Massive deletion in AZFb/b+c and azoospermia with Sertoli cell only and/or maturation arrest

Genetics of male infertility

PURPOSE OF REVIEW

The aim of this study was to outline the role of genetic abnormalities, including chromosomal anomalies, single-gene mutations, epigenetic changes, and mitochondrial DNA (mtDNA) defects, in male factor infertility.

RECENT FINDINGS

Recent advances in genetic research have brought incredible new perspectives to understanding male infertility, thanks in large part to next-generation sequencing. Chromosomal abnormalities like Klinefelter syndrome and Y chromosome microdeletions remain key contributors, with new insights into their variable presentations and impact on sperm retrieval. Advanced discoveries in genes such as CFTR and ADGRG2 have reframed our approach to conditions like CBAVD, while epigenetic disruptions and mitochondrial DNA mutations are revealing previously unrecognized mechanisms behind impaired spermatogenesis and sperm motility. Rare copy number variations and genetic syndromes like Kallmann and Noonan further underscore the complex interplay between systemic disorders and male fertility.

SUMMARY

The field of genetic infertility is rapidly evolving, offering new insights into the molecular mechanisms behind impaired spermatogenesis and fertility. These findings highlight the importance of integrating genetic testing into infertility evaluations to guide personalized management strategies.

Computer-assisted sperm analysis of the epididymal spermatozoa in dromedary camels suffering from penile and preputial pathological problems

Dromedary camels are the most vulnerable animals to penile and preputial pathology due to the aggressive nature of mating and injuries during transit, which could impair the semen quality. Hence, this study was performed to monitor the penile and preputial pathological conditions in male dromedary camels, as well as their impact on epididymal spermatozoa, by utilizing computer-assisted sperm analysis (CASA) and correlation analysis with testosterone concentrations. A total of 60 male dromedary camels were examined for penile and preputial pathological problems. The camels were grouped based on the absence or presence of the pathology conditions: (i) camels with normal penis and prepuce, (ii) camels with balanoposthitis, (iii) camels with penile trauma, (iv) camels with prolapsed prepuce, (v) camels with phimosis, and (vi) camels with penile tumors. The results revealed that there were significant increases in sperm concentration (Conc., M/ml), curvilinear velocity (VCL, μm/s), eat-cross frequency (BCF, Hz), and straightness (STR, VSL/VAP) of the epididymal tail semen in camels with prolapsed prepuce. There were increases in progressive motility (PR), VCL, straight line velocity (VSL, μm/s), average path velocity (VAP, μm/s), BCF, and STR in the sperms of the group with phimosis, but the differences were non-statistically significant. Furthermore, the CASA parameters of the epididymal tail semen in the group with penile tumor showed an increase in PR (%), VCL, VSL, VAP, BCF, and STR (%) compared to those in the group with normal penis and prepuce. However, the CASA parameters of the epididymal body in the group with penile tumor showed a significant increase in vitality, total motility (TM), non-progressive motility (NP), mean angular degree (MAD), linearity (LIN, VSL/VCL), VSL, amplitude of lateral head displacement (ALH, μm), VAP, BCF, and STR compared to those in the group with normal penis and prepuce. There were no discernible differences in testosterone concentrations among the groups. There was a negative correlation (p < 0.05, r = 0.411-0.459) between testosterone concentration and CASA parameters of the epididymal tail semen in camels with penile and preputial pathological conditions. In comparison, there were no discernible differences in correlation (p > 0.5, r = 0.074-0.360) between testosterone concentration and CASA parameters of the epididymal body and head semen in camels with penile and preputial pathology. In conclusion, the semen quality of male dromedary camels could be affected by the penile and preputial pathological problems, while the testosterone concentration was not affected.

DDX58 expression promotes inflammation and growth arrest in Sertoli cells by stabilizing p65 mRNA in patients with Sertoli cell-only syndrome

Sertoli cell -only syndrome (SCOS) is a type of testicular pathological failure that causes male infertility and no effective treatment strategy, is available for this condition. Moreover, the molecular mechanism underlying its development remains unknown. We identified DExD/H-Box helicase 58 (DDX58) as a key gene in SCOS based on four datasets of testicular tissue samples obtained from the Gene Expression Synthesis database. DDX58 was significantly upregulated in SCOS testicular Sertoli cells. Moreover, high expression of DDX58 was positively correlated with the expression of several testicular inflammatory factors, such as IL -1β, IL-18, and IL-6. Interestingly, DDX58 could be induced in the D-galactose (D-gal)-stimulated TM4 cell injury model. Whereas silencing of DDX58 inhibited D-gal -mediated p65 expression, inflammatory cytokine release, and growth arrest. Mechanistically, we found that DDX58 acts as an RNA-binding protein, which enhances p65 expression by promoting mRNA stability. Furthermore, p65 gene silencing decreased the expression of inflammatory cytokines and inhibition of cell growth in D-gal-induced cells. In conclusion, our findings demonstrate that DDX58 promotes inflammatory responses and growth arrest in SCOS Sertoli cells by stabilizing p65 mRNA. Accordingly, the DDX58/p65 regulatory axis might be a therapeutic target for SCOS.

Mild androgen insensitivity syndrome: the current landscape

OBJECTIVE

Mild Androgen Insensitivity (MAIS) belongs to the Androgen Insensitivity Syndrome (AIS) spectrum, an X-linked genetic disease that is the most common cause of differences in sex development (DSD). Unfortunately, AIS studies mainly focus on the partial and the complete phenotype, and the mild phenotype (MAIS) has been barely reported. Our purpose is to explore the MAIS facets, clinical features, and molecular aspects.

METHODS

We collected all reported MAIS cases in the medical literature and presented them based on the phenotype and the molecular diagnosis.

RESULTS

We identified 49 different AR mutations in 69 individuals in the literature. We compared the AR mutations presented in MAIS individuals with AR mutations previously reported in other AIS phenotypes (CAIS and PAIS) regarding the type, location, genotype-phenotype correlation, and functional studies.

CONCLUSION

This review provides a landscape of the mild phenotype of AIS. Most MAIS patients present with male infertility. Therefore, AR gene sequencing should be considered during male infertility investigation, even in males with typically male external genitalia. In addition, MAIS can be part of other medical conditions, such as X-linked spinal and bulbar muscular atrophy (Kennedy's disease).

The Fate of Leydig Cells in Men with Spermatogenic Failure

The steroidogenic cells in the testicle, Leydig cells, located in the interstitial compartment, play a vital role in male reproductive tract development, maintenance of proper spermatogenesis, and overall male reproductive function. Therefore, their dysfunction can lead to all sorts of testicular pathologies. Spermatogenesis failure, manifested as azoospermia, is often associated with defective Leydig cell activity. Spermatogenic failure is the most severe form of male infertility, caused by disorders of the testicular parenchyma or testicular hormone imbalance. This review covers current progress in knowledge on Leydig cells origin, structure, and function, and focuses on recent advances in understanding how Leydig cells contribute to the impairment of spermatogenesis.

Aetiological analysis and diagnosis of reproductive disorders in male dromedary camels

The purpose of this paper was to analyse the aetiology and methods of diagnosing reproductive disorders in male dromedary camels. Male camel infertility manifests as one of three conditions: post-coital infertility (IG), inability to copulate (IC) and lack of sexual desire (LSD). IG is mainly a testicular disorder that is linked to a deteriorated seminogram, arrested spermatogenesis, Sertoli cell-only syndrome and testicular degeneration. For IG diagnosis, semen analysis, testicular biopsy and fine-needle aspiration are gold standards. Testicular ultrasonography was generally inefficient. High serum FSH was found in IG camels with oligo- and azoospermia, implying primary spermatogenesis defects. The testis-expressed protein (TEX101) and the epididymis-expressed protein (ECM1) are reliable biomarkers for distinguishing between obstructive and non-obstructive azoospermia. IC manifests in two forms: phimosis (PHI) and erectile dysfunction (ED). PHI is frequently linked to preputial and penile pathologies, as well as leucocytosis, neutrophilia and elevated nitric oxide metabolites. The majority of camels with ED have normal genital organs, and the condition is associated with an increase in cardiac troponin I. LSD is a rare disorder brought on by hormonal imbalances, high temperatures, stress and debilitating diseases. In conclusion, IG diagnosis necessitates semen analysis, testicular biopsy or fine-needle aspiration, and FSH testing, whereas IC diagnosis requires preputial and penile examinations. Diagnostic aids include serum and seminal biomarkers.

Effect of Zinc, Selenium, and Vitamin E Administration on Semen Quality and Fertility of Male Dromedary Camels with Impotentia Generandi

This study aimed to investigate the effect of zinc (Zn), selenium (Se), and vitamin E (Vit E) administration on semen quality and fertility in male dromedary camels with impotentia generandi (IG, post-coital infertility). Factors that may affect response to treatment were investigated. Thirty-three IG-affected and five fertile camels were included. Case history was obtained, and breeding sound examination was performed. Semen was collected using electroejaculation. IG-camels were classified according to initial sperm count, body condition score, age, duration of infertility, IG-type, and testicular size. IG-camels were treated with a combination of intramuscular injections of Vit E (α-tocopherol acetate, 1 mg/kg bw) and Se (sodium selenite, 0.088 mg/kg bw) once every week for three successive weeks and by daily oral administration of 360 mg of zinc gluconate for 5 successive weeks. Semen quality was estimated before and after treatment. IG-treated camels were allowed to mate females in estrus, and conception rates were calculated. The results showed that sperm cell concentration, sperm motility, and viability significantly increased, while sperm abnormality significantly decreased after treatment (P < 0.01). Positive correlations were observed between initial sperm cell count and post-treated sperm count (P = 0.001), sperm motility (P = 0.01), and viability (P = 0.002). Other variables and their interactions did not affect response to treatment. Conception rates improved after treatment. In conclusion, Zn, Se, and Vit E administration improved semen quality and fertility in male dromedary camels with impotentia generandi. Initial sperm count can be used to predict the degree of camel response to treatment.

Histology and sperm retrieval among men with Y chromosome microdeletions

In this review of Y chromosome microdeletions, azoospermia factor (AZF) deletion subtypes, histological features and microTESE sperm retrieval rates are summarized after a systematic literature review. PubMed was searched and papers were identified using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Approximately half of infertile couples have a male factor contributing to their infertility. One of the most common genetic etiologies are Y chromosome microdeletions. Men with Y chromosome microdeletions may have rare sperm available in the ejaculate or undergo surgical sperm retrieval and subsequent intracytoplasmic sperm injection to produce offspring. Azoospermia or severe oligozoospermia are the most common semen analysis findings found in men with Y chromosome microdeletions, associated with impaired spermatogenesis. Men with complete deletions of azoospermia factor a, b, or a combination of any loci have severely impaired spermatogenesis and are nearly always azoospermic with no sperm retrievable from the testis. Deletions of the azoospermia factor c or d often have sperm production and the highest likelihood of a successful sperm retrieval. In men with AZFc deletions, histologically, 46% of men demonstrate Sertoli cell only syndrome on biopsy, whereas 38.2% have maturation arrest and 15.7% have hypospermatogenesis. The microTESE sperm retrieval rates in AZFc-deleted men range from 13-100% based on the 32 studies analyzed, with a mean sperm retrieval rate of 47%.

Molecular cytogenetic characterization of a mosaic small supernumerary marker chromosome derived from chromosome Y in an azoospermic male: A case report

RATIONALE

Small supernumerary marker chromosomes (sSMCs) can be usually discovered in the patients with mental retardation, infertile couples, and prenatal fetus. We aim to characterize the sSMC and explore the correlation between with sSMC and male infertility.

PATIENT CONCERNS

A 26-year-old Chinese male was referred for infertility consultation in our center after 1 year of regular unprotected coitus and no pregnancy.

DIAGNOSIS

Cytogenetic G-banding analysis initially described a mosaic karyotype 47,X,Yqh-,+mar[28]/46,X,Yqh-[22] for the proband, while his father showed a normal karyotype. The chromosome microarray (CMA) analysis showed there existed a duplication of Yp11.32q11.221, a deletion of Yq11.222q12, a duplication of 20p11.1 for the patient. Azoospermia factor (AZF) microdeletion analysis for the patient showed that he presented a de novo AZFb+c deletion. Fluorescence in situ hybridization further confirmed the sSMC was an sSMC(Y) with SRY signal, Y centromere, and Yq deletion.

INTERVENTIONS

The patient would choose artificial reproductive technology to get his offspring according to the genetic counseling.

OUTCOMES

The sSMC in our patient was proved to be an sSMC(Y), derived from Yq deletion. The spermatogenesis failure of the proband might be due to the synthetic action of sSMC(Y) mosaicism and AZFb+c microdeletion.

LESSONS

It is nearly impossible to detect the chromosomal origin of sSMC through traditional banding techniques. The molecular cytogenetic characterization could be performed for identification of sSMC so that comprehensive genetic counseling would be offered.

Molecular microdeletion analysis of infertile men with karyotypic Y chromosome abnormalities

Objectives

To investigate azoospermic factor (AZF) microdeletions in infertile men from northeastern China with karyotypic Y chromosome abnormalities.

Methods

G-banding of metaphase chromosomes and karyotype analysis were performed in all infertile male patients. Genomic DNA was isolated and used to analyze classical AZF microdeletions by PCR. The regions and sequence-tagged sites of AZFa (SY86, SY84), AZFb (SY127, SY134, SY143), and AZFc (SY152, SY254, SY255, SY157) were sequenced by multiplex PCR.

Results

A total of 190 Y chromosome abnormality carriers were found, of whom 35 had AZF microdeletions. These were most common in 46,X,Yqh− patients, followed by 45,X/46,XY patients. Most microdeletions were detected in the AZFb + c region, including 48.57% of all AZF microdeletion cases. AZF partial deletions were also seen in these patients. Overall, AZF microdeletions were detected in 38.5% Y chromosome abnormality carriers, and most were observed in 46,X,Yqh− individuals. Loss of SY152 was seen in all 35 patients, with SY254/SY255 detected in 34 of 35 patients.

Conclusions

AZF microdeletions were detected in 38.5% of Y chromosome abnormality carriers. This indicates that AZF microdeletion screening is advisable for individuals with karyotypic Y chromosome abnormalities.

Azoospermia Factor C Subregion of the Y Chromosome

The azoospermia factor (AZF) region on the Y chromosome consists of genes required for spermatogenesis. Among the three subregions, the AZFc subregion located at the distal portion of AZF is the driver for genetic variation in Y chromosome. The candidate gene of AZFc is known as deleted in azoospermia gene, which is studied with interest because it is involved in germ cell development and most frequently deleted genes leading to oligozoospermia and azoospermia. Recently, two partial deletions in AZFc gr/gr and b2/b3 are characterized at the molecular level which showed homologous recombination between amplicons, affecting spermatogenesis process. There are novel methods and commercially available kits for accurate screening and characterization of microdeletions. It is important to detect the AZFc microdeletions through genetic screening and counseling those infertile men who planned to avail assisted reproduction techniques such as undergoing intracytoplasmic sperm injection or in vitro fertilization.

Outcomes of intracytoplasmic sperm injection in oligozoospermic men with Y chromosome AZFb or AZFc microdeletions

We investigated whether the presence of Y chromosome azoospermia factor (AZF) microdeletions impacts upon the outcomes of intracytoplasmic sperm injection (ICSI) using fresh ejaculated spermatozoa. Sixteen oligozoospermia patients with Y chromosome AZFb or AZFc microdeletions and undergoing ICSI cycles between March 2013 and November 2014 were studied. Twenty-six infertile men with normal Y chromosomes and also undergoing IVF/ICSI in the same time period were used as controls. A retrospective case-control study approach was used. Among the 16 cases, 12 (75%, 12/16) had deletions of AZFc markers (sY152, sY254 and sY255), one (6.25%, 1/16) had a deletion of sY152, and two (12.5%, 2/16) had deletions of sY152, sY254, sY255 and sY157. AZFb microdeletions were found in one patient (6.25%, 1/16). There were no significant differences between groups for cleaved embryo rate, high-grade embryo rate, blastocyst formation rate, embryo implantation rate, clinical pregnancy rate and delivery rate. The clinical outcomes of ICSI for oligozoospermic patients with Y chromosome AZF microdeletion are comparable to those of infertile patients with normal Y chromosomes. Our findings indicate that ICSI should be offered to patients with an AZFc deletion and that oligozoospermia patients with AZFb microdeletions are likely to father children.

A significant effect of the TSPY1 copy number on spermatogenesis efficiency and the phenotypic expression of the gr/gr deletion

AZFc deletions cause a significant phenotypic heterogeneity with respect to spermatogenesis; however, the reason for this is poorly understood. Recently, testis-specific protein Y-encoded 1 (TSPY1) copy number variation (CNV) was determined to be a potential genetic modifier of spermatogenesis. We performed a large-scale cohort study to investigate the effect of TSPY1 CNV on spermatogenesis and to elucidate the possible contribution of TSPY1 genetic variation to the phenotypic expression of AZFc deletions. Haplogrouping of the Y-chromosome and quantification of the TSPY1 copy number were performed in 2272 Han Chinese males with different spermatogenic statuses (704 males with the b2/b4 or gr/gr deletion and 1568 non-AZFc-deleted males). Our data revealed that the TSPY1 copy number distributions were significantly different among non-AZFc-deleted males with different spermatogenic phenotypes. Lower sperm production and an elevated risk of spermatogenic failure were observed in males with fewer than 21 TSPY1 copies and in those with more than 55 copies relative to men with 21-35 copies. Similar results were observed in males with the gr/gr deletion. These findings indicate that TSPY1 CNV affects an individual's susceptibility to spermatogenic failure by modulating the efficiency of spermatogenesis and strongly suggest that there is a significant quantity effect of the TSPY1 copy number on the phenotypic expression of the gr/gr deletion. To our knowledge, this CNV is the first independent genetic factor that has been clearly observed to influence the spermatogenic status of gr/gr deletion carriers. A combined genetic analysis of the TSPY1 copy number and the gr/gr deletion could inform the clinical counselling of infertile couples.

Biotechnological approaches to the treatment of aspermatogenic men

Aspermatogenesis is a severe impairment of spermatogenesis in which germ cells are completely lacking or present in an immature form, which results in sterility in approximately 25% of patients. Because assisted reproduction techniques require mature germ cells, biotechnology is a valuable tool for rescuing fertility while maintaining biological fatherhood. However, this process involves, for instance, the differentiation of preexisting immature germ cells or the production/derivation of sperm from somatic cells. This review critically addresses four potential techniques: sperm derivation in vitro, germ stem cell transplantation, xenologous systems, and haploidization. Sperm derivation in vitro is already feasible in fish and mammals through organ culture or 3D systems, and it is very useful in conditions of germ cell arrest or in type II Sertoli-cell-only syndrome. Patients afflicted by type I Sertoli-cell-only syndrome could also benefit from gamete derivation from induced pluripotent stem cells of somatic origin, and human haploid-like cells have already been obtained by using this novel methodology. In the absence of alternative strategies to generate sperm in vitro, in germ cells transplantation fertility is restored by placing donor cells in the recipient germ-cell-free seminiferous epithelium, which has proven effective in conditions of spermatogonial arrest. Grafting also provides an approach for ex-vivo generation of mature sperm, particularly using prepubertal testis tissue. Although less feasible, haploidization is an option for creating gametes based on biological cloning technology. In conclusion, the aforementioned promising techniques remain largely experimental and still require extensive research, which should address, among other concerns, ethical and biosafety issues, such as gamete epigenetic status, ploidy, and chromatin integrity.

Cytogenetic abnormalities and Y-chromosome microdeletions in infertile Syrian males

Infertility is an important health issue affecting numerous couples. Approximately 30-50% of the cases of male infertility is due to unknown reasons. The main genetic factors involved in male infertility are chromosomal abnormalities and Y chromosome microdeletions within the Yq11 region. The genes controlling spermatogenesis located in the Yq11 region are termed azoospermia factor genes (AZF). Klinefelter syndrome (KS) is the most common of the chromosomal anomalies in the infertile male. AZF microdeletions on the Y chromosome are the most frequent genetic cause of male infertility. Screening for microdeletions in the AZFa, b and c regions of the Y chromosome showed a marked variation among different studies. The present study aimed to investigate the prevalence of such deletions in Syrian men. A total of 162 infertile males (97 azoospermic, 49 oligospermic and 16 severely oligospermic) were screened for chromosomal abnormalities and Y chromosome microdeletions using 28 markers in the AZF region. Twenty (12.34%) patients had chromosomal rearrangements, 17 of them showed sex chromosome abnormalities (11 of 17 patients within the azoospermic group had a KS of 64.7%), 2 patients had apparently balanced autosomal rearrangements, while 1 patient had an inversion. Of the 162 infertile men, 46 patients (28.4%) had Y chromosome microdeletions within the AZF-regions. Most frequently hit were the AZFc (34.8%), followed by the AZFbc, AZFa, AZFac, AZFbc, AZFb, AZFd, AZFab, AZFad, AZFbd, AZFabc and the AZFbcd. Combined AZF deletions involving three regions with chromosomal abnormalities were observed in one case. The higher frequency of AZF deletions in our study was comparable with frequencies in other countries and regions of the world, possibly due to the elevated number of the sequence-tagged site (STS) markers used for this screening.

Sex, rebellion and decadence: the scandalous evolutionary history of the human Y chromosome

It can be argued that the Y chromosome brings some of the spirit of rock&roll to our genome. Equal parts degenerate and sex-driven, the Y has boldly rebelled against sexual recombination, one of the sacred pillars of evolution. In evolutionary terms this chromosome also seems to have adopted another of rock&roll's mottos: living fast. Yet, it appears to have refused to die young. In this manuscript the Y chromosome will be analyzed from the intersection between structural, evolutionary and functional biology. Such integrative approach will present the Y as a highly specialized product of a series of remarkable evolutionary processes. These led to the establishment of a sex-specific genomic niche that is maintained by a complex balance between selective pressure and the genetic diversity introduced by intrachromosomal recombination. Central to this equilibrium is the "polish or perish" dilemma faced by the male-specific Y genes: either they are polished by the acquisition of male-related functions or they perish via the accumulation of inactivating mutations. Thus, understanding to what extent the idiosyncrasies of Y recombination may impact this chromosome's role in sex determination and male germline functions should be regarded as essential for added clinical insight into several male infertility phenotypes. This article is part of a Special Issue entitled: Molecular Genetics of Human Reproductive Failure.

Genetic screening for chromosomal abnormalities and Y chromosome microdeletions in Chinese infertile men

PURPOSES

To investigate the frequency and type of both chromosomal abnormalities and Y chromosome microdeletions and analyze their association with defective spermatogenesis in Chinese infertile men.

METHODS

This is a single center study. Karyotyping using G-banding and screening for Y chromosome microdeletion by multiplex polymerase chain reaction(PCR)were performed in 200 controls and 1,333 infertile men, including 945 patients with non-obstructive azoospermia and 388 patients with severe oligozoospermia.

RESULTS

Out of 1,333 infertile patients, 154(11.55%) presented chromosomal abnormalities. Of these, 139 of 945 (14.71%) were from the azoospermic and 15 of 388 (3.87%) from the severe oligozoospermic patient groups. The incidence of sex chromosomal abnormalities in men with azoospermia was 11.53% compared with 1.03% in men with severe oligozoospermia (P < 0.01). Also 144 of 1,333(10.80%) patients presented Y chromosome microdeletions. The incidence of azoospermia factor(AZF) microdeletion was 11.75% and 8.51% in patients with azoospermia and severe oligozoospermia respectively. Deletion of AZFc was the most common and deletions in AZFa or AZFab or AZFabc were found in azoospermic men. In addition, 34 patients had chromosomal abnormalities among the 144 patients with Y chromosome microdeletions. No chromosomal abnormality and microdeletion in AZF region were detected in controls.

CONCLUSIONS

There was a high incidence (19.80%) of chromosomal abnormalities and Y chromosomal microdeletions in Chinese infertile males with azoospermia or severe oligozoospermia. These findings strongly suggest that genetic screening should be advised to infertile men before starting assisted reproductive treatments.

A rare Y chromosome constitutional rearrangement: a partial AZFb deletion and duplication within chromosome Yp in an infertile man with severe oligoasthenoteratozoospermia

We report a case of an infertile man with severe oligoasthenoteratozoospermia with a partial azoospermia factor b (AZFb) deletion and duplication region within chromosome Yp11.2. The hormonal profile was normal for serum concentrations of follicle-stimulating hormone, luteinizing hormone, testosterone and oestradiol. The patient, who showed a 46,XY karyotype, had an approximate 2.4 Mb inherited duplication region in Yp11.2 and a de novo partial AZFb deletion, which spanned 5.25 Mb including eight protein coding genes and four non-coding transcripts, but did not remove the RBMY gene family. Both proximal and distal breakpoints of the deletion were outside any palindromic region or inverted repeat sequence and intra-chromosomal non-allelic homologous recombination could not have been the deletion mechanism. The partial AZFb deletion in our case diminished sperm production, but did not completely extinguish spermatogenesis. Considering severe oligozoospermia, spermatozoa in the patient's ejaculate were used for intracytoplasmic sperm injection, resulting in two twin pregnancies.

The likelihood of finding mature sperm cells in men with AZFb or AZFb-c deletions: six new cases and a review of the literature (1994-2010)

OBJECTIVE

To reassess the predictive value of detecting sperm cells in men with AZFb or AZFb-c deletions.

DESIGN

Retrospective analysis of previously reported men with AZFb or AZFb-c deletions and the addition of six new cases.

SETTING

Fertility institution.

PATIENT(S)

Men with both sequence tagged site marker identification and testicular cytology/histology findings.

INTERVENTION(S)

Systematic review of reported men with microdeletions that included eligibility, data extraction and analysis.

MAIN OUTCOME MEASURE(S)

Availability of sperm cells for intracytoplasmic sperm injection (ICSI) in men with AZFb/AZFb-c microdeletions.

RESULT(S)

The average prevalences reported for AZFb, AZFb-c, partial AZFb, and partial AZFb-c in azoospermic men were 0.9%±0.07%, 2.7%±0.93%, 1.23%±0.9%, and 1%±0.6%, respectively. Sperm cells were identified in 7% and 3% of the 28 and 71 men with complete AZFb and AZFb-c and in 57% and 43% of the 14 and 7 men with partial AZFb and AZFb-c deletions, respectively. The likelihood of finding sperm cells in men with complete versus partial AZFb and AZFb-c deletions was significantly lower. As yet, no clinical or chemical pregnancy after ICSI in cases with complete AZFb/b-c microdeletions has been reported.

CONCLUSION(S)

Determining the extent of AZFb or AZFb-c deletions is critical considering the frequency and the reasonable prospect of finding sperm cells in partial AZFb/AZFb-c deletions. Referring men with complete AZFb/b-c microdeletions to testicular sperm extraction/ICSI programs should be revaluated.

Structural variation of the human genome: mechanisms, assays, and role in male infertility

Genomic disorders are defined as diseases caused by rearrangements of the genome incited by a genomic architecture that conveys instability. Y-chromosome related dysfunctions such as male infertility are frequently associated with gross DNA rearrangements resulting from its peculiar genomic architecture. The Y-chromosome has evolved into a highly specialized chromosome to perform male functions, mainly spermatogenesis. Direct and inverted repeats, some of them palindromes with highly identical nucleotide sequences that can form DNA cruciform structures, characterize the genomic structure of the Y-chromosome long arm. Some particular Y chromosome genomic deletions can cause spermatogenic failure likely because of removal of one or more transcriptional units with a potential role in spermatogenesis. We describe mechanisms underlying the formation of human genomic rearrangements on autosomes and review Y-chromosome deletions associated with male infertility.

Genetic dissection of the AZF regions of the human Y chromosome: thriller or filler for male (in)fertility?

The azoospermia factor (AZF) regions consist of three genetic domains in the long arm of the human Y chromosome referred to as AZFa, AZFb and AZFc. These are of importance for male fertility since they are home to genes required for spermatogenesis. In this paper a comprehensive analysis of AZF structure and gene content will be undertaken. Particular care will be given to the molecular mechanisms underlying the spermatogenic impairment phenotypes associated to AZF deletions. Analysis of the 14 different AZF genes or gene families argues for the existence of functional asymmetries between the determinants; while some are prominent players in spermatogenesis, others seem to modulate more subtly the program. In this regard, evidence supporting the notion that DDX3Y, KDM5D, RBMY1A1, DAZ, and CDY represent key AZF spermatogenic determinants will be discussed.

The AZFc region of the Y chromosome: at the crossroads between genetic diversity and male infertility

BACKGROUND

The three azoospermia factor (AZF) regions of the Y chromosome represent genomic niches for spermatogenesis genes. Yet, the most distal region, AZFc, is a major generator of large-scale variation in the human genome. Determining to what extent this variability affects spermatogenesis is a highly contentious topic in human reproduction.

METHODS

In this review, an extensive characterization of the molecular mechanisms responsible for AZFc genotypical variation is undertaken. Such data are complemented with the assessment of the clinical consequences for male fertility imputable to the different AZFc variants. For this, a critical re-evaluation of 23 association studies was performed in order to extract unifying conclusions by curtailing methodological heterogeneities.

RESULTS

Intrachromosomal homologous recombination mechanisms, either crossover or non-crossover based, are the main drivers for AZFc genetic diversity. In particular, rearrangements affecting gene dosage are the most likely to introduce phenotypical disruptions in the spermatogenic profile. In the specific cases of partial AZFc deletions, both the actual existence and the severity of the spermatogenic defect are dependent on the evolutionary background of the Y chromosome.

CONCLUSIONS

AZFc is one of the most genetically dynamic regions in the human genome. This property may serve as counter against the genetic degeneracy associated with the lack of a meiotic partner. However, such strategy comes at a price: some rearrangements represent a risk factor or a de-facto causative agent of spermatogenic disruption. Interestingly, this precarious balance is modulated, among other yet unknown factors, by the evolutionary history of the Y chromosome.