Boy With an Interstitial 1q (q31q41) DuplicationConfirmed by Fluorescent In Situ Hybridisation

Anna Sillen,1 Claes Wadelius,1 and Goran Anneren1,2*1Department of Clinical Genetics, Uppsala University Children’s Hospital, Uppsala, Sweden2Department of Pediatrics, Uppsala University Children’s Hospital, Uppsala, Sweden

A 20-year-old man with multiple anomaliescaused by a de novo duplication of the longarm of chromosome 1 is presented. The pa-tient suffers from severe mental retarda-tion, epilepsy, bronchial stenosis, and minoranomalies (e.g., hirsutism, midface dyspla-sia, and beaked nose). A G-banding analysisof the patient’s chromosomes showed addi-tional segments in chromosome 1. Fluores-cent in situ hybridisation analysis with achromosome 1 painting probe showed thatthe extra material originated from chromo-some 1. Further analysis with cosmidprobes demonstrated that the region involv-ing chromosome bands 1q31 to q41 is pre-sent in a tandem duplication. Am. J. Med.Genet. 80:163–168, 1998. © 1998 Wiley-Liss, Inc.

KEY WORDS: chromosome 1; duplication1q syndrome; dup(1)(q31q41);FISH; cosmid

INTRODUCTION

Chromosome 1 is the largest human chromosomeand accounts for approximately 300 Mb of DNA, whichis roughly 10% of the human genome. Trisomy of thewhole chromosome 1 is not compatible with life and isnever observed prenatally, but partial duplications ofeither the short or the long arm have been reported.The largest duplication of chromosome 1 reported in alive-born child involved the region 1q24-qter [Zuffardiet al., 1977]. Interstitial duplications of 1q are rarelyseen [Flatz and Fonatsch, 1979; Furforo et al., 1996;Lungarotti et al., 1980; Palmer et al., 1977; Schinzel,

1979; Steffensen et al., 1977]. In most of reported caseswith duplications of chromosome 1 a rearrangementhas occurred with involvement of another chromosomeas results from unbalanced translocations [Chia et al.,1988; DuPont et al., 1994; Fryns et al., 1980; Johnson,1991; Kennerknecht et al., 1993; Liberfarb et al., 1979;Rasmussen et al., 1990; Rehder and Friedrich, 1979;Rosenthal et al., 1987; Schinzel, 1981; Watson et al.,1990; Verschuuren-Bemelmans et al., 1995]. In thosecases it is difficult to separate the duplication 1q phe-notype from that of the other involved chromosome.Cases with duplications involving chromosome 1qalone, when a de novo structural rearrangement hasoccurred, are not very common [Garver et al., 1976;Palmer et al., 1977; Pan et al., 1977; Steffenssen et al.,1977; Flatz and Fonatsch, 1979; Schinzel, 1979; Lun-garotti et al., 1980; Mewar et al., 1994; Duba et al.,1997], but are the most informative for delineating aduplication 1q syndrome. It is then important to iden-tify the duplicated region in order to make a correctgenotype-phenotype correlation.

In this report a patient with a syndrome caused by ade novo structural rearrangement of the long arm ofchromosome 1 is presented. The clinical findingsaroused a suspicion of a 1q duplication. A terminal du-plication of the long arm dup(1q) was cytogeneticallysuspected. Fluorescent in situ hybridisation (FISH)with painting probe verified the duplication. The finalconfirmation with specific FISH markers of the 1q re-gion demonstrated an interstitial tandem duplication,dup(1q) (q31q41).

CLINICAL REPORT

The propositus, a 20-year-old male, was the secondchild of a gravida 6 mother, who had had four previousearly miscarriages. The parents were healthy and non-consanguineous. Pregnancy and birth were uneventful.The child was born after 39 weeks of gestation. Birthweight was 3,150 g, length 49 cm, and head circumfer-ence 33 cm. A preaxial polydactyly on the right handwas corrected surgically. He had downward-slantingpalpebral fissures, low-set ears, prominent occiput, andbilateral retained testes. He had muscular hypotonia.At the age of 6 months a chromosomal analysis wasperformed, because of failure to thrive and the abnor-mal physical appearance.

Contract grant sponsor: Savstaholm Foundation; Contractgrant sponsor: Swedish Medical Research Council; Contractgrant number: B95–19X–05445–17B; Contract grant number:K97-19X-09747-07B; Contract grant sponsor: Ingabritt and ArneLundberg Research Foundation.

*Correspondence to: Goran Anneren, M.D., Ph.D., Departmentof Clinical Genetics, Uppsala University Children’s Hospital, S-751 85 Uppsala, Sweden. E-mail: Goran.Anneren@ped.uas.lul.se

Received 2 February 1998; Accepted 23 June 1998

American Journal of Medical Genetics 80:163–168 (1998)

© 1998 Wiley-Liss, Inc.

At the age of 8 months, severe psychomotor retarda-tion was manifested, and in addition he had autisticbehavior. At 14 months he could sit without support,but not walk or talk. He started to walk at the age of 5.5years. He has never been able to say a single word.Brain-stem audiometry at the age of 3 and 7 years,respectively, revealed normal hearing. No IQ testinghas been performed, but he is severely mentally re-tarded with an IQ score below 30.

Between the ages of 6 months and 5 years he hadrepeated attacks of bronchopneumonia and twice hehad to be treated in a respirator. At 15 months he hadsevere respiratory problems as a sequel of pneumonia,which resulted in cardiac arrest and subsequent treat-ment for one month in a respirator. After that he de-veloped left-sided hemiplegia and severe epilepsy.Bronchoscope examination showed a stenosis of the leftbronchus. Immunological examinations at the age of 5years showed normal immuoglobulin serum levels andnormal leukocyte function. From the age of 5 years hewas free from pneumonia, but at the age of 19 years hehad another episode of pneumonia and severe respira-tory problems and was again treated in a respirator for2 months. He also developed a thoracolumbar scoliosis.His bilateral testicular retention was surgically treatedat 4 and again at 10 years of age. Ocular and cardiacexamination by ultrasound gave normal results. At theage of 16 years physical examination showed (Fig. 1) :long face, very coarse hair, downward-slanting palpe-bral fissures, hypertrichosis, bushy eyebrows, low-setears, a large beaked nose, a long philtrum, and thinupper lip. Height was 160 cm, weight 58 kg, and headcircumference 54 cm. He had a slight scoliosis. He didnot talk but could walk without support.

CYTOGENETIC AND FISH STUDIES

Chromosomal analysis was carried out on whole-blood cultures using standard G-banding technique.The patient and both parents were analysed.

For chromosome painting analysis a whole chromo-some 1 paint probe (Oncor, Boehringer MannheimScandinavia AB, Sweden) was used. Other probes con-sisted of Alu-PCR fragments from YACs situated in the1q telomeric region and cosmids located in 1q, whichwere hybridised to the metaphase spreads. The YACswere 816d3, 906g7, 882f1, 872d5, 848h10, 940a4, and736a10 (CEPH, Paris, France). The cosmids werecYS1-36, -236, -11, -411, -178, -107, -54, -15, -72, -271,and -14 (Japanese Collection of Research Bioresources,Osaka, Japan). The location of the cosmids, accordingto mapping by FISH (http://www.nihs.go.jp/cellbank/wwwjcrb.html) is shown in Figure 2. Probes were la-beled by nick-translation with biotin-11-dUTP or di-goxygenin-11-dUTP (Boehringer Mannheim, Scandi-navia AB, Sweden).

A cell line of the patient’s lymphocytes was estab-lished, from which metaphase spreads were prepared,using the standard 3:1 (v/v) methanol:acetic acid fixa-tion. The slides were covered by a coverslip and dena-tured prior to hybridisation in 60 ml of 70% formam-ide/2 × SSC at 72°C for 2 min on a heating block and

followed by dehydration in a cold ethanol series. Fivehundred ng aliquots of each cosmid or Alu-PCR prod-uct, or 1 mg of painting probe, were precipitated in thepresence of 5 mg salmon sperm DNA and 5 mg humanCotI DNA. The DNA was resuspended in 10 ml hybridi-sation solution (50% formamide, 10% dextran sulfate, 2× SSC, pH 4 5.0, 0.05 M phosphate buffer). The probeswere denatured in a water bath at 72°C for 5 min fol-lowed by prehybridisation at 37°C for 1 hr. The hybridi-sation took place overnight at 37°C. Posthybridisationwashes were 5 min at 72°C in 1 × SSC, followed by 4 ×SSC/Tween at room temperature for 30 min.

Biotinylated probes were detected using Texas Red(TRITC)- or FITC-conjugated avidin (Vector, Burlin-game, CA), while digoxygenin-labeled probes were de-tected with rhodamine- or FITC-conjugated antidi-goxygenin (Boehringer Mannheim). Slides were coun-terstained with DAPI (Sigma-Aldrich, Stockholm,Sweden) and mounted with antifade solution.

Hybridisations were evaluated visually with a Zeissaxiophot epifluorescence microscope equipped with acooled CCD camera (Photometrix, Tucson, AZ) and afilter-wheel set for visualisation of the different fluo-rescence colours. Software was the Quips SmartCap-ture FISH from Vysis. Paper copy images were pro-duced by a Tektronix Phaser 440 printer.

Fig. 1. The patient at age 16 years.

164 Sillen et al.

RESULTS

The chromosomal investigation showed two extrabands on the distal end of the long arm of chromosome1 (46, XY, 1q+) (Fig. 3). The parental karyotypes werenormal. From a search in the POSSUM data base aduplication of chromosome 1q was suspected, but thepatient did not have a congenital malformation of theheart, hypospadias, cleft lip and palate, or thick lips, asreported in patients with this chromosomal abnormal-ity [Duba et al., 1997; Flatz and Fonatsch, 1979]. InTable I, the clinical observations from the present caseare listed together with previously reported cases withchromosomal aberrations involving 1q, but without in-volvement of other chromosomes.

Hybridisation with a chromosome 1–specific paintprobe also showed signal from the additional segmenton 1q (Fig. 4). The cosmids cYS1-54, -15, -72, -271, and-14 hybridised to both the additional 1q segment and tothe normal chromosomes, indicating the duplicated re-

gion. The remaining cosmids and the Alu-PCR prod-ucts from YACs mapping to 1qtel, showed normal hy-bridisation patterns. Thus, the boy’s karyotype is46,XY,dup(1)(q31q41). Figure 5 presents the dual col-our hybridisation with the cosmids cYS1-15 and cYS1-14. The distance between the probe signals in the du-plicated region suggests that it is a tandem duplica-tion.

DISCUSSION

Patients with partial trisomy 1q demonstrate a widerange of manifestations of variable severity. Some phe-notypic findings that are common in these patients whodo not have other chromosomal aberrations involvedare: mental retardation, large anterior fontanel, car-diac defects, and high arched palate, but the variabilityis large (Table I). Several authors have tried to delin-eate a ‘‘partial trisomy 1q syndrome,’’ but problemshave arisen. The wide variety of anomalies has madethe definition difficult. As most reported cases withpartial trisomy 1q also have other chromosomal aber-rations, it has been difficult to establish whether thephenotype is caused by the partial trisomy 1q or by the

Fig. 2. Ideogram of the long arm of chromosome 1, with the localisationof cosmids and YACs used for probe material. The cosmids, which hybri-dised to the duplicated region, are printed in bold and the duplicated regionis indicated by a bar.

Fig. 3. The two chromosomes 1 of the patient showing the tandemduplication dup(1)(q31q41) in one of the chromosomes. The additional seg-ment of the q arm is indicated by arrows.

Interstitial 1q Duplication 165

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other coexisting chromosome aberration. In two cases,chromosome 18 has been involved [Liberfarb et al.,1979; Rosenthal et al., 1987] and in three cases, chro-mosome 15 [DuPont et al., 1994; Kennerknecht et al.,1993; Verschuuren-Bemelmans et al., 1995]. Therehave also been reports involving inversions and/or de-letions of chromosome 1 segments together with partialtrisomy of others [Clark et al., 1994; Duba et al., 1997;Mewar et al., 1994].

The phenotypic variances reported in patients inwhom only a chromosome 1q duplication exist might beexplained by the differences in the segments duplicated(Table I). The most common duplicated segments are inthe 1q32q-qter region [Clark et al., 1994; Duba et al.,1997; Fryns et al., 1980; Rehder and Friedrich, 1979;Schinzel, 1981] or the 1q42-qter region [Chia et al.,1988; Johnson, 1991; Kennerknecht et al., 1993; Liber-farb et al., 1979]. Even among patients having certainduplicated segments in common, the observed anoma-lies are variable, although it must be noted that a mo-lecular characterisation of the duplicated segment wasseldom performed.

Our patient, with a de novo interstitial duplication of1q31q41, has some highly characteristic findings, suchas bronchial stenosis, duplication of thumbs, peculiarface, and autistic behaviour. Many phenotypic charac-teristics in the present boy were also observed in thepatient described by Duba et al. [1997]. In addition tothe preaxial polydactyly noted in both patients, there

was stenosis of the trachea in the patient presented byDuba et al. and stenosis of the left bronchus in ourpatient. Stenosis of the airways is a very rare conditionand based on the chromosomal region shared by thesetwo patients, 1q32-q41. A gene causing the tracheal/bronchial stenosis might reside in this region.

The physical appearance, especially the coarse hairand facial features, of our patient is rather similar tothe patient described by Schinzel [1981]. Furthermore,his hirsutism has been noted in other patients withchromosomal aberrations involving 1q [Liberfarb et al.,1979; Rosenthal et al., 1987; Schinzel, 1981; Versch-uuren-Bemelmans et al., 1995].

In the majority of previously reported cases of partialtrisomy 1q, the karyotype has been based solely onGTG banding. When a duplicated region is small it canbe difficult to trace the origin of the extra segment. Tobetter define the aberration, FISH analysis has to beperformed and only four cases of partial trisomy 1qwere analysed by this method [Chen et al., 1994 ; Dubaet al., 1997; DuPont et al., 1994; Mewar et al., 1994].Only when several cases with a FISH-verified partialtrisomy 1q as the sole chromosomal aberration havebeen investigated and in which the breakpoints areidentified can duplication 1q syndromes be defined.

Fig. 4. FISH analysis with a whole chromosome 1 painting probe, de-tected by FITC-avidin with hybridisation signal from the whole chromo-some 1.

Fig. 5. Dual colour hybridisation with probes made from the cosmidscYS1-15 and cYS1-14, detected by FITC-avidin (green) and rhodamine-antidigoxygenin (red), respectively. The closeness of the probes makes thegreen and red signals appear yellow.

Interstitial 1q Duplication 167

ACKNOWLEDGMENTS

This study was supported financially by the Savsta-holm Foundation, the Swedish Medical ResearchCouncil (grant no. B95-19X-05445-17B and K97-19X-09747-07B) and the Ingabritt and Arne Lundberg Re-search Foundation.

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