Trisomy 4q26--4qter by t(4;18)(q26;q23)mat translocation]

Partial trisomy 4q and perhaps monosomy 8qter was observed in a malformed girl, due to malsegregation of a t(4;18)(q26;q23)mat. Her phenotype was in agreement with the partial trisomy 4q syndrome, and she died 5 months after birth.     

A maternal inherited translocation t(1;22)(q11;p11) in two infertile brothers

We report two infertile brothers presenting with azoospermia and oligozoospermia. Cytogenetic studies using G-banding and FISH analysis on lymphocyte cultures revealed an autosomal balanced reciprocal translocation t(1;22)(q11;p11) in both males. The same translocation was found in their mother, but not in a third fertile brother and maternal uncle suggesting that this translocation might compromise the male but not the female gametogenesis in this family.     

Partial trisomy 11q syndrome (11q23.1-->11qter) due to de novo t (11q; 13q) detected by multicolor fluorescence in situ hybridisation

In this report we describe the identification of a de novo 46, XX, 13q + by multicolour fluorescence in situ hybridisation (M-FISH), as a partial distal 11q trisomy (11q23.1-->11qter). The clinical phenotype association with this distal 11q trisomy is briefly reviewed.     

Fine mapping of the constitutional translocation t(11;22)(q23;q11)

Translocation t(11;22)(q23;q11) is the most common constitutional reciprocal translocation in man. Balanced carriers are phenotypically normal, except for decreased fertility, an increased spontaneous abortion rate and a possible predisposition to breast cancer in some families. Here, we report the high resolution mapping of the t(11;22)(q23;q11) breakpoint. We have localised the breakpoint, by using fluorescence in situ hybidisation (FISH) walking, to a region between D11S1340 and WI-8564 on chromosome 11, and D22S134 and D22S264 on chromosome 22. We report the isolation of a bacterial artificial chromosome (BAC) clone spanning the breakpoint in 11q23. We have narrowed down the breakpoint to an 80-kb sequenced region on chromosome 11 and FISH analysis has revealed a variation of the breakpoint position between patients. In 22q11, we have sequenced two BACs (BAC2280L11 and BAC41C4) apparently mapping to the region; these contain low copy repeats (LCRs). Southern blot analysis with probes from BAC2280L11 has revealed different patterns between normal controls and translocation carriers, indicating that sequences similar/identical to these probes flank the translocation breakpoint. The occurrence of LCRs has previously been associated with genomic instability and "unclonable" regions. Hence, the presence of such repeats renders standard translocation breakpoint cloning techniques ineffective. Thus, we have used high resolution fiber-FISH to study this region in normal and translocation cases by using probes from 22q11, LCRs and 11q23. We demonstrate that the LCR containing the gap in 22q11 is probably substantially larger than the previous estimates of 100 kb. Using fiber-FISH, we have localised the breakpoint in 22q11 to approximately 20-40 kb from the centromeric border of the LCR (i.e. the telomeric end of AC006547) and have confirmed the breakpoint position on 11q23.     

Partial trisomies 13 and 22 due to nondisjunction of a maternal reciprocal translocation,t(13;22)(q22;q11)

Summary A family is reported in which the propositus has an extra G-like chromosome with an unusual G-banding pattern. Cytogenetic family studies showed that the mother is a carrier of a balanced reciprocal translocation t(13;22), which does not affect the size and morphology of the chromosomes involved. The propositus has a 47,XY,+der(22),t(13;22)(q22;q11) karyotype and is therefore partially trisomic for the distal third of the long arm of chromosome 13 and for a very small part of chromosome 22. The clinical findings are presented and compared with those of other reported cases of partial trisomies 13 and 22.     

Trisomy 12p due to an adjacent 1 segregation of a maternal reciprocal translocation t(12;18) (p11;q23).

A 5, 9-12-year-old with trisomy 12 pdue to a maternal reciprocal translocation adjacent 1 segregation is presented. Comparison of his phenotype with that of other patients reported in the literature confirm the existence of a trisomy syndrome.     

Familial translocation t(10;21)(q22;q22)

Summary A family is described with a translocation t(10;21)(q22;q22) transmitted through three generations. This family was studied for the apparition of several miscarriages and two sisters with multiple malformations. Both children had a probably partial trisomy of chromosome 10 and a monosomy of chromosome 21 due to a maternal adjacent-2 meiotic segregation.     

Trisomy 6qter resulting from a familial (6;10) (q23;q26) translocation

An infant deceased at 2 months of age was found to have a 46,XY,-10, +der(10),t (6;10) (q23;q26) mat karyotype. Since the clinical findings were similar to those of the trisomy 6qter syndrome, the present observation agrees with the assignment of the 6q23----qter segment as the pathogenetic determiner of this entity.     

Trisomy 3 (p23-pter) resulting from maternal translocation, t (3 ; 4)(p23 ; q35).

We describe a patient with partial trisomy 3p resulting from maternal translocation, t(3:4)(p23;q35). The male newborn who died at the age of 22 hours presented with distinct facial features including a square-shaped face with prominent forehead and depressed temporal regions, prominent cheeks, short broad nose, left cleft lip and cleft palate, malformed ears, and a receding mandible. Further findings were flexion deformities of the fingers with finger-like thumbs and mild cutaneous syndactyly 2/3 and 4/5, hypoplastic penis and scrotum with no palpable testes. He probably had a congenital heart defect and situs inversus abdominalis. Many of these features have been reported in other patients with distal trisomy 3p.     

A common breakpoint on 11q23 in carriers of the constitutional t(11;22) translocation

Structural chromosomal rearrangements occur commonly in the general population. Individuals that carry a balanced translocation are at risk of having unbalanced offspring; therefore, the frequency of translocations in couples with recurrent spontaneous abortions is higher than that in the general population. The constitutional t(11;22) translocation is the most common recurrent non-Robertsonian translocation in humans and may serve as a model to determine the mechanism that causes recurrent meiotic translocations. We previously localized the t(11;22) translocation breakpoint to a region on 22q11 within a low-copy repeat, termed "LCR22." To define the breakpoint on 11q23 and to ascertain whether this region shares homology with LCR22 sequences, we performed haplotype analysis on patients with der(22) syndrome. We found that the breakpoint on 11q23 occurred between two genetic markers, D11S1340 and APOC3-tetra, both being present within a single bacterial-artificial-chromosome clone. To determine whether the breakpoint occurred within the same region among a larger set of carriers, we performed FISH mapping studies. The breakpoints were all within the same clone, suggesting that this region may harbor sequences that are prone to breakage. We narrowed the breakpoint interval, in both derivative chromosomes from two unrelated carriers, to a 190-bp, AT-rich repeat, which indicates that this repeat may mediate recombination events on chromosome 11. Interestingly, the LCR22s harbor AT-rich repeats, suggesting that this sequence motif may mediate recombination events in nonhomologous chromosomes during meiosis.     

Partial trisomy of 11 and 22 due to familial translocation t(11;22) (q23;q11), inherited in three generations

Summary A 1-year-old girl with partial trisomy of 11 (q23qter) and 22 (pterq11) is presented. She had severe mental retardation, cleft palate, congenital heart disease, congenital dislocation of the hip, and other anomalies.The extra acrocentric chromosome was identified as der(22),t(11;22) (q23;q11) from a familial translocation and by G-and R-banding methods. The mother and the maternal grandfather were carriers of balanced rcp(11;22) (q23;q11) translocations.The possible relations between phenotypic features and the karyotypes of partial trisomy 11 and 22 are discussed.     

Trisomy 6q22 leads to 6qter due to maternal 6;21 translocation. Case report review of the literature

Partial trisomy for the long arm of chromosome 6, involving 6q22 leads to 6qter, was observed in a 2-month-old male infant. The mother was 6q;21p translocation carrier. A review of the previously published cases with trisomies of different 6q segments suggests that the critical segment responsible for the clinically recognizable phenotype of 6q trisomy seems to be limited to bands 6q26 and/or 6q27.     

Segregation and fertility analysis in an autosomal reciprocal translocation, t(1;8)(q41;q23.1).

We report a previously undescribed autosomal reciprocal translocation, t(1;8)(q41;q23.1). It segregates in three families whose common origin lies at least 11 generations back. No examples of unbalanced karyotypes were encountered. Moreover, there was no circumstantial evidence that such live births had occurred during earlier generations. Couples in which one spouse was a translocation carrier were compared to related couples with normal karyotypes. The 15 carrier families had significantly more spontaneous abortions (32%) than the 22 normal couples (10%), irrespective of the sex of the carrier parent. However, the mean number of children was equal in both groups (2.0 and 2.4). Carrier families produced 17 children with a balanced translocation and seven with a normal karyotype. This deviates significantly (P = .04) from the expected 1:1 ratio. We conclude that this malsegregation helps to maintain the translocation in the population. These results show that empirically derived 1:1 segregation ratios previously reported in series that combine many different translocations do not apply to all individual translocations.     

The position of t(11;22)(q23;q11) constitutional translocation breakpoint is conserved among its carriers

The t(11;22)(q23;q11) translocation is the most common recurrent balanced translocation described in humans. Carriers are phenotypically normal and often go undetected until diagnosis as a result of infertility investigations or following the birth of chromosomally unbalanced offspring. Efficient diagnostics of t(11;22) is important for children born to carriers of the translocation and for prenatal and pre-implantation diagnosis. The translocation breakpoint on chromosome 22 is located within a region containing low copy repeats, and this site is one of the last unfilled gaps in the sequence of this chromosome. This autosome harbors multiple other low copy repeats, which have been entirely sequenced. We report a combined sequencing and fiber FISH breakpoint characterization in five translocation carriers. From one carrier a cosmid library was constructed, and two chimeric cosmids (cos4_der11 and cos6_der22) were sequenced, which showed that strong palindromes (or inverted repeats) occur on both chromosomes. The translocation breakpoints occur at the tip of both inverted repeats. The palindrome on chromosomes 22 and 11 is composed of 852 and 166 bases, respectively. Four additional carriers were studied using fiber FISH with a resolution limit of 2 kb. Analysis of breakpoints on the DNA sequence level, or at the level of fiber FISH, indicate that they occur at the same position on both chromosomes in all five carriers. Using cos6_der22, PAC 158L19 and BAC 3009A19, we demonstrate that FISH is an attractive alternative in molecular diagnostics of t(11;22), as PCR assays are not reliable, due to the presence of numerous copies of low copy repeats.     

Partial trisomy 18(q11 leads to qter) in an infant and aborted fetus resulting from a balanced paternal translocation t(13;18)(q32:q11).

Partial trisomy 18 is described in a two month old female with severe mental, motor and growth retardation, associated with multiple congenital anomalies characteristic of complete trisomy 18. Trisomy for almost all of 18q resulted from adjacent I segregation of a paternally inherited translocation t(13; 18)(q32:q11). The balanced translocation was observed in three generations of the family. Partial trisomy 18q identical to that observed in the proband was found in a subsequent miscarriage.     

Sperm chromosome analysis of two men heterozygous for reciprocal translocations: t(1;9)(q22;q31) and t(16;19)(q11.1;q13.3).

Sperm chromosome complements were analysed in two men who were heterozygous carriers of reciprocal translocations. A total of 363 sperm were karyotyped after in vitro penetration of hamster oocytes, including 180 sperm from a male with a t(1;9)(q22;q31) and 183 from a male with a t(16;19)(q11.1;q13.3). All possible 2:2 and 3:1 meiotic segregations were observed for both translocations. The frequencies of alternate, adjacent 1, adjacent 2, and 3:1 segregations were 46%, 38%, 13%, and 4% for the t(1;9) and 40%, 28%, 31%, and 1% for the t(16;19), respectively. Within the alternate segregation group, the number of normal sperm was not significantly different from the number of sperm carrying a balanced form of the translocation for either of the translocations, as expected. There was no evidence for an interchromosomal effect of either translocation, since the frequencies of numerical abnormalities unrelated to the translocation were within the normal range observed in sperm from control donors. The percentage of sperm with an unbalanced form of the translocation was 54% for the t(1;9) and 61% for the t(16;19).     

Distal monosomy of the long arm of chromosome 6 (6q25----6qter) inherited by maternal translocation t(6q;17q)

Two half-sisters with distal monosomy of the long arm of chromosome 6 (q25----qter) inherited by maternal translocation t(6q;17q) were investigated. The clinical manifestations of these patients are compared with eight cases reported in the literature for further characterization of the 6q-syndrome. The cytogenetic diagnosis of alterations involving small chromosome fragments and the different origins of this type of deletion are also discussed.