Molecular cytogenetic characterization of an insertional translocation, ins(6;7)(p25;q33q34): deletion/duplication of 7q33-34 and clinical correlations

A balanced insertional translocation between chromosomes 6 and 7, ins(6;7)(p25;q33q34) has been extensively investigated. The insertional translocation was found in several members of a three-generation family, where some were healthy balanced carriers while others had clinical symptoms due to deletion or duplication of 7q33-34. The deleted/duplicated segment could only be detected using high resolution banding and fluorescent in situ hybridization. A number of BAC/PAC clones located on chromosome 6 and 7 were used to characterize the breakpoint regions in detail and to determine the size of the deletion, which was 7.6 Mb, containing up to 68 genes. However, the insert on chromosome 6 was only 7.4 Mb, due to a deletion of 227 kb at the distal breakpoint on 7q. This small deletion was also found in the "balanced" carriers, and although the chromosome segment contains at least eight genes, none of the carriers seem to be affected by haploinsufficiency, since the phenotype is apparently normal. This is the first detailed characterization and phenotype correlation of such a deletion/duplication of distal 7q.     

Insertional translocations: report of two new families and review of the literature

We describe two families with insertional translocations. In the first, a large family ascertained because of repeated pregnancy loss, the insertional translocation, ins(1;3)(q32;p13pter), was found to be segregating through three generations. In the second family, ascertained through a proposita with congenital malformations, multiple spontaneous abortions also occurred. The father had an insertional translocation, inv 4(p14,q21.1)ins(7,4)(q32;q21.1 q23). These cases illustrate that recurrent fetal wastage may be caused by insertional translocations and in fact may be the only clinical manifestation of this unusual type of chromosome rearrangement.     

Familial partial 7q monosomy resulting from segregation of an insertional chromosome rearrangement.

A family with an insertional type of chromosome rearrangement involving chromosomes 7 and 13 is reported. An interstitial deletion of a segment of chromosome 7 (7q32 leads to 34) had been inserted into the long arm of chromosome 13 at breakpoint q32. Segregation of this chromosome rearrangement gave rise to three subjects who were monosomic for the involved segment of chromosome 7. The karyotypes were: 46,XX, or XY,der(7)ins(13;7) (q32;q32q34). All three subjects were mentally retarded and had minor dysmorphic features. The Kidd, Colton, and Kell blood group systems were investigated, but were not informative.     

Inv(4)(p16q21). A five-generation pedigree with 24 carriers and no recombin ants

A familial inv(4)(p16q21) ascertained through a woman who had a thanatophoric dwarf daughter and two abortions is presented. She and 23 other relatives were carriers, but no recombinants were found. The proportion of abortions and neonatal deaths in carriers' offspring was similar to that in non-carriers. A random segregation of the inverted chromosome was observed. The analysis of the present and previous familial chromosome 4 pericentric inversions indicates that: the breakpoint in q, with a limit between q21 and q25 determines the occurrence of inherited unbalances, and most recombinant chromosomes have duplication of the larger distal segment.     

Partial duplication 8q12----q21.2 in two sibs with maternally derived insertional and reciprocal translocations: case reports and review of partial duplications of chromosome 8

We report on two sibs with duplication of the segment 8q12----8q21.2 resulting from malsegregation of a maternal insertional translocation: [inv ins (5;8)(p13;q12q21.2)]. The mother also carries a reciprocal translocation [t(1;6)(q31;q5)], which was transmitted in the balanced state to the propositi and to a phenotypically normal son and daughter. The literature on two translocations occurring in one individual and on insertional rearrangements is reviewed in terms of reproductive risks to balanced carriers. The two affected infants have a previously undescribed partial duplication of an interstitial segment of 8q and a pattern of abnormalities distinct from those seen in other partial duplications of 8. These infants are reviewed with 78 other cases of partial duplications of chromosome 8 with regard to phenotype-karyotype correlations.     

Trisomy 1q24----1q41 in two sibs with an insertion in an inverted chromosome 4.

We report two patients whose karyotype revealed an additional segment 1q inserted into an inverted chromosome 4. The patients were partially trisomic for the region 1q24----1q41, karyotype 46,XY or XX, inv ins(4;1)inv(4)(q28;q24q41)(p15 . 3q28), while in the mother the chromosomal aberration was balanced. The inserted segment was inverted. In six patients from three other families with insertions, the segment 1q25----1q32 was inserted into the short arm of chromosome 1. In another patient, the segment 1q25----1q42 of the mother was inverted and inserted into the long arm of chromosome 6. These findings suggest an increased susceptibility for a segment of the long arm of chromosome 1 to be inserted and inverted in rearrangements.     

Molecular cytogenetic studies of duplication 9q32→q34.3 inserted into 9q13

Fluorescence in situ hybridization (FISH) studies using whole chromosome 9 painting probe, classical satellite (9q12-specific) probe and abl cosmid probe (locus: 9q34) were performed on a female infant who was born with multiple congenital anomalies and the karyotype 46,XX, 9q+. The results of FISH confirm the euchromatic nature of the extra material on the long arm of chromosome 9, and provide evidence that it is of chromosome 9 origin. The structural rearrangement has probably resulted from an insertion of a duplicated segment 9q32→q34.3 into band q13, as shown by the abl cosmid probe. The clinical features in this patient are similar to the previously reported cases of partial trisomy 9q3.     

Partial duplication 8q12→q21.2 in two sibs with maternally derived insertional and reciprocal translocations

We report on two sibs with duplication of the segment 8ql2→8q21.2 resulting from malsegregation of a maternal insertional translocation: [inv ins (5;8)(pl3;ql2q2l.2)]. The mother also carries a reciprocal translocation [t (l;6)(q31;q5)], which was transmitted in the balanced state to the propositi and to a phenotypically normal son and daughter. The literature on two translocations occurring in one individual and on insertional rearrangements is reviewed in terms of reproductive risks to balanced carriers. The two affected infants have a previously undescribed partial duplication of an interstitial segment of 8q and a pattern of abnormalities distinct from those seen in other partial duplications of 8. These infants are reviewed with 78 other cases of partial duplication of chromosome 8 with regard to phenotype-karyotype correlations.     

一个涉及1号和7号染色体插入易位家系的鉴定

目的 确定一个有反复流产史且常规G显带发现有7q末端缺失病例的核型,探讨染色体末端区域插入易位的形成机理。方法 应用显微切割制备的7号特异性全染色体探针和7q亚端粒（7q36→qter)探针,与病例的中期分裂相进行荧光原位杂交（fluorescence in situ hybridization,FISH)。结果 发现了该病例为常规G显带难以妈现的1号和7号染色体之间的插入易位,7q36→qter区域没有插入到1号染色体中,其异常核型来源于其母亲。结论 为染色体末端区域的插入易位仍然为一个三断裂重排。细胞遗传学上见到的末端缺失为中间缺失提供了实验证据,FISH与显微切割技术相结合。是检出染色体微小结构异常的一个强有力的工具。     

Molecular cytogenetic diagnosis of Williams syndrome

Williams syndrome (WS) is characterized by distinct facial changes, growth deficiency, mental retardation, and congenital heart defect (particularly supravalvular aortic stenosis), associated at times with infantile hypercalcemia. Molecular genetic studies have indicated that hemizygosity at the elastin locus (7q11.23) causes WS. The purpose of this study was to confirm that this regional deletion, involving the elastin locus, is the cause of WS in Japan, and to clarify the correlation between the phenotype and the elastin locus. Thirty-two patients with WS and thirty of their relatives were examined by fluorescent in situ hybridization (FISH), using the WS chromosome region (WSCR) probe. All patients had cardiovascular disease (100%), 30 had typical WS facial changes (94%), 31 had mental retardation or developmental delay (97%), 16 were small-for-date at birth (50%), 14 had short stature (44%), and 13 had dental anomalies (41%). No relatives showed any manifestation of WS. Hemizygosity for a region of 7q11.23, involving the elastin locus, was found in all WS patients, but was not found in the 30 relatives. © 1996 Wiley-Liss, Inc.     

Clinical variability of partial duplication 1q: a clinical report and literature review

A female baby with multiple congenital malformations was born to a father previously known as a carrier of reciprocal translocation, t(1;18)(q25;p11). Her chromosome constitution was 46,XX,-18,der18,t(1;18)(q25;p11)pat, namely, partial duplication 1q25----qter. The main manifestations were: macrocephaly, hirsutism, camptodactyly, eye defects, lymphedema, and duodenal atresia. This patient illustrates the phenotype variability expected from such a large duplication of chromosome 1.     

Duplication 14(q24.3q31) in a father and daughter: Delineation of a possible imprinted region

A number of clinical reports have described children with a variety of congenital anomalies in association with uniparental disomy (upd) of chromosome 14, suggesting that at least some genes on chromosome 14 are subject to parent of origin, or imprinting, effects. However, little else is known about this putative imprinting of chromosome 14. Both maternal and paternal upd have been observed, but a consistent phenotype has only been suggested for the former. Here we report on a child with developmental delay, microcephaly, distinct facial findings, and who has a duplication of 14q24.3q31. The same cytogenetic abnormality was found in her phenotypically normal father. We hypothesize that this segment of chromosome 14 contains maternally silenced genes, and that this duplicated segment defines an imprinted region on chromosome 14. Alternatively, this cytogenetic duplication may be unrelated to the girl's phenotypic anomalies, and this duplication may contain genes that are not subject to dosage effect. Am. J. Med. Genet. 71:361–365, 1997. © 1997 Wiley-Liss, Inc.     

Segregation of a paternal insertional translocation results in partial 4q monosomy or 4q trisomy in two siblings

A genetics evaluation was requested for a 6-week-old infant with multiple congenital malformations including mild craniofacial anomalies, truncal hypotonia, hypospadias, and a ventriculoseptal defect. Blood obtained for chromosome analysis revealed an abnormal chromosome 4. Paternal chromosome analysis showed a 46,XY, inv ins (3;4) (p21.32; q25q21.2), inv(4)(p15.3q21.2) karyotype. Therefore, the proband's chromosome 4 was the unbalanced product of this insertional translocation from the father resulting in partial monosomy 4q. Additionally, the derivative 4 had a pericentric inversion which was also seen in the father's chromosome 4. During genetic counseling, the proband's 2-year-old brother was evaluated. He was not felt to be abnormal in appearance, but was described as having impulsive behavior. Chromosome analysis on this child revealed 46,XY,der(3)inv ins(3;4)(p21.32;q25q21.2)pat. This karyotype results in partial trisomy 4q. FISH using two-color “painting” probes for chromosomes 3 and 4 confirmed the G-banded interpretation in this family. The segregation seen in this family resulted in both reciprocal products being observed in the two children, with partial 4q monosomy showing multiple congenital anomalies, and partial 4q trisomy showing very few phenotypic abnormalities. © 1995 Wiley-Liss, Inc.     

Interstitial deletion of chromosome 1 del (1) (q32 q42): case report and review of the literature

We describe the case of a female infant with multiple congenital anomalies who was found to have a de novo distal intestinal del (1) (q32 q42). The clinical features of other reports of similar deletions are briefly reviewed. No characteristic phenotype seems to be as yet definable due to the limited number of cases published.     

Lip pits and deletion 1q32----41

A patient with an interstitial deletion of chromosome 1q[del(1q32----41)] was found to have, among other anomalies, congenital lower-lip pits. Lip pits are rare and are found mainly in association with the van der Woude syndrome and the popliteal pterygium syndrome; we cannot find a report of their association with a chromosome anomaly. To our knowledge, interstitial deletion of the segment 1q32----41 has not been reported. This observation raises the possibility that the van der Woude syndrome may be due to a submicroscopic deletion of chromosome 1q.     

Testing candidate loci on chromosomes 1 and 6 for genetic linkage to Peutz-Jeghers' disease

Peutz-Jeghers' syndrome (PJS) is a disease with autosomal dominant inheritance, which is characterised by gastrointestinal hamartomata and characteristic melanin pigmentation. Three candidate sites for a PJS locus have recently been proposed, chromosomes 1p31-p32, 6q25 and 6p11-cen. At the first of these sites, a multipoint LOD score of 4.00 had been found, strongly suggesting genetic linkage to PJS. The last two candidate sites were suggested by the chromosomal breakpoints of a patient with an inv(6) and PJS. We have analysed up to 34 families in order to test each of the three candidate sites for linkage to PJS. No evidence was found in support of a Peutz-Jeghers' syndrome locus on chromosome 1p31-p32. The candidate region on 6q25 was also excluded. The region close to the centromere of chromosome 6 has not been excluded and there is some evidence of linkage to a marker near 6cen, although genetic heterogeneity in PJS must be proposed to account for a gene at this site.     

Multiple congenital defects associated with trisomy for long arm of No. 4.

The clinical and cytogenetic findings of a male infant with multiple congenital anomalies and trisomy for the distal third of the long arm of No. 4 are described. The abnormal chromosome was inherited from the mother who had a balanced translocation, t(4;9)(q31;q34). Trisomy for the long arm of No. 4 has previously been described in only 3 patients.     

Familial cryptic translocation (2;17) ascertained through recurrent spontaneous abortions

We report a young woman who presented with a reproductive history of three recurrent spontaneous abortions (RSA) and two neonatal deaths. Comparative genomic hybridization (CGH) was used to determine the chromosomal composition of the patient's last miscarriage. It showed the presence of monosomy for the distal end of chromosome 2 long arm (segment 2q37.2 to qter) and trisomy for the distal end of chromosome 17 long arm (segment 17q25 to qter). The mother was found to be a carrier for a cryptic translocation between chromosomes 2 and 17 long arms by fluorescence in situ hybridization using a subtelomeric probe for 17q. Retrospective CGH analysis on one baby who died neonatally showed that he had inherited the maternal translocation in the same unbalanced state as the last pregnancy loss. His detailed postmortem examination is reported.     

Mosaicism for a tandem duplication dup(1)(q12q22) in an 18 year old female.

The clinical features and cytogenetic results of an 18 year old mentally handicapped female found to be a mosaic for a tandem duplication of chromosome 1 (46,XX,dup(1)(q12q22)/46,XX) are reported. The case is compared with the three previously described cases and possible mechanisms for the origin of the duplication are discussed. This patient was not found to have features of Proteus syndrome which was previously reported in a subject mosaic for a tandem duplication involving chromosome (1)(q11q25).     

First report of management and outcome of pregnancies associated with hereditary orotic aciduria

Two pregnancies in a 25-year-old woman with hereditary orotic aciduria who was managed prenatally on uridine therapy are described. The first pregnancy resulted in an infant with multiple congenital anomalies and a 47, xx, inv(4)(p12q25), + der(22)t(11;22)(p23;q11) karyotype. The proposita was found to be a carrier of a de novo 11;22 translocation and a pericentric inversion of chromosome 4. Subsequently, several carriers of orotic aciduria in this family were identified with the inverted chromosome 4. The second pregnancy resulted in a normal male with an inverted chromosome 4.