Prenatal Detection and Molecular Characterizationof a De Novo Duplication of the Distal Long Arm ofChromosome 19

Philip D. Cotter,1 Leslie D. McCurdy,1 Irina F. Gershin,1 Arvind Babu,1,2 Judith P. Willner,1 andRobert J. Desnick1*1Department of Human Genetics, Mount Sinai School of Medicine, New York, New York2Division of Medical Genetics, Department of Pediatrics, Beth Israel Medical Center, New York, New York

A tandem duplication of the distal long armof chromosome 19 was identified in a 10week fetus by analysis of chorionic villi. Thefetal karyotype from two primary cultureswas 46,XY,dir dup(19)(q13.2q13.4). The ori-gin of the extra material was confirmed byfluorescence in situ hybridization using achromosome 19 whole chromosome probe.Parental chromosomes were normal, indi-cating a de novo origin of the extra chromo-some material. This is the first case ofdup(19q) detected by prenatal diagno-sis. Molecular studies demonstrated thatthe duplication involved a maternal chro-mosome 19. Am. J. Med. Genet. 71:325–328,1997. © 1997 Wiley-Liss, Inc.

KEY WORDS: chromosome 19; duplication;chorionic villus sampling;prenatal diagnosis

INTRODUCTION

Partial trisomy of the long arm of chromosome 19 isan uncommon aneusomy [Boyd et al., 1992; Trautmannet al., 1993; Valerio et al., 1993]. The characteristicphenotype comprises microcephaly, heart malforma-tions, anomalies of the genito-urinary tract and/or thegastrointestinal system, growth retardation, and de-velopmental delay. Most previous reports of partial tri-somy 19q involved cytogenetic abnormalities that re-sulted from adjacent-1 segregation of familial balancedtranslocations [Boyd et al., 1992; Valerio et al., 1993].The remaining two patients had a de novo trisomy ofdistal 19q, in conjunction with either a deletion of 16q

[Trautmann et al., 1993] or a small 10q26.3 monosomy[James et al., 1996]. In this communication, the prena-tal diagnosis of a de novo tandem duplication of thedistal long arm of chromosome 19 is described. Thecytogenetic abnormality identified in chorionic villiwas confirmed by fluorescence in situ hybridization(FISH) by using a whole chromosome paint for chromo-some 19. In addition, molecular analysis was used todetermine the parental origin of the duplication.

CASE REPORT

Chorionic villus sampling (CVS) was performed at 10weeks of gestation on a 39-year-old gravida 1 womanwho was referred for prenatal diagnosis because of ma-ternal age. There was a history of exposure to severalmedications taken just prior to conception and for 5subsequent weeks. These included topical acne prepa-rations (Retin A 0.1% daily, hydroquinone 4% daily,and benzoyl peroxide 10% daily); minocycline hy-drochloride; decongestants (Loratidine [Claritint],diphenhydramine, and pseudoephedrine); anti-inflam-matory agents (beclomethasone and nedocromil so-dium); H2 blockers (ranitidine hydrochloride and ci-metidine hydrochloride); nonsteroidal anti-inflamma-tory agents (etodolic acid and ibuprofen); and a minortranquilizer (alprazolam). X-ray studies of the lowerlimbs were performed at 6 weeks after the last men-strual period.

Cytogenetic analysis of 20 cells from two primaryCVS cultures identified an apparent duplication of thedistal long arm of chromosome 19; 46,XY,dirdup(19)(q13.2q13.4) (Fig. 1). A FISH study was per-formed using a whole chromosome paint for chromo-some 19 (Cambio, Cambridge, UK) according to themethod of Pinkel et al. [1986] with fluorescein-avidindetection (Vector, Burlingame, CA). As shown in Fig-ure 2, FISH analysis confirmed the chromosome 19 ori-gin of the extra material. Parental chromosomes (20metaphases) were normal.

After genetic counseling, the couple elected to havean amniocentesis to confirm that the abnormality wasof fetal, and not extraembryonic, origin. Ultrasound ex-amination prior to amniocentesis demonstrated a cys-

Contract grant sponsor: National Institutes of Health; Contractgrant numbers: 5 P30 HD28822, 2 M01 RR00071.

*Correspondence to: Dr. R.J. Desnick, Professor and Chairman,Department of Human Genetics, Box 1498, Mount Sinai School ofMedicine, New York, NY 10029.

Received 4 September 1996; Accepted 17 January 1997

American Journal of Medical Genetics 71:325–328 (1997)

© 1997 Wiley-Liss, Inc.

tic hygroma. The couple elected not to proceed with theconfirmatory amniocentesis and terminated the preg-nancy at 13 weeks by dilatation and extraction, whichprevented further characterization of the fetal syn-drome. The karyotype was confirmed from fetal tissue.

Genomic DNA was extracted from fetal tissue andparental blood using standard techniques [Sambrooket al., 1989]. Molecular studies were performed withchromosome 19q microsatellite markers D19S112,D19S178, D19S218, D19S246, and D19S553 (Research

Fig. 2. Fluorescence in situ hybridization with a chromosome 19 whole chromosome paint showing the duplicated segment to be of chromosome 19origin.

Fig. 1. Partial karyotype and ideogram of direct duplication of 19q, dir dup(19)(q13.2q13.4). Arrows indicate the extent of the region of duplication.

326 Cotter et al.

Genetics, Huntsville, AL). Each marker was PCR-amplified and visualized as described [Wang and We-ber, 1992]. Analysis of D19D553 in the fetus showed asingle paternal allele and two maternal alleles (Fig. 3),indicating that the duplicated material was of mater-nal origin; D19S246 (Fig. 3) and the remaining mark-ers were not informative (data not shown).

DISCUSSION

The identification of extra chromosomal material atprenatal diagnosis is always problematic, particularlywhen de novo. It is important to identify precisely theorigin of the additional material for prediction of phe-notype and prognosis. Frequently, the origin of the ex-tra chromosomal material can be only inferred fromG-banded chromosomes. Recently, Leana-Cox et al.[1993] demonstrated the utility of the FISH method foridentifying the chromosomal origin of the extra mate-rial in patients with duplications identified by G-banding. In the prenatal diagnosis described here,FISH with a chromosome 19 whole chromosome paintwas used to confirm the origin of a tandem duplicationof the distal long arm of chromosome 19 in chorionicvilli from a 10-week-old fetus (Fig. 2).

Trisomy 19q is uncommon and most of previouslyreported patients resulted from adjacent-1 segregationof familial balanced translocations [Boyd et al., 1992;Valerio et al., 1993]. One patient was reported withtrisomy distal 19q due to a de novo unbalanced trans-location [James et al., 1996]. The only other patientdescribed had a de novo duplication of distal 19q com-bined with a de novo deletion of 16q [Trautmann et al.,1993]. The fetus described here is the first case of a denovo dup(19q) identified at prenatal diagnosis. On thebasis of the size of the duplication (19q13.2→q13.4) and

reports of liveborn infants with similar trisomies, thepredicted phenotype would be severe, including car-diac, gastrointestinal, and other malformations [Rivaset al., 1985; Valerio et al., 1993]. The presence of acystic hygroma in this case may be the precursor of thelow hairline, short neck, and excess skin seen in live-born infants with dup(19q) [Schmid, 1979].

None of the medications to which maternal gameteswere exposed prior to, or at the time of conception, hasbeen associated with chromosomal breakage in hu-mans. Interestingly, hydroquinone, formed as a me-tabolite of benzene in humans, has been shown to causeDNA adducts by reacting with guanine; however itsgenotoxicity appears low [Blacker et al., 1993]. In thiscase, exposure was minimal, as a 4% solution of hyd-roquinone was applied topically only once a day.

Tandem duplications of chromosomal material arerare. They are thought to result from an insertion ortranslocation involving the other homologue, or un-equal crossing-over or sister chromatid exchange atmeiosis [Therman, 1986; Blouin et al., 1991]. It is in-teresting to note that 5 of the 14 reported cases of tri-somy 19q resulted from adjacent-1 segregation oftranslocations between 19q and an acrocentric shortarm [Lange and Alfi, 1976; Rivas et al., 1985; Boyd etal., 1992; Valerio et al., 1993]. Valerio et al. [1993] hy-pothesized that homology between regions on 19q andacrocentric short arms might account for this phenom-enon. Chromosome 19 has been noted to be rich in re-petitive sequences, particularly Alu elements [Holm-quist, 1992], which may be involved in the origin oftandem duplications.

The parental origin of tandem duplications has beeninvestigated in Charcot-Marie-Tooth disease Type IA(CMT1A), which is caused by a 1.5 Mb duplication at17p11.2 [Pentao et al., 1992]. De novo duplications in

Fig. 3. Microsatellite markers demonstrating maternal origin of the duplicated region. With respect to D19S553 the fetus inherited allele 1 from thefather and alleles 3 and 4 from the mother. D19S246 is uninformative but showed three alleles in the fetus. Additional faint non-specific amplificationproducts were also visible for both markers.

De Novo Duplication 19q 327

CMT1A are almost always paternal in origin resultingfrom unequal crossing-over at meiosis-I [Palau et al.,1993; Blair et al., 1996]. To our knowledge, only asingle case of CMT1A has been reported due to a du-plication of maternal origin [Blair et al., 1996]. Thehigher incidence of paternally-derived duplicationsmay occur because of a higher frequency of misalign-ment at male meiosis or a higher tolerance of sper-matogenesis for derivative chromosomes [Palau et al.,1993].

Molecular analysis of larger chromosomal tandemduplications has been reported in only two cases[Blouin et al., 1991; Breslau-Siderius et al., 1993]. Thepatient described by Breslau-Siderius et al. [1993] hada 5q tandem duplication, which was proposed to havearisen from unequal crossing-over at paternal meio-sis-I [Breslau-Siderius et al., 1993]. In contrast, Blouinet al. [1991] reported a patient with a de novo tandemduplication of 21q, in whom they demonstrated a ma-ternal meiotic origin for the dup(21q). The presence ofone paternal and two maternal alleles in the fetus (Fig.3) showed that the dup(19q) was maternal in origin.Since chromosome 19 is rich in repetitive sequences[Holmquist, 1992] and pairing of homologues at meio-sis is thought to involve alignment of repetitive se-quences [Chandley, 1989], the 19q duplication mayhave resulted from unequal exchange or crossing overdue to the misalignment of these repetitive sequences.However, the molecular data cannot distinguish be-tween an insertion, homologous translocation, or un-equal crossing-over as the mechanism involved in thetandem duplication reported here. Analysis of a largernumber of tandem duplications would be required todetermine whether there is a predominant parent oforigin or not involved in the etiology of these rear-rangements.

ACKNOWLEDGMENTS

The authors are grateful to Florina Hristescu for ex-pert technical assistance and to Alison Smith for skill-ful genetic counseling. This work was supported bygrants from the National Institutes of Health for theMount Sinai Child Health Research Center (5 P30HD28822) and for the Mount Sinai General ClinicalResearch Center (2 M01 RR00071).

REFERENCESBlacker AM, Schroeder RE, English JC, Murphy SJ, Krasavage WJ, Simon

GS (1993): A two-generation reproduction study with hydroquinone inrats. Fund Appl Toxicol 21:420–424.

Blair IP, Nash J, Gordon MJ, Nicholson GA (1996): Prevalence and originof de novo duplications in Charcot-Marie-Tooth disease type 1A: Firstreport of a de novo duplication with a maternal origin. Am J HumGenet 58:472–476.

Blouin JL, Aurias A, Creau-Goldberg N, Apiou F, Alcaide-Loridan C, BruelA, Prieur M, Kraus J, Delabar JM, Sinet PM (1991): Cytogenetic andmolecular analysis of a de novo tandem duplication of chromosome 21.Hum Genet 88:167–174.

Boyd E, Grass FS, Parke JC, Knutson K, Stevenson RE (1992): Duplicationof distal 19q: Clinical report and review. Am J Med Genet 42:326–330.

Breslau-Siderius EJ, Wijnen JT, Dauwerse JG, De Peter JM, Beemer FA,Khan PM (1993): Paternal duplication of chromosome 5q11.2-5q14 in amale born with craniostenosis, ear tags, kidney dysplasia and severalother anomalies. Hum Genet 92:481–485.

Chandley AC (1989): Asymmetry in chromosome pairing: A major factor inde novo mutation and the production of genetic disease in man. J MedGenet 26:546–552.

Holmquist GP (1992): Chromosome bands, their chromatin flavors, andtheir functional features. Am J Hum Genet 51:17–37.

James C, Jauch A, Robson L, Watson N, Smith A (1996): A 31⁄2-year-old girlwith distal trisomy 19q defined by FISH. J Med Genet 33:795–797.

Lange M, Alfi OS (1976): Trisomy 19q. Ann Genet 19:17–21.

Leana-Cox J, Levin S, Surana R, Wulfsberg E, Keene CL, Raffel LJ, Sul-livan B, Schwartz S (1993): Characterization of de novo duplications ineight patients by using fluorescence in situ hybridization with chromo-some-specific DNA libraries. Am J Hum Genet 52:1067–1073.

Palau F, Lofgren A, De Jonghe P, Bort S, Nelis E, Sevilla T, Martin JJ,Vilchez J, Prieto F, Van Broeckhoven C (1993): Origin of the de novoduplication in Charcot-Marie-Tooth disease type 1A: Unequal nonsis-ter chromatid exchange during spermatogenesis. Hum Mol Genet 2:2031–2035.

Pentao L, Wise CA, Chinault AC, Patel PI, Lupski JR (1992): Charcot-Marie-Tooth type 1A duplication appears to arise from recombinationat repeat sequences flanking the 1.5 Mb monomer unit. Nat Genet2:292–300.

Pinkel D, Straume T, Gray JW (1986): Cytogenetic analysis using quanti-tative, high-sensitivity, fluorescence hybridization. Proc Natl Acad SciUSA 83:2934–2938.

Rivas F, Garcıa-Cruz D, Rivera H, Plascencia ML, Gonzalez RM, Cantu JM(1985): 19q distal trisomy due to a de novo (19;22)(q13.2;p11) translo-cation. Ann Genet 28:113–115.

Sambrook J, Fritsch EF, Maniatis T (1989): ‘‘Molecular Cloning: A Labo-ratory Manual.’’ Cold Spring Harbor, NY: Cold Spring Harbor Labora-tory.

Schmid W (1979): Trisomy for the distal third of the long arm of chromo-some 19 in brother and sister. Hum Genet 46:263–270.

Therman E (1986): ‘‘Human Chromosomes: Structure, Behaviour, Effects.’’New York: Springer-Verlag, p 222.

Trautmann U, Pfeiffer RA, Seufert-Satomi U, Tietze HU (1993): Simulta-neous de novo interstitial deletion of 16q21 and intercalary duplicationof 19q in a retarded infant with minor dysmorphic features. J MedGenet 30:330–331.

Valerio D, Lavorgna F, Scalona M, Conte A (1993): A new case of partialtrisomy 19q (q13.2-qter) owing to an unusual maternal translocation. JMed Genet 30:697–679.

Wang Z, Weber JL (1992): Continuous linkage map of human chromosome14 short tandem repeat polymorphisms. Genomics 13:532–536.

328 Cotter et al.