Isodicentric Y chromosomes and sex disorders as byproducts of homologous recombination that maintains palindromes.

Massive palindromes in the human Y chromosome harbor mirror-image gene pairs essential for spermatogenesis. During evolution, these gene pairs have been maintained by intrapalindrome, arm-to-arm recombination. The mechanism of intrapalindrome recombination and risk of harmful effects are unknown. We report 51 patients with isodicentric Y (idicY) chromosomes formed by homologous crossing over between opposing arms of palindromes on sister chromatids. These ectopic recombination events occur at nearly all Y-linked palindromes. Based on our findings, we propose that intrapalindrome sequence identity is maintained via noncrossover pathways of homologous recombination. DNA double-strand breaks that initiate these pathways can be alternatively resolved by crossing over between sister chromatids to form idicY chromosomes, with clinical consequences ranging from spermatogenic failure to sex reversal and Turner syndrome. Our observations imply that crossover and noncrossover pathways are active in nearly all Y-linked palindromes, exposing an Achilles' heel in the mechanism that preserves palindrome-borne genes.

Genetic characterization of a missense mutation in the X-linked TAF7L gene identified in an oligozoospermic man†.

Although hundreds of knockout mice show infertility as a major phenotype, the causative genic mutations of male infertility in humans remain rather limited. Here, we report the identification of a missense mutation (D136G) in the X-linked TAF7L gene as a potential cause of oligozoospermia in men. The human aspartate (D136) is evolutionally conserved across species, and its change to glycine (G) is predicted to be detrimental. Genetic complementation experiments in budding yeast demonstrate that the conserved aspartate or its analogous asparagine (N) residue in yeast TAF7 is essential for cell viability and thus its mutation to G is lethal. Although the corresponding D144G substitution in the mouse Taf7l gene does not affect male fertility, RNA-seq analyses reveal alterations in transcriptomic profiles in the Taf7l (D144G) mutant testes. These results support TAF7L mutation as a risk factor for oligozoospermia in humans.

A contiguous microdeletion syndrome at Xp23.13 with non-obstructive azoospermia and congenital cataracts.

Non-obstructive azoospermia accounts for 10-15% of male infertility, resulting in 60% of all cases of azoospermia and affecting about 1% of the male population. About 30% of these cases are due to Y chromosome microdeletions, chromosome abnormalities, or hormonal disorders. Pathogenic variants in genes on the sex chromosomes have key roles in spermatogenic failure. The co-occurrence of azoospermia and congenital cataracts ranges between 1 in 165,000 and 1 in 500,000. Our 28-year-old patient with normal intelligence and abnormally shaped teeth presented with both disorders. A microarray revealed a microdeletion at Xp23.13 with a whole NHS gene deletion as well as a contiguous deletion of two other genes [SCML1 and RAI2]. This observation represents the first report of non-obstructive azoospermia with congenital cataracts and a contiguous deletion of the SCML1 gene, a transcript of which is exclusively expressed in the testis. SCML1 is the putative culprit gene, which requires functional study or animal experiments. Our analysis of 60 known spermatogenesis failure-related genes by whole-exome sequencing revealed no other candidate. The Nance-Horan syndrome due to pathogenic variants in the NHS gene at Xp23.13 including whole gene deletion does not have azoospermia as a feature. Our report adds to the completeness of genetic counseling for an individual with azoospermia and congenital cataracts.

AZFc deletions and spermatogenic failure: a population-based survey of 20,000 Y chromosomes.

Deletions involving the Y chromosome's AZFc region are the most common known genetic cause of severe spermatogenic failure (SSF). Six recurrent interstitial deletions affecting the region have been reported, but their population genetics are largely unexplored. We assessed the deletions' prevalence in 20,884 men in five populations and found four of the six deletions (presented here in descending order of prevalence): gr/gr, b2/b3, b1/b3, and b2/b4. One of every 27 men carried one of these four deletions. The 1.6 Mb gr/gr deletion, found in one of every 41 men, almost doubles the risk of SSF and accounts for ∼2% of SSF, although <2% of men with the deletion are affected. The 1.8 Mb b2/b3 deletion, found in one of every 90 men, does not appear to be a risk factor for SSF. The 1.6 Mb b1/b3 deletion, found in one of every 994 men, appears to increase the risk of SSF by a factor of 2.5, although <2% of men with the deletion are affected, and it accounts for only 0.15% of SSF. The 3.5 Mb b2/b4 deletion, found in one of every 2,320 men, increases the risk of SSF 145 times and accounts for ∼6% of SSF; the observed prevalence should approximate the rate at which the deletion arises anew in each generation. We conclude that a single rare variant of major effect (the b2/b4 deletion) and a single common variant of modest effect (the gr/gr deletion) are largely responsible for the AZFc region's contribution to SSF in the population.

Polymorphism for a 1.6-Mb deletion of the human Y chromosome persists through balance between recurrent mutation and haploid selection.

Many human Y-chromosomal deletions are thought to severely impair reproductive fitness, which precludes their transmission to the next generation and thus ensures their rarity in the population. Here we report a 1.6-Mb deletion that persists over generations and is sufficiently common to be considered a polymorphism. We hypothesized that this deletion might affect spermatogenesis because it removes almost half of the Y chromosome's AZFc region, a gene-rich segment that is critical for sperm production. An association study established that this deletion, called gr/gr, is a significant risk factor for spermatogenic failure. The gr/gr deletion has far lower penetrance with respect to spermatogenic failure than previously characterized Y-chromosomal deletions; it is often transmitted from father to son. By studying the distribution of gr/gr-deleted chromosomes across the branches of the Y chromosome's genealogical tree, we determined that this deletion arose independently at least 14 times in human history. We suggest that the existence of this deletion as a polymorphism reflects a balance between haploid selection, which culls gr/gr-deleted Y chromosomes from the population, and homologous recombination, which continues to generate new gr/gr deletions.

The Y chromosome and male infertility.

PURPOSE OF REVIEW: Therapies for the treatment of severe male factor infertility have advanced well beyond our knowledge of the conditions we are treating. An intact Y chromosome is necessary for optimal spermatogenesis. It is imperative for the clinician to understand the molecular basis and clinical implications of anomalies that might afflict the Y chromosome. RECENT FINDINGS: The molecular geography of the Y chromosome has recently been described, allowing correlations to be made to various clinical states of severe spermatogenic compromise. Microdeletions of parts of the Y chromosome are found in a small number of men with spermatogenic failure involving, predominantly, three regions termed AZFa, AZFb, and AZFc. SUMMARY: It is necessary that a Y chromosomal microdeletion assay be carried out prior to any intervention using ejaculated sperm or prior to any surgical procedure to try to find spermatozoa in an azoospermic man.

The genetic basis of male reproductive failure.

Evolving therapies have allowed the use of sperm from men with spermatogenic compromise, obstructive azoospermia, and sperm functional deficiency, enabling these men to procreate when unable to do so naturally. The genetic basis of only a portion of these conditions is known and research must be pursued into the genetic underpinnings of those that have not yet been delineated. Education and provision of information to patients is the responsibility of all involved in the care of men with reproductive failure. The author concentrates on some of the known causes of nonobstructive azoospermia and obstructive azoospermia with a well-established genetic cause such as congenital bilateral absence of the vas deferens.

Common urologic diseases in older men and their treatment: how they impact fertility.

As men age, medical and surgical diseases involving the genitourinary tract become more common. The conditions themselves, if not their treatments, can negatively impact the fertility potential of an affected man. Many older men maintain the desire to father children, so it is critical to understand the disturbed anatomy and physiology involved to properly counsel that individual. Should this or that treatment regimen be employed? Should sperm banking be undertaken before institution of a permanently ablative/suppressive therapy? What are the long-term consequences of one therapy over another vis-à-vis sperm production, sperm quality, and/or sperm transport? In this context, some of the more common genitourinary afflictions of the older male and the treatment options that are available will be discussed.

Concepts in diagnosis and therapy for male reproductive impairment.

An accurate medical history and directed physical examination are essential in diagnosis of male infertility. We review the hormonal assessments and specific genetic analyses that are useful additional tests, and detail other evidence-based examinations that are available to help guide therapeutic strategies. By contrast with female infertility treatments-especially hormonal manipulations to stimulate or enhance oocyte production-spermatogenesis and sperm quality abnormalities are much more difficult to affect positively. In general, a healthy lifestyle can improve sperm quality. A few men have conditions in which evidence-based therapies can increase their chances for natural conception. In this second of two papers in The Lancet Diabetes and Endocrinology Series on male reproductive impairment, we examine the agreements and controversies that surround several of these conditions. When we are not able to cure, correct, or mitigate the cause of conditions such as severe oligozoospermia, non-remedial ductal obstruction, and absence of sperm fertilising ability, assisted reproductive technologies, such as in-vitro fertilisation (IVF) with intracytoplasmic sperm injection (ICSI), can be used as an adjunctive measure to allow for biological paternity. Not considered possible just two decades ago, azoospermia due to testicular failure, including 47,XXY (Klinefelter syndrome), is now treatable in approximately 50% of cases when combining surgical harvesting of testicular sperm and ICSI. Although genetic fatherhood is now possible for many men previously considered sterile, it is crucial to discover and abrogate causes as best possible, provide reliable and evidenced-based therapy, consider seriously the health and wellness of any offspring conceived, and always view infertility as a possible symptom of a more general or constitutional disease.

Novel concepts in the aetiology of male reproductive impairment.

Infertility is a widespread problem and a male contribution is involved in 20-70% of affected couples. As a man's fertility relies on the quantity and quality of his sperm, semen analysis is generally used as the proxy to estimate fertility or gain insight into the underlying reasons for infertility. Male reproductive impairment might result from factors that affect sperm production, quality, function, or transport. Although in most men the origin of infertility remains unexplained, genetic causes are increasingly being discovered. In this first of two papers in The Lancet Diabetes and Endocrinology Series on male reproductive impairment, we propose a novel, clinically based aetiological construct with a genetic focus, and consider how this might serve as a helpful way to conceptualise a diagnostic algorithm.

The diagnosis of male infertility: an analysis of the evidence to support the development of global WHO guidance-challenges and future research opportunities.

BACKGROUND: Herein, we describe the consensus guideline methodology, summarize the evidence-based recommendations we provided to the World Health Organization (WHO) for their consideration in the development of global guidance and present a narrative review of the diagnosis of male infertility as related to the eight prioritized (problem or population (P), intervention (I), comparison (C) and outcome(s) (O) (PICO)) questions. Additionally, we discuss the challenges and research gaps identified during the synthesis of this evidence. OBJECTIVE AND RATIONALE: The aim of this paper is to present an evidence-based approach for the diagnosis of male infertility as related to the eight prioritized PICO questions. SEARCH METHODS: Collating the evidence to support providing recommendations involved a collaborative process as developed by WHO, namely: identification of priority questions and critical outcomes; retrieval of up-to-date evidence and existing guidelines; assessment and synthesis of the evidence; and the formulation of draft recommendations to be used for reaching consensus with a wide range of global stakeholders. For each draft recommendation the quality of the supporting evidence was then graded and assessed for consideration during a WHO consensus. OUTCOMES: Evidence was synthesized and recommendations were drafted to address the diagnosis of male infertility specifically encompassing the following: What is the prevalence of male infertility and what proportion of infertility is attributable to the male? Is it necessary for all infertile men to undergo a thorough evaluation? What is the clinical (ART/non ART) value of traditional semen parameters? What key male lifestyle factors impact on fertility (focusing on obesity, heat and tobacco smoking)? Do supplementary oral antioxidants or herbal therapies significantly influence fertility outcomes for infertile men? What are the evidence-based criteria for genetic screening of infertile men? How does a history of neoplasia and related treatments in the male impact on (his and his partner's) reproductive health and fertility options? And lastly, what is the impact of varicocele on male fertility and does correction of varicocele improve semen parameters and/or fertility? WIDER IMPLICATIONS: This evidence synthesis analysis has been conducted in a manner to be considered for global applicability for the diagnosis of male infertility.

A multi-institutional randomized controlled trial of adjuvant Web-based teaching to medical students.

PURPOSE: To investigate the impact of an adjuvant Web-based teaching program on medical students' learning during clinical rotations. METHOD: From April 2003 to May 2004, 351 students completing clinical rotations in surgery-urology at four U.S. medical schools were invited to volunteer for the study. Web-based teaching cases were developed covering four core urologic topics. Students were block randomized to receive Web-based teaching on two of the four topics. Before and after a designated duration at each institution (ranging one to three weeks), students completed a validated 28-item Web-based test (Cronbach's alpha = .76) covering all four topics. The test was also administered to a subset of students at one school at the conclusion of their third-year to measure long-term learning. RESULTS: Eighty-one percent of all eligible students (286/351) volunteered to participate in the study, 73% of whom (210/286) completed the Web-based program. Compared to controls, Web-based teaching significantly increased test scores in the four topics at each medical school (p < .001, mixed analysis of variance), corresponding to a Cohen's d effect size of 1.52 (95% confidence interval [CI], 1.23-1.80). Learning efficiency was increased three-fold by Web-based teaching (Cohen's d effect size 1.16; 95% CI 1.13-1.19). Students who were tested a median of 4.8 months later demonstrated significantly higher scores for Web-based teaching compared to non-Web-based teaching (p = .007, paired t-test). Limited learning was noted in the absence of Web-based teaching. CONCLUSIONS: This randomized controlled trial provides Class I evidence that Web-based teaching as an adjunct to clinical experiences can significantly and durably improve medical students' learning.

TEX11 is mutated in infertile men with azoospermia and regulates genome-wide recombination rates in mouse.

Genome-wide recombination is essential for genome stability, evolution, and speciation. Mouse Tex11, an X-linked meiosis-specific gene, promotes meiotic recombination and chromosomal synapsis. Here, we report that TEX11 is mutated in infertile men with non-obstructive azoospermia and that an analogous mutation in the mouse impairs meiosis. Genetic screening of a large cohort of idiopathic infertile men reveals that TEX11 mutations, including frameshift and splicing acceptor site mutations, cause infertility in 1% of azoospermic men. Functional evaluation of three analogous human TEX11 missense mutations in transgenic mouse models identified one mutation (V748A) as a potential infertility allele and found two mutations non-causative. In the mouse model, an intronless autosomal Tex11 transgene functionally substitutes for the X-linked Tex11 gene, providing genetic evidence for the X-to-autosomal retrotransposition evolution phenomenon. Furthermore, we find that TEX11 protein levels modulate genome-wide recombination rates in both sexes. These studies indicate that TEX11 alleles affecting expression level or substituting single amino acids may contribute to variations in recombination rates between sexes and among individuals in humans.

Ejaculatory dysfunction.

Ejaculatory dysfunction may occur after many different disorders ranging from traumatic spinal cord injury to diabetes mellitus. With an understanding of the many facets and nuances of the ejaculatory apparatus, both anatomic and neurologic, the well-versed clinician can proceed along a safe, efficient, and appropriate treatment algorithm to help affected men and their partners achieve parenthood.

The natural history of endocrine function and spermatogenesis in Klinefelter syndrome: what the data show.

Once thought to be a chromosomal aberration associated with absolute sterility, Klinefelter syndrome may now be potentially treatable by testicular sperm retrieval coupled with intracytoplasmic sperm injection. With these therapeutic advances, azoospermic 47,XXY men now may have an opportunity for biological paternity. However, our knowledge of the basic mechanisms underlying germ cell loss and Leydig cell compromise is lagging, and is just now beginning to evolve and provide answers to some of the field's most vexing questions: how to maximize and preserve fertility in Klinefelter males many years or even decades before they wish to actively pursue fatherhood. This article reviews the development of the androgenic and spermatogenic compartments of the Klinefelter testis through puberty, and recommends that it is only with a clear understanding of the basic facts that a rational, considered approach to fertility optimization and preservation can be determined.

Clinical evaluation of the infertile male with respect to genetic etiologies.

Severe male factor infertility may have a presently identifiable genetic basis. Y chromosomal microdeletions (e.g., an AZFc microdeletion), karyotypic anomalies (e.g., Klinefelter Syndrome), and mutations in both alleles of the cystic fibrosis transmembrane conductance regulator (CFTR) gene may be found, depending upon the etiology of the reproductive compromise. Which patients should be tested, what are the tests that can be performed, when should those tests be ordered, and what might a positive outcome mean, are all critically valuable clinical questions for the couple that help guide evaluation and management. It is imperative that they be asked and results discussed prior to any intervention such as testis tissue extraction, microsurgical epididymal sperm aspiration, or intracytoplasmic sperm injection so that the couple can incorporate them in their decisions moving forward vis-à-vis their reproductive choices and options. The role of reproductive medicine clinicians should not be limited to just helping couples establish a pregnancy, but instead be expanded to educating them about the reasons and causes of their reproductive failure that affect not only them as individuals but also may have implications for their offspring.