY QUESTION

Is there an association between sperm DNA methylation profiles and asthenozoospermia?

SUMMARY ANSWER

DNA methylation, at specific CpGs but not at the global level, was significantly different between low motile sperm cells of asthenozoospermic individuals and high motile sperm cells of normozoospermic controls.

WHAT IS KNOWN ALREADY

Aberrant DNA methylation, both globally and restricted to a specific gene locus, has been associated with male infertility and abnormal semen parameters.

STUDY DESIGN, SIZE, DURATION

This was a case-control study investigating the differences in DNA methylation at CpGs in promoter regions between high and low motile sperm cells from eight normozoospermic controls and seven asthenozoospermic patients.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The liquid hybridization capture-based bisulfite sequencing method was used to determine DNA methylation at CpGs in promoter regions. The global inter-individual and intra-individual methylation variability were estimated by evaluating the methylation variance between and within different motile sperm fractions from the same or different individuals. Asthenozoospermia-associated differentially methylated or variable CpGs and differentially methylated regions were identified by comparing the DNA methylation of high motile sperm cells from normozoospermic controls with that of low motile sperm cells from asthenozoospermic patients.

MAIN RESULTS AND THE ROLE OF CHANCE

In this study, we determined the global DNA methylation level (24.7%), inter-individual variance (14.4%) and intra-individual differences between high and low motile sperm fractions (3.9%). We demonstrated that there were no statistically significant differences in either the global DNA methylation level or global methylation variability between sperm from men with normozoospermia or asthenozoospermia. Between high motile sperm from men with normozoospermia and low motile sperm from men with asthenozoospermia, we identified 134 differentially methylated CpGs, 41 differentially methylated regions and 134 differentially variable CpGs. The genomic distribution patterns of the differential methylation spectrum suggested that gene expression may be affected in low motile sperm cells of asthenozoospermic patients. Finally, through a functional analysis, we detected 16 differentially methylated or variable genes that are required for spermatogenesis and sperm motility or dominantly expressed in testis.

LIMITATIONS, REASONS FOR CAUTION

The sample size in this study was limited, although the participants in the two groups were carefully selected and well matched. Our results must be verified in larger cohorts with the use of different techniques. Furthermore, our results were descriptive, and follow-up studies will be needed to elucidate the effect of differential methylation profiles on asthenozoospermia.

WIDER IMPLICATIONS OF THE FINDINGS

Our study identified asthenozoospermia-associated DNA methylation profiles and proposed a list of genes, which were suggested to be involved in the regulation of sperm motility through an alteration of DNA methylation. These results will provide promising clues for understanding the effect of DNA methylation on sperm motility and asthenozoospermia.

STUDY FUNDING/COMPETING INTERESTS

This study was funded primarily by the National Natural Science Foundation of China, Shenzhen Project of Science and Technology and the National Basic Research Program of China. The authors have no competing interests.

DNAJB13, a type II HSP40 family member, localizes to the spermatids and spermatozoa during mouse spermatogenesis

BACKGROUND

Hundreds of HSP40s derived from various species have been identified, of which several proteins are involved in spermatogenesis. DNAJB13 is a type II HSP40/DnaJ protein. In a previous study, we cloned mouse Dnajb13, which is up-regulated in cryptorchidism. To date, however, little is known about the localization and functions of DNAJB13 during spermatogenesis. This study intends to identify the expression pattern of DNAJB13 during mammalian spermatogenesis.

RESULTS

RT-PCR and western blot revealed that the Dnajb13 gene and DNAJB13 protein were expressed not only in the testis but also in several other ciliated cell-containing tissues like the trachea, lung and oviduct. Quantitative PCR showed that the expression of Dnajb13 mRNA in testis was detectable as early as postnatal week 1, and sharply increased from postnatal week 3. Western blotting and immunohistochemistry determined that the DNAJB13 protein, which was located in the cytoplasm of spermatids and the sperm flagellum, was detectable from postnatal week 4.

CONCLUSIONS

Based on the spatiotemporal expression observed in the cytoplasm of spermatids and sperm flagella, we suggest that DNAJB13 participates in spermiogenesis and the motility of mature spermatozoa.

Molecular chaperones, cochaperones, and ubiquitination/deubiquitination system: involvement in the production of high quality spermatozoa

Spermatogenesis is a complex process in which mitosis, meiosis, and cell differentiation events coexist. The need to guarantee the production of qualitatively functional spermatozoa has evolved into several control systems that check spermatogenesis progression/sperm maturation and tag aberrant gametes for degradation. In this review, we will focus on the importance of the evolutionarily conserved molecular pathways involving molecular chaperones belonging to the superfamily of heat shock proteins (HSPs), their cochaperones, and ubiquitination/deubiquitination system all over the spermatogenetic process. In this respect, we will discuss the conserved role played by the DNAJ protein Msj-1 (mouse sperm cell-specific DNAJ first homologue) and the deubiquitinating enzyme Ubpy (ubiquitin-specific processing protease-y) during the spermiogenesis in both mammals and nonmammalian vertebrates.

New insights into placozoan sexual reproduction and development

Unraveling animal life cycles and embryonic development is basic to understanding animal biology and often sheds light on phylogenetic relationships. A key group for understanding the evolution of the Metazoa is the early branching phylum Placozoa, which has attracted rapidly increasing attention. Despite over a hundred years of placozoan research the life cycle of this enigmatic phylum remains unknown. Placozoa are a unique model system for which the nuclear genome was published before the basic biology (i.e. life cycle and development) has been unraveled. Four organismal studies have reported the development of oocytes and one genetic study has nourished the hypothesis of sexual reproduction in natural populations at least in the past. Here we report new observations on sexual reproduction and embryonic development in the Placozoa and support the hypothesis of current sexual reproduction. The regular observation of oocytes and expressed sperm markers provide support that placozoans reproduce sexually in the field. Using whole genome and EST sequences and additional cDNA cloning we identified five conserved sperm markers, characteristic for different stages in spermatogenesis. We also report details on the embryonic development up to a 128-cell stage and new ultrastructural features occurring during early development. These results suggest that sperm and oocyte generation and maturation occur in different placozoans and that clonal lineages reproduce bisexually in addition to the standard mode of vegetative reproduction. The sum of observations is best congruent with the hypothesis of a simple life cycle with an alternation of reproductive modes between bisexual and vegetative reproduction.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 4: intercellular bridges, mitochondria, nuclear envelope, apoptosis, ubiquitination, membrane/voltage-gated channels, methylation/acetylation, and transcription factors

As germ cells divide and differentiate from spermatogonia to spermatozoa, they share a number of structural and functional features that are common to all generations of germ cells and these features are discussed herein. Germ cells are linked to one another by large intercellular bridges which serve to move molecules and even large organelles from the cytoplasm of one cell to another. Mitochondria take on different shapes and features and topographical arrangements to accommodate their specific needs during spermatogenesis. The nuclear envelope and pore complex also undergo extensive modifications concomitant with the development of germ cell generations. Apoptosis is an event that is normally triggered by germ cells and involves many proteins. It occurs to limit the germ cell pool and acts as a quality control mechanism. The ubiquitin pathway comprises enzymes that ubiquitinate as well as deubiquitinate target proteins and this pathway is present and functional in germ cells. Germ cells express many proteins involved in water balance and pH control as well as voltage-gated ion channel movement. In the nucleus, proteins undergo epigenetic modifications which include methylation, acetylation, and phosphorylation, with each of these modifications signaling changes in chromatin structure. Germ cells contain specialized transcription complexes that coordinate the differentiation program of spermatogenesis, and there are many male germ cell-specific differences in the components of this machinery. All of the above features of germ cells will be discussed along with the specific proteins/genes and abnormalities to fertility related to each topic.

Molecular cloning and characterization of a novel transcript variant of Mtsarg1 gene

Mtsarg1 (Mus musculus testis and spermatogenesis cell apoptosis-related gene 1) gene with 1103 bp in full length had been cloned previously (GenBank accession number: AF399971, 2002; re-designated as Spata3, Mus musculus spermatogenesis-associated 3, 2007). In the present study, we identified a novel transcript variant of Mtsarg1, named Mtsarg1-beta which is 887 bp in length (GenBank accession numbers: EU259321 and EF546784, 2007, designated as Spata3 variant 4) by reverse transcription-polymerase chain reaction (RT-PCR), cloning and sequencing. Mtsarg1-beta which has high similarity with Mtsarg1 contains an entire open reading frame of 417 bp encoding a protein consisting of 138 amino acids. Mtsarg1-beta protein is a non-secretory protein with a theoretic molecular mass around 14.79 kD and an isoelectric point of 9.74, which shares the 100 N-terminal amino acids with Mtsarg1 followed by 38 amino acids differing from Mtsarg1. Multi-tissue RT-PCR results and Northern blot analysis for adult DBA/2 mice showed that Mtsarg1-beta and Mtsarg1 mRNAs were specifically expressed in testis at high level. RT-PCR results also showed that Mtsarg1-beta and Mtsarg1 mRNAs were not expressed in mouse GC-1 spermatogonia. In situ hybridization revealed that both Mtsarg1 and probably Mtsarg1-beta mRNAs were mainly expressed in mouse spermatocytes. Subcellular localization analysis suggested that Mtsarg1 protein was mainly localized in nucleus while Mtsarg1-beta protein was mainly localized in cytoplasm. All these results indicate that Mtsarg1 and Mtsarg1-beta may play an important role in mouse testicular function and in spermatocyte development.

Molecular cloning of a novel rat gene Tsarg1, a member of the DnaJ/HSP40 protein family

Beginning with a mouse gene mTSARG3, which was related to apoptosis of spermatogenic cells, bioinformatics was applied and a predicted novel rat gene full-length cDNA sequence was attained. Gene-specific primers were designed for PCR in rat testis cDNA library. A new gene Tsarg1 (GenBank Accession No. AY380804) was cloned, which is related to apoptosis in rat spermatogenic cells. The gene whose full cDNA length is 1176 bp containing 8 exons and 7 introns is located in rat chromosome 1q32-1q33, which encoded a protein containing 316 amino acid residues and being a new member of HSP40 protein family since the sequence contains the highly conserved J domain, which is present in all DnaJ-like proteins and is supported to have a critical role in DnaJ-DnaK protein-protein interactions. The results of RT-PCR and Northern blot analysis showed that Tsarg1 was specifically expressed in rat testis, which probably inhibits rat testis spermatogenic cell apoptosis.

Molecular Cloning and Preliminary Function Study of a Novel Human Gene, TSARG7, Related to Spermatogenesis

A novel human gene TSARG7 (GenBank accession No. AY513610) was identified from a human testis cDNA library by using the mTSARG7 gene (GenBank accession No. AY489184) as an electronic probe. The gene whose full cDNA length is 2,463 bp containing 12 exons and 11 introns is located in the human chromosome 8p11.21. The predicted protein encoded by this gene contains 456 amino acids with a theoretical molecular weight of 56,295 dalton and isoelectric point of 9.13. It is a new member of the acyltransferase family since its sequence possesses the highly conserved PlsC domain existing in all acyltransferase-like proteins. Two groups, the TSARG7 and mTSARG7, the TSARG7 and Au041707, share 97% identity in the 456 amino acids. Expression of the TSARG7 gene is restricted to the testis. Subcellular localization studies show that the EGFP-tagged TSARG7 protein was localized in the cytoplasm of GC-1 cells. The TSARG7 mRNA expression was initiated in the testis of a 13-year-old boy, and its level increased steadily along with spermatogenesis and sexual maturation of the human. The results of heat stress experiment demonstrate that TSARG7 expression has a relation with temperature. In conclusion, our study suggests that we have cloned a novel human gene and this gene may play an important role in human spermatogenesis and sexual maturation.

Molecular cloning of a novel mouse testis-specific spermatogenic cell apoptosis inhibitor gene mTSARG7 as a candidate oncogene

A novel mouse gene, mTSARG7 (GenBank accession No. AY489184), with a full cDNA length of 2279 bp and containing 12 exons and 11 introns, was cloned from a mouse expressed sequence tag (GenBank accession No. BE644543) that was significantly up-regulated in cryptorchidism. The gene was located in mouse chromosome 8A1.3 and encoded a protein containing 403 amino acid residues that was a new member of the acyltransferase family because the sequence contained the highly conserved phosphate acyltransferase (PlsC) domain existing in all acyltransferase-like proteins. The mTSARG7 protein and AU041707 protein shared 83.9% identity in 402 amino acid residues. Expression of the mTSARG7 gene was restricted to the mouse testis. The results of the in situ hybridization analysis revealed that the mTSARG7 mRNA was expressed in mouse spermatogonia and spermatocytes. Subcellular localization studies showed that the EGFP-tagged mTSARG7 protein was localized in the cytoplasm of GC-1 spg cells. The mTSARG7 mRNA expression was initiated in the mouse testis in the second week after birth, and the expression level increased steadily with spermatogenesis and sexual maturation of the mouse. The results of the heat stress experiment showed that the mTSARG7 mRNA expression gradually decreased as the heating duration increased. The pcDNA3.1 Hygro(-)/mTSARG7 plasmid was constructed and introduced into GC-1 spg cells by liposome transfection. The mTSARG7 can accelerate GC-1 spg cells, causing them to traverse the S-phase and enter the G2-phase, compared with the control group where this did not occur as there was no transfection of mTSARG7. In conclusion, our results suggest that this gene may play an important role in spermatogenesis and the development of cryptorchid testes, and is a testis-specific apoptosis candidate oncogene.