Renée H. Martin

Chromosomal analysis of sperm from men with idiopathic infertility using sperm karyotyping and fluorescence in situ hybridization

OBJECTIVE To determine if idiopathic infertile men having oligozoospermia, asthenozoospermia, or teratozoospermia have an elevated risk of transmitting chromosomal abnormalities to their offspring. DESIGN Sperm chromosomal complements from five somatically normal infertile men were assayed using the human sperm-hamster oocyte fusion system and the disomy frequencies for chromosomes 1, 12, and the sex chromosomes were determined using fluorescence in situ hybridization. SETTING Infertile men and normal donors were volunteers in an academic research environment. PATIENTS Five men with the appropriate semen characteristics were recruited among patients concerned about their infertility. INTERVENTIONS Sperm fused with hamster oocytes resulting in sperm chromosomes or the sperm nuclei were prepared for fluorescence in situ hybridization. MAIN OUTCOME MEASURE Structural and numerical abnormalities assessed by sperm karyotypes and the disomy frequency determined by fluorescence in situ hybridization analysis. RESULTS The infertile men showed increased frequencies of numerical abnormalities and total abnormalities as determined by sperm karyotyping. Analysis of sperm nuclei by fluorescence in situ hybridization indicated a significant increase in the frequency of disomy for chromosome 1 and XY disomy. CONCLUSIONS Sperm from infertile men may contain an increased frequency of chromosomal abnormalities.

The chromosome constitution of 1000 human spermatozoa

SummaryChromosomal analysis of 1000 spermatozoa from 33 normal men was performed using in vitro fertilization of zonafree golden hamster eggs. The frequency of abnormal sperm complements was 8.5%: 5.2% were aneuploid and 3.3% had a structural chromosome abnormality. The frequencies of hyperhaploid (2.4%) and hypohaploid (2.7%) sperm complements were not significantly different and all chromosome groups were represented among the aneuploid complements. The majority (22/33) of structurally abnormal complements had a chromosome break. The percentages of X and Y-bearing sperm were 53.9% and 46.1%, which is significantly different from the expected one to one ratio.

Aneuploidy in human sperm: a review of the frequency and distribution of aneuploidy, effects of donor age and lifestyle factors.

Application of fluorescence in situ hybridization (FISH) analysis has opened the way for comprehensive studies on numerical chromosome abnormalities in human sperm. During the last decade, more than five million sperm from approximately 500 normal men were analyzed by a number of laboratories from around the world by this approach. Except for chromosome 19 which has been analyzed in only one study, all other chromosomes have been examined by two or more studies with considerable differences in disomy frequency for an individual chromosome among studies. The mean disomy frequency is 0.15% for each of the autosomes and 0.26% for the sex chromosomes. Most chromosomes analyzed have an equal distribution of disomy with the exception of chromosomes 14, 21, 22 and the sex chromosomes, which display significantly higher disomy frequencies. Slight but significant increases in disomy frequency with advancing paternal age were observed for some chromosomes, in particular for the sex chromosomes. Some lifestyle factors such as smoking, alcohol drinking and caffeine consumption have been investigated and no consistent association between disomy frequency and any type of lifestyle factors has been established. The question of whether different geographic and ethnic groups of men have inherent differences in frequency of disomic sperm has been investigated by two studies with conflicting results.

Human Male Recombination Maps for Individual Chromosomes

Meiotic recombination is essential for the segregation of chromosomes and the formation of normal haploid gametes, yet we know very little about the meiotic process in humans. We present the first (to our knowledge) recombination maps for every autosome in the human male obtained by new immunofluorescence techniques followed by centromere-specific multicolor fluorescence in situ hybridization in human spermatocytes. The mean frequency of autosomal recombination foci was 49.8+/-4.3, corresponding to a genetic length of 2,490 cM. All autosomal bivalents had at least one recombination focus. In contrast, the XY bivalent had a recombination focus in 73% of nuclei, suggesting that a relatively large proportion of spermatocytes may be at risk for nondisjunction of the XY bivalent or elimination by meiotic arrest. There was a very strong correlation between mean length of the synaptonemal complex (SC) and the number of recombination foci per SC. Each bivalent presented a distinct distribution of recombination foci, but in general, foci were near the distal parts of the chromosome, with repression of foci near the centromere. The position of recombination foci demonstrated positive interference, but, in rare instances, foci were very close to one another.

Variation in the frequency and type of sperm chromosomal abnormalities among normal men

SummaryThe chromosomal constitution of 1582 human sperm from 30 normal men of proven fertility was investigated after sperm penetration of hamster eggs. A minimum of 30 sperm chromosome complements were analysed per donor so that the distribution and variation in the frequency and type of sperm chromosomal abnormalities could be assessed. The mean frequency of sperm chromosomal abnormalities in individual men was 10.4% (±6.0%) with a range of 0–24.7%. For numerical abnormalities the mean was 4.7% (±2.9%) with a range of 0–10% and for structural abnormalities the mean was 6.2% (±6.0%) with a range of 0–23.1%. The 95% confidence intervals for the mean of an individual male were 0–10.5% for numerical abnormalities, 0–18.2% for structural abnormalities, and 0–22.4% for total abnormalities. There was a significant excess of hypohaploid complements compared with hyperhaploid complements. Since hypohaploid complements could be caused by technical artefact, a conservative estimate of aneuploidy was obtained by doubling the frequency of hyperhaploid sperm, yielding an estimate of 2.4% aneuploidy. The proportion of X-bearing (53%) and Y-bearing (47%) sperm did not differ significantly. These results were compared to the other two large studies of sperm chromosome complements from normal men.

Aneuploidy in human sperm: results of two- and three-color fluorescence in situ hybridization using centromeric probes for chromosomes 1, 12, 15, 18, X, and Y

To understand the mechanisms that affect aneuploidy, fluorescence in situ hybridization (FISH), using chromosome-specific centromeric probes, was employed to screen a large population of human sperm for numerical errors. To determine the true rate of disomy for chromosomes 1, 12, 15, and 18, two-color FISH was performed, and for the gonosomes, three-color FISH. The use of multiple, differently colored probes allows one to distinguish a true disomic sperm from a diploid cell. A minimum of 10,000 sperm nuclei from each of five donors was scored per set of centromeric probes, giving a total of 165,330 sperm nuclei. The disomy frequencies for autosomes 1, 12, 15, and 18 were found to be similar, with a mean of 0.10% (range, 0.05%-0.16%) for chromosome 1, 0.16% (0.10%-0.25%) for chromosome 12, 0.11% (0.07%-0.20%) for chromosome 15, and 0.11% (0.08%-0.17%) for chromosome 18. For the sex chromosomes, the mean frequency of disomy was found to be 0.43% (range, 0.23%-0.71%), with XX disomy accounting for 0.07% (0.03%-0.10%), YY disomy 0.21% (0.10%-0.43%), and XY disomy 0.15% (0.08%-0.24%). The incidence of disomic sperm for the sex chromosomes was significantly increased, compared to the frequency of disomy for the autosomes (chi 2 = 218.61, P < 0.0001). Diploidy was observed in 0.05%-0.47% of the sperm nuclei counted. Interdonor heterogeneity for disomy frequencies was found to exist for the sex chromosomes and for chromosomes 1 and 15, suggesting significant variation among normal men.

A detailed method for obtaining preparations of human sperm chromosomes

A detailed technique is described for obtaining preparations of the chromosome complements of human sperm by fertilization of hamster eggs and analysis of the male pronucleus. Some of the more difficult aspects and important steps are emphasized. Technical data from 17 consecutive experiments are presented to provide an estimate of the number of karyotypes which can be obtained in an experiment.

An increased frequency of human sperm chromosomal abnormalities after radiotherapy.

13 cancer patients were studied before radiotherapy (RT) and at regular intervals after RT to determine the effect of RT on chromosomal abnormalities in sperm. The men were 19-47 years old and received testicular radiation doses of 0.4-5.0 Gray. Human pronuclear sperm chromosomes were analysed after penetration of zona-pellucida-free hamster eggs. Unfortunately the hamster egg penetration rates were exceedingly low, both before and after RT and this limited the number of sperm chromosome complements which could be analysed. Before RT, the frequency of abnormal sperm chromosome complements was 0% (0/9). After RT, the majority of men were azoospermic for 24 months but complements could be analysed from 4 men. In the first 12 months the frequency of abnormalities was 13% (1/8) and at 24 months it was 13% (7/55). By 36 months after RT, most men had recovered sperm production and the frequency of abnormalities in 8 men was 21% (18/86), which is significantly higher than the rate in control donors (8.5%). For individual men the range was 6-67%, and there was a significant correlation between testicular radiation dose and the frequency of sperm chromosomal abnormalities. The frequencies of both numerical and structural abnormalities were significantly increased after RT. This is the first evidence that radiation may increase the frequency of chromosomal abnormalities in human gametes.

The frequency of aneuploidy among individual chromosomes in 6,821 human sperm chromosome complements

The human sperm/hamster egg fusion technique has been used to analyse 6,821 human sperm chromosome complements from 98 men to determine if all chromosomes are equally likely to be involved in aneuploid events or if some chromosomes are particularly susceptible to nondisjunction. The frequency of hypohaploidy and hyperhaploidy was compared among different chromosome groups and individual chromosomes. In general, hypohaploid sperm complements were more frequent than hyperhaploid complements. The distribution of chromosome loss in the hypohaploid complements indicated that significantly fewer of the large chromosomes and significantly more of the small chromosomes were lost, suggesting that technical loss predominantly affects small chromosomes. Among the autosomes, the observed frequency of hyperhaploid sperm equalled the expected frequency (assuming an equal frequency of nondisjunction for all chromosomes) for all chromosome groups. Among individual autosomes, only chromosome 9 showed an increased frequency of hyperhaploidy. The sex chromosomes also showed a significant increase in the frequency of hyperhaploidy. These results are consistent with studies of spontaneous abortions and liveborns demonstrating that aneuploidy for the sex chromosomes is caused by paternal meiotic error more commonly than aneuploidy for the autosomes.

Is there a relationship between sperm chromosome abnormalities and sperm morphology

This review explores the relationship between sperm chromosomal constitution and morphology. With the advent of techniques for obtaining information on the chromosome complements of spermatozoa, this relationship has been studied in fertile men and in men with a high frequency of chromosomal abnormalities. Using human sperm karyotype analysis, no relationship between sperm chromosome abnormalities and morphology was found in fertile men, translocation carriers or post-radiotherapy cancer patients. Fluorescence in situ hybridization (FISH) analysis has not generally revealed a specific association between morphologically abnormal sperm and sperm chromosome abnormalities, but has indicated that teratozoospermia, like other forms of abnormal semen profiles (aesthenozoospermia, oligozoospermia) is associated with a modest increase in the frequency of sperm chromosome abnormalities. However, FISH studies on some infertile men and mouse strains have suggested that certain types of morphologically abnormal spermatozoa, such as macrocephalic multitailed spermatozoa, are associated with a very significantly increased frequency of aneuploidy. Thus, there may be an association between sperm morphology and aneuploidy in infertile men with specific abnormalities.