染色体46,XY,t(18;21)(q11;q22)平衡易位携带者一例

目的报道染色体46,XY,t(18;21)(q11;q22)平衡易位携带者1例。方法采用外周血淋巴细胞培养法,G显带。结果染色体核型分析为46,XY,t(18;21)(q11;q22)。结论平衡易位是导致不良孕产的重要原因,也是导致男性不育的常见原因。如查出平衡易位携带者,给予他们正确的优生指导及产前诊断,对降低出生缺陷的发病率有重要的作用。     

Analysis of human sperm chromosome complements from a male heterozygous for a reciprocal translocation t(11;22)(q23;q11)

A reciprocal translocation between chromosomes 11 and 22 (t(11;22)(q23;q11)) is a site-specific translocation that is of particular interest because of the propensity for 3:1 segregation of the chromosomes during meiosis. There have been no published reports of chromosomally unbalanced offspring born as a result of adjacent 1 or 2 meiotic segregations in a heterozygote for this translocation. This could be explained by a meiotic mechanism which produces only 3:1 chromosomal segregations or by differential embryonic survival in which 2:2 adjacent segregations do not produce a viable pregnancy. To distinguish between these two possibilities, sperm chromosome complements from a man heterozygous for this 11;22 translocation were studied. The human sperm chromosomes were analysed after fertilization of zona pellucida-free golden hamster eggs. All possible 2:2 (alternate, adjacent 1, adjacent 2) and 3:1 segregations were observed and these segregations occurred in approximately equal frequencies. The frequency of other chromosome abnormalities, unrelated to the translocation, did not appear to be increased. These results indicate that the 11;22 translocation does not specifically cause 3:1 disjunction of chromosomes but that this segregation of chromosomes is more likely to result in a viable pregnancy.     

Partial trisomy 6q, due to balanced maternal translocation (6;22) (q21; p13) or (q21; pter)

We report a stillborn infant with partial trisomy 6q who had several major congenital malformations not previously associated with this chromosomal aberration. These included occipital encephalocele, ambiguous genitalia with imperforate anus, omphalocele and unilateral hydronephrosis. The infant's karyotype was 46, XY,-22, der(22), t(6;22)(q21; p13) or (q21;pter)mat. The mother and maternal grandmother are balanced translocation carriers.     

Sperm analysis by FISH in a case of t(17; 22) (q11; q12) balanced translocation: case report

Individual sperm from men with balanced translocations have different chromosomal contents. Thus, an estimation of the overall sperm chromosomal imbalance of such patients could help to give the couple an adapted genetic counselling. We report here the study of a balanced translocation carrier, t(17;22) (q11;q12) whose reproductive history reported four miscarriages. Moreover, he had an abnormal semen analysis with oligoteratozoospermia. The meiotic segregation pattern was examined in 700 sperm, using fluorescence in-situ hybridization (FISH). Nineteen percent of the sperm had balanced translocations or were normal. All other sperm were unbalanced (81%) and their distribution was observed as follows: the frequencies of adjacent 1, adjacent 2 and 3:1 segregations were 12.9, 5.8 and 46.8% respectively. Among the segregations scored, 13.7% were related to second meiotic division abnormalities. Less than 2% of the total sperm scored were not explained. The 3:1 segregation was present at a very high rate, which is very unusual. In cases of balanced translocations, we believe that no general features can be drawn. Thus, the FISH technique may be very helpful for genetic counselling, which remains an important step and must be done with care.     

Segregation of chromosomes in sperm of a t(X;18)(q11;p11.1) carrier inherited from his mother: case report

Balanced reciprocal translocations are the most common structural abnormalities; most involve two autosomes while a few involve a gonosome (X or Y chromosome) and an autosome. These rearrangements are usually associated with infertility and/or a higher risk of chromosomal imbalances among offspring. This 26 years old man was first seen because of a 3-year history of primary infertility. He had been found to have a translocation, t(X;18)(q11;p11.1), inherited from his mother when he was 9 years old. Semen analysis showed a very severe oligoasthenoteratozoospermia (OAT). A total of 447 spermatozoa were analysed using three-colour fluorescent in situ hybridization (FISH). The alternate segregation pattern, leading to a normal or balanced chromosomal content, was found in 54.36% of the spermatozoa studied. The frequencies of Adjacent I, Adjacent II, 3:1 segregation and diploidy (or 4:0 segregation) were 8.28, 5.14, 22.37 and 2.01%, respectively. Balanced reciprocal translocations between an autosome and the X chromosome lead to important disruptions in human spermatogenesis. Almost all the males with an X-autosome translocation have azoospermia. The man reported here had very severe OAT and is the first in whom the meiotic segregation pattern was analysed. This case further emphasizes the interest in performing FISH studies in infertile males with a chromosomal translocation to provide them with a personalized imbalance risk.     

一例母源性46,Y,der(X)t(X;Y)(p22;q11)染色体非平衡易位患儿的遗传学分析

目的对1例临床表征为身材矮小、鼻根部内陷、双侧隐睾、智力低下患儿进行遗传学分析,探讨该染色体结构异常与临床表征之间的关系。方法应用G显带染色体核型分析及染色体微阵列分析(chromosomal microarray analysis,CMA)技术对患儿进行遗传学检测,并对其父母进行外周血染色体核型分析。结果G显带分析结果显示患儿染色体核型为46,Y,der(X)t(X;Y)(p22;q11),mat。CMA检测结果提示患儿X染色体短臂Xp22.33p22.31存在约8.3 Mb片段缺失,Y染色体长臂Yq11.221qter存在约43.3 Mb片段重复。其父亲染色体核型正常,母亲染色体核型结果为46,X,der(X)t(X;Y)(p22;q11)。结论患儿携带母源性der(X)t(X;Y)(p22;q11)染色体非平衡易位,携带者的表型与其性别以及X染色体缺失片段的大小和位置密切相关。男性携带者智力障碍、生长发育落后等异常表型较女性更为严重。     

Homozygosity for a Y/22 chromosome translocation: t(Y;22) (q12;p12/13)

A newborn girl, homozygous for a balanced Y/22 chromosome translocation is described. This unique karyotype was detected during prenatal chromosome studies in the first pregnancy of a 26-year-old woman. Amniocentesis was performed because of clinical evaluation of severe fetal growth retardation in the 28th week of gestation. The cytogenetic results were confirmed using a lymphocyte culture after birth in the 30th week. Subsequent chromosome studies of the parents were hampered by the fact that the pregnancy was thought to be the result of artificial insemination with donorsperm. Nevertheless both, consanguineous, parents were shown to be carriers of the same, singular, chromosome translocation and the spermdonor could be excluded from paternity by bloodgroup- and HLA studies. Distamycin-A-DAPI chromosome staining and DNA studies of the mother were used to confirm the involvement of the Y-chromosome in this translocation. The probanda is developing quite normally at the age of 21 months.     

A child with a t(11;19)(q14–21;p12) in a pulmonary mucoepidermoid carcinoma

 We report on a mucoepidermoid carcinoma (MEC) of the lung in a 6-year-old girl with a t(11;19)(q14–21;p12) as the sole karyotypic abnormality. An apparently identical t(11;19) has been reported previously in a MEC originating from the major and minor salivary glands. Our findings indicate that the t(11;19) is intimately associated with the mucoepidermoid phenotype and may be used as a diagnostic marker for this tumour type. Received: 30 March 1998 / Accepted: 22 April 1998     

A de novo translocation, 14q21q,with a microchromosome—14p21p

A familial translocation, t(14;21)(14p21p;14q21q), in a mother and her child is described. The translocation was ascertained through the birth of a Down syndrome baby with the chromosome constitution 47,XX,-14, +der 14, +der 21,t(14;21)(q11; p12) mat. A 1:3 segregation in the maternal meiosis is suggested for the evolution of the unbalanced chromosome state. The main translocated chromosome 14q21q mimics the product of a Robertsonian translocation, while the 14p21p chromosome has the morphology of a satellited microchromosome. The cytogenetic nature of this translocation is discussed.     

Sperm chromosome analysis in a man heterozygous for a reciprocal translocation 46,XY t(12;20)(q24.3;q11)

Sperm chromosome complements were studied in a man who carried a reciprocal translocation t(12;20)(q24.3;q11). A total of 113 spermatozoa were karyotyped after in-vitro penetration of hamster eggs. 2:2 and 3:1 meiotic segregations were observed with the following frequencies: alternate 47%, adjacent 1 42%, adjacent 2 10%, 3:1 2%. For alternate segregations, the number of normal spermatozoa (25) was not significantly different from the number of spermatozoa carrying a balanced form of the translocation (28), as theoretically expected. The proportion of spermatozoa with an unbalanced form of the translocation was 53%. There was no evidence for an interchromosomal effect since the frequencies of numerical and structural abnormalities (unrelated to the translocation) were within the normal range of control donors.     

Re-evaluation of GM2346 from a del(16)(q22) to t(4;16)(q35;q22.1)

Reassessment of the cytogenetics of a patient previously karyotyped as del(16)(q22) demonstrates the presence of a balanced translocation, t(4;16)(q35;q22.1). This patient should not be included in any future comparison involving the clinical features of patients with deletions of the long arm of chromosome 16.     

Monosomy 10qter due to a balanced familial translocation: t(10;16)(q25.2;q24)

A third case of monosomy 10q is described. The infant was severely malformed and died at day 9 post partum. The clinical symptoms are compatible with the two previous cases.     

Unbalanced karyotype with normal phenotype in a family with translocation (8;13) (p21;q22)

We describe a family with translocation (8;13) (p21;q22), in which both unbalanced products of adjacent-1 segregation occurred. Two members of the family have partial trisomy 8p with partial monosomy 13q; two others have partial monosomy 8p with partial trisomy 13q. The latter are both phenotypically normal, which is a highly unusual observation. One of these is, in addition, a carrier of a de novo balanced translocation between chromosomes 2 and 19. The risk for unbalanced progeny is discussed.     

Bipolar affective disorder partially cosegregates with a balanced t(9;11)(p24;q23.1) chromosomal translocation in a small pedigree

Analysis of an extended pedigree in which a balanced t(9;11)(p24;q23.1) translocation was found to cosegregate with bipolar affective disorder revealed that five of 11 translocation carriers had bipolar affective disorder and one carrier had unipolar depression. There were no affected individuals in the pedigree without the balanced translocation. We hypothesized that gene(s) or gene regulatory regions disrupted by the translocation might be contributing to the bipolar affective disorder in a dominant fashion. To test this hypothesis, we isolated the derivative chromosome 9 and derivative chromosome 11 in somatic cell hybrids and identified the nearest flanking markers on chromosome 9 (D9S230 and D9S2011E/HRFX3) and chromosome 11 (EST00652 and CRYA2). YAC contigs were constructed in the region of flanking markers for both chromosomes 9 and 11. Chromosome 11 breakpoint was localized within an 8-kb region in a small insert (100 kb) YAC. Chromosome 9 breakpoint was localized within approximately 2 Mb region. Several genes and ESTs including EST00652, CRYA2, DRD2, 5HTR3 on chromosome 11 and VLDLR and SLC1A1 on chromosome 9 were mapped within the vicinity of the breakpoint but were shown not to be disrupted by the translocation breakpoint. Although several possibilities exist regarding the role of the balanced translocation in developing bipolar affective disorder in this pedigree, including a chance cosegregation, identification of a disrupted gene or gene regulatory region with the help of physical mapping resources described in this study may help to identify the presence of a susceptibility gene for this disorder. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 81:81–91, 1998. © 1998 Wiley-Liss, Inc.     

Translocation (16;21)(p11;q22) in acute monoblastic leukemia with erythrophagocytosis

A patient with acute monoblastic leukemia with erythrophagocytosis and a t(16;21) (p11;q22), poor response to chemotherapy, early relapse, and a short survival of ten months is presented. Hematologically, this patient could be considered as a case of FAB M5b/t(8;16) but without the characteristic chromosomal translocation, i.e., there is no visible alteration on chromosome 8 and the breakpoint on chromosome 16 appears to be very proximal. These findings are briefly discussed in the light of other variants.     

Melkersson-Rosenthal syndrome and de novo autosomal t(9;21)(p11;p11) translocation

In this report we describe a 26-year-old female with the typical clinical symptoms and signs of Melkersson-Rosenthal syndrome, an autosomal dominant disorder with variable expression, and a de novo t(9;21)(p11;p11), and suggest that the "Melkersson-Rosenthal gene" is located at 9p11.     

Sperm chromosome complements in a man heterozygous for a reciprocal translocation t(2; 3)(q24;p26)

Sperm chromosome complements were studied in a man heterozygousfor a reciprocal translocation t(2; 3)(q24;p26). This man wasidentified during a family study after his sister was investigatedfor amenorrhea. A total of 92 spermatozoa were karyotyped afterin-vitro penetration of hamster eggs. The frequencies of alternate,adjacent 1, adjacent 2 and 3: 1 segregations were 55.4, 36.1,7.2 and 1.2% respectively. For alternate segregations, the numberof normal spermatozoa (n < 25) was not significantly differentfrom the number of spermatozoa carrying a balanced form of thetranslocation (n < 21), as theoretically expected. The proportionof spermatozoa with an unbalanced form of the translocationwas 44.6%. There was no evidence for an interchromosomal effectsince the frequencies of numerical and structural abnormalities(unrelated to the translocation) were within the normal rangeof control donors.     

Site-specific reciprocal translocation,t(11;22) (q23;q11), in several unrelated families with 3:1 meiotic disjunction

We have studied 32 unrelated families with a site-specific reciprocal translocation between chromosomes 11 and 22 [t(11;22) (q23;q11)]. In translocation heterozygotes 3:1 meiotic segregation occurs and results in abnormal progeny who carry the der(22) as a supernumerary chromosome. Phenotypic findings consistent with 47,XX (or XY), +der(22), t(11;22) include mental retardation, preauricular skin tag and/or sinus, ear anomaly, palate anomaly, micrognathia, congenital heart disease, and genital anomalies in males. The frequency of abortions among offspring of male and female heterozygotes is increased. Segregation analysis shows that the risk for unbalanced offspring to be born to female heterozygotes may be as high as 10%, and that there may be a significant risk to male heterozygotes as well. The overall carrier frequency among progeny of 11;22 translocation carriers is 70.6%. The occurrence of multiple 11;22 translocation events is supported by de novo occurrence of the translocation, familial heteromorphic variants of the der(22), and varied racial and ethnic backgrounds of the families. To our knowledge, with the exclusion of centric fusion translocations, this represents the only example of nonrandom exchange in a constitutional chromosomal rearrangement.