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

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.

The effects of Y chromosome microdeletions on in vitro fertilization outcomes, health abnormalities in offspring and recurrent pregnancy loss

Male factor infertility accounts for approximately 50% of all infertility evaluations. A common cause of severe oligozoospermia and azoospermia is Y chromosome microdeletions (YCMs). Men with these genetic microdeletions must typically undergo assisted reproductive technology (ART) procedures to obtain paternity. In this review, we performed a thorough and extensive search of the literature to summarize the effects of YCMs on in vitro fertilization (IVF) outcomes, health abnormalities in offspring and recurrent pregnancy loss (RPL). The PubMed database was searched using specific search terms and papers were identified using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Sperm retrieval amongst men with complete AZFa and/or AZFb deletions is extremely rare and thus data on ARTs is largely unavailable. In AZFc-deleted men undergoing assisted reproduction, the collective fertilization rate (FR) is 59.8%, the clinical pregnancy rate is 28.6% and the live birth rate is 23.4%. When successful, the YCM is always transmitted to the male offspring and the deletion size either remains unchanged or widens. YCMs generally result in decreased fertilization, clinical pregnancy and live birth rates compared to men with intact Y chromosomes during ART interventions. There is a minimal or absent association of YCMs with abnormalities in the offspring or RPL.

Microdissection testicular sperm extraction in five Japanese patients with non-mosaic Klinefelter's syndrome

Cases

Microdissection testicular sperm extraction (micro‐TESE) was performed on five Japanese men with non‐mosaic Klinefelter's syndrome (KS) and non‐obstructive azoospermia in the authors' department. Here is reported the operative results and partner's clinical course for two cases where spermatozoa could be acquired. Also encountered was a man with non‐mosaic KS with the partial deletion of azoospermia factor (AZF)b. Because this is rare, it is reported in detail in the context of the previous literature. This case series describes the first experience of micro‐TESE by gynecologists in the current department.

Outcome

The egg collection date was adjusted to the micro‐TESE day by using the modified ultra‐long method. Intracytoplasmic sperm injection (ICSI) was implemented for two men whose spermatozoa were acquired by micro‐TESE, with these progressing to the blastocyst stage. Subsequently, one case conceived after the transfer of fresh embryos and a healthy baby was delivered. However, spermatozoa could not be retrieved from the man with non‐mosaic KS who was harboring the partial deletion of AZFb.

Conclusion

These findings suggest that ovulation induction by using the modified ultra‐long method with micro‐TESE and ICSI on the same day represents an effective treatment option for men with non‐mosaic KS. As there are cases where AZF deletion is recognized among patients with non‐mosaic KS, screening before micro‐TESE is strongly recommended.

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.

Complete Azoospermia Factor b Deletion of Y Chromosome in an Infertile Male With Severe Oligoasthenozoospermia: Case Report and Literature Review

OBJECTIVE

To report on a male patient with complete deletion of azoospermia factor b (AZFb) who presented with severe oligoasthenozoospermia, but who successfully fathered a child via intracytoplasmic sperm injection (ICSI).

MATERIALS AND METHODS

Karyotype analysis of peripheral blood lymphocytes was performed by standard G-banding. Y chromosome microdeletions were detected by multiplex polymerase chain reaction amplification using AZF-specific, sequence-tagged site markers. The ICSI procedure was performed using ejaculated motile spermatozoa.

RESULTS

Cytogenetic analysis of the patient revealed a normal male karyotype, 46,XY. Multiplex polymerase chain reaction screening showed complete deletion of AZFb demonstrated by the absence of specific sequence-tagged site markers sY121, sY127, sY134, and sY143. Following successful ICSI, an ultrasound scan of the patient's partner revealed a single pregnancy with cardiac activity. A healthy boy was born by cesarean section at 38 weeks of gestation. Genetic testing 2 years later revealed that the infant had inherited his father's AZFb deletion.

CONCLUSION

Evidence from this case supports the fact that carriers of AZFb deletions can sometimes produce spermatozoa and father a son with the same AZFb deletion. This possibility reinforces the need for genetic counseling in patients with Y chromosome microdeletions.

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.

Unusual maternal uniparental isodisomic x chromosome mosaicism with asymmetric y chromosomal rearrangement

Infertile men with azoospermia commonly have associated microdeletions in the azoospermia factor (AZF) region of the Y chromosome, sex chromosome mosaicism, or sex chromosome rearrangements. In this study, we describe an unusual 46,XX and 45,X mosaicism with a rare Y chromosome rearrangement in a phenotypically normal male patient. The patient's karyotype was 46,XX[50]/45,X[25]/46,X,der(Y)(pter→q11.222::p11.2→pter)[25]. The derivative Y chromosome had a deletion at Yq11.222 and was duplicated at Yp11.2. Two copies of the SRY gene were confirmed by fluorescence in situ hybridization analysis, and complete deletion of the AZFb and AZFc regions was shown by multiplex-PCR for microdeletion analysis. Both X chromosomes of the predominant mosaic cell line (46,XX) were isodisomic and derived from the maternal gamete, as determined by examination of short tandem repeat markers. We postulate that the derivative Y chromosome might have been generated during paternal meiosis or early embryogenesis. Also, we suggest that the very rare mosaicism of isodisomic X chromosomes might be formed during maternal meiosis II or during postzygotic division derived from the 46,X,der(Y)/ 45,X lineage because of the instability of the derivative Y chromosome. To our knowledge, this is the first confirmatory study to verify the origin of a sex chromosome mosaicism with a Y chromosome rearrangement.

In silico prediction of structure and functions for some proteins of male-specific region of the human Y chromosome

Male-specific region of the human Y chromosome (MSY) comprises 95% of its length that is functionally active. This portion inherits in block from father to male offspring. Most of the genes in the MSY region are involved in male-specific function, such as sex determination and spermatogenesis; also contains genes probably involved in other cellular functions. However, a detailed characterization of numerous MSY-encoded proteins still remains to be done. In this study, 12 uncharacterized proteins of MSY were analyzed through bioinformatics tools for structural and functional characterization. Within these 12 proteins, a total of 55 domains were found, with DnaJ domain signature corresponding to be the highest (11%) followed by both FAD-dependent pyridine nucleotide reductase signature and fumarate lyase superfamily signature (9%). The 3D structures of our selected proteins were built up using homology modeling and the protein threading approaches. These predicted structures confirmed in detail the stereochemistry; indicating reasonably good quality model. Furthermore the predicted functions and the proteins with whom they interact established their biological role and their mechanism of action at molecular level. The results of these structure-functional annotations provide a comprehensive view of the proteins encoded by MSY, which sheds light on their biological functions and molecular mechanisms. The data presented in this study may assist in future prognosis of several human diseases such as Turner syndrome, gonadal sex reversal, spermatogenic failure, and gonadoblastoma.

Interstitial 4q Deletion and Isodicentric Y-Chromosome in a Patient with Dysmorphic Features

We present a 2-year-old boy with a de novo 46,XY,idic(Y)(q11.221),del(4)(q26q31.1) karyotype. G-banding, FISH, MLPA, and SNP-array techniques were used to characterize the 24-Mb deletion in 4q and the breakpoint in the isodicentric Y-chromosome region between 15,982,252 and 15,989,842 bp. The patient presented with mild facial dysmorphism, hemangioma, mild frontal cerebral atrophy, and Dandy-Walker variant. Essentially, this case reveals that patients can present more complex genomic imbalances than initially suspected.

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.

AZFb microdeletions and oligozoospermia--which mechanisms?

OBJECTIVE

To characterize the deletion patterns and its breakpoints in oligozoospermic patients presenting AZFb and AZFc microdeletions and to understand the recombination mechanisms underlying these microdeletions.

DESIGN

Case report.

SETTING

Genetics Department of Faculty of Medicine of Porto, Porto, Portugal.

PATIENT(S)

Two men with severe oligozoospermia and two men with nonobstructive azoospermia identified as having different AZFb+c deletion patterns via Y chromosome microdeletion analysis.

INTERVENTION(S)

Definition of microdeletions and the fine characterization of the respective breakpoints by sequence-tagged sites (STS) polymerase chain reaction (PCR) and single-nucleotide variant (SNV) PCR.

MAIN OUTCOME MEASURE(S)

Study of the fine structure of the Y-chromosome and discussion of the putative mechanisms involved in each microdeletion pattern.

RESULT(S)

From the four patients studied, three deletion patterns were identified: IR4/distal-P2 (25%; 1 of 4), P5/proximal-P1 (50%; 2 of 4), and P5/distal-P1 (25%; 1 of 4). Although severe oligozoospermia is normally associated with AZFc, a complete AZFb deletion was found in one case.

CONCLUSION(S)

Analysis of these patients has revealed a new putative region that may be involved in spermatogenesis conservation.

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.