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.

Deletions at chromosome regions 7q11.23 and 7q36 in a patient with Williams syndrome.

We report on a patient with Williams syndrome and a complex de novo chromosome rearrangement, including microdeletions at 7q11.23 and 7q36 and additional chromosomal material at 7q36. The nature of this additional material was elucidated by spectral karyotyping and first assigned to chromosome 22. Subsequent fluorescence in situ hybridization (FISH) experiments showed that it consisted of satellite material only. Refinement of the 7q36 breakpoint was performed with several FISH probes, showing a deletion distal to the triphalangeal thumb (TPT) region. The phenotype of the patient principally results from the microdeletion of the 7q11.23; the small deletion at 7qter and the extra satellite material may not be of clinical significance.

Etiological studies of severe or familial hypospadias.

PURPOSE: Hypospadias is a congenital anomaly occurring in 1250 to 1830 live male births, of which 20% involve a severe type. The recurrence risk in families is high. In the majority of cases the underlying etiology remains unknown, which hampers further management based on the specific requirements associated with a specific etiology. MATERIALS AND METHODS: In a single center study 63 unselected cases of severe hypospadias were studied for all presently known causes of hypospadias using clinical as well as molecular biological techniques. Also, 16 families with hypospadias were analyzed for possible androgen receptor gene mutations. RESULTS: In 31% of cases of severe hypospadias the underlying etiology was identified. Of these 31% of cases 17% were due to complex genetic syndromes, 9.5% were due to chromosomal anomalies, and 1 involved the vanishing testes syndrome, the androgen insensitivity syndrome and 5alpha-reductase type 2 deficiency, respectively. Based on hormone stimulation tests Leydig cell hypoplasia and disorders of testosterone biosynthesis were suspected in some patients but not confirmed by mutation analysis of the respective genes. Familial hypospadias was due to androgen insensitivity in only 1 family but no other etiologies were identified in this group. CONCLUSIONS: Using patient history, physical examination, karyotyping, hormonal evaluation, including human chorionic gonadotropin testing in prepubertal cases and additional biochemical and molecular genetic evaluation, an etiological diagnosis was made in 31% of cases of severe hypospadias. This diagnosis has implications for further patient treatment. In addition, familial hypospadias is rarely due to the androgen insensitivity syndrome.

An unbalanced submicroscopic translocation t(8;16)(q24.3;p13.3)pat associated with tuberous sclerosis complex, adult polycystic kidney disease, and hypomelanosis of Ito.

We report on a familial submicroscopic translocation involving chromosomes 8 and 16. The proband of the family had a clinical picture suggestive of a large deletion in the chromosome 16p13.3 area, as he was affected with tuberous sclerosis complex (TSC) and had alpha thalassaemia trait, and his half brother, who also had TSC, may have suffered additionally from polycystic kidney disease (PKD). FISH studies provided evidence for a familial translocation t(8;16)(q24.3;p13.3) with an unbalanced form in the proband and a balanced form in the father and in a paternal aunt. The unbalanced translocation caused the index patient to be deleted for the chromosome 16p13.3-pter region, with the most proximal breakpoint described to date for terminal 16p deletions. In addition, FISH analysis showed a duplication for the distal 8q region. Since the index patient also had hypomelanosis of Ito (HI), either of the chromosomal areas involved in the translocation may be a candidate region for an HI determining gene. Furthermore, it is noteworthy that both carriers of the balanced translocation showed a nodular goitre, while the proband has hypothyroidism.

Interchromosomal insertions. Identification of five cases and a review.

In five families with questionable chromosome rearrangements, we identified an interchromosomal insertion by fluorescent in situ hybridization (FISH). In case 1 with a dir ins (5;11)(p14;q14q24) in three generations, the mentally retarded and microcephalic proband showed a 5p14-->pter deletion. In case 2, a duplication (13)(q21.31--> q31.2) combined with a deletion (11)(q14-->q22) segregated from a reciprocal ins(11;13)(q14q122)(q21.32q31.2), causing a mixed phenotype with psychomotor retardation, caput quadratum, choanal atresia, and pes equinovarus. In case 3, a dir ins (18;5)(q21.3;p13.1p14) was associated with spontaneous abortions, in case 4, the proband with mental retardation, microcephaly, and a heart defect showed a pure trisomy of (12)(q13-->q15), which had segregated from a carrier of an ins (18;12)(p11.3;q13q15). In case 5, a duplication of (10)(q26.3-->q25.2) segregated from an inv ins(5;10)(q15;q26.3q25.2), which was passed on directly from a mother to her son,with mental retardation. In all families the elucidation of the insertional translocation (IT) considerably increased the associated genetic risks of carriers. For the review, we collected data from 81 articles on 87 IT probands on ascertainment, origin, familial transmittance, progeny, and genetic risks of IT carriers. We also discussed the recombinant chromosomes and complex rearrangements associated with ITs, and listed chromosome regions occurring solely as deletions, or solely as duplications, or as both to facilitate genotype/phenotype correlations. We conclude that ITs are rare chromosomal rearrangements with an 1:80,000 incidence, of which nearly 80% were referred because of congenital abnormalities and mental retardation. A maternal origin was seen in 59.5%, a paternal origin in 26.6%, and 13.9% were de novo. No notable difference in fertility between male and female IT carriers was noticed. Bias of ascertainment was excluded in 15 familial cases and led to an estimate of the genetic risks for IT carriers of 32.0-36.0%. The mean size of the inserted regions occurring solely as duplications (n=39) measures 0.96% of the haploid autosomal length (HAL), and of regions solely occurring as deletions (n=14) 0.47% HAL. In the families where both aneusomies occurred, the size of the insertions ranged between 0.22 and 1.21% HAL. Overall, the findings fit with the general idea that a surplus of genetic material is tolerated more easily than a deficiency.

CHARGE association-related ocular pathology in a newborn with partial trisomy 19q and partial monosomy 21q, from a maternal translocation (19;21) (q13.1;q22.3).

We report a novel case of partial trisomy 19q and concomitant partial monosomy 21q, segregated from a maternal translocation (19;21) (q13.1;q22.3), identified by spectral karyotyping. Clinical examination revealed dysmorphic features of the face and limbs, cleft palate, bilateral colobomas with associated bilateral colobomatous optic nerve cysts, hearing loss, and a cardiac anomaly. At autopsy, the dysmorphic features and cleft palate were confirmed. The ocular histopathology is described in detail and the cardiac anomaly was further specified. The combination of phenotype features is diagnostic of the CHARGE (coloboma, heart malformation, atresia choanae, retarded growth and development, and/or CNS anomalies, genital hypoplasia, ear anomalies and/or deafness) association. This case also has some phenotypic features in common with previous cases of partial trisomy 19q. The importance of a complete autopsy in cases with multiple congenital anomalies and/or genetic abnormalities is emphasized. This will allow optimal genetic counseling and contribute to our understanding of developmental biology.

Submicroscopic Xpter deletion in a boy with growth and mental retardation caused by a familial t(X;14).

In a 3-year-old boy with short stature, developmental delay, and dry skin, steroid sulphatase deficiency and a submicroscopic terminal deletion of Xp were found. Except for the short stature, no major clinical signs of X-linked recessive chondrodysplasia punctata could be observed. His mother had lowered steroid sulphatase activity compatible with carriership for X-linked ichthyosis and a submicroscopic translocation (X;14)(p22.31;p11.1). This finding combined with a normal amplification of exons 1, 5, and 10 of the STS gene from propositus' DNA suggested a breakpoint upstream of the STS gene. The submicroscopic maternal translocation had important implications for genetic counseling. This case report illustrates that contiguous gene syndrome related to the Xpter region may have an atypical clinical presentation and the usefulness of combined clinical, biochemical, molecular, and fluorescence in situ hybridization analysis.

Chromosome 22q11 deletions in patients with selected outflow tract malformations.

The incidence of 22q11 deletions and its effect on the phenotype were established in 170 patients with selected outflow tract malformations and transposition of the great arteries (conotruncal defects). Cases were seen both prospectively and retrospectively. All patients had a dysmorphological evaluation by the clinical geneticist and a cytogenetic analysis including FISH analysis for 22q11 deletions. A chromosomal abnormality was present in 29 patients, including a 22q11 deletion in 22/170 patients (13%). The 22q11 deletion was found in 11% of tetralogy of Fallot, in 11% of pulmonary atresia and VSD, in 44% of pulmonary atresia. VSD and collateral arteries, in 20% of truncus arteriosus, in 60% of interrupted aortic arch and in 25% patients with aberrant subclavian artery. They were absent in double outlet right ventricle or in transposition of the great arteries. No parental deletion was found. All patients had clinical characteristics of the velocardiofacial syndrome. This study confirms a high incidence of chromosome 22q11 deletions in patients with selected outflow tract malformations, with great clinical impact for further management and genetic counseling.

Chromosome studies in 1792 males prior to intra-cytoplasmic sperm injection: the Dutch experience.

The chance of a male with severe oligozoospermia or azoospermia achieving a pregnancy has undergone a revolutionary increase with the introduction of the intracytoplasmic sperm injection technique (ICSI). However, since ICSI circumvents part of the natural sperm selection mechanisms, the possible transmission of genetic defects to the offspring is a major concern. Cytogenetic analysis is a relatively simple technique to identify at least the carriers of a chromosomal aberration before starting the ICSI procedure. In order to assess the frequency of chromosomal aberrations in male ICSI candidates, we have performed a nationwide cytogenetic study. Of the 1792 males examined, 72 (4.0%) revealed a chromosomal aberration, and one individual even had two. Numerical sex chromosomal aberrations and Robertsonian translocations predominated, followed by reciprocal translocations, inversions and supernumerary marker chromosomes. The different implications, in case a chromosomal aberration is encountered prior to ICSI, are discussed.

Two cases of Robertsonian translocations in oligozoospermic males and their consequences for pregnancies induced by intracytoplasmic sperm injection.

Two case histories are presented documenting structural chromosome abnormalities in infertile males. The abnormalities were detected only after application of intracytoplasmic sperm injection (ICSI) was repeatedly unsuccessful or resulted in an abnormal pregnancy. A mosaic Robertsonian translocation 45,XY,der(13;13)(q10; q10)/46,XY,t(13;13)(p10;p10), der(13p;13p) incompatible with normal offspring was found in a male with extreme oligozoospermia after three subsequent ICSI treatments were unsuccessful and one had resulted in a spontaneous abortion. A second case involved a Robertsonian translocation 45,XY,der(13;14)(q10;q10) which was detected in a male with extreme oligozoospermia after ultrasound abnormalities were found in an ICSI-induced twin pregnancy. Amniocentesis showed an unbalanced 46,XY,+13,der(13;14)(q10;q10) karyotype in one twin and a Robertsonian 45,XX,der(13;14)(q10;q10) karyotype in the other twin. Chromosome analysis of males with abnormal sperm characteristics is advised prior to ICSI.

Determination of the parent of origin in nine cases of prenatally detected chromosome aberrations found after intracytoplasmic sperm injection.

Prenatal cytogenetic analysis of 71 fetuses conceived by intracytoplasmic sperm injection (ICSI) resulted in the detection of nine (12.7%) chromosome aberrations including two cases of 47,XXY, four cases involving a 45,X cell line and three autosomal trisomies. Molecular analysis of the parental origin of the deleted or supernumerary chromosome was performed by using polymorphic microsatellite markers. Six cases involving a sex chromosome abnormality were found to be of paternal origin while the two trisomic cases that could be analysed were of maternal origin. Two cases involved the same infertile couple who had two consecutive ICSI pregnancies terminated because of a chromosome abnormality. The replaced embryos in both cases originated from a single batch of ICSI fertilized oocytes of which part was used to initiate the first pregnancy and part was cryopreserved and used to initiate the second pregnancy.

Variable FMR1 gene methylation of large expansions leads to variable phenotype in three males from one fragile X family.

The fragile X syndrome is caused by an expanded CGG repeat (> 200 units, full mutation) at the 5' end of the FMR1 gene, which is associated with methylation of a CpG island upstream of the FMR1 gene and down regulation of the transcription. We describe three related males with full mutations in the FMR1 gene, as defined by size, but with different percentages of unmethylated alleles (+/-90%, 35%, and 15%, respectively) as studied in leucocytes. Normal mental status was observed in the male who showed 90% lack of methylation, whereas his two cousins were retarded. The mentally normal male did show some minor facial features of the fragile X syndrome; the FMR protein was detectable in 75% of his leucocytes. In all three cases, the proportion of unmethylated FMR1 genes corresponded to the percentage of leucocytes showing FMR1 protein production. Our results indicated a direct relationship between methylation and the ability to produce FMR protein. These cases will be discussed in relation to the phenotypic effects of incompletely methylated full mutations in the FMR1 gene as observed by others.

The fragile X phenotype in a mosaic male with a deletion showing expression of the FMR1 protein in 28% of the cells.

The instability of the CGG repeat region of FMR1 is not restricted to the CGG repeat but expands to flanking sequences as well. A mosaic fragile X male is reported with a deletion of part of the CGG repeat and 30 bp immediately 3' of the repeat, thus confirming the presence of a hotspot for deletions in the CGG region of FMR1. The deletion, detected in 28% of his lymphocytes, did not impair the transcription and translation of FMR1, suggesting that regulatory elements are not present in the deleted region. The patient has the characteristic fragile X phenotype and assuming that the mosaic pattern detected in the lymphocytes reflects the mosaic pattern in brain, 28% expression of FMRP may not be sufficient for normal cognitive functioning.

Recurrence of DiGeorge syndrome: prenatal detection by FISH of a molecular 22q11 deletion.

We report on a prenatal diagnosis by FISH of a familial 22q11 deletion associated with DiGeorge syndrome (DGS). The deletion was seen in the proband with symptoms of full DGS, in the physically normal father, and in a subsequent pregnancy. After birth this child showed hypocalcaemia, a T cell deficit, and a right sided aortic arch.

A chromosome 21-specific cosmid cocktail for the detection of chromosome 21 aberrations in interphase nuclei.

Fluorescent in situ hybridization (FISH) with a 21q11-specific probe (CB21c1) consisting of three non-overlapping cosmids has been applied to interphase amniocytes of pregnancies at increased risk for fetal aneuploidy (N = 78) and to interphase lymphocytes, cultured and uncultured, of patients referred for Down syndrome (N = 19 and 28, respectively). In the uncultured amniocytes, six chromosome aberrations were detected: three cases of trisomy 21, a triploidy, a de novo 46,XX,t(21q21q), and a mosaic 46,XY/47,XY,+dic(21)(q11)/48,XY,+dic(21)(q11),+del(21)(q11). In 15 cultured and 20 uncultured blood samples, FISH correctly diagnosed trisomy 21 (full or mosaic) at the interphase level, which was confirmed in all cases by subsequent karyotyping. Because of specific and strong signals in interphase nuclei, CB21c1 appears to be a useful tool for the rapid detection of chromosome 21 abnormalities.

DNA diagnosis of Prader-Willi and Angelman syndromes with the probe PW71 (D15S63).

Previously, 158 nuclear families with probands suspected of having either Prader Willi (PWS) or Angelman syndrome (AS) were analyzed with polymorphic DNA markers from the 15q11-13 region. These cases have been re-evaluated with the probe PW71 (D15S63), which detects parent-of-origin-specific alleles after digestion with a methylation-sensitive restriction enzyme (HpaII). Application of PW71 to DNA samples isolated from leucocytes, confirmed the deletions and uniparental disomies detected earlier by marker analysis, and resolved 50% of the previously uninformative (n = 18) cases. PW71 and restriction fragment length polymorphism analysis indicated that, in all resolved cases, disomies of the 15q11-13 region were present. The use of PW71 increased the percentage of disomies detected in our PWS and AS patient groups. Almost 50% of our PWS patients and 17% of the AS patients showed a disomy of maternal or paternal origin, respectively. DNA of first trimester chorionic villi and of fibroblast cultures was not suitable for analysis with PW71 because of different methylation patterns. The application of PW71 is recommended for the diagnosis of the PWS and AS, with respect to DNA samples from blood.

DNA diagnosis of the fragile X syndrome in a series of 236 mentally retarded subjects and evidence for a reversal of mutation in the FMR-1 gene.

The cloning of the FMR-1 gene and the identification of an expanded CGG repeat in DNA of fragile X patients has made reliable DNA diagnosis feasible. Southern blotting and PCR assays of the CGG repeat in an unselected series of 236 mentally retarded subjects resulted in the identification of 10 new fragile X families. Reevaluation of previously assessed fragile X families resulted in the first observation of the presence of a reversal of mutation in the FMR-1 gene.