Separation of retinoblastoma and esterase D loci in a patient with sporadic retinoblastoma and del(13)(q14.1q22.3)

Hum Genet (1984) 68:258-259

© Springer-Verlag 1984

Separation of retinoblastoma and esterase D loci in a patient with sporadic retinoblastoma and del(13)(q14.1q22.3) Robert S. Sparkes 1, Maryellen C. Sparkes a, Robert E. Kalina 2, Roberta A. Pagon 2'3, Darrell J. Saik 3'4, and Christine M. Disteche 4 aDivision of Medical Genetics, Departments of Medicine, Pediatrics and Psychiatry, UCLA School of Medicine and Center for the Health Sciences, Los Angeles 2Departments of Ophthalmology, 3Pediatrics, and 4Pathology, University of Washington School of Medicine and Childrens Orthopedic Hospital and Medical Center, Seattle, USA Summary. A chromosome 13 deletion in a patient with sporadic retinoblastoma appears to have separated the loci for retinoblastoma and esterase D. This study indicates that: (1) the retinoblastoma locus is distinct from the esterase D locus; and (2) the linear order of these genes is centromere-esterase D-retinoblastoma.

Introduction Retinoblastoma is a developmental eye tumor which has received considerable recent attention from geneticists. Based on the following, about 40% of cases have an hereditary basis (Vogel 1979): autosomal dominant inheritance in some cases with 80-90% penetrance; all bilateral cases are hereditary; and 15-20% of unilateral cases are hereditary. A small group of retinoblastoma patients have a constitutional chromosome deletion of the long arm of chromosome 13 affecting band q14 (Francke 1976; Yunis and Ramsay 1978). Our earlier studies had mapped the genetic locus for esterase D to this band through the study of retinoblastoma patients with different partial deletions of chromosome 13 (Sparkes et al. 1980). Subsequent studies showed close genetic linkage of esterase D and the genes for the inherited form of retinoblastoma (Sparkes et al. 1983). We now report studies of a patient with sporadic retinoblastoma and a chromosome deletion of the long arm of 13 that appears to have deleted the retinoblastoma locus but not the esterase D locus.

Case report The patient (EL) is a 29A2-year-old white girl who was found to have bilateral retinoblastoma at 13 months of age. She was born after a term pregnancy with birth weight 3.3kg, birth length 52cm, and head circumference 34.3 cm. Long segment Hirschsprung disease was diagnosed at 3 days of age and resection of additional aganglionic colon was required at 2 months of age. Recurrent bowel obstruction, diarrhea, and poor feeding required two months of parenteral alimentation and prolonged, intermittent hospitalization during the first year of life.

Offprint requests to: Robert S. Sparkes, Department of Medicine, UCLA Center for the Health Sciences, Los Angeles, CA 90024, USA

Generalized hypotonia, poor oral control, and developmental delay were first evaluated at 10 months of age, at which time her developmental quotient (DQ) was 60-70. At 16 months of age, her developmental age as assessed by the Gesell Developmental Schedule was 10-11 months; however, by 29 months she had made little developmental progress and her D Q was in the 35-40 range. There was persistent drooling and inability to eat solid or textured foods. She could sit independently for long periods, but would not bear weight on her legs and had no expressive language. A left esotropia was noted at seven months of age and leukokoria was noted two weeks prior to confirmation of the diagnosis of bilateral retinoblastoma at 13 months of age at the University of Washington. The right eye had a 6 x 8 disc diameter white retinal tumor with calcium deposits located nasal to the optic disc. The left eye showed a total retinal detachment and a large inferior exophytic retinal tumor. Evaluation for metastasis was negative. The left eye was enucleated and histopathologic examination confirmed the diagnosis of retinoblastoma without optic nerve or choroidal invasion. The right eye was treated with 4950 rads of external beam radiation. The tumor showed a mixed regression pattern and has remained inactive for 13 months following treatment. A t 29 months of age, her height was 80.5cm (less than the 5th percentile), weight 10.5kg (5th percentile), and head circumference was 48cm (25th percentile). Except for generalized hypotonia and developmental delay, her physical examination was unremarkable. Her extremities, including the thumbs, were normal; renal ultrasound examination was normal. There was no evidence of congenital heart disease or structural brain anomalies by cranial computerized tomography.

Family history. Complete eye examinations of the parents were normal. There was no family history of ocular disease or Hirschsprung disease. Chromosome findings Peripheral blood lymphocyte studies on two occasions with G (28 cells) and R (16 cells) banding showed all cells with 46,XX,del(13)(q14.1q22.3) (Fig. 1). The best estimate of the break in band q14 is within q14.1 (Fig. 2). Analysis of a skin fibroblast culture showed the same findings in all 50 cells examined; it is believed that this excludes a 6% mosaieism within the culture at the 95% confidence level (Hook 1977). Chromosome studies on both parents were normal.

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Fig.1. Full karyotype of the patient using R banding. The a r r o w points to the deleted chromosome 13

Fig.2. Three partial G-banded karyotypes of the pairs 13 from the patient. The deleted chromosome is the right member of each pair. The a r r o w s to the left of each normal chromosome 13 indicate the breakpoints (13q14.1 and 13q22.3)

Therefore, we conclude that the patient has lost the retinoblastoma locus on the deleted c h r o m o s o m e 13. Prior studies of retinoblastoma patients with the 1 3 q - c h r o m o s o m e abnormality have shown 50% esterase D activity reflecting a haploid state (Sparkes et al. 1980; Dryja et al. 1983); the present case is the first exception to this correlation. First, we were concerned that chromosomal mosaicism could account for this lack of association, especially since the initial enzyme studies were done on red blood cells and it has not been possible to obtain bone marrow studies. H o w e v e r , we feel that mosaicism would not account for the results from the fibroblast culture. Therefore, we conclude that the esterase D locus has not been lost with the c h r o m o s o m e deletion. Earlier studies have m a p p e d the esterase D locus to band 13q14, but its exact position has not been established. All of these factors taken together lead us to interpret our findings in the present case to m e a n that the retinoblastoma locus has been deleted with the c h r o m o s o m e deletion, but the esterase D locus has not been so affected. The possibility cannot be excluded that the c h r o m o s o m e break has "inactivated" the retinoblastoma gene and not the esterase D gene, but we believe this would not alter the following considerations. If our interpretation is correct, the results from the study of the present patient indicate that the esterase D and the retinoblastoma loci are different. They also suggest that the esterase D locus maps closer to the centromere of chromosome 13 than does the retinoblastoma locus with both loci close to 13q14.1. A l t h o u g h genetic linkage studies of families suggest that these two loci are very close to one another, they must be sufficiently far apart that the c h r o m o s o m e deletion could break the c h r o m o s o m e between the two loci. This has implications for those investigators who have considered trying to isolate the retinoblastoma gene by first isolating the esterase D gene and then walking along c h r o m o s o m e 13 to the retinoblastoma gene. This work was supported in part by grants MCH927 and HD-04612 from the U.S. Public Health Service and by a National Institutes of Health Grant GM 15253.

Acknowledgements.

EsteraseDstudies Initial red blood cell esterase D studies showed an electrophoretic type 1-1 with 67.8 units of activity, which is within the normal range (Sparkes et al. 1979, 1981). A subsequent study of the patient's red blood cells confirmed the type 1-1 and showed 58.9 units of activity; studies on the parents at the same time showed the m o t h e r to have an electrophoretic type 2-1 with 60.9 units of activity, while the father had type 1-1 with 71.0 units of activity. Esterase D activity on a fibroblast culture from the patient showed a type 1-1 with 31.5 units of activity, while a control fibroblast culture of electrophoretic type 2-1 had 32.1 units of activity, both of which are within our normal range (Sparkes et al. 1980).

Discussion Based upon the sporadic occurrence of the retinoblastoma in the patient and based upon prior studies of patients with retinoblastoma and a c h r o m o s o m e deletion affecting 13q14, we believe it is reasonable to assume that the patient's retinoblastoma is related to her 1 3 q - c h r o m o s o m e abnormality. Current thinking relates the retinoblastoma in the chromosome deletion cases to deletion of the retinoblastoma locus.

References Dryja TP, Bruns GAP, Gallie B, Petersen R, Green W, Rapaport JM, Albert DM, Gerald PS (1983) Low incidence of deletion of the esterase D locus in retinoblastoma patients. Hum Genet 64:151-155 Francke U (1976) Retinoblastoma and chromosome 13. Cytogenetics 16:131-134 Hook EB (1977) Exclusion of chromosomal mosaicism: tables of 90%, 95%, and 99% confidence limits and comments on use. Am J Hum Genet 29 : 94-97 Sparkes RS, Targum S, Gershon E, Sensabaugh GF, Sparkes MC, Crist M (1979) Evidence for a null allele at the esterase D (EC 3.1.1.1) locus. Hum Genet 46:319-323 Sparkes RS, Sparkes MC, Wilson MG, Towner JW, Benedict W, Murphree AL, Yunis JJ (1980) Regional assignment of genes for human esterase D and retinoblastoma to chromosome band 13q14. Science 208:1042-1044 Sparkes RS, Murphree AL, Lingua RW, Sparkes MC, Field LL, Funderburk SJ, Benedict WF (1983) Gene for hereditary retinoblastoma assigned to human chromosome 13 by linkage to esterase D. Science 219 : 971-973 Vogel F (1979) Genetics of retinoblastoma. Hum Genet 52:1-54 Yunis JJ, Ramsay N (1978) Retinoblastoma and subband deletion of chromosome 13. Am J Dis Child 132:161-163 Received May 3, 1984 / Revised July 17, 1984