A de novo complex chromosomal rearrangement with a translocation 7;9 and 8q insertion in a male carrier with no infertility: Case report
Tao Cai1,4,
Ping Yu2,
Danilo A. Tagle2,
David Lu3,
Yiwang Chen3 and
Jiahui Xia1
1 National Laboratory of Medical Genetics, Hunan Medical University, Changsha, Peoples' Republic of China,
2 Genetics and Molecular Biology Branch, National Human Genome Research Institute, National Institute of Health, Building 49, Room 3A23, 49 Convent Drive MSC 4442, Bethesda, MD 208924442, and
3 Veterans Affairs Medical Center and Georgetown University Medical Center, Washington, DC 20016, USA
 |
Abstract
|
---|
A de novo complex chromosomal rearrangement (CCR) involving chromosomes 7, 8 and 9 in a male carrier was ascertained through his healthy wife's recurrent spontaneous abortions. Six pregnancies over eight years resulted in four spontaneous abortions and two livebirths who died perinatally due to abnormal vital signs. Cytogenetic analyses utilizing high resolution chromosome banding technique showed a deletion of band in a der(7) chromosome and an extra band inserting at 8q21.2. Another extra band was also observed at the band 9p24, but it could not be karyotypically determined. Fluorescent in-situ hybridization using chromosome 7 and 8 specific microdissected library as probes confirmed the insertion of a segment from the translocated chromosome 7 into a chromosome 8, and additionally revealed a translocation between chromosomes 7 and 9. The karyotype of the CCR carrier was determined as 46,XY,t(7;9)(q22;p24),ins(8;7)(q21.2;q22q32).ish der(9)(wcp7+);ins(8;7)(wcp8+,wcp7+). Comparing with previously reported male CCR carriers with our case, we conclude that male CCR carriers may not always present with infertility or subfertility phenotypes. This may suggest that rare transmission of male carriers could result from abnormal chromosomal rearrangements during meiosis and gametogenesis in addition to frequent infertility.
Key words:
carrier/complex chromosomal rearrangement/infertility/male
 |
Introduction
|
---|
Complex chromosomal rearrangements (CCRs) are defined as reciprocal exchanges between three or more chromosomes. It has been observed that most CCR carriers are female, and a few are male (Joseph and Thomas, 1982
; Saadallah and Hulten, 1985
; Gorski et al., 1988
). Most male CCR carriers have been ascertained by infertility of adult male carriers (Chandley et al., 1975
; Joseph and Thomas, 1982
; Siffroi et al., 1997
), and a few ascertained by abnormal children or recurrent abortion (Walker et al., 1985
; Gorski et al., 1986
; Madan et al., 1997
). Male CCR carriers are often sterile due to genital hypoplasia or spermatogenic arrests caused by the complexity of the meiotic configurations (Chandley, 1981
; Jaafar et al., 1993), and may be ascertained by infertility evaluations (Joseph and Thomas, 1982
; Saadallah and Hulten, 1985
; Gorski et al., 1988
). Therefore, it was suggested that rare transmission of male CCR carriers or a higher prevalence of female carriers is due to infertility or subfertility (Gorski et al., 1988
). It is not clear, however, whether the lower prevalence of male carriers may also result from a higher frequency of abnormal chromosomal rearrangements during meiosis and gametogenesis.
In this report, we present a novel case of an adult male CCR carrier with no reduction in fertility. To understand the cytogenetic and clinical significance of this case, previously reported male CCR carriers are also reviewed.
 |
Clinical findings
|
---|
A couple, a 35-year-old man and a 32-year-old woman, were referred by a cytogenetics consultant because the woman had had six pregnancies resulting in four spontaneous abortions and two abnormal infants who died perinatally during the couple's 8 years of marriage. No family history of congenital anomalies, hereditary diseases, or sterility was determined from either the husband or wife. The couple had no abnormal symptoms and the physical examinations showed both to be phenotypically normal, including their reproductive systems. The four spontaneous abortions (8, 12, 28, and 37 weeks) and two abnormal infants (16 and 36 weeks) had occurred at irregular times and suggested a possible chromosomal problem, since there was no evidence of any uterine abnormality or any other underlying disease during the pregnancies. The fourth and sixth pregnancies resulted in the same phenotypically abnormal livebirths, where the infants were born with slow and irregular breathing, no detectable pulse, paleness, low body temperature and failure to elicit crying response. These two infants were clarified as `clinically abnormal' and died a few minutes after birth. The third pregnancy resulted in a stillbirth at 28 weeks. The infant of 28 weeks was very small for that developmental age and had `feet deformity'. The first, second and fifth abortions occurred in the first trimester. The chromosomal status of these fetuses was not investigated.
 |
Cytogenetic studies and fluorescent in-situ hybridization (FISH)
|
---|
Chromosomal analysis of both parents was carried out on peripheral blood cultures after 72 h of incubation. Metaphase spreads were prepared for G banding and high-resolution staining as previously reported (Zhang et al., 1990
). The wife had a normal karyotype both by G banding and high-resolution staining (data not shown). However, metaphases from the husband revealed an interstitial deletion of band 7q22
>q32 in der(7) chromosome and an extra band inserting at 8q21.2 (Figure 1
). Additionally, an extra band seemed to be present on 9p24, but it could not be karyotypically determined. The parents of the husband were also karyotyped and both were found to be normal (data not shown).

View larger version (31K):
[in this window]
[in a new window]
|
Figure 1. Partial karyotype of complex translocations that involve chromosome 7, 8, and 9. An ideogram at high resolution is at the right of each chromosome pair. `der' stands for derivative homologue. Arrows indicate breakpoints and their region.
|
|
To identify complex chromosomal rearrangements or subtle translocations, FISH with chromosome-specific painting probes was performed as described previously (Deng et al., 1992
). The chromosome 7 library probing of metaphase spreads from the husband identified extra chromosomal material inserted in band 8q21.2, one abnormal chromosome 7 (signal on 7p and 7q11
q22), one normal chromosome 7, and an additional band on 9p24 (Figure 2A
). Thus, the FISH results confirmed that the insertion in the der(8) was derived from chromosome 7 in der(7), and additionally revealed a translocation between chromosomes 7 and 9. Furthermore, the chromosome 8 library probing of metaphase spreads demonstrated the interstitial insertion at 8q21.2 (Figure 2B
). Therefore, the karyotype of the husband was determined as 46,XY,t(7;9)(q22;p24),ins(8;7)(q21.2;q22q32). ish der(9)(wcp7+);ins(8;7)(wcp8+,wcp7+).

View larger version (28K):
[in this window]
[in a new window]
|
Figure 2. FISH using microdissection probe pools. (A) Chromosome 7 probing. An arrow indicates the derivative of chromosome 7. Two arrowheads indicate an interstitial insertion in chromosome 8 (q21.2) and an extra band on the end of chromosome 9 (p24), respectively. (B) Chromosome 8 probing. An arrowhead indicates the insertion material in chromosome 8 (q21.2).
|
|
 |
Discussion
|
---|
We have described a de novo male CCR carrier ascertained through his wife's recurrent spontaneous abortions. It was previously observed that transmission of a CCR was usually maternal since the male CCR carriers had an increased risk of primary infertility or subfertility (Saadallah and Hulten, 1985
; Gorski et al., 1988
; Madan et al., 1997
; Siffroi et al., 1997
). Only a few cases of male transmission of the CCR were observed with no apparent reduction in fertility in the male carriers (Meer et al., 1981
; Rothlisberger et al., 1999
). In most previously described cases, the presence of the complex meiotic configurations due to pairing of the chromosomes in CCRs produced disruption of spermatogenesis. In certain cases, the presence of infertility may be due to pre- and post-implantation losses rather than disruption of spermatogenesis (Johannisson et al., 1988
).
In the present case, the male carrier did not appear to have primary infertility, yet no viable offspring have been produced. The incidence (100%) of abnormal pregnancy outcome (4/6 spontaneous abortions plus 2/6 malformed children) is much higher than that (53.7%) in 25 CCR carrier families (Gorski et al., 1988
). This suggests a higher risk of producing embryos with chromosomal anomalies formed during meiotic malsegregation of parental chromosomes in our case.
Furthermore, we compared 10 previously described male CCR carriers (Table I
) with our case, and found that five cases (45%) were ascertained by infertility or subfertility, and six (55%) ascertained by their abnormal children or spontaneous abortions. Therefore, in addition to original infertility as a cause, the lower prevalence of male carriers than that of female carriers can also be associated with abnormal nonviable chromosomal rearrangements during meiosis and gametogenesis.
There are several possibilities for a higher incidence of abnormal pregnancy outcome in our case. At the pachytene stage, the normal and abnormal chromosomes 7, 8, and 9 are likely to have two possible configurations: (i) as a hexavalent, or (ii) the chromosomes may associate as a bivalent of the chromosomes 8 and a tetravalent between chromosomes 7 and 9. The first configuration may be less likely because the homologous segment between the normal chromosome 7 and abnormal chromosome 8 is small (Figure 3A
). The second configuration is relatively symmetrical (Figure 3B
), which may favour alternate segregation over adj-1 and adj-2 modes.

View larger version (20K):
[in this window]
[in a new window]
|
Figure 3. Theoretical pachytene configuration. (A) Synapsis of t(7q22;9p24) and pairing of the homologous segments between the abnormal chromosome 8 and chromosome 7; (B) Independent synapsis of t(7q22;9p24) and chromosome 8 homologs.
|
|
Either of these configurations will give rise to many possible combinations of rearranged chromosomes in the embryos. The unbalanced results of 3:3 segregations, and all 2:4, 1:5 and 0:6 segregations are most likely to produce much greater genotypic imbalance, and are expected to be nonviable, with most or all resulting in early pregnancy loss. The only combinations that are likely to produce a viable progeny, however, are the normal, the balanced carrier, and those having an additional or missing copy of 7q22 to 7q32. Additional detailed studies of abortus material from families with known translocation carriers will be helpful in further investigation of meiotic malsegregation and potential interchromosomal effects of rearranged chromosomes.
The normal phenotype of this case suggests that the breakpoints at 7q22, 7q32, 8q21.1, and 9p24 in balanced CCRs are not in active or critical functional chromosomal segments and probably do not include
ubmicroscopic deletions (Cleary and Sklar, 1985
; Troster et al., 1985
; Sharpe and Errington, 1999
). In other words, it is likely that these chromosomal breakpoints might not include genes or gene regulatory regions whose disruptions may give rise to physical dysfunction and clinical phenotypes. This is also observed in more than 30 reported carriers with simple chromosome rearrangements involving 7q22, 7q32, and 9p24 (Daniel et al., 1989
). Additional studies on CCRs and molecular cloning of the breakpoint sites, like 7q22 and 9p24, could provide insights into the molecular mechanism predisposing to genomic instability that can lead to CCRs.
 |
Acknowledgments
|
---|
We thank Dr L.-Y.Li for clinical data and J.-J.Fu and Q.Pan for technical help.
 |
Notes
|
---|
4 To whom correspondence should be addressed at: Experimental Medical Section, NIDCR, NIH, Building 30, Room 112,30 Convent Dr. MSC 4322, Bethesda, MD 208924322 USA. E-mail: tao.cai{at}nih.gov 
 |
References
|
---|
Bass, H.N. and Sparkes, R.S. (1979) Two balanced translocations in three generations of a pedigree: t(7;10) (q11;q22) and t(14;21) (14qter to cen to 21qter)1. J. Med. Genet., 16, 215218.[Abstract]
Bourrouillou, G., Rolland, M. and Colombies, P. (1983) Secondary 18q2 due to a paternal double translocation. J. Genet. Hum., 31, 243249.[ISI][Medline]
Burns, J.P., Koduru, P.R., Alonso, M.L. et al. (1986) Analysis of meiotic segregation in a man heterozygous for two reciprocal translocations using the hamster in vitro penetration system. Am. J. Hum. Genet., 38, 954964.[ISI][Medline]
Chandley, A.C. (1981) The origin of chromosomal aberrations in man and their potential for survival and reproduction in the adult human population. Ann. Genet., 24, 511.[ISI][Medline]
Chandley, A.C., Edmond, P., Christie, S. et al. (1975) Cytogenetics and infertility in man. I. Karyotype and seminal analysis: results of a five-year survey of men attending a subfertility clinic. Ann. Hum. Genet., 39, 231254.[ISI][Medline]
Cleary, M.L. and Sklar, J. (1985) Nucleotide sequence of a t(14;18) chromosomal breakpoint in follicular lymphoma and demonstration of a breakpoint-cluster region near a transcriptionally active locus on chromosome 18. Proc. Natl Acad. Sci. USA, 82, 74397443.[Abstract]
Daniel, A., Hook, E.B. and Wulf, G. (1989) Risks of unbalanced progeny at amniocentesis to carriers of chromosome rearrangements: data from United States and Canadian laboratories. Am. J. Med. Genet., 33, 1453.[ISI][Medline]
Deng, H.X., Yoshiura, K., Dirks, R.W. et al. (1992) Chromosome-band-specific painting: chromosome in situ suppression hybridization using PCR products from a microdissected chromosome band as a probe pool. Hum. Genet., 89, 1317.[ISI][Medline]
Gorski, J.L., Emanuel, B.S., Zackai, E.H. et al. (1986) Complex chromosomal rearrangement and multiple spontaneous abortions. Hum. Genet., 74, 326.[ISI][Medline]
Gorski, J.L., Kistenmacher, M.L., Punnett, H.H. et al. (1988) Reproductive risks for carriers of complex chromosome rearrangements: analysis of 25 families. Am. J. Med. Genet., 29, 247261.[ISI][Medline]
Johannisson, R., Lohrs, U. and Passarge, E. (1988) Pachytene analysis in males heterozygous for a familial translocation (9;12;13) (q22; q22; q32) ascertained through a child with partial trisomy 9. Cytogenet. Cell Genet., 47, 160166.[ISI][Medline]
Joseph, A., and Thomas, I.M. (1982) A complex rearrangement involving three autosomes in a phenotypically normal male presenting with sterility. J. Med. Genet., 19, 375377.[ISI][Medline]
Madan, K., Nieuwint, A.W. and van Bever, Y. (1997) Recombination in a balanced complex translocation of a mother leading to a balanced reciprocal translocation in the child. Review of 60 cases of balanced complex translocations. Hum. Genet., 99, 806815.[ISI][Medline]
Meer, B., Wolff, G. and Back, E. (1981) Segregation of a complex rearrangement of chromosomes, 6, 7, 8, and 12 through three generations. Hum. Genet., 58, 221225.[ISI][Medline]
Rodriguez, M.T., Martin, M.J. and Abrisqueta, J.A. (1985) A complex balanced rearrangement involving four chromosomes in an azoospermic man. J. Med. Genet., 22, 6667.[Abstract]
Rothlisberger, B., Kotzot, D., Brecevic, L. et al. (1999) Recombinant balanced and unbalanced translocations as a consequence of a balanced complex chromosomal rearrangement involving eight breakpoints in four chromosomes. Eur. J. Hum. Genet., 7, 873883.[ISI][Medline]
Saadallah, N. and Hulten, M. (1985) A complex three breakpoint translocation involving chromosomes, 2, 4, and 9 identified by meiotic investigations of a human male ascertained for subfertility. Hum. Genet., 71, 312320.[ISI][Medline]
Sharpe, M.E. and Errington, J. (1999) Upheaval in the bacterial nucleoid. An active chromosome segregation mechanism. Trends Genet., 15, 7074.[ISI][Medline]
Siffroi, J.P., Benzacken, B., Straub, B. et al. (1997) Assisted reproductive technology and complex chromosomal rearrangements: the limits of ICSI. Mol. Hum. Reprod., 3, 847851.[Abstract]
Troster, H., Spring, H., Meissner, B. et al. (1985) Structural organization of an active, chromosomal nucleolar organizer region (NOR) identified by light microscopy, and subsequent TEM and STEM electron microscopy. Chromosoma, 91, 151163.[ISI][Medline]
Walker, S., Howard, P.J. and Hunter, D. (1985) Familial complex autosomal translocations involving chromosomes, 7, 8, and 9 exhibiting male and female transmission with segregation and recombination. J. Med. Genet., 22, 484491.[Abstract]
Zhang, H., Xia, J., Li, L. et al. (1990) The high resolution G band of human chromosomes at 1200 band stage. I. Chuan Hsueh Pao, 17, 418421.[Medline]
Submitted on June 27, 2000;
accepted on September 22, 2000.