Cellular ontogeny of RBMY during human spermatogenesis and its role in sperm motility

FertilitY Predictor-a machine learning-based web tool for the prediction of assisted reproduction outcomes in men with Y chromosome microdeletions

PURPOSE

Y chromosome microdeletions (YCMD) are a common cause of azoospermia and oligozoospermia in men. Herein, we developed a machine learning-based web tool to predict sperm retrieval rates and success rates of assisted reproduction (ART) in men with YCMD.

METHODS

Data on ART outcomes of men with YCMD who underwent ART were extracted from published studies by performing a systematic review. This data was used to develop a web-based predictive algorithm using machine learning.

RESULTS

FertilitY Predictor classifies the type of YCMD into AZFa, AZFb, AZFc, their combinations, and gr/gr deletions based on the genetic markers as input. Further, it predicts the probability of sperm retrieval, fertilization rate, clinical pregnancy rate, and live birth rate based on the type of YCMD. Validation studies demonstrated its high accuracy and predictability for sperm retrieval, clinical pregnancy rates, and live birth rates. The tool predicts that men with deletions have a chance of sperm retrieval that varies with type of deletions, the clinical pregnancy rates and live birth rates are lower in men with AZF deletions. A trial version of the tool is available at http://fertilitypredictor.sbdaresearch.in .

CONCLUSIONS

FertilitY Predictor allows users to classify AZFa, AZFb, AZFc, and gr/gr deletions and also predict the outcomes of ART based on the type of deletions.

TRIAL REGISTRATION

PROSPERO (CRD42022311738).

Azoospermia factor c microdeletions and outcomes of assisted reproductive technology: a systematic review and meta-analysis

OBJECTIVE

To investigate whether Azoospermia Factor c (AZFc) microdeletions affect Assisted Reproductive Technology (ART) outcomes.

DESIGN

Systematic review and meta-analysis.

SETTING

Not applicable.

PATIENTS

Infertile men with and without AZFc microdeletions.

INTERVENTION(S)

Electronic databases were searched for case-control studies reporting sperm retrieval rates and outcomes of ART in infertile men with and without AZFc microdeletions from inception to April 2023. Study quality was assessed using the Newcastle-Ottawa Scale. Summary effect sizes (odds ratio [OR] with 95% confidence interval [CI]) were calculated for both categories of infertile men.

MAIN OUTCOME MEASURES

The primary outcome was successful sperm retrieval and the secondary outcomes were outcomes of ART.

RESULTS

Case-control studies reporting sperm retrieval rates and ART outcomes in men with AZFa and AZFb deletions were unavailable. On the basis of the data from 3,807 men, sperm retrieval rates were found to be higher in men with AZFc microdeletions compared to their non-deleted counterparts [OR = 1.82, 95% CI 0.97, 3.41], but the difference was not statistically significant. A significantly lower fertilization rate (OR = 0.61, 95% CI [0.50, 0.74]), clinical pregnancy rate (OR = 0.61, 95% CI [0.42, 0.89]), and live birth rate (OR = 0.54, 95% CI [0.40, 0.72]) were observed in men with AZFc deletions compared with men without deletions. There was no statistically significant difference in rates of embryo cleavage, blastocyst formation, good-quality embryos, implantation, and miscarriage between the two groups. On correcting for female factors, the fertilization rate (OR = 0.76, 95% CI [0.71, 0.82]), cleavage rate (OR = 0.54, 95% CI [0.41, 0.72]), clinical pregnancy rate (OR = 0.39, 95% CI [0.30, 0.52]), and live birth rate (OR = 0.48, 95% CI [0.35, 0.65]) were significantly lower in men with AZFc deletions compared with controls.

CONCLUSIONS

Presence of AZFc microdeletions adversely affects outcomes of ART in infertile men. Further in-depth studies delineating the role of the AZF genes in embryonic development are necessary to understand the full-impact of this finding.

CLINICAL TRIAL REGISTRATION NUMBER

CRD42022311738.

Omics and Male Infertility: Highlighting the Application of Transcriptomic Data

Male infertility is a multifaceted disorder affecting approximately 50% of male partners in infertile couples. Over the years, male infertility has been diagnosed mainly through semen analysis, hormone evaluations, medical records and physical examinations, which of course are fundamental, but yet inefficient, because 30% of male infertility cases remain idiopathic. This dilemmatic status of the unknown needs to be addressed with more sophisticated and result-driven technologies and/or techniques. Genetic alterations have been linked with male infertility, thereby unveiling the practicality of investigating this disorder from the “omics” perspective. Omics aims at analyzing the structure and functions of a whole constituent of a given biological function at different levels, including the molecular gene level (genomics), transcript level (transcriptomics), protein level (proteomics) and metabolites level (metabolomics). In the current study, an overview of the four branches of omics and their roles in male infertility are briefly discussed; the potential usefulness of assessing transcriptomic data to understand this pathology is also elucidated. After assessing the publicly obtainable transcriptomic data for datasets on male infertility, a total of 1385 datasets were retrieved, of which 10 datasets met the inclusion criteria and were used for further analysis. These datasets were classified into groups according to the disease or cause of male infertility. The groups include non-obstructive azoospermia (NOA), obstructive azoospermia (OA), non-obstructive and obstructive azoospermia (NOA and OA), spermatogenic dysfunction, sperm dysfunction, and Y chromosome microdeletion. Findings revealed that 8 genes (LDHC, PDHA2, TNP1, TNP2, ODF1, ODF2, SPINK2, PCDHB3) were commonly differentially expressed between all disease groups. Likewise, 56 genes were common between NOA versus NOA and OA (ADAD1, BANF2, BCL2L14, C12orf50, C20orf173, C22orf23, C6orf99, C9orf131, C9orf24, CABS1, CAPZA3, CCDC187, CCDC54, CDKN3, CEP170, CFAP206, CRISP2, CT83, CXorf65, FAM209A, FAM71F1, FAM81B, GALNTL5, GTSF1, H1FNT, HEMGN, HMGB4, KIF2B, LDHC, LOC441601, LYZL2, ODF1, ODF2, PCDHB3, PDHA2, PGK2, PIH1D2, PLCZ1, PROCA1, RIMBP3, ROPN1L, SHCBP1L, SMCP, SPATA16, SPATA19, SPINK2, TEX33, TKTL2, TMCO2, TMCO5A, TNP1, TNP2, TSPAN16, TSSK1B, TTLL2, UBQLN3). These genes, particularly the above-mentioned 8 genes, are involved in diverse biological processes such as germ cell development, spermatid development, spermatid differentiation, regulation of proteolysis, spermatogenesis and metabolic processes. Owing to the stage-specific expression of these genes, any mal-expression can ultimately lead to male infertility. Therefore, currently available data on all branches of omics relating to male fertility can be used to identify biomarkers for diagnosing male infertility, which can potentially help in unravelling some idiopathic cases.

RBM22, a Key Player of Pre-mRNA Splicing and Gene Expression Regulation, Is Altered in Cancer

RNA-Binding Proteins (RBP) are very diverse and cover a large number of functions in the cells. This review focuses on RBM22, a gene encoding an RBP and belonging to the RNA-Binding Motif (RBM) family of genes. RBM22 presents a Zinc Finger like and a Zinc Finger domain, an RNA-Recognition Motif (RRM), and a Proline-Rich domain with a general structure suggesting a fusion of two yeast genes during evolution: Cwc2 and Ecm2. RBM22 is mainly involved in pre-mRNA splicing, playing the essential role of maintaining the conformation of the catalytic core of the spliceosome and acting as a bridge between the catalytic core and other essential protein components of the spliceosome. RBM22 is also involved in gene regulation, and is able to bind DNA, acting as a bona fide transcription factor on a large number of target genes. Undoubtedly due to its wide scope in the regulation of gene expression, RBM22 has been associated with several pathologies and, notably, with the aggressiveness of cancer cells and with the phenotype of a myelodysplastic syndrome. Mutations, enforced expression level, and haploinsufficiency of RBM22 gene are observed in those diseases. RBM22 could represent a potential therapeutic target in specific diseases, and, notably, in cancer.

Human AZFb deletions cause distinct testicular pathologies depending on their extensions in Yq11 and the Y haplogroup: new cases and review of literature

Genomic AZFb deletions in Yq11 coined “classical” (i.e. length of Y DNA deletion: 6.23 Mb) are associated with meiotic arrest (MA) of patient spermatogenesis, i.e., absence of any postmeiotic germ cells. These AZFb deletions are caused by non-allelic homologous recombination (NAHR) events between identical sequence blocks located in the proximal arm of the P5 palindrome and within P1.2, a 92 kb long sequence block located in the P1 palindrome structure of AZFc in Yq11. This large genomic Y region includes deletion of 6 protein encoding Y genes, EIFA1Y, HSFY, PRY, RBMY1, RPS4Y, SMCY. Additionally, one copy of CDY2 and XKRY located in the proximal P5 palindrome and one copy of BPY1, two copies of DAZ located in the P2 palindrome, and one copy of CDY1 located proximal to P1.2 are included within this AZFb microdeletion. It overlaps thus distally along 2.3 Mb with the proximal part of the genomic AZFc deletion. However, AZFb deletions have been also reported with distinct break sites in the proximal and/or distal AZFb breakpoint intervals on the Y chromosome of infertile men. These so called “non-classical” AZFb deletions are associated with variable testicular pathologies, including meiotic arrest, cryptozoospermia, severe oligozoospermia, or oligoasthenoteratozoospermia (OAT syndrome), respectively. This raised the question whether there are any specific length(s) of the AZFb deletion interval along Yq11 required to cause meiotic arrest of the patient’s spermatogenesis, respectively, whether there is any single AZFb Y gene deletion also able to cause this “classical” AZFb testicular pathology? Review of the literature and more cases with “classical” and “non-classical” AZFb deletions analysed in our lab since the last 20 years suggests that the composition of the genomic Y sequence in AZFb is variable in men with distinct Y haplogroups especially in the distal AZFb region overlapping with the proximal AZFc deletion interval and that its extension can be “polymorphic” in the P3 palindrome. That means this AZFb subinterval can be rearranged or deleted also on the Y chromosome of fertile men. Any AZFb deletion observed in infertile men with azoospermia should therefore be confirmed as “de novo” mutation event, i.e., not present on the Y chromosome of the patient’s father or fertile brother before it is considered as causative agent for man’s infertility. Moreover, its molecular length in Yq11 should be comparable to that of the “classical” AZFb deletion, before meiotic arrest is prognosed as the patient’s testicular pathology.

Evolutionary and functional analysis of RBMY1 gene copy number variation on the human Y chromosome

Human RBMY1 genes are located in four variable-sized clusters on the Y chromosome, expressed in male germ cells and possibly associated with sperm motility. We have re-investigated the mutational background and evolutionary history of the RBMY1 copy number distribution in worldwide samples and its relevance to sperm parameters in an Estonian cohort of idiopathic male factor infertility subjects. We estimated approximate RBMY1 copy numbers in 1218 1000 Genomes Project phase 3 males from sequencing read-depth, then chose 14 for valid ation by multicolour fibre-FISH. These fibre-FISH samples provided accurate calibration standards for the entire panel and led to detailed insights into population variation and mutational mechanisms. RBMY1 copy number worldwide ranged from 3 to 13 with a mode of 8. The two larger proximal clusters were the most variable, and additional duplications, deletions and inversions were detected. Placing the copy number estimates onto the published Y-SNP-based phylogeny of the same samples suggested a minimum of 562 mutational changes, translating to a mutation rate of 2.20 × 10-3 (95% CI 1.94 × 10-3 to 2.48 × 10-3) per father-to-son Y-transmission, higher than many short tandem repeat (Y-STRs), and showed no evidence for selection for increased or decreased copy number, but possible copy number stabilizing selection. An analysis of RBMY1 copy numbers among 376 infertility subjects failed to replicate a previously reported association with sperm motility and showed no significant effect on sperm count and concentration, serum follicle stimulating hormone (FSH), luteinizing hormone (LH) and testosterone levels or testicular and semen volume. These results provide the first in-depth insights into the structural rearrangements underlying RBMY1 copy number variation across diverse human lineages.

Germline deletion of Cdyl causes teratozoospermia and progressive infertility in male mice

Chromodomain Y (CDY) is one of the candidate genes for male dyszoospermia related to Y chromosome microdeletion (YCM). However, the function of CDY in regulating spermatogenesis has not been completely determined. The mouse Cdyl (CDY-like) gene is the homolog of human CDY. In the present study, we generated a germline conditional knockout (cKO) model of mouse Cdyl. Significantly, the Cdyl^cKO male mice suffered from the defects in spermatogonia maintenance and spermatozoon morphogenesis, demonstrating teratozoospermia and a progressive infertility phenotype in early adulthood. Importantly, patterns of specific histone methylation and acetylation were extensively changed, which disturbed the transcriptome in Cdyl^cKO testis. Our findings indicated that Cdyl is crucial for spermatogenesis and male fertility, which provides novel insights into the function of CDY gene, as well as the pathogenesis of YCM-related reproductive failure.

Copy number variation of functional RBMY1 is associated with sperm motility: an azoospermia factor-linked candidate for asthenozoospermia

STUDY QUESTION

What is the influence of copy number variation (CNV) in functional RNA binding motif protein Y-linked family 1 (RBMY1) on spermatogenic phenotypes?

SUMMARY ANSWER

The RBMY1 functional copy dosage is positively correlated with sperm motility, and dosage insufficiency is an independent risk factor for asthenozoospermia.

WHAT IS KNOWN ALREADY

RBMY1, a multi-copy gene expressed exclusively in the adult testis, is one of the most important candidates for male infertility in the azoospermia factor (AZF) region of the Y-chromosome. RBMY1 encodes an RNA-binding protein that serves as a pre-mRNA splicing regulator during spermatogenesis, and male mice deficient in Rbmy are sterile.

STUDY DESIGN, SIZE, DURATION

A total of 3127 adult males were recruited from 2009 to 2016; of this group, the dosage of RBMY1 functional copy were investigated in 486 fertile males. In the remaining 2641 males with known spermatogenesis status, 1070 Y-chromosome haplogroup (Y-hg) O3* or O3e carriers without chromosomal aberration or known AZF structure mutations responsible for spermatogenic impairment, including 506 men with normozoospermia and 564 men with oligozoospermia or/and asthenozoospermia, were screened, and the RBMY1 functional copy dosage and copy conversion were determined to explore their associations with sperm phenotypes. The correlation between RBMY1 dosage and its mRNA level or RBMY1 protein level and the correlation between sperm RBMY1 level and motility were analysed in 15 testis tissue samples and eight semen samples. Ten additional semen samples were used to confirm the subcellular localization of RBMY1 in individual sperm.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All the Han volunteers donating whole blood, semen and testis tissue were from southwest China. RBMY1 copy number, copy conversion, mRNA/protein amount and protein location in sperm were detected using the AccuCopy® assay method, paralog ratio test, quantitative PCR, western blotting and immunofluorescence staining methods, respectively.

MAIN RESULTS AND THE ROLE OF CHANCE

This study identified Y-hg-independent CNV of functional RBMY1 in the enrolled population. A difference in the distribution of RBMY1 copy number was observed between the group with normal sperm motility and the group with asthenozoospermia. A positive correlation between the RBMY1 copy dosage and sperm motility was identified, and the males with fewer than six copies of RBMY1 showed an elevated risk for asthenozoospermia relative to those with six RBMY1 copies, the most common dosage in the population. The RBMY1 copy dosage was positively correlated with its mRNA and protein level in the testis. Sperm with high motility were found to carry more RBMY1 protein than those with relatively low motility. The RBMY1 protein was confirmed to predominantly localize in the neck and mid-piece region of sperm as well as the principal piece of the sperm tail. Our population study completes a chain of evidence suggesting that RBMY1 influences the susceptibility of males to asthenozoospermia by modulating sperm motility.

LIMITATIONS REASONS FOR CAUTION

High sequence similarity between the RBMY1 functional copies and a large number of pseudogenes potentially reduces the accuracy of the copy number detection. The mechanism underlying the CNV in RBMY1 is still unclear, and the effect of the structural variations in the RBMY1 copy cluster on the copy dosage of other protein-coding genes located in the region cannot be excluded, which may potentially bias our observations.

WIDER IMPLICATIONS OF THE FINDINGS

Asthenozoospermia is a multi-factor complex disease with a limited number of proven susceptibility genes. This study identified a novel genomic candidate independently contributing to the condition, enriching our understanding of the role of AZF-linked genes in male reproduction. Our finding provides insight into the physiological and pathological characteristics of RBMY1 in terms of sperm motility, supplies persuasive evidence of the significance of RBMY1 copy number analysis in the clinical counselling of male infertility resulting from asthenozoospermia.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by the National Natural Science Foundation of China (Nos. 81370748 and 30971598). The authors have no conflicts of interest.

Genetics of the human Y chromosome and its association with male infertility

The human Y chromosome harbors genes that are responsible for testis development and also for initiation and maintenance of spermatogenesis in adulthood. The long arm of the Y chromosome (Yq) contains many ampliconic and palindromic sequences making it predisposed to self-recombination during spermatogenesis and hence susceptible to intra-chromosomal deletions. Such deletions lead to copy number variation in genes of the Y chromosome resulting in male infertility. Three common Yq deletions that recur in infertile males are termed as AZF (Azoospermia Factor) microdeletions viz. AZFa, AZFb and AZFc. As estimated from data of nearly 40,000 Y chromosomes, the global prevalence of Yq microdeletions is 7.5% in infertile males; however the European infertile men are less susceptible to Yq microdeletions, the highest prevalence is in Americans and East Asian infertile men. In addition, partial deletions of the AZFc locus have been associated with infertility but the effect seems to be ethnicity dependent. Analysis of > 17,000 Y chromosomes from fertile and infertile men has revealed an association of gr/gr deletion with male infertility in Caucasians and Mongolian men, while the b2/b3 deletion is associated with male infertility in African and Dravidian men. Clinically, the screening for Yq microdeletions would aid the clinician in determining the cause of male infertility and decide a rational management strategy for the patient. As these deletions are transmitted to 100% of male offspring born through assisted reproduction, testing of Yq deletions will allow the couples to make an informed choice regarding the perpetuation of male infertility in future generations. With the emerging data on association of Yq deletions with testicular cancers and neuropsychiatric conditions long term follow-up data is urgently needed for infertile men harboring Yq deletions. If found so, the information will change the current the perspective of androgenetics from infertility and might have broad implication in men health.

Simplified approach for in-vitro production and purification of cell derived Cancer Antigen 15-3

Cancer antigen 15-3 (CA15-3) is a key biomarker, currently used for understanding the onset and prognosis of breast cancer. In present investigation, CA15-3 has been purified from the culture supernatant of breast cancer T47-D cell line with 76% yield and 3350 fold purification. Isolated CA15-3 was analyzed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting (western blotting), chemiluminescence immunoassay (CLIA) and Fourier-transform infrared spectroscopy (FTIR). CA15-3 is a monomeric protein with an apparent molecular mass in between ∼250-350kDa. The FTIR spectroscopy revealed similar profiles of T47-D derived CA15-3 and commercially available CA15-3 protein. With the easy availability of T47-D cell line and a simple purification approach described here will support for the large scale production of CA15-3 to be used for various clinical and diagnostic applications.

Y-chromosomal genes affecting male fertility: A review

The mammalian sex-chromosomes (X and Y) have evolved from autosomes and are involved in sex determination and reproductive traits. The Y-chromosome is the smallest chromosome that consists of 2-3% of the haploid genome and may contain between 70 and 200 genes. The Y-chromosome plays major role in male fertility and is suitable to study the evolutionary relics, speciation, and male infertility and/or subfertility due to its unique features such as long non-recombining region, abundance of repetitive sequences, and holandric inheritance pattern. During evolution, many holandric genes were deleted. The current review discusses the mammalian holandric genes and their functions. The commonly encountered infertility and/or subfertility problems due to point or gross mutation (deletion) of the Y-chromosomal genes have also been discussed. For example, loss or microdeletion of sex-determining region, Y-linked gene results in XY males that exhibit female characteristics, deletion of RNA binding motif, Y-encoded in azoospermic factor b region results in the arrest of spermatogenesis at meiosis. The holandric genes have been covered for associating the mutations with male factor infertility.

Errors in RNA-Seq quantification affect genes of relevance to human disease

Background

RNA-Seq has emerged as the standard for measuring gene expression and is an important technique often used in studies of human disease. Gene expression quantification involves comparison of the sequenced reads to a known genomic or transcriptomic reference. The accuracy of that quantification relies on there being enough unique information in the reads to enable bioinformatics tools to accurately assign the reads to the correct gene.

Results

We apply 12 common methods to estimate gene expression from RNA-Seq data and show that there are hundreds of genes whose expression is underestimated by one or more of those methods. Many of these genes have been implicated in human disease, and we describe their roles. We go on to propose a two-stage analysis of RNA-Seq data in which multi-mapped or ambiguous reads can instead be uniquely assigned to groups of genes. We apply this method to a recently published mouse cancer study, and demonstrate that we can extract relevant biological signal from data that would otherwise have been discarded.

Conclusions

For hundreds of genes in the human genome, RNA-Seq is unable to measure expression accurately. These genes are enriched for gene families, and many of them have been implicated in human disease. We show that it is possible to use data that may otherwise have been discarded to measure group-level expression, and that such data contains biologically relevant information.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-015-0734-x) contains supplementary material, which is available to authorized users.

Currently recognized clinically relevant and known genes for human reproduction and related infertility with representation on high-resolution chromosome ideograms

OBJECTIVE

To provide an update of currently recognized clinically relevant candidate and known genes for human reproduction and related infertility plotted on high resolution chromosome ideograms (850 band level) and represented alphabetically in tabular form.

METHOD

Descriptive authoritative computer-based website and peer-reviewed medical literature searches used pertinent keywords representing human reproduction and related infertility along with genetics and gene mutations. A master list of genes associated with human reproduction and related infertility was generated with a visual representation of gene locations on high resolution chromosome ideograms. GeneAnalytics pathway analysis was carried out on the resulting list of genes to assess underlying genetic architecture for infertility.

RESULTS

Advances in genetic technology have led to the discovery of genes responsible for reproduction and related infertility. Genes identified (N=371) in our search primarily impact ovarian steroidogenesis through sex hormone biology, germ cell production, genito-urinary or gonadal development and function, and related peptide production, receptors and regulatory factors.

CONCLUSIONS

The location of gene symbols plotted on high resolution chromosome ideograms forms a conceptualized image of the distribution of human reproduction genes. The updated master list can be used to promote better awareness of genetics of reproduction and related infertility and advance discoveries on genetic causes and disease mechanisms.

Differentiation of primordial germ cells from induced pluripotent stem cells of primary ovarian insufficiency

STUDY QUESTION

Can the induced pluripotent stem cells (iPSCs) derived from women with primary ovarian insufficiency (POI) differentiate into germ cells for potential disease modeling in vitro?

SUMMARY ANSWER

The iPSC lines derived from POI patients with 46, X, del(X)(q26) or 46, X, del(X)(q26)9qh+ could differentiate into germ cells and expressed lower levels of genes in the deletion region of the X chromosome.

WHAT IS KNOWN ALREADY

iPSC technology has been envisioned as an approach for generating patient-specific stem cells for disease modeling and for developing novel therapies. It has also been confirmed that iPSCs differentiate into germ cells.

STUDY DESIGN, SIZE, DURATION

We compared the differentiation ability of germ cells and the gene expression level of germ cell-related genes in the X chromosome deletion region of iPSC lines derived from POI patients (n = 2) with an iPSC line derived from normal fibroblasts (n = 1).

PARTICIPANTS/MATERIALS, SETTING, METHODS

We established three iPSC lines from two patients with partial Xq deletion-induced POI and normal fibroblasts by overexpressing four factors: octamer-binding transcription factor 4 (OCT4), sex-determining region Y-box 2 (SOX2), Nanog homeobox (NANOG), and lin-28 homolog (LIN28), using lentiviral vectors. We then generated stable-transfected fluorescent reporter cell lines under the control of the Asp-Glu-Ala-Asp box polypeptide 4 (DDX4, also called VASA) promoter, and selected clonal derived sublines. We induced subline differentiation into germ cells by adding Wnt3a (30 ng/ml) and bone morphogenetic protein 4 (100 ng/ml). After 12 days of differentiation, green fluorescent protein (GFP)-positive and GFP-negative cells were isolated via fluorescence-activated cell sorting and analyzed for endogenous VASA protein (immunostaining) and for germ cell markers and genes expressed in the deleted region of the X chromosome (quantitative RT-PCR).

MAIN RESULTS AND THE ROLE OF CHANCE

The POI- and normal fibroblast-derived iPSCs had typical self-renewal and pluripotency characteristics. After stable transfection with the VASA-GFP construct, the sublines POI1-iPS-V.1, POI2-iPS-V.1 and hEF-iPS-V.1 produced green fluorescent cells in the differentiated cultures, and the percentage of GFP-positive cells increased over the 12 days of differentiation to a maximum of 6.9 ± 0.33%, 5.3 ± 0.57% and 8.5 ± 0.29%, respectively, of the total cell population. Immunohistochemical analysis confirmed that endogenous VASA was enriched in the GFP-positive cells. Quantitative reverse transcription-PCR revealed significantly higher expression of germ cell markers [PR domain containing 1, with ZNF domain (PRDM1, BLIMP1), developmental pluripotency-associated 3 (DPPA3, STELLA), deleted in azoospermia-like (DAZL), and VASA (DDX4)] in GFP-positive cells than in GFP-negative cells. Moreover, the GFP-positive cells from POI-iPSCs had reduced expression of the family with sequence similarity 122C (FAM122C), inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase gamma (IKBKG), and RNA binding motif protein, X-linked (RBMX), genes located in the deleted region of the X chromosome and that are highly expressed in differentiated germ cells, compared with cells from normal iPSCs.

LIMITATIONS, REASONS FOR CAUTION

Gene expression profiling indicated that the germ cells differentiated from POI-iPSCs were pre-meiotic. Therefore, how the differentiated primordial germ cells could progress further to meiosis and form follicles remains to be determined in the study of POI.

WIDER IMPLICATIONS OF THE FINDINGS

Our results might provide an in vitro model for studying germ cell development in patients with POI.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by grants from the Major State Basic Research Development Program of China (No. 2012CB944901), the National Science Foundation of China (No. 81222007 and 81471432), the Program for New Century Excellent Talents in University and the Fundamental Research Funds for Central Universities (No. 721500003). The authors have no competing interests to declare.

TRIAL REGISTRATION NUMBER

Not applicable.

Expression analysis of RNA-binding motif gene on Y chromosome (RBMY) protein isoforms in testis tissue and a testicular germ cell cancer-derived cell line (NT2)

BACKGROUND

RNA-binding motif gene on Y chromosome (RBMY), a germ cell-specific nuclear protein, is known as a key factor in spermatogenesis and disorders associated with this protein have been recognized to be related to male infertility. Although it was suggested that this protein could have different functions during germ cell development, no studies have been conducted to uncover the mechanism of this potential function yet. Here, we analyzed the expression pattern of RBMY protein isoforms in testis compared to NT2, a testicular germ cell cancer-derived cell line, to test probability of differential expression of RBMY protein isoforms at different spermatogenesis stages.

METHODS

Full length and a segment of RBMY gene were cloned and expressed in E. coli. Anti-human RBMY antibody was produced in rabbit using the recombinant proteins as antigen. Western-blot and immunofluorescence were conducted for detection and comparison of RBMY protein isoforms.

RESULTS

Selected segment of RBMY protein resulted in producing a mono-specific antibody. As results shows, only the longest isoform of RBMY was expressed at protein level in NT2 cell line, while three isoforms of this protein were detected in the whole testis lysate.

CONCLUSION

The results imply that different alternative splicing may happen in testis cells and probably difference of RBMY function during spermatogenesis is due to the differential expression of RBMY protein isoforms. These results and further experiments on RBMY isoforms can help to obtain a better understanding of the function of this protein, which may increase our knowledge about spermatogenesis and causes of male infertility.