Human Reproduction vol.6 no.9 pp. 1252-1258, 1991
Differential distribution of aneuploidy in human gametes
according to their sex
Franck Pellestor
CNRS-UPR 8402-Laboratoire de Biologie de la Reproduction,
Faculti de M&iecine, 2 rue Ecole de M&lecine, F-34059
Montpellier, France
Introduction
The last decade has witnessed the development of a new area
of cytogenetic investigation: the chromosomal analysis of human
gametes. Chromosomal aberrations are known to be the major
reason for pre- and post-implantation human embryo wastage and
some estimates suggest that half of all human concepti have a
chromosomal abnormality (Boue" et al., 1975). Consequently,
cytogenetic analysis of human gametes is an important tool for
the investigation of formation, transmission and aetiology of
chromosomal aberrations.
Analysis of human sperm chromosomes is based on the original
system of interspecific fertilization of hamster eggs by human
spermatozoa (Yanagimachi et al., 1976). Since the pioneering
sperm chromosome analysis of Rudak et al. (1978), several
studies have been performed on a large number of healthy men
(Brandriff etal., 1985; Martin et al., 1987). However, accurate
1252
Materials and methods
Techniques for obtaining chromosome complements of human
gametes have been previously detailed in several reports.
Schematically, the procedure for analysis of human sperm
chromosomes is as follows: in-vitro capacitated spermatozoa were
co-cultured for 1 — 3 h with zona pellucida-free hamster oocytes
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The cytogenetic study of human gametes is a new and
important source of information because most chromosomal
abnormalities originate from meiotic disorders. The frequency
and type of abnormalities were analysed in both spermatozoa
and mature oocytes. A total of 13 975 human sperm
chromosome complements and 1897 oocyte chromosome
complements were analysed. In the present study, pooled
cytogenetic data on human gametes have been examined to
determine and compare the distribution of non-disjunctions
in male and female gametes. Human spermatozoa are
characterized by a significant excess of hypohaploidy and an
equal distribution of aneuploidies among all chromosome
groups, whereas mature oocytes display an equal ratio of
hypohaploidy to hyperhaploidy and a high variability in the
distribution of non-disjunction: in particular, there is a
significant over-representation of aneuploidies in both D and
G chromosome groups. This indicates that non-disjunction
is not a random event in female meiosis and, consequently,
that there are differences in the meiotic process between the
sexes. Meiotic and environmental factors which could explain
the non-random malsegregation of chromosomes in female
meiosis are discussed. The role of maternal age as a cause
of aneuploidy is questioned.
Key words: aneuploidy/chromosome/meiosis/oocyte/spermatozoa
data on the incidence of sperm abnormalities have been difficult
to gather and it has taken 10 years to collect sufficient data both
to determine the mean frequency of chromosome abnormalities
in human spermatozoa (—10%; Martin et al., 1987) and to
investigate their aetiologies (Martin and Rademaker, 1987;
Pellestor and Sele, 1991).
For many years, cytogenetic analysis of female gametes was
seldom possible for technical and ethical reasons. Consequently
only a small amount of data was collected on the chromosomal
normality of human oocytes (Edwards, 1968; Jagiello et al.,
1976). The introduction and development of in-vitro fertilization (TVF) techniques have provided a unique opportunity to
perform widespread cytogenetic investigations of human oocytes.
Indeed, 30—50% of oocytes recovered during IVF procedures
fail to be fertilized and can therefore be used for chromosomal
analysis. Studies have been focused on the direct assessment of
abnormality rates but preliminary estimates were inconsistent
because of the small number of complements analysed. Recently
several groups have reported results from large samples of oocyte
karyotypes (Plachot et al., 1988; Bongso et al., 1988; Pellestor
et al., 1989b; Benkhalifa et al., 1990) which suggest that a high
proportion of human oocytes (25-30%) may be chromosomally
abnormal.
All of these studies have thus provided direct and precise
information concerning paternal and maternal contribution to the
genesis of chromosomal abnormalities at conception.
With regard to the occurrence of aneuploidy, these data agree
with results from epidemiological surveys of liveborns and
spontaneous abortions which have indicated the strong
predominance of extra chromosomes with maternal origin in
autosomal trisomies (Juberg and Mowrey, 1983; Gait et ai,
1989). Such observations lead to the question of whether the
meiotic process of malsegregation might be different in the two
sexes. Pooled results from chromosome analyses of human
gametes provide important baseline data to investigate this
fundamental question. The purpose of the present report was to
determine and compare the distribution of aneuploidy in male
and female gametes. Data are discussed with reference to
epidemiological studies on the parental origin of non-disjunction.
This study is based on published results as well as new material.
Distribution of aneuploidy in human gametes
complements have been compared by x 2 analysis. However,
since the hypohaploidies may have been due to technical loss of
chromosomes, a conservative estimate of aneuploidy rates was
obtained, for each chromosome group, by doubling the
frequencies of hyperhaploidies. Thus, three values were
considered in the present study, namely the observed frequencies
of aneuploidy corresponding to the sum of hypohaploidies and
hyperhaploidies, the estimated frequencies of aneuploidy (2 x
hyperhaploidy rates) and the expected frequencies of aneuploidy
for an equal distribution of non-disjunctions among all
chromosomes.
The Z-test for independent proportion was performed to analyse
the repartition of aneuploidies in the different chromosome
groups.
Results
A summary of sperm chromosome analysis on healthy men is
presented in Table I. Only the observed frequency of aneuploidy
is indexed in this table but some authors have exclusively
considered the estimated frequency of aneuploidy. If this
correction was introduced, the overall rate of structural
aberrations was definitely higher than that of numerical
abnormalities (9.4% versus 3.0%). On the other hand, in human
oocytes, aneuploidy was the most frequently observed
abnormality (Table II). There was a large variability in the
reported frequencies of oocyte chromosome abnormalities,
ranging from 3.0% to 57.1%. The mean frequency of
abnormalities estimated on these pooled data was 24.0% with
22.9% aneuploidies and 1.2% structural aberrations. In all,
>13 000 normal sperm chromosome complements and 1800
mature oocyte chromosome complements were reported.
Unfortunately, details of abnormal karyotypes were not published
in all studies, so that the analysis of the distribution of nondisjunction could be performed only on 1552 oocyte karyotypes
and 7070 sperm karyotypes.
The results of this analysis are summarized in Tables III and
IV. In spermatozoa, there was a highly significant excess
(X2 = 10.18; P < 0.01) of hypohaploidies over hyperhaploidies, whereas the overall numbers of hypohaploidies and
Table I. Summary of cytogenetic studies of normal human spermatozoa
Reference
Rudak et al. (1978)'
Martin et al. (1983f
Karruguchi and Mikamo (1986)
Jenderny and Rohrborn (1987)*
Brandriff « al. (1988)
including Brandriff et al. (1985f
Benet et al. (1988)
Martin (1990)
including Martin et al. {1987f and Martin et al. (1983)
Present study
Cumulative data
Donor
No.
Age (years)
1
33
4
6
20
//
3
83
30
10
127
23
24-44
24-39
7
19-49
21-49
9
9
22-55
20-31
Number of
karyotypes
60
1000
1091
129
5000
2468
505
5629
1582
1561
13 975
Frequency of
aneuploidy (%)
5.0
5./
0.9
1.6
9
1.6
11.1
4.2
4.7
6.1
Frequency of
structural
aberrations (%)
1.7
3.3
13.0
3.9
6.9
7.7
6.9
9.4
6.2
3.5
Data given in italics refer to contrasting sets in which results are included also in subsequent analyses by the same author
"Studies providing details of karyotypes.
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in Biggers-Whitten-Whittingham medium (BWW) to allow
interspecific fertilization to occur. The oocytes were then cultured
overnight in Ham's F10 medium. Colcemid was added to the
Ham's F10 medium to prevent syngamy, thus enabling the
chromosomes of hamster and human sperm pronuclei to be
analysed independently. Oocytes were then fixed directly on slides
according to the technique of Tarkowski (1966) and fixed
preparations were examined using a light microscope. Several
laboratories use chromosome banding techniques (G, Q or R
banding) to improve chromosome analysis (Martin et al., 1986;
Benet et al., 1986; Pellestor et al., 1989).
Cytogenetic analysis of human oocytes was performed on ova
failing to fertilize after insemination in vitro. The methodology
of the FVF programmes, including follicle stimulation, oocyte
recovery, fertilization and culture, have been described previously
(Bongso et al., 1988; Pellestor and Sele, 1988). Fertilization
failure was assessed on the basis of the lack of pronuclei on the
day after insemination and absence of cleavage within 48 h.
Unfertilized oocytes were then individually fixed. Fixation
techniques used included the air-drying technique of Tarkowski
(1966), the modified Tarkowski methods (Viega et al., 1987;
Djalali et al., 1988; Pieters et al., 1989) or gradual fixation
techniques (Wramsby and Liedholm, 1984). Preparations were
generally stained using a Giemsa solution but some laboratories
were successful in performing chromosome banding (Martin
et al, 1986; Pellestor and Sele, 1988). According to the stage
of oocyte maturation, metaphase I and metaphase II chromosome
complements were observed. Nevertheless, only data on
metaphase II, which represented the large majority of spreads
obtained, were informative enough about the occurrence of
aneuploidy in female gametes and were thus included in the
present study.
In order to determine the distribution of non-disjunction in
human gametes, both numbers and groups of chromosomes have
been considered because some of the reported karyotypes were
classified only by group. This reflect the difficulties encountered
in establishing the correct karyotypes of human gametes,
particularly oocytes, which often display very condensed
chromosomes or separated chromatids.
The overall proportions of hypohaploid and hyperhaploid
F.Pellestor
hyperhaploidies were similar (x2 = 1 -69; P > 0.05) in oocyte
chromosome complements. In both male and female gametes,
all chromosome groups showed aneuploidies but the distribution
of non-disjunction was quite different between the sexes. In
spermatozoa, the partition of aneuploidies among chromosome
groups was almost equal (Table HI). Indeed, there were no
significant differences (Z < 1.96; P > 0.05) between estimated
and expected rates of aneuploidy in B, C, D, E, F and G groups
as well as in the sex chromosomes. Only the A group displayed
a significantly lower frequency than expected (8.1% estimated
versus 13.0% expected; P < 0.05). In oocytes (Table IV),
analysis of the distribution of aneuploidy demonstrated that in
all groups except E and F, both observed and estimated
frequencies of aneuploidy varied significantly from the theoretical
Table II. Summary of cytogenetic studies of unfertilized human oocytes
Age of
women
(years)
Number of
metaphase II
analysed
Frequency of
aneuploidy (%)
Wramsby and Liedholm (1984)
Michelmann and Mettler (1985)
Martin et al. (1986)
Wramsby and Fredga (1987)
Viega et aL (1987)
Wramsby et al. (1987)
Plachot etal. (1988)
Bongso et al. (1988)
Van Blerkom and Henry (1988)
Djalali et al. (1988)
Papadopoulos el al. (1989)
Ma et al. (1989)
Pieters et al. (1989)
Benkhalifa et al. (1990)
Present study
Cumulative data
?
22-42
24-35
22-38
?
25-38
25-42
27-42
32-40
24-39
7
24-39
8
33
50
52
102
21
316
251
135
96
25
65
28
302
413
1897
25 0
3.0
30.0
50.0
10.8
57.1
24.0
21.1
8.1
27.1
24.0
26.1
21 4
24.8
27.3
22.9
9
21-42
22-40
Frequency of
structural
aberrations (%)
4.0
1 9
4.9
04
24 0
0.7
1.3
Table III. Distribution of non-disjunctions in aneuploid sperm chromosome complements according to chromosome groups
Chromosome
group
A*
B
C
D
E
F
G
Sex chromosomes
11/8
11/10
41/27
30/15
32/14
20/7
26/11
7/5
178/97
Observed
frequencies of
aneuploidy (%)
Frequencies
of 2x
hypertiaploidy (%)
Expected
frequencies of
aneuploidy (%)
6.8
7.9
24.6
16.3
16.6
9.7
13.4
4.3
8.1
11.2
27.6
15.2
14 2
7.1
11.2
51
13.0
8.7
305
13.0
13.0
8.7
8.7
4.4
•Significant difference between the frequency of 2 x hyperhaptoidy and the expected frequency of aneuploidy.
Table IV. Distnbution of non-disjunctions in aneuploid oocyte chromosome complements according to chromosome groups
Chromosome
group
A*
B*
C*
D*
E
F
G*
8/10
11/8
68/44
65/52
51/36
32/20
59/66
294/236
Observed
frequencies of
aneuploidy (%)
Frequencies
of 2 x
hypertiaploidy (%)
Expected
frequencies of
aneuploidy (%)
34
3.6
21.1
22.1
16.4
9.8
23.4
4.2
3.4
18.6
22 0
14.2
8.4
28.1
13.0
8.7
34.9
13.0
13.0
8.7
8.7
•Significant difference between the frequency of 2 x hypertiaploidy and the expected frequency of aneuploidy.
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Reference
Distribution of aneuploidy in human gametes
frequencies (Z > 1.96; P < 0.05). Some groups (A, B and C)
showed lower frequencies than expected, whereas the D and
particularly the G groups exhibited a much higher frequency than
expected. On the other hand, E and F groups displayed similar
observed, estimated and expected frequencies of aneuploidy
(Z = 0.23 and 0.77 respectively; P > 0.05).
Discussion
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Until the present time, both sperm and oocyte cytogenetic studies
have provided important data on the incidence and aetiology of
chromosomal abnormalities in man. However, the comparative
analysis of those results yields new information on the genesis
of chromosomal abnormalities. With regard to the occurrence
of meitoic non-disjunction, there are two major theoretical
assumptions: first, the process of non-disjunction should produce
an equal number of hypohaploid and hyperhaploid cells, and
second, all chromosomes are identically involved in
non-disjunction events. In reality, the occurrence and distribution of aneuploidies seems to be more complex.
For both spermatozoa and oocytes, some analyses reported a
significant excess of hypohaploidies over hyperhaploidies. The
imbalance is particularly evident in spermatozoa where the total
number of indexed hypohaploidies is twice that of hyperhaploidies
(Table HI). Traditionally, this excess of hypohaploidy is attributed
to artefactual loss of chromosomes during fixation and a
conservative estimate of aneuploidy is given by doubling the
hyperhaploidy rate. Even though this approach seems to be
justified in sperm chromosome analysis because of some aspects
of the technique used for obtaining chromosome preparations (use
of zona-free oocytes, simultaneous fixation of several oocytes,
blowing on the slide), such a procedure could be excessive in
the assessment of human oocyte aneuploidy. Indeed, the risk of
artefactual chromosome loss is lower during human oocyte
fixation because human oocytes still retain the zona pellucida and
are individually manipulated. On the other hand, abnormalities
of meiotic chromosome pairing and segregation seem to be much
more common among oocytes than spermatozoa (Speed, 1988)
and some cellular mechanisms have been described which could
explain the loss of chromosomes during oogenesis, such as the
displacement of chromosomes from the metaphase plate (Ford
and Lester, 1982), anaphase lag (Martin, 1984) or alterations
in the cytoskeleton (Eichenlaub-Ritter et al., 1988). The
prevalence of hypohaploidy in oocytes might therefore be the
unexpected consequence of the strong propensity for chromosome
non-disjunction in female meiosis. This suggestion is supported
by the results of hamster zygote analysis in which significantly
more hypohaploidies are found (Mikamo and Kamiguchi, 1983).
Nevertheless, in the particular case of in-vitro unfertilized
oocytes, results must be interpreted with caution because it is
not possible to establish with certainty that the IVF processes
are innocuous in this respect. We are faced with the question
of whether data obtained from this selected population of oocytes
can really reflect the in-vivo aneuploidy rate. Indeed, certain
methodological factors might bias the findings and account for
the high rate of chromosomal abnormalities observed in oocytes
relative to spermatozoa.
First, all the oocytes examined were from hormone-induced
ovulation. Thus, it could be argued that the protocol of hyperstimulation could lead to an increase in the frequency of
chromosomal abnormalities. In mammals, several studies have
reported a possible deleterious effect of hormonal stimulation on
different stages of reproduction (Fujimoto et al., 1974; Laufer
et al., 1983; Sato and Marrs, 1986) but no increase in the
incidence of aneuploidy was reported (Feichheimer and Beatty,
1974; Laing et al., 1984). In man, induced ovulation was
suspected to increase the frequency of abnormalities in abortuses
(Boue" and Boue", 1973) but this hypothesis has not been confirmed
by direct cytogenetic analysis of human oocytes and embryos.
No correlations have been found between the incidence of
aneuploidy and different modes of follicular stimulation (Plachot
et al., 1988; Van Blerkom and Henry, 1988; Pellestor et al.,
1989b). However, Wramsby et al. (1987) suggested that ovarian
stimulation could also induce the maturation of abnormal gametes,
which would become atretic without stimulation. The recent study
of Tarin and Pellicer (1990) has indicated that an excessive
ovarian response to gonadotrophins results in both an increase
of diploid oocytes without extrusion of the first polar body and
a higher incidence of premature condensation of sperm
chromosomes, suggesting a relative cytoplasmic immaturity
which could explain the low fertilization and implantation rates
obtained after exaggerated follicular hyperstimulation. On the
other hand, Van Blerkom and Henry (1988) made the intriguing
suggestion that chromosomal abnormalites might be more likely
to be 'patient-specific' than a direct consequence of ovarian
stimulation. This hypothesis should be investigated, since it might
skew the reported incidence of aneuploidy if such women
contribute a large number of oocytes that fail to fertilize in vitro.
In fact, the effect of follicular stimulation could be accurately
evaluated by comparing aneuploidy rates in oocytes recovered
in stimulated cycles versus oocytes recovered in spontaneous
cycles. However, such an analysis is impractical because FVF
is seldom performed in unstimulated women.
Another factor that may have to be taken into account in
chromosomal analysis of human oocytes is the in-vitro ageing
of oocytes. Indeed, if the conditions of oocyte culture (pH,
temperature, %CO2, composition of media used) are sufficiently
uniform to be comparable, the duration of culture before oocytes
can be deemed unfertilized varies between published protocols
from 40 to 60 h. Consequently, it could be argued that variations in the reported frequencies of aneuploidy could be related
to culture times. The major effect of oocyte ageing is spindle
instability and chromosome scattering (Szollosi, 1975). This
process provides a cytological basis for non-disjunction and
chromosome loss but it is not observed in human oocytes before
72 h of postovulatory ageing (Eichenlaub-Ritter et al., 1988).
Some investigations have also proven the morphological (Ortiz
et al., 1982) and biochemical (Gifford et al., 1987) integrity of
human oocyte cultured for 24 to 60 h post-recovery. On the other
hand, it must be noted that Martin et al. (1986) and Wramsby
et al. (1987), who analysed freshly recovered and noninseminated oocytes, reported incidences of aneuploidy similar
to those resulting from a study of in-vitro unfertilized oocytes.
As shown in Tables III and IV, all chromosome groups are
represented among aneuploidies but the distribution of nondisjunctions differs radically between male and female gametes.
F.PeUestor
Such a specific process of non-disjunction has already been
postulated to explain the prevalence of trisomy 16 in spontaneous
abortions (Hassold and Jacobs, 1984) but the present data disagree
with this hypothesis. In both male and female gametes, there is
no significant increase in the incidence of non-disjunction for
chromosome 16 and the E chromosome group displays similar
observed, estimated and expected frequencies of aneuploidy
(Tables HI and IV). This finding indicates that the incidence of
these specific trisomies in spontaneous abortion results mainly
from the differentia] viability of trisomies during embryonic
development.
With regard to the sex chromosomes, no comparative analysis
of aneuploidy is possible between male and female gametes in
the present study, since the X chromosome is not formally
identified in all oocyte complement sets. Nevertheless, it is
interesting to note the conformity of the low rate of non autosomal
gonosome aneuploidy in spermatozoa (Table UJ), whereas
epidemiological studies have reported the predominance of
paternal aetiology in sex chromosome aneuploidy (Jacobs et al.,
1988). In the 45,X Turner syndrome, the single X is maternal
in origin in 75% of cases, suggesting the prevalence of paternal
non-disjunction. Recent studies have permitted identification of
the existence of parental genomic imprinting (Surani et al., 1986;
Swain et al., 1987). The resulting differential expression of
maternal and paternal genomes seems directly to affect embryonic
development. According to this new data and the strong tendency
of the 45,X conceptus to abort early, it could be assumed that
a 45,X conceptus bearing a paternal X chromosome is less
susceptible to elimination in utero. On the other hand, no
significant increase of hyperhaploidy is observed in spermatozoa.
Only three cases (0.04%) of Y disomy have been reported among
the 7070 pooled sperm karyotypes. This value is consistent with
1256
the 0.1% incidence of XYY males observed among newborns
but differs significantly (P < 0.05) from the results of a direct
estimation (from 0.18 to 2.0%) on human spermatozoa, using
quinacrine staining techniques or in-situ hybridization
(Pawlowitzki and Pearson, 1972; Guttenbach and Schmid, 1990).
Therefore, a reduced fertilization efficiency of 24,YY
spermatozoa was suggested. This hypothesis of sperm selection
has already been debated. In particular, sperm studies of human
translocation carriers have clearly demonstrated that such a prezygotic selection against chromosomally abnormal spermatozoa
does not occur (Pellestor et al., 1989a).
Consequently, these considerations lead to the hypothesis that
two different causative mechanisms might be involved in the
human meiotic process of non-disjunction: a basic mechanism
producing equalized distribution of aneuploidy among all
chromosomes and another mechanism, restricted to the maternal
first meiotic division, which results in a higher frequency of
non-disjunction and an unequal involvement of chromosomes in
aneuploid events. One could suppose that this modified process
reflects both special features of oocyte chromosomes through
meiosis I (extended pachytene bivalent, great length of synaptonemal complex complement, persistent relationship with the
nucleus) and the particular physiological process of female
meiosis. Because of the duration of the first maternal meiotic
division, harmful environmental effects might accumulate and
influence chromosome segregation.
A major aetiological factor that must be considered in the
analysis of the occurrence of aneuploidy is parental ageing. In
spermatozoa, Martin and Rademaker (1987) found no direct
relationship between age and the incidence of numerical
abnormalities. This is consistent with the findings of large surveys
on newborns and abortuses in which no significant effect of
paternal age on incidence of trisomies was detected (Hook and
Cross, 1982). Conversely, the influence of maternal age is well
established and epidemiological studies have clearly indicated that
the occurrence of autosomal trisomies is maternal age dependent
(Ferguson-Smith and Yates, 1984; Hassold and Chiu, 1985).
Nevertheless, the cause of age-related aneuploidy still remains
obscure. Since the large majority of trisomies are the result of
maternal errors in meiosis I, most of the hypotheses to account
for this correlation have focussed on the female meiotic prophase.
The 'production line' hypothesis proposed by Henderson and
Edwards (1968) assumes the last formed oocytes during the
woman's fetal development to be htoth the most susceptible to
trisomy and the last to be ovulated. Other hypotheses state that
the occurrence of abnormalities is linked to the physiological
ageing of the reproductive system. Thus, delayed ovulation and
hormonal imbalances have been implicated (Page et al., 1983).
In addition, a few authors have suggested that the incidence of
abnormalities could be unrelated to maternal age but due to
reduced intrauterine selection (Ayme" and Lippman-Hand, 1982).
An alternative assumption was proposed by Brook et al. (1984),
who suggested that increased age-dependent aneuploidy could
be determined not by chronological ageing but by biological
ageing and consequently that any factor which depletes the oocyte
pool could increase the maternal age effect on aneuploidy.
Because of these conflicting hypotheses, results from
cytogenetic studies of human oocytes can provide essential
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In spermatozoa, the distribution of aneuploidies is in good
agreement with the assumption of an equal occurrence of
malsegregation among all chromosomes. On the other hand, the
large fluctuations in the distribution observed in oocytes indicates
that non-disjunction is not a random event in female meiosis.
In particular, there is a significant excess of non-disjunction in
the acrocentric D and G groups (Table IV), which cannot be
attributed to an artefactual loss or gain of chromosomes since
the ratio of hypohaploidy/hyperhaploidy is close to 1:1 in both
these groups. A prevalence of aneuploidy in human oocyte
acrocentric chromosomes is consistent with data obtained from
abortuses and liveborns (Juberg and Mowrey, 1983; Hassold
et al., 1984). Both of these surveys have demonstrated the strong
predominance of maternal meiosis I non-disjunction in the
occurrence of trisomies for D and G chromosome groups. Thus,
our observation suggests that the maternal meiotic process
involves a preferential mechanism of non-disjunction targetted
to acrocentric chromosomes. This suggestion is supported by
some reports on die nuclear and nucleolar process during
oogenesis. Garcia et al. (1989) reported the persistence of nucleoli
in human oocytes until the later stages of meiosis, whereas no
nucleoli are observed in male cells after the pachytene stage. The
complex relationships between nucleoli and both nucleolar and
non-nucleolar chromosomes could increase the risk of nondisjunction of acrocentric chromosomes (Vagner-Capodano et al.,
1987).
Distribution of aneuploidy in human gametes
References
Ayme'.S. and Lippman-Hand.A. (1982) Maternal age effect in
aneuploidy: does altered embryonic selection play a role? Am. J. Hum.
Genet., 34, 558-565.
Benet,J., Genesca,A., Navarro,J., Egozcue,J. and Templado.C. (1986)
G-banding of human sperm chromosomes. Hum. Genet., 73,
181-182.
Benet,J., Genesca.A., Navarro,J., Egozcue.E. and Templado.C. (1988)
Chromosomal abnormalities in motile human sperm from normal men.
Hum. Reprod., 3 (Suppl.), 105.
Benkhalifa,D., Geneix,A., Janny.L., Boucher,D. and Malet.P. (1990)
Chromosome aberrations in human oocytes. Proceedings of the Fifth
International Congress on Early Fetal Diagnosis, Prague.
Bongso,A., Chye,N.S., Ratnam.S., Sathananthan,H. and Wong,P.C.
(1988) Chromosome anomalies in human oocytes failing to fertilize
after insemination in vitro. Hum. Reprod., 3, 645—649.
Boue'.J.G. and Bou6,A. (1973) Increased frequency of chromosomal
anomalies in abortions after induced ovulation. Lancet, ii, 679—680.
Bou6,J.G., Boue\A. and Lazar,P. (1975) Retrospective and prospective
epidemiological studies of 1500 karyotyped spontaneous human
abortions. Teratology, 12, 11 —26.
Brandriff,B., Gordon,L., Asworth.L. et al. (1985) Chromosomes of
human sperm: variability among normal individuals. Hum. Genet.,
70, 18-24.
Brandriff,B.F., Gordon,L.A., Moore,D.,II and Carrano.A.V. (1988)
An analysis of structural aberrations in human sperm chromosomes.
Cytogenet. Cell Genet., 47, 29-36.
Brook,J.D., Gosden,R.G. and Chandley,A.C. (1984) Maternal aging
and aneuploid embryos. Evidence from the mouse that biological and
not chronological age is the important influence. Hum. Genet., 66,
41-45.
Djalali,M., Rosenbusch,B., Wolf.M. and Sterzik.K. (1988) Cytogenetics
of unfertilized human oocytes. J. Reprod. Fertil., 84, 647-652.
Edwards,R.G. (1968) Meiosis in oocytes and the origin of mongolism
and infertility in older mothers. Proceedings of the Sixth World
Congress on Fertility and Sterility, Tel Aviv.
Eichenlaub-Ritter.U., Stahl,A. and Luciani,J.M. (1988) The
microtubular cytoskeleton and chromosomes of unfertilized human
oocytes aged in vitro. Hum. Genet., 80, 259—264.
Feichheimer.N.S. and Beatty,R.A. (1974) Chromosomal abnormalities
and sex ratio in rabbit blastocysts. J. Reprod. Fertil., 37, 331 - 3 4 1 .
Ferguson-Smith,M.A. and Yates.J.R.W. (1984) Maternal age specific
rates for chromosome aberrations and factors influencing them; report
of a collaborative European study on 52965 amniocenteses. Prenat.
Diagn., 4, 5—44.
Ford.J.H. and Lester,P. (1982) Factors affecting the displacement of
chromosomes from the metaphase plate. Cytogenet. Cell Genet., 33,
327-332.
Fujimoto,S., Pahlavan,N. and Dukelow,W.R. (1974) Chromosome
abnormalities in rabbit preimplantaton blastocysts induced by
superovulation. J. Reprod. Fertil., 40, 177-181.
Galt,J., Boyd,E., ConnorJ.M. and Ferguson-Smith.M.A. (1989)
Isolation of chromosome 21-specific DNA probes and their use in
the analysis of nondisjunction in Down syndrome. Hum. Genet., 81,
113-119.
Garcia,M., Dietrich.A., Pujol,R. and Egozcue.J. (1989) Nucleolar
structures in chromosome and SC preparations from human oocytes
at first meiotic prophase. Hum. Genet., 82, 147 — 153.
Gifford.D.J., Fleetham.J.A., Mahadevan.M.M., Taylor,P.J. and
Schultz,G.A. (1987) Protein synthesis in mature human oocytes.
Gamete Res., 18, 97-107.
Guttenbach.M. and Schmid.M. (1990) Determination of Y chromosome
aneuploidy in human sperm nuclei by non-radioactive in situ hybridization. Am. J. Hum. Genet., 46, 553-558.
Hassold,T. and Chiu,D. (1985) Maternal age-specific rates of numerical
chromosome abnormalities with special reference to trisomy. Hum.
Genet., 70, 11-17.
Hassold.T.J. and Jacobs,P.A. (1984) Trisomy in man. Annu. Rev.
Genet., 18, 69-97.
Hassold,T., Chiu.D. and Yanane,J.A. (1984) Parental origin of
autosomal trisomies. Ann. Hum. Genet., 48, 129—144.
Henderson,S.A. and Edwards,R.G. (1968) Chiasma frequency and
maternal age in mammals. Nature, 218, 2 2 - 2 8 .
Hook,E.B. and Cross,P.K. (1982) Paternal age and Down's syndrome
genotypes diagnosed prenatally: no association in New York State
data. Hum. Genet., 62, 167-174.
Jacobs.P., Hassold,T., Whittington.E. et al. (1988) Klinefelters
syndrome: an analysis of the origin of the additional sex chromosome
using molecular probes. Ann. Hum. Genet., 52, 93-109.
Jagiello,G., Ducayen,M., FangJ.S. and GraffeoJ. (1976) Cytogenetic
observations in mammalian oocytes. In Pearson,P.L. and Lewis,K.R.
(eds), Chromosomes Today, Vol. 5. John Wiley and Sons, New York,
pp. 4 3 - 6 3 .
Jendemy.J. and R6hrborn,G. (1987) Chromosome analysis of human
sperm. Hum. Genet., 76, 385-388.
Juberg,R.C. and Mowrey.P.N. (1983) Origin of non-disjunction in
trisomy 21 syndrome: all studies compiled, parental age analysis and
international comparisons. Am. J. Med. Genet., 16, 111 — 116.
Kamiguchi,Y. and Mikamo,K. (1986) An improved, efficient method
for analysing human sperm chromosomes using zona-free hamster
ova. Am. J. Hum. Genet., 38, 724-740.
Laing,S.C, Gosden.R.G. and Fraser.H.M. (1984) CytogeneOc analysis
of mouse oocytes after experimental induction of follicular overripening. J. Reprod. Fertil, 70, 387-393.
Laufer.N., Pratt,B.M., DeChemey,A.H., Naftolin,F., Merino.M. and
Markert,C.L. (1983) The in vivo and in vitro effects of clomiphene
citrate on ovulation, fertilization, and development of cultured mouse
oocytes. Am. J. Obstet. Gynecoi, 147, 633-639.
Ma,S., Kalousek.D.K., Zouves.C, Yuen.B.H., Gonel.V. and
Moon.Y.S. (1989) Chromosome analysis of human oocytes failing
to fertilize in vitro. Fertil. Steril., 51, 992-997.
Martin,R.H. (1984) Comparison of chromosomal abnormalities in
hamster egg and human sperm pronuclei. Biol. Reprod., 31, 819—825.
Martin,R.H. (1990) Chromosomal analysis of human spermatozoa.
J. In Vitro Fertil. Embryo Transfer, 7, 196.
Martin.R.H. and Rademaker,A.W. (1987) The effect of age on
the
1257
frequency of sperm chromosomal abnormalities in normal men. Am.
J. Hum. Genet., 41, 484-492.
Downloaded from http://humrep.oxfordjournals.org/ at Pennsylvania State University on September 12, 2016
information. Unfortunately the early data were inconsistent.
Whereas Plachot et al. (1988) reported an increasing rate of
aneuploidy in unfertilized oocytes from women >35 years of
age, no correlation was found between maternal age and
aneuploidy within different age groups in several other reports
(Pellestor and Sele, 1988; Djalali et al., 1988; Benkhalifa et al.,
1990).
Consequently, investigations on the relationship between
aneuploidy and maternal age must continue. In order to increase
the accuracy of the cytogenetic analysis, a study must be centred
on disomies, particularly those of acrocentrics such as
chromosome 21. A correlation between maternal ageing and
aneuploidy is likely to be more obvious in these cases than in
an overall study of all chromosomal non-disjunctions. Such a
study will require large numbers of oocyte karyotypes and
represents a new direction for further investigation of the human
oocyte.
F.PeUestor
1258
to gonadotropins: a cytogenetic analysis of unfertilized human oocytes.
Fertil. Steril., 54, 665-670.
Tarkowski,A.K. (1966) An air-drying method for chromosome
preparation from mouse eggs. Cytogenetics, 5, 394—400.
Vagner-Capodano,A.M., Hartung.M. and Stahl,A. (1987) Nucleolus,
nucleolar chromosomes, and nucleolus-associated chromatin from
early diplotene to dictyotene in the human oocyte. Hum. Genet., 75,
140-146.
Van BlerkomJ. and Henry,G. (1988) Cytogenetic analysis of living
human oocytes: cellular basis and developmental consequences of
pertubations in chromosomal organization and complement. Hum.
Reprod., 1,111-190.
Veiga.A., Calderon,G., Santalo.J., Barri,P.N. and Egozcue.J. (1987)
Chromosome studies in oocytes and zygotes from an PVF programme.
Hum. Reprod., 2, 425-430.
Wramsby.H. and Fredga,K. (1987) Chromosome analysis of human
oocytes failing to cleave after insemination in vitro. Hum. Reprod.,
1, 137-142.
Wramsby,H. and Liedholm.P. (1984) A gradual fixation method for
chromosomal preparations of human oocytes. Fertil. Steril., 41,
736-738.
Wramsby.H., Fredga.K. and Liedholm.P. (1987) Chromosomal analysis
of human oocytes recovered from preovulatory follicles in stimulated
cycles. N. Engl. J. Med., 316, 121-124.
Yanagimachi.R., Yanagimachi,H. and Rogers,B.J. (1976) The use of
zona-free animal ova as a test system for the assessment of the
fertilizing capacity of human spermatozoa. Biol. Reprod., 15,
471-476.
Received on March 20, 1991; accepted on June 17, 1991
Downloaded from http://humrep.oxfordjournals.org/ at Pennsylvania State University on September 12, 2016
Martin,R.H. Balkan.W., Burns,K., Rademaker.A.W., Lin.C.C. and
Rudd.N.L. (1983) The chromosome constitution of 1000 human
spermatozoa. Hum. Genet., 63, 305—309.
Martin.R.H., Mahadevan,M.M., Taylor,P.J. el at. (1986) Chromosomal
analysis of unfertilized human oocytes. J. Reprod. Fertil., 78,
673-678.
Martin.R.H., Rademaker,A.W., Hildebrand.K. et al. (1987) Variation
in the frequency and type of sperm chromosomal abnormalities among
normal men. Hum. Genet., 77, 108—114.
Michelmann,H.W. and Mettler,L. (1985) Cytogenetic investigations on
human oocytes and early human embryonic stages. Fertil. Steril., 43,
320-322.
Mikamo.I. and Kamiguchi.Y. (1983) Primary incidences of spontaneous
chromosomal anomalies and their origins and causal mechanisms in
the Chinese hamster. Muted. Res., 108, 265-278.
Ortiz,M.E., Salvatierra.A.M., Lopel.J., Fernandez,E. and
Croxatto,H.B. (1982) Post-ovulatory aging of human ova: I. Light
microscopic observations. Gamete Res., 6, 11 — 17.
Page.R.D., Kirkpatrick-Keller.D. and Butcher.R.L. (1983) Role of age
length of oestrous cycle in alteration of the oocyte and intrauterine
environment in the rat. J. Reprod. Fertil., 69, 2 3 - 2 8 .
Papadopoulos,G., Randall.J. andTempleton.A.A. (1989) The frequency
of chromosome anomalies in human unfertilized oocytes and uncleaved
zygotes after insemination in vitro. Hum. Reprod., 4, 568—573.
Pawlowitzki,I.H. and Pearson,P.L. (1972) Chromosomal aneuploidy
in human spermatozoa. Humangenetik, 16, 119—122.
Pellestor,F. and Sele,B. (1988) Assessment of aneuploidy in the human
female by using cytogenetics of IVF failures. Am. J. Hum. Genet.,
42, 274-283.
Pellestor,F. and Sele,B. (1991) Relationship between sexual abstinence
of men and chromosomally abnormal spermatozoa. J. Reprod. Fertil.,
91, 6 5 - 7 1 .
Pellestor,F., Sele,B., Jalbert,H. and Jalbert.P. (1989a) Direct segregation
analysis of reciprocal translocations: a study of 283 sperm karyotypes
from four carriers. Am. J. Hum. Genet., 44, 464—473.
Pellestor,F., Sele.B. and Raymond,L. (1989b) Human oocytes
chromosome analysis. Am. J. Hum. Genet., 45, A104.
Pieters.M.H.E.C, Geraedts.J.P.M., Dumoulin,J.C.M. et al. (1989)
Cytogenetic analysis of in vitro fertilization (IVF) failures. Hum.
Genet., 81, 367-370.
Plachot.M., Veiga,A., Montagut.J., de Gronchy,J., Calderon,G.,
Lepretre,S., Junca,A.-M., Santalo,J., Carles,E., Mandelbaum.J.,
Barri.P., Degoy.I., Cohen,J., Egozcue,J., Sabatier,J.C. and SalatBarouxJ. (1988) Are clinical and biological FVF parameters correlated
with chromosomal disorders in early life: a multicentric study. Hum.
Reprod., 3, 627-635.
Rudak.E., Jacobs,P.A. and Yanagimachi,R. (1978) Direct analysis of
the chromosome constitution of human spermatozoa. Nature, 274,
911-913.
Sato,F. and Marrs,R. (1986) The effect of pregnant mare serum
gonadotrophin on mouse embryos fertilized in vivo or in vitro.
J. In Vitro Fertil. Embryo Transfer, 3, 353-357.
Speed,R.M. (1988) The possible role of meiotic pairing anomalies in
the atresia of human fetal oocytes. Hum. Genet., 78, 260-266.
Surani.M.A.H., Barton,S.C. and Norris,M.L. (1986) Nuclear transplantation in the mouse: heritable differences between prenatal
genomes after activation of the embryonic genome. Cell, 45,
127-136.
Swain,J.L., Stewart,T.A. and Leder.P. (1987) Parental legacy
determines methylation and expression of an autosomal transgene:
a molecular mechanism for parental imprinting. Cell, 50, 719—727.
Sz6llosi,D. (1975) Mammalian eggs ageing in the fallopian tubes. In
Blandeau,R.J. (ed.), Ageing Gametes. Karger, Basel, pp. 98—121.
Tarin J.J. and Pellicer.A. (1990) Consequences of high ovarian response