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A 22q11.2 Deletion That Excludes UFD1L and CDC45L in a Patient with Conotruncal and Craniofacial Defects

1999; Elsevier BV; Volume: 65; Issue: 2 Linguagem: Inglês

10.1086/302514

1537-6605

Sulagna C. Saitta, James McGrath, Holly Mensch, Tamim H. Shaikh, Elaine H. Zackai, Beverly S. Emanuel,

Peptidase Inhibition and Analysis

To the Editor: Microdeletions of chromosome 22q11.2 occur with a high frequency in the general population, with an estimated incidence of 1/3,000–1/4,000 (Burn and Goodship Burn and Goodship, 1996Burn J Goodship J Congenital heart disease.in: Rimoin DL Conner JM Pyeritz RE Emery AEH Emery and Rimoin's principles and practice of medical genetics. Vol 1. Churchill Livingstone, New York1996: 767-803Google Scholar). They have been shown to be associated with the malformation phenotypes of velocardiofacial syndrome (VCFS [MIM 192430]), DiGeorge syndrome (DGS [MIM 188400]), and conotruncal anomaly face syndrome (CAFS [MIM 217095]) (Emanuel et al. Emanuel et al., 1999aEmanuel BS Budarf ML Scambler PJ The genetic basis of conotruncal cardiac defects: the chromosome 22q11.2 deletion.in: Harvey R Rosenthal N Heart development. Academic Press, San Diego1999: 463-478Crossref Google Scholar). Deletions of this region have also been demonstrated in some patients with the autosomal dominant form of Opitz G/BBB syndrome (MIM 145410) (McDonald-McGinn et al. McDonald-McGinn et al., 1995McDonald-McGinn DM Driscoll DA Bason L Christensen K Lynch D Sullivan K Canning D et al.Autosomal dominant “Opitz” GBBB syndrome due to a 22q11.2 deletion.Am J Med Genet. 1995; 59: 103-113Crossref PubMed Scopus (120) Google Scholar). Significant phenotypic overlap is found among these entities, including conotruncal cardiac defects, craniofacial anomalies, learning disabilities, and cleft palate. The spectrum of clinical findings shows considerable variability, even within families (McLean et al. McLean et al., 1993McLean SD Saal HM Spinner NB Emanuel BS Driscoll DA Velo-cardio-facial syndrome: intrafamilial variability of the phenotype.Am J Dis Child. 1993; 147: 1212-1216Crossref PubMed Scopus (32) Google Scholar). Although the overwhelming majority (>85%) of patients have deletions of the same ∼3-Mb region (Emanuel et al. Emanuel et al., 1999aEmanuel BS Budarf ML Scambler PJ The genetic basis of conotruncal cardiac defects: the chromosome 22q11.2 deletion.in: Harvey R Rosenthal N Heart development. Academic Press, San Diego1999: 463-478Crossref Google Scholar), several reports have described patients with atypical, shorter deleted segments nested within the large typically deleted region (TDR) (Levy et al. Levy et al., 1995Levy A Demczuk S Aurias A Depetris D Mattei MG Philip N Interstitial 22q11 deletions excluding the ADU breakpoint in a patient with DGS.Hum Mol Genet. 1995; 4: 2417-2418Crossref PubMed Scopus (54) Google Scholar; Kurahashi et al. Kurahashi et al., 1996Kurahashi H Nakayama T Osugi Y Tsuda E Masuno M Imaizumi K Kamiya T et al.Deletion mapping of 22q11 in CATCH22 syndrome: identification of a second critical region.Am J Hum Genet. 1996; 58: 1377-1381PubMed Google Scholar; O'Donnell et al. O'Donnell et al., 1997O'Donnell H McKeown C Gould C Morrow B Scambler P Detection of an atypical 22q11 deletion that has no overlap with the DiGeorge syndrome critical region.Am J Hum Genet. 1997; 60: 1544-1548Abstract Full Text PDF PubMed Google Scholar; McQuade et al. McQuade et al., in pressMcQuade L, Christodoulou J, Budarf ML, Sachdev R, Wilson M, Emanuel B, Colley A. A further case of a 22q11.2 deletion with no overlap of the minimal DiGeorge syndrome critical region (MDGCR): the involvement of the TBX1 and COMT genes in the deletion and the clinical phenotype. Am J Med Genet (in press)Google Scholar). Recently, a small, 20-kb deletion within the TDR was reported in a patient with a classic VCFS/DGS phenotype. This smaller deletion disrupts the UFD1L and CDC45L genes, the products of which (in particular, UFD1L) have been suggested to play important roles in craniofacial and cardiac development resulting in the phenotype (Shaikh et al. Shaikh et al., 1999Shaikh TH Gottlieb S Sellinger B Chen F Roe BA Oakey RJ Emanuel BS et al.Characterization of CDC45L: a gene in the 22q11.2 deletion region expressed during murine and human development.Mamm Genome. 1999; 10: 322-326Crossref PubMed Scopus (12) Google Scholar; Yamagishi et al. Yamagishi et al., 1999Yamagishi H Garg V Matsuoka R Thomas T Srivastava D A molecular pathway revealing a genetic basis for human cardiac and craniofacial defects.Science. 1999; 283: 1158-1161Crossref PubMed Scopus (229) Google Scholar). However, several of the aforementioned patients (some of whom have cardiac and craniofacial defects) have deletions that do not include the region containing these genes. These observations suggest that additional sequences within the TDR affect early craniofacial and cardiac morphogenesis. Additionally, a patient with features of DGS and with a microdeletion that falls outside the TDR but that does not overlap with any of the known deletions was recently described (Rauch et al. Rauch et al., 1999Rauch A Pfeiffer RA Leipold G Singer H Tigges M Hofbeck M A novel 22q11.2 microdeletion in DiGeorge syndrome.Am J Hum Genet. 1999; 64: 659-667Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar). This patient had craniofacial abnormalities and an interrupted aortic arch (type B) with truncus arteriosus, the same defect seen in the patient described by Yamagishi et al. (Yamagishi et al., 1999Yamagishi H Garg V Matsuoka R Thomas T Srivastava D A molecular pathway revealing a genetic basis for human cardiac and craniofacial defects.Science. 1999; 283: 1158-1161Crossref PubMed Scopus (229) Google Scholar). The report by Rauch et al. further emphasizes the likelihood that the 22q11.2-related cardiac defects are unlikely to result from defects involving a single gene within the TDR. We have identified a patient, CH98-18 (Emanuel et al. Emanuel et al., 1998Emanuel BS Budarf ML Shaikh T Driscoll D Blocks of duplicated sequence define the endpoints of DGS/VCFS 22q11.2 deletions.Am J Hum Genet Suppl. 1998; 63: A11Abstract Full Text Full Text PDF PubMed Scopus (112) Google Scholar), with a novel deletion of chromosome 22q11.2. His deletion is distal to the usual 3-Mb deletion found in most patients with VCFS and appears to overlap with a portion of the deleted region described by Rauch et al. (Rauch et al., 1999Rauch A Pfeiffer RA Leipold G Singer H Tigges M Hofbeck M A novel 22q11.2 microdeletion in DiGeorge syndrome.Am J Hum Genet. 1999; 64: 659-667Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar). The deletion does not overlap with any of the previously described “minimal critical regions” for VCFS/DGS. The patient was born to a 33-year-old mother at 35 wk gestation. The pregnancy was complicated by a weight gain of 70 lbs and premature rupture of membranes. The baby was delivered by cesarean section, because of breech presentation, with Apgar scores of 7 at 1 min and 8 at 5 min. Physical examination at birth was notable for an appropriate-for-gestational-age infant with hypertelorism, posteriorly rotated ears, micrognathia, a loud cardiac murmur, hypospadias, descended testes, single palmar creases, and 5th-finger clinodactyly bilaterally. Renal and cranial ultrasounds were normal. Echocardiography showed the presence of truncus arteriosus type II and a ventricular septal defect. Borderline hypocalcemia was also present. The patient had surgical repair of his truncus arteriosus at age 3 wk and a replacement graft at age 7 mo. Motor development was normal. The patient sat at age 6 mo and walked at age 14 mo. However, he had expressive-speech delay, speaking his first words at age 21 mo. At age 26 mo, he had speech appropriate for an 18-month-old. During a recent physical examination at age 26 mo (fig. 1), short stature, microcephaly, a prominent glabella, partially attached earlobes, a broad nasal bridge, a broad nasal tip with a crease, hypoplastic nasal alae, anteverted nares, a featureless philtrum, a down-turned mouth, a bifid uvula, and normal hearing and vision were noted. Endocrine evaluation including thyroid-function and growth-hormone panels was unremarkable. Immunologic studies including surface markers for T-cell, B-cell, and NK lineages, myeloid markers, leukocyte adhesion, and Wiskott-Aldrich–associated proteins were all normal. Proliferative responses to mitogen-stimulation tests were also normal, as were functional-antibody responses. GTG-banded chromosomes prepared directly from peripheral-blood lymphocytes showed a normal 46,XY karyotype, and FISH was negative for a deletion when the N25 (Oncor) probe was used (fig. 2A). In addition, CH98-18 did not have a deletion for a number of other cosmid-based FISH markers within the TDR, including D22S788, ZNF74, HCF2, and cHKAD26 (fig. 2B) (Emanuel et al. Emanuel et al., 1998Emanuel BS Budarf ML Shaikh T Driscoll D Blocks of duplicated sequence define the endpoints of DGS/VCFS 22q11.2 deletions.Am J Hum Genet Suppl. 1998; 63: A11Abstract Full Text Full Text PDF PubMed Scopus (112) Google Scholar). With the exception of cHKAD26, cosmids used for FISH were isolated by colony hybridization from the chromosome 22–specific cosmid library (LL22NCO3) generated at the Lawrence Livermore Laboratories. The cosmid that contains the cHKAD26 locus was provided by the Japanese Cancer Research Resources Bank. A cosmid, 83C5, containing the portions of the UFD1L and CDC45L genes deleted in the patient of Yamagishi et al. (Shaikh et al. Shaikh et al., 1999Shaikh TH Gottlieb S Sellinger B Chen F Roe BA Oakey RJ Emanuel BS et al.Characterization of CDC45L: a gene in the 22q11.2 deletion region expressed during murine and human development.Mamm Genome. 1999; 10: 322-326Crossref PubMed Scopus (12) Google Scholar) was also used for FISH and was not deleted (data not shown). We determined that a cosmid located distally in the TDR (107D7) was not deleted (fig. 2B). Because the clinical findings in the patient, including truncus arteriosus, a bifid uvula, hypoplastic alar nasi, and a history of hypocalcemia, were consistent with those seen in VCFS, additional analysis was undertaken. Use of a series of cosmid and bacterial artificial-chromosome–derived probes for FISH demonstrated, initially with a cosmid for locus D22S801, that a deletion adjacent to the TDR was present (fig. 2A,b and B). Both of CH98-18's parents were analyzed by FISH with the cosmid for D22S801 and were found not to have a deletion, indicating a de novo origin of the deletion. We and others have implicated blocks of duplicated DNA sequence containing BCRL and GGTL elements in the mechanism etiologic for the 22q11.2 deletions (Emanuel et al. Emanuel et al., 1998Emanuel BS Budarf ML Shaikh T Driscoll D Blocks of duplicated sequence define the endpoints of DGS/VCFS 22q11.2 deletions.Am J Hum Genet Suppl. 1998; 63: A11Abstract Full Text Full Text PDF PubMed Scopus (112) Google Scholar, Emanuel et al., in pressEmanuel BS, Goldmuntz E, Budarf ML, Shaikh T, McGrath J, McDonald-McGinn D, Zackai EH, et al (1999b) Blocks of duplicated sequence define the endpoints of DGS/VCFS 22q11.2 deletions. In: Clark E, Nakazawa M, Takao A (eds) Etiology and morphogenesis of congenital heart disease. Futura, Armonk, NY (in press)Google Scholar; Edelmann et al. Edelmann et al., 1999Edelmann L Pandita RK Morrow BE Low-copy repeats mediate the common 3-Mb deletion in patients with velo-cardio-facial syndrome.Am J Hum Genet. 1999; 64: 1076-1086Abstract Full Text Full Text PDF PubMed Scopus (254) Google Scholar). We predicted, on the basis of the presence of additional BCRL and GGTL duplicated sequences distal to the TDR, that CH98-18's deletion might involve one of these elements. Thus, the extent of his deletion was investigated on the basis of the map of the region immediately distal to the TDR. This region contains the immunoglobulin-λ light-chain locus (IGLL), within which are located BCRL4 and a copy of GGTL (Kawasaki et al. Kawasaki et al., 1995Kawasaki K Minoshima S Schooler K Kudoh J Asakawa S de Jong PJ Shimizu N The organization of the human immunoglobulin λ gene locus.Genome Res. 1995; 5: 125-135Crossref PubMed Google Scholar). The IGLL locus has been completely characterized in a cosmid contig (Kawasaki et al. Kawasaki et al., 1995Kawasaki K Minoshima S Schooler K Kudoh J Asakawa S de Jong PJ Shimizu N The organization of the human immunoglobulin λ gene locus.Genome Res. 1995; 5: 125-135Crossref PubMed Google Scholar) and has been sequenced (Kawasaki et al. Kawasaki et al., 1997Kawasaki K Minoshima S Nakato E Shibuya K Shintani A Schmeits JL Wang J et al.One-megabase sequence analysis of the human immunoglobulin λ gene locus.Genome Res. 1997; 7: 250-261Crossref PubMed Scopus (162) Google Scholar). Using the cosmid and sequence reagents, we moved distally from D22S801 (LN80) into the IGLL to detect the deletion end point (DEP). To insure that the germline genomic configuration of this region was being investigated, all studies were performed on cultured peripheral-blood lymphocytes. We determined that, although cosmid 61E11 is deleted, 102D1 is the first cosmid not deleted in CH98-18 (fig. 2A and B). In the sequenced contig, these cosmids are separated by ∼40 kb that contain BCRL4 and GGTL. Using DNA sequence information for 102D1, we designed PCR-based 2.0-kb FISH probes and determined that both ends of this cosmid, which is immediately distal to the BCRL4/GGTL duplicated sequence in the IGLL locus, are present (GenBank). These probes are present, then, on both homologues. Results for one of these probes are shown in figure 2A. Thus, our patient's telomeric DEP involves a duplicated-sequence block that contains BCRL4 and GGTL sequences. The presence of a DEP in the vicinity of the BCRL4/GGTL duplication suggests unequal crossing-over in the formation of the patient's deletion. Additional cosmids distal to 102D1 were examined by FISH, and all were present on both homologues (data not shown). These cosmids included 48A11, 9C5, 75C12, and 81A12 from the previously published IGLL contig (Kawasaki et al. Kawasaki et al., 1995Kawasaki K Minoshima S Schooler K Kudoh J Asakawa S de Jong PJ Shimizu N The organization of the human immunoglobulin λ gene locus.Genome Res. 1995; 5: 125-135Crossref PubMed Google Scholar), as well as the commercially available M-BCR probe (Oncor). The region distal to 102D1, extending to the M-BCR probe, was deleted in the family described by Rauch et al. (Rauch et al., 1999Rauch A Pfeiffer RA Leipold G Singer H Tigges M Hofbeck M A novel 22q11.2 microdeletion in DiGeorge syndrome.Am J Hum Genet. 1999; 64: 659-667Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar). Thus, our patient has a novel deletion of chromosome 22q11.2 and features of VCFS, including hypoplastic alar nasi, a bifid uvula, and truncus arteriosus, a cardiac lesion characteristic of the deletion. In a previous study, ∼35% of patients with persistent truncus arteriosus were demonstrated to have standard deletions of 22q11.2 (Goldmuntz et al. Goldmuntz et al., 1998Goldmuntz E Clark BJ Mitchell LE Jawad AF Cuneo BF Reed L McDonald-McGinn D et al.Frequency of 22q11 deletions in patients with conotruncal defects.J Am Coll Cardiol. 1998; 32: 492-498Abstract Full Text Full Text PDF PubMed Scopus (442) Google Scholar). To determine whether CH98-18's distal deletion might be related to his particular heart defect, we subsequently analyzed 15 other patients with truncus arteriosus who did not have a deletion when the N25 probe was used. None of these patients had a deletion of D22S801 (B. S. Emanuel, unpublished data). Furthermore, patient CH98-18 has hypertelorism, anteverted nares, a grooved nasal tip, and hypospadias, which, although reported in VCFS, are more commonly described in Opitz G/BBB syndrome (Robin et al. Robin et al., 1996Robin NH Opitz JM Muenke M Opitz G/BBB syndrome: clinical comparisons of families linked to Xp22 and 22q, and a review of the literature.Am J Med Genet. 1996; 62: 305-317Crossref PubMed Scopus (66) Google Scholar). Opitz G/BBB is a heterogeneous disorder first described in 1969 (Opitz et al. 1969a, Opitz et al., 1969bOpitz JM Summitt RL Smith DW The BBB syndrome: familial telecanthus with associated congenital anomalies.Birth Defects. 1969; 5: 86-94Google Scholar) and linked to the X chromosome (MIM 300000) and 22q11 (Robin et al. Robin et al., 1995Robin NH Feldman GJ Aronson AL Mitchell HF Weksberg R Leonard CO Burton BK et al.Opitz syndrome is genetically heterogenous, with one locus on Xp22, and a second locus on 22q11.2.Nat Genet. 1995; 11: 459-461Crossref PubMed Scopus (87) Google Scholar). The X-linked form has subsequently been associated with mutations of the MID1 gene located on Xp22 (Quaderi et al. Quaderi et al., 1997Quaderi NA Schweiger S Gaudenz K Franco B Rugarli EI Berger W Feldman GJ et al.Opitz G/BBB syndrome, a defect of midline development, is due to mutations in a new RING finger gene on Xp22.Nat Genet. 1997; 17: 285-291Crossref PubMed Scopus (295) Google Scholar; Gaudenz et al. Gaudenz et al., 1998Gaudenz K Roessler E Quaderi N Franco B Feldman G Gasser DL Wittwer B et al.Opitz G/BBB syndrome in Xp22: mutations in the MID1 gene cluster in the carboxy-terminal domain.Am J Hum Genet. 1998; 63: 703-710Abstract Full Text Full Text PDF PubMed Scopus (56) Google Scholar). Patients with features of Opitz G/BBB and an autosomal dominant mode of inheritance have also been reported (Opitz Opitz, 1987Opitz JM G syndrome (hypertelorism with esophageal abnormality and hypospadias, or hypospadias-dysphagia, or “Opitz-Frias” or “Opitz-G” syndrome)—perspective in 1987 and bibliography.Am J Med Genet. 1987; 28: 275-285Crossref PubMed Scopus (49) Google Scholar; Robin et al. Robin et al., 1995Robin NH Feldman GJ Aronson AL Mitchell HF Weksberg R Leonard CO Burton BK et al.Opitz syndrome is genetically heterogenous, with one locus on Xp22, and a second locus on 22q11.2.Nat Genet. 1995; 11: 459-461Crossref PubMed Scopus (87) Google Scholar). Because of phenotypic overlap with the 22q11.2 deletion, several patients were assayed for and were found to have deletions of 22q11.2 (McDonald-McGinn et al. McDonald-McGinn et al., 1995McDonald-McGinn DM Driscoll DA Bason L Christensen K Lynch D Sullivan K Canning D et al.Autosomal dominant “Opitz” GBBB syndrome due to a 22q11.2 deletion.Am J Med Genet. 1995; 59: 103-113Crossref PubMed Scopus (120) Google Scholar). These patients all had the typical 3-Mb deletion commonly seen in VCFS/DGS. Analysis of several additional Opitz G/BBB cases without TDR deletions has failed to demonstrate a distal deletion similar to the one described in the present report (B. S. Emanuel, unpublished data). Therefore, the deletion reported here is atypical of that seen with a VCFS/DGS phenotype, and it is also atypical of those deletions that have been seen with autosomal dominant Opitz syndrome. It is notable that CH98-18's deletion does not encompass the region containing the UFD1L and CDC45L genes. He does, however, like the patient described by Rauch et al., have a cardiac defect similar to that seen in the patient described by Yamagishi et al. These cases with deletions distal to the TDR argue against the hypothesis that UFD1L and CDC45L alone are sufficient to cause the cardiac defect and craniofacial features typically seen in VCFS/DGS. It is more likely that our patient's phenotype is the result of haploinsufficiency of other genes located in this distal deleted region, which may, perhaps, function with UFD1L and CDC45L in a common developmental pathway. Alternatively, our patient's deletion raises the possibility of either a “position effect” on genes within the TDR or a more complex mechanism etiologic for features of the disorder, because his deletion is distal to the TDR and appears not to include any of the genes described within the TDR. Our patient's deletion is contained within the deletion described by Rauch et al. (Rauch et al., 1999Rauch A Pfeiffer RA Leipold G Singer H Tigges M Hofbeck M A novel 22q11.2 microdeletion in DiGeorge syndrome.Am J Hum Genet. 1999; 64: 659-667Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar); however, the phenotypes are not concordant. Both patient CH98-18 and the proband from the study by Rauch et al. have persistent truncus arteriosus. Nonetheless, there are no signs of Optiz G/BBB in any members of the family (including the proband) described by Rauch et al. However, since all of the subjects described in their report were female, only the laryngoesophageal anomalies and hypertelorism would be pertinent findings. Thus, it becomes apparent, when one is studying such “atypical” patients, that delineating a minimal critical region as causal for the VCFS/DGS phenotype spectrum may be of limited applicability. Findings from this patient and the others discussed here imply that disruption of more than one gene most likely contributes to the phenotype. Further definition of the mechanisms that lead to these deletions and of the involvement of the duplicated-sequence blocks found in the region (Emanuel et al. Emanuel et al., 1998Emanuel BS Budarf ML Shaikh T Driscoll D Blocks of duplicated sequence define the endpoints of DGS/VCFS 22q11.2 deletions.Am J Hum Genet Suppl. 1998; 63: A11Abstract Full Text Full Text PDF PubMed Scopus (112) Google Scholar; Edelmann et al. Edelmann et al., 1999Edelmann L Pandita RK Morrow BE Low-copy repeats mediate the common 3-Mb deletion in patients with velo-cardio-facial syndrome.Am J Hum Genet. 1999; 64: 1076-1086Abstract Full Text Full Text PDF PubMed Scopus (254) Google Scholar) would enable a greater understanding of (1) why these deletions and their subsequent phenotypes are so frequently encountered and (2) the role that sequences on 22q11.2 have in their etiology. This work was supported by National Institutes of Health grants DC02027 and HL51533 (to B.S.E, H.M., and E.H.Z.) and HD 26979 (to B.S.E.) from the Mental Retardation and Developmental Disabilities Research Center. S.C.S. is supported by Medical Genetics Research Training grant MH1-T32-GM-08638.