Prognostic value of Y deletion analysis: How reliable is the outcome of Y deletion analysis in providing a sound prognosis?

Y chromosomal microdeletions at the azoospermia factor (AZF) locus have been implicated as one of the major causes of idiopathic male infertility. The availability of intracytoplasmic sperm injection (ICSI) in treating a variety of male infertility has raised the risk of the transmission of Y microdeletions from father to son. In many IVF centres, Y microdeletion analysis has been used as a diagnostic tool for genetic counselling of infertile couples. Presently, the only prognosis that can be derived from Y microdeletion analysis is that the affected male offspring would benefit from proper clinical management of their infertility. Prognoses based on the pattern of Y microdeletions in relation to phenotype are rather subjective and inconclusive because of insufficient data to derive a definitive correlation whose significance can be determined by statistical analysis. Standardization of the number and choice of sequence-tagged sites (STS), whose deletions result in defective spermatogenesis, for the polymerase chain reaction (PCR) analysis of Y microdeletions would enhance its reliability in the interpretation of the results which is crucial for therapeutic decision-making. Furthermore, in-depth understanding of the gene functions in male infertility, especially at the AZF locus, would contribute greatly to the quality of the prognostic value of Y microdeletion analysis.     

Achievement of pregnancy in globozoospermia with Y chromosome microdeletion after ICSI

Pregnancy achieved with sperm from a patient with globozoospermia is rare, even after ICSI, since the activation of the oocyte may not occur in this disorder. Therefore, activation of the oocytes by piezoelectricity or calcium ionophores has been suggested, although spontaneous activation of the oocyte after ICSI has been reported in some cases. We report a successful pregnancy in a couple in which the male partner had globozoospermia with microdeletions in the Y chromosome with no further assisted activation after ICSI. During the diagnostic study of the husband, increased numerical chromosome abnormalities after fluorescent in-situ hybridization (FISH) and microdeletions in AZFa; sY86 and AZFb; sY 131 were detected. Out of the 13 oocytes injected, four fertilized and a twin pregnancy was obtained after replacement of four embryos. Healthy twin girls were delivered after a term pregnancy. Some patients with globozoospermia may also have Y chromosome microdeletions, which subsequently may be inherited by the male offspring in cases of achievement of pregnancy.     

Microdeletions of the Y chromosome and intracytoplasmic sperm injection: from gene to clinic

Intracytoplasmic sperm injection (ICSI) is a successful treatment option for severe male infertility, although the aetiology of the disorder remains unclear in most cases. Recently, microdeletions in the AZF region of the Y chromosome have been detected in men with azoospermia or severe oligozoospermia. In this study we investigated the prevalence of microdeletions in the AZF region of the Y chromosome in a population of men undergoing ICSI, and looked for clinical characteristics of men with and without this deletion. Blood was drawn from 164 men, who were on the waiting list for ICSI treatment: 19 were azoospermic, 111 oligozoospermic and 34 normozoospermic (after previous total fertilization failure). A total of 100 men with proven fertility served as a control. Microdeletions in the AZFc region were present in seven of the 111 oligozoospermic men (6.3%). Compared with oligozoospermic men without microdeletions, men with microdeletions had a lower concentration of follicle stimulating hormone (FSH), a lower number of motile spermatozoa and a lower frequency of abnormal findings at andrological history or examination. No microdeletions were found in the azoospermic, normozoospermic and control groups. In conclusion, microdeletions in the AZFc region are relatively frequently found in men with severe unexplained oligozoospermia. In the ICSI era this finding has an important impact because this form of male infertility is now potentially hereditary. Therefore we recommend DNA screening (and genetic counselling) before ICSI, especially in men with normal FSH, severe oligozoospermia and no abnormal clinical andrological findings.      

Genetic risk factors in infertile men with severe oligozoospermia and azoospermia.

BACKGROUND: Male infertility due to severe oligozoospermia and azoospermia has been associated with a number of genetic risk factors. METHODS: In this study 150 men from couples requesting ICSI were investigated for genetic abnormalities, such as constitutive chromosome abnormalities, microdeletions of the Y chromosome (AZF region) and mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. RESULTS: Genetic analysis identified 16/150 (10.6%) abnormal karyotypes, 8/150 (5.3%) AZFc deletions and 14/150 (9.3%) CFTR gene mutations. An abnormal karyotype was found both in men with oligozoospermia and azoospermia: 9 men had a sex-chromosomal aneuploidy, 6 translocations were identified and one marker chromosome was found. Y chromosomal microdeletions were mainly associated with male infertility, due to testicular insufficiency. All deletions identified comprised the AZFc region, containing the Deleted in Azoospermia (DAZ) gene. CFTR gene mutations were commonly seen in men with congenital absence of the vas deferens, but also in 16% of men with azoospermia without any apparent abnormality of the vas deferens. CONCLUSIONS: A genetic abnormality was identified in 36/150 (24%) men with extreme oligozoospermia and azoospermia. Application of ICSI in these couples can result in offspring with an enhanced risk of unbalanced chromosome complement, male infertility due to the transmission of a Y-chromosomal microdeletion, and cystic fibrosis if both partners are CFTR gene mutation carriers. Genetic testing and counselling is clearly indicated for these couples before ICSI is considered.     

Decreased fertilization rate and embryo quality after ICSI in oligozoospermic men with microdeletions in the azoospermia factor c region of the Y chromosome

Microdeletions of the azoospermia factor (AZF) region of the Y chromosome occur in between 1 and 29% of oligozoospermic and azoospermic men, and most deletions are found in the AZFc region. These men can father children when intracytoplasmic sperm injection (ICSI) is used, but the success rate is unclear. Thus, the success rate of 19 ICSI treatments in eight couples with a microdeletion in the AZFc region of the Y chromosome was analysed retrospectively. These were compared with a control group of 239 ICSI treatments in 107 couples undergoing ICSI treatment with ejaculated spermatozoa. The fertilization rate was significantly lower in the group of Y-deleted men (55%; 95% CI: 41-69%) compared with controls (71%; 95% CI: 67-74%; P < 0.01). The embryo quality was also significantly poorer among Y-deleted men (P<0.001). Pregnancy, implantation and take-home baby rates were not significantly lower in the Y-deleted group. This study shows that ICSI in oligozoospermic men with microdeletions in the AZFc region of the Y chromosome leads to a lower fertilization rate and poorer embryo quality.     

The incidence and possible relevance of Y-linked microdeletions in babies born after intracytoplasmic sperm injection and their infertile fathers

Microdeletions linked to deletion intervals 5 and 6 of the Ychromosome have been associated with male factor infertility.Members from at least two gene families lie in the region containingazoospermia factor (AZF), namely YRRM and DAZ. With the adventof intracytoplasmic sperm injection (ICSI), it is possible formen with severe male factor infertility to produce a child.The genetic consequences of such a procedure have been questioned.This report describes the first study of a population (32 couples)of infertile fathers and their sons born after ICSI. The objectiveswere firstly to determine the incidence and map location ofY chromosome microdeletions and to compare the frequencies withother population studies involving severe male factor infertility,and secondly to formulate a working hypothesis concerning developmentalaetiology of Y chromosome microdeletions. The incidence of microdeletionsin the ICSI population was shown to be 9.4% (within the range9–18% reported for populations of severe male factor infertilitypatients). Microdeletions in two out of three affected fatherisonpairs mapped in the region between AZFb and AZFc and the thirdinvolved a large microdeletion in AZFb and AZFc. Of three affectedfather/son pairs, microdeletions were detected in the bloodof one infertile propositus father and three babies. Assumingthat the gonomes of the ICSI-derived babies are direct reflectionsof those of their fathers' germ lines, it is possible that twoof three infertile fathers were mosaic for intact Y and microdeletedY chromosomes. In such cases, the developmental aetiology ofthe microdeletion may be due to a de-novo microdeletion arisingas a post-zygotic mitotic error in the infertile propositusfather, thus producing a mosaic individual who may or may nottransmit the deletion to his ICSI-derived sons depending onthe extent of primordial germ cell mosaicism. In one of threeaffected fathers, the microdeletion detected in his blood wasalso detected in his ICSI-derived son. In this case the de-novoevent giving rise to the microdeletion may have occurred dueto a post- (or pre-) meiotic error in the germ line of thisfather's normally fertile father (i.e. the ICSI-derived baby'sgrandfather). aetiology/intracytoplasmic sperm injection/Y-chromosome microdeletions     

Combined cytogenetic and Y chromosome microdeletion screening in males undergoing intracytoplasmic sperm injection

We evaluated the frequency of chromosomal aberrations and microdeletions of the Y chromosome in a sample of 204 patients included in an intracytoplasmic sperm injection (ICSI) programme. The prevalence of Y chromosome deletions in males with severely or only moderately reduced sparm counts is mainly unknown, so that patients were chosen with sperm counts ranging from mild oligozoospermia to azoospermia. While six out of 158 (3.8%) patients showed constitutional chromosomal aberrations, only two out of 204 (0.98%) patients were diagnosed with a microdeletion of Yq11. One had a terminal deletion in subinterval 6 of Yq11.23 which included the DAZ gene and a corresponding sperm count < 0.1 x 10(6) spermatozoa/ml. The second patient had an isolated deletion of marker Y6PH54c, a more proximal site in subinterval 5 on Yq11.23, but repeatedly showed sperm counts of 3-8 x 10(8) spermatozoa/ml. Thus, of the 158 patients who underwent a combined cytogenetic and Y- microdeletion screening, eight patients (5.1%) showed chromosomal abnormalities, either at the cytogenatic (n = 6) or the molecular level (n = 2). In conclusion, although rare in number, microdeletions of the Y chromosome can also be observed in patients with moderately reduced sperm counts. A more proximal site of the deletion breakpoint does not necessarily imply a more severe impairment of spermatogenesis than a distal deletion site. In our sample, the overall frequency of constitutional chromosomal aberrations exceeded the incidence of microdeletions of the Y chromosome even in patients with idiopathic azoo- or severe oligozoospermia.      

424例非梗阻性无精子症和严重少精子症患者的细胞与分子遗传学研究

目的探讨非梗阻性无精子症和严重少精子症患者的细胞与分子遗传学特点。方法应用染色体核型分析、Y染色体微缺失检测和荧光原位杂交（FISH）、PCR等技术对非梗阻性无精子症（n=291）和严重少精子症患者（n=133）男性不育患者（共424例）进行细胞和分子遗传学检测。结果424例患者中有98例明确为遗传异常引起的,其中66例检测到染色体畸变,44例Y染色体微缺失检测见缺失,12例患者染色体核型和微缺失检测均见异常。部分AZF缺失患者精液或睾丸中有精子,但其生精功能呈进行性下降的特点。结论男性不育最常见的遗传学病因为K linefelter综合征和Y染色体AZFc缺失。Y染色体微缺失检测对Y染色体长臂异染色质区缺失是否为多态性具有明确诊断的作用。细胞与分子遗传学检测为男性不育的诊断、治疗和预后以及ICSI治疗前遗传咨询提供重要依据。     

Y染色体微缺失父子间垂直遗传分析

目的对Y染色体微缺失男性不育患者家系分析,探讨Y染色体微缺失父子间的自然垂直遗传。方法调查12例Y染色体无精子症因子(azoospermia factor,AZF)微缺失不育患者直系男性家族成员,取外周血抽提DNA进行改良多重PCR,绘制男子不育家系系谱图。结果12例家系中2例存在AZFc微缺失的家族遗传性。10例AZF微缺失患者仅本人存在缺失,没有家族遗传性。结论Y染色体AZFc微缺失有生育子代可能,并将这种微缺失自然垂直遗传给男性后代,且相同遗传类型可有不同的临床表型。     

208例男性不育遗传学病因分析研究

目的对208例男性不育患者进行遗传学分析,探讨染色体畸变、Y染色体微小缺失与男性不育的关系。方法采用外周血染色体核型分析技术对208例男性不育患者进行染色体核型分析,再利用改良多重PCR技术对染色体核型正常患者进行Y染色体AZF区域检测。结果 208例男性不育患者中,发现染色体异常者36例,占17.31%;Y染色体微小缺失者6例,占2.88%。结论染色体畸变及Y染色体微小缺失与男性不育关系紧密,染色体核型分析技术与Y染色体AZF检测技术相结合可提高男性不育患者的诊断水平与遗传异常检出率。     

男性不育的遗传学研究及在ICSI中的意义

目的在细胞遗传学基础上,建立和应用一套检测Y染色体微缺失和雄激素受体基因外显子A突变的分子诊断方法,以便研究男性不育发病机制,为临床辅助生殖技术提供遗传咨询。方法对139例原发不育患者采用外周血染色体G显带、C显带技术,并选择其中40例应用多重PCR和PCR-SSCP银染进行DAZ基因及雄激素受体基因外显子A突变检测。结果139例原发不育患者G、C显带发现54例染色体核型异常,3例DAZ基因缺失,5例雄激素受体基因外显子A发生点突变。结论通过细胞遗传学检查和DAZ基因及雄激素受体基因外显子A突变检测,从遗传学角度探讨了男性不育的病因,对卵浆单精子显微注射技术提供了理论依据。     

男性不育患者Y染色体微缺失筛查方法的建立和初步应用

目的 建立一套Y染色体微缺失的多重PCR筛查方法，对无精症或少精症男性不育患者进行Y染色体微缺失的常规筛查。方法 建立5套稳定和可靠的多重PCR筛查方法，对进行单精子卵细胞浆注射治疗的87例无精症和少精症患者及进行睾丸活检的30例无精症患者做Y染色体微缺失的检测。结果 共有19例发现微缺失(16．2％)，其中61例少精症患者中发现11例(18．0％)，56例无精症患者中发现8例(14．3％)。结论 Y染色体微缺失的多重PCR筛查方法是易行和可靠的，对无精症和少精症患者有必要进行Y染色体微缺失的常规筛查。     

安徽地区87例男性不育患者的遗传学病因分析

目的研究染色体异常、SRY基因突变及Y染色体AZF基因微缺失等遗传学病因与男性不育的关系。方法采用染色体G显带对87例男性不育患者进行核型分析,采用PCR技术对患者SRY基因突变及Y染色体AZF基因微缺失进行检测。结果87例男性不育患者中发现染色体异常25例（28．74％）;XX男性反转1例（1．15％）;AZF微缺失4例（4．60％）。总的遗传学异常检出率为34．48％。结论染色体异常及Y染色体AZF微缺失等是引起男性不育的重要遗传学病因。     

Prevalence of chromosomal abnormalities in 2078 infertile couples referred for assisted reproductive techniques

BACKGROUND: This study analyses the prevalence of karyotype changes and Yq11 microdeletions among couples referred for assisted reproduction techniques. METHODS: Prior to receiving either IVF or ICSI treatment, each partner of 2078 infertile couples was screened for karyotype changes by GTG-banding technique on peripheral lymphocytes. No subject presented with obvious phenotype of chromosomal rearrangement. All the oligo/azoospermic men with normal karyotype were further investigated by PCR for Yq11 microdeletions. RESULTS: Eighty-two out of 2078 couples (3.95%) had one partner carrying a chromosomal change, and 10 out of 202 (4.95%) men showed Yq11 microdeletions. The chromosomal rearrangements were 44 (2.1%) translocations, 23 (1.1%) gonosomal mosaics, six (0.3%) 47,XXY, five (0.24%) marker chromosomes, three (0.14%) inversions and one (0.05%) duplication. Frequency of anomalies in men and women were similar: 42 and 40 cases respectively. CONCLUSIONS: Partners of infertile couples requiring IVF or ICSI treatment appear to be affected by higher frequency of chromosomal rearrangements than the general population. Categories with greater risk were represented by men with sperm cell count <20 x 10(6) sperm/ml, and women with history of pregnancy loss.     

Screening for microdeletions of Y chromosome genes in patients undergoing intracytoplasmic sperm injection.

The potential of assisted reproduction techniques to transmit genetic defects causing male infertility raises questions concerning the need for a systematic genetic screen and counselling. Deletions of the long arm of the Y chromosome are frequently associated with a failure of spermatogenesis. The search for Y specific sequences and for the gene families RNA binding motif (RBM) and deleted in azoospermia (DAZ) have been introduced in many laboratories. The incidence of Y microdeletions varies widely between studies, from 1-55%. These differences are mainly related to study design. The highest incidence of microdeletions has been reported in well selected idiopathic azoospermic patients. Since microdeletions have been reported also in non-idiopathic patients, it is important to define what is the deletion frequency in unselected patients. We report Y chromosome microdeletion screening in 134 unselected patients undergoing intracytoplasmic sperm injection (ICSI). In the first part of the study we tested six Y chromosome markers. We found three patients with microdeletions (2.2%). Subdivision of the study population revealed a deletion incidence of 4.7% in azoospermic/cryptozoospermic patients; an incidence of 7% in idiopathic patients and an incidence of 16% in idiopathic azoospermic/cryptozoospermic patients. The second part of the study consisted of a screen for the presence of the Y chromosome genes, DBY, CDY, XKRY, eIF-1A, DAZ and BPY2. No additional gene-specific deletions were found. Further data on gene specific screening are needed especially for selected idiopathic patients.     

男性不育患者Y染色体微缺失的研究

目的研究无精子症和少精子症患者与Y染色体位点缺失的相关性，建立Y染色体微缺失的分子诊断方法。方法采用多重PCR技术对53例染色体核型正常的无精子症和少精子症患者以及5例正常男性的无精子因子（azoospermia factor，AZF）区域的6个STS位点进行检测。结果5例精液正常男性未检出Y染色体微缺失；53例患者中6例有AZF区域的微缺失，总缺失率为11．3％。结论Y染色体微缺失是严重生精障碍的重要原因之一，无精子因子（AZF）候选基因在精子发生过程中可能起重要作用。     

Results of cytogenetic analysis in men with severe subfertility prior to intracytoplasmic sperm injection

Intracytoplasmic sperm injection (ICSI) is increasingly [>ecomingthe treatment of choice for severe male subfertil-ity. Cytogeneticevaluation of men with andrological subfer-tility reveals anincreased incidence of chromosomal abnormalities when comparedwith the normal population. We performed chromosomal analysison the male partners of 32 couples referred for andrologicalsubfertility. In two of these men, constitutional chromosomaltranslocations were diagnosed prior to ICSI [(45, XY, t(21,-22)(pll; qll) and 46, XY, t(22; Y)(pll;ql2)]. Since ICSI bypassesmany potential barriers of fertilization, successful pregnancycan t>e achieved despite the presence of severely impairedspermatozoa in a population at high risk for chromosomal aberrations.It is well known that the presence of a chromosomal aberrationplays a significant role in partial >r complete spermatogenicarrest ICSI does not seem to increase the risk of fetal chromosomalabnormalities when a spermatozoon from a chromosomally normalmale is used. To exclude a higher risk for spontaneous abortionand fetal chromosomal abnormalities, we advocate cytogeneticscreening of males with severe male subfertility who opt forICSI.     

Male infertility: analysis of the markers and genes on the human Y chromosome

The long arm of the human Y chromosome is required for male fertility. Deletions in three different regions can cause severe spermatogenic defects ranging from non-obstructive azoospermia to oligozoospermia. Use of intracytoplasmic sperm injection (ICSI) may allow Y chromosome defects to be passed from father to son. Thus, numerous reports have stressed the need to offer genetic testing to infertile men who select ICSI and a number of reproductive clinics have begun to do so. The primary objectives of this review were: firstly, to discuss the characteristics of the published set of polymerase chain reaction markers and how these characteristics affect interpretation of Y chromosome deletion analysis and secondly, to summarize the recent literature pertaining to the genes on the Y chromosome.      

ICSI and the transmission of X-autosomal translocation: a three-generation evaluation of X;20 translocation: case report

Published reports show that male carriers of an X-autosome translocation, which is either inherited from their mother or is de novo, are generally sterile, regardless of the position of the breakpoint in the X chromosome. We report a three-generation propagation of such a translocation in a family with a case of male factor infertility. Due to the condition of severe oligozoospermia, the proband and his wife underwent ICSI, which resulted in the birth of a normal healthy female. Cytogenetic (chromosome) analyses and X-chromosome inactivation (XCI) assays were done on the family. The cytogenetic analysis of the proband, a man with severe oligozoospermia, revealed an X-autosomal translocation, 46,Y,t(X;20)(q10;q10), which was inherited from his mother. His brother had the same translocation. Amniocentesis and post-natal umbilical cord analyses revealed that the female infant carried the same translocation as her father. XCI studies showed highly skewed inactivation of the normal X chromosome in the female infant, her paternal grandmother, and her mother who had a normal karyotype. In contrast to the data from the literature, our study suggests that men with a certain type of X-autosomal translocation could conceive children through ICSI in conditions in which a few spermatogonia are able to complete meiosis II. The literature involving X-autosomal translocation in males is also reviewed and the importance of the study of X-chromosomal inactivation in female infants discussed.     

Androgen receptor CAG polymorphism (Xq11-12) status and human spermatogenesis: a prospective analysis of infertile males and their offspring conceived by intracytoplasmic sperm injection

We determined the association of androgen receptor (AR) (CAG)n lengths among fertile and infertile males and offspring conceived by intracytoplasmic sperm injection (ICSI). Assessment of (CAG)n repeats in the AR was performed in a Caucasian population by gene sequencing in fertile men (n=13), infertile men (n=64), boys conceived after ICSI (n=21), and boys conceived naturally (n=11). In the AZF region of the Y chromosome, a total of 22 STSs were analyzed by multiplex PCR; selected spermatozoa were also analyzed by fluorescent in situ hybridization (FISH) for chromosomes 18, 21, X, and Y. The average age was 43.7+/-7 yr for infertile, 44.8+/-7 yr for fertile men, and 5.0+/-0.5 yr for the children. The mean (CAG)n was 22.2+/-3 for the infertile men and 19.3+/-5 for fertile controls. There was a significant difference in CAG repeat length in the severely oligo-/azoo-spermic men vs. controls (p=0.02). An inverse correlation was evident between CAG length and semen parameters. For ICSI male children, the AR (CAG)n lengths were 21.4+/-3.2 vs. 20.8+/-3.4 for boys conceived naturally. While all peripheral karyotypes of fertile and infertile men were normal, de novo gonosomal abnormalities were observed in the ICSI offspring. The incidence of Y microdeletions was 1.6% in infertile men; all the ICSI sons had an intact Y chromosome. In conclusion, severely oligo- and azoospermic men had longer CAG repeat length than fertile controls, suggesting that certain AR gene mutations may have a negative effect on spermatogenesis. An increased incidence of de novo gonosomal abnormalities was found in the ICSI offspring when compared to children conceived naturally. Our assessment of the polymorphic region of the AR gene, in the absence of other specific genomic abnormalities, suggests that the fertility of children conceived by ICSI may be conserved.