- Email: [email protected]
An inherited pericentric chromosomal inversion (46, inv3 [p-q+]) associated with skeletal anomalies
456
September, 1971 T h e J o u r n a l o[ P E D I A T R I C S
An inherited pericentric chromosomal inversion (46, inv3 [p-q+]) associated with skeletal anomalies A [amily is described in which the propositus and his mother possess identical skeletal anomalies of the fingers and toes. Cytogenetic investigation revealed an abnormal No. 3 chromosome in both peripheral lymphocytes and fibroblasts o[ these individuals. On the basis of morphologic, autoradiographic, and measurement data, this chromosome is interpreted as representing a pericentric inversion o/ a No. 3.
Maimon M. Cohen and Ronald G. Davidson BUFFALO~ N. Y.
A M o N G the structural chromosome rearrangements, pericentric inversions are relatively infrequent. Nonetheless, the published cases of autosomal pericentric inversions have involved chromosome groups A, ~-G B, 7 Cff "10 D, ~-~:~ a n d G14-1~ a n d include both sporadic and familial cases. This paper describes a family in which both mother a n d son were afflicted with identical skeletal anomalies of the extremities and show the first reported instance of a pericentric inversion in chromosome No. 3 (46, inv3 [p-q+]) 9
CASE REPORTS The propositus was a 3-1nonth-old, Caucasian male infant referred to the Division of Human From the Division o[ H u m a n Genetics, Department o[ Pediatrics, State University o[ New York at Buffalo School o[ Medicine, and Children's Hospital o[ Buffalo. Supported in part by a grant [rorn the United States Children's Bureau (Project No. 417). Reprint address: Mabnon M. Cohen, M.D., 86 Hodge Ave., Buffalo, N. Y. 14222. Vol. 79, No. 3, pp. 4.56-462
Genetics because of the presence of multiple malformations and a positive family history for deformities of the extremities. The infant's mother had a full-term, normal pregnancy preceded by several years of irregular menstrual periods and apparent sterility. She was treated with various hormone preparations during the year prior to conception, and from conception through the first few weeks of pregnancy she took clomiphene citrate (Clomid). Labor was complicated by premature rupture of the membranes followed by slow irregular labor and delivery by cesarean section 5 days later. There were no problems in the neonatal period. Physical examination at birth and at 3 months of age revealed the following anomalies: bilateral inferior colobomata of the irides, a high-arched palate, a thin upper lip with absent philtrum, low-set ears, a midline prominence of the forehead, a sclerosing capillary hemangioma on the anterior aspect of the left leg (less than one square inch in size), and marked anomalies of the hands and feet (Figs. l and 2). When the infant was 3 months of age, height and weight were between the fiftieth and seventyfifth percentiles, but the head circumference was
Volume 79 Number 3
Chromosomal inversion with skeletal anomalies
45 7
Fig. 1. Photographs of the hands and feet of the propositus and his mother~ illustrating syndactyly and absence of digits. A and B, Dorsal and palmar aspects of the infant's right hand. C and D, Dorsal and palmar aspects of the infant's left hand. E and F, The infant's feet. G and H. The mother's hands and feet. between the tenth and twenty-fifth percentiles. In addition, head control was absent and the infant was abnormally placid during the examination. Prognosis for normal mental development is guarded. Family history revealed the mother to have congenital anomalies of the hands and feet similar to those of the propositus (Fig. 1). She had no other detectable defects and seemed to be of normal intelligence. Other maternal relatives had minimal anomalies of the extremities:
A paternal first cousin of the mother was reported to have had polydactyly and a great aunt to have had 2 webbed toes; 2 of the mother's 3 sisters had unilateral clinodaetyly of the fi~th finger. The propositus is an only child. The father was raised in an orphanage and knows nothing about his family history. MATERIALS
AND METHODS
Cytogenetie studies. Cytogenetic studies were performed on 8 family members; the
458
Cohen and Davidson
The ]ournal o[ Pediatrics September 1971
Fig. 2. Radiographs of the hands and feet of the propositus. propositus, his parents and maternal grandparents, and his mother's 3 sisters. Chromosome preparations were obtained by means of a micromethod (Chromosome Medium 1A, Grand Island Biological Co., Grand Island, N. Y.) using 4 to 5 drops of whole blood as inoculum. At least 30 cells per individual were microscopically and/or photographically studied in detail. In addition, fibroblast cultures were propagated from skin biopsies obtained from the propositus and his mother. Cultures were harvested and slides prepared by slight modification of the method of Moorhead and associates? 6 Autoradiographic studies were performed on leukocyte cultures of the mother of the propositus. Tritiated thymidine (Schwartz Bioresearch Corporation, specific activity 3C per milIimole) was added to the cultures, at
a final concentration of 1 /xc per milliliter, for the final 5 hours of culture. Colcemide (0.05 /xg per milliliter) was added for the last 2 hours of incubation. Prepared slides were dipped in Kodak Nuclear Tract (NTB3) emulsion and incubated at 4 ~ C. for 10 days. After development and staining, 17 cells with moderate labeling and informative patterns were located and photographed. The silver grains were then reduced by using a 10 per cent solution of potassium ferricyanide (30 minutes) followed by 24 per cent sodium thiosulfate (severaI dips) and rinsing in distilled water. Those cells previously photographed were located and rephotographed without the overlying silver grains. In this way, a direct comparison was possible and the labeled chromosomes could be identified. Chromosome measurement. Chromosomal
Volume 79 Number 3
Chromosomal inversion with skeletal anomalies
459
Table I. Chromosomal measurement ratios and tests of significance based on data from 25 cells of both the propositus and his mother A. Derived ratios Length
..
Arm ratio
Subject
Normal 3/2
Inverted 3/2
Average B/2
Normal 3/2
Inverted 3/2
Average B/2
Prop*situs Mean S.D.
0.8457 0.0048
0.8569 0.0006
0.8059 0.0032
1.136 0.005
2.022 0.047
2.220 0.027
Mother Mean S.D.
0.8597 0.0054
0.8581 0.0006
0.8067 0.0025
1.138 0.001
2.058 0.124
2.247 0.256
B. t Tests . Test 3/2 vs. inverted 3/2 Inverted 3/2 vs. average B/2 ~Denotes
statistical significance
Length Propositus 0.76 - N.S. 4.10 ~
I
Arm ratio
Mother 0.01 - N.S. 4.634
Propositus 19.43 ~ 3.654
[
Mother 39.48 ~ 10.53 ~
at the 0.01 level of probability.
measurements were obtained from 25 cells of both the propositus and his mother. Length and a r m ratio measurements were derived as described by Cohen and associates ~8 from positive photographic prints (8 x 10 inches). T h e chromosomes measured included pairs No. 2 and 3 and the 4 to 5 (B) group. Length values were obtained for each chromatid arm of each chromosomal pair per cell. An average of the four B group chromosomes in the cell was taken to yield a representative 4-5 element. T o obviate intercell contraction differences, all values obtained were divided by the average length of chromosome No. 2 in that cell. T h e No. 2 pair was chosen since it is large, accurately identifiable in every cell, and possesses no obvious secondary constriction which might affect its length. RESULTS
K a r y o t y p i c findings. All 8 family members examined had a modal n u m b e r of 46 chromosomes. However, in the propositus and his mother, only one metacentric member of the No. 3 pair could be found (Fig. 3). I n addition, an extra chromosome with an arm ratio simulating a B group element was seen. This chromosome, however, appeared larger than the other B group chromosomes and
f17-TS)
'k _ ':i
~EXCHrOMOSOMeS
Fig. 3. Karyotype of the propositus. All chromosomes appear normal except for one member of the number 3 pair representing a pericentric inversion (arrow). A similar chromosome was present in the mother's karyotype. Note the small Y chromosome which was also observed in the father's karyotype. approximated the over-all length of the missing No. 3. This "marker" chromosome was considered to represent a pericentric inversion of the missing No. 3. A similar karyotypic abnormality was observed in the
460
Cohen and Davidson
Fig. 4. Autoradiographs and partial karyotypes of the group A and B chromosomes in 3 cells from the mother. The inversion chromosome (arrow) has a pattern similar to that of the normal No. 3 except that the late-labeling centrorneric area has been shifted. fibroblast cultures derived from the skin biopsies in both the propositus and his mother. Since this anomaly was present in all cells examined from both tissues (125 cells in each person), mosiacism is unlikely. All other family members examined had normal karyotypes. Also, the propositus possessed an inordinately small Y chromosome, approximately one half the length of the G group chromosome (Fig. 3). This small Y chromosome was also present in his father. Chromosome measurements. Statistical evaluation of the mensuration data (Table I) supported the concept of a pericentric inversion. The measurements for these chromosomes in both the propositus and his mother were not significantly different from each other. The statistical analyses (t test) indicate that, in both cases, there were no significant differences between the over-all length of the no~mal No. 3 chromosome and
The Journal o[ Pediatrics September 1971
the inverted No. 3 (t = 0.76 and 0.01 for propositus and mother, respectively). However, highly significant values (p < 0.01) were obtained when testing for: (1) length of the inversion chromosome versus the average of the B group chromosomes, (2) arm ratios of the normal and inversion No. 3's, and (3) arm ratio between the inversion and the average of the B(4-5) chromosomes. Therefore, although the total length of the inversion chromosome could not be distinguished from the normal No. 3, it was easily separated by arm ratio differences. In addition, this chromosome was discernible from the B group chromosomes both on the basis of length and arm ratio. Therefore, it appeared as a unique element in the karyotypes of both the propositus and his mother. Autoradiography. Autoradiographic findings of 20 informatively labeled cells derived from the mother's leukocytes also indicate that the marker is indeed an inverted No. 3. Fig. 4 illustrates partial karyotypes of 3 cells showing chromosomes of the A and B groups (Nos. 1-5). These late replication patterns indicate that only one normal No. 3, as described by Schmid 1~ and German, ~9 is present in each cell. The amount of label present over both the normal No. 3 and the inversion chromosome is quite comparable in all cells and falls within the limits of replication asynchrony observed within a pair of homologues. However, the intrachromosomal distribution of silver grains differs in the 2 chromosomes. The No. 3 pair usually has a concentration of grains over the centromere region which is apparently one of the last areas to replicate its DNA. Additionally, the distal portions of the arms are sometimes "hot." The inversion chromosome also illustrates this pattern, but even though the centromere has been shifted from its median position by the inversion, it is still late replicating. The distal portion of the 2 No. 3's, however, have similar labeling patterns. DISCUSSION'
Pericentric inversion is a chromosomal rearrangement not frequently encountered in
Volume 79 Number 3
Chromosomal inversion with skeletal anomalies
man. la Since almost all chromosomal groups have been involved in inversions, a wide range of phenotypic deviation has been associated with this type of aberration. The family described in this report represents the first in which the No. 3 pair is involved; it is also the first instance in which a striking skeletal abnormality, limited only to the carriers of the anomaly, has been reported. T h a t the abnormal chromosome observed indeed represents a pericentric inversion is supported by evidence from morphology, mensuration, and autoradiography. T h e karyotypes of both the propositus and his mother, although possessing a modal n u m b e r of 45 chromosomes, are obviously missing one m e m b e r of the No. 3 pair. It is fortunate that No. 3 is easily identifiable in all cells and that the chromosome involved in the inversion is discernible. T h e inversion chromosome is the same length as a normal No. 3, but its arm ratio is aberrant. This identification is borne out by the measurement data on both the propositus and his mother. T h e total length of the abnormal No. 3 is not distinguishable from that of the normal No. 3, but is significantly greater than the length of the B group chromosomes. W h e n the parameter of arm ratio is used, the inverted chromosome is distinctive from all other elements measured. T h e autoradiographs indicate maintenance of the latereplicating areas of a normal No. 3 in the centromere and distal regions, but in an inverted order. Therefore, the fact that the over-all length of this chromosome has not been altered, but the centromere position and arm ratio have been changed, as documented by morphology, mensuration, and autoradiography, strongly supports the concept that the abnormal chromosome represents a pericentric inversion. The problem of causality is raised since the propositus and his mother have identical skeletal abnormalities and the chromosomal aberration. It is tempting to speculate that since no other relatives of the family are similarly affected, either clinically or chromosomally, the inversion is responsible for the skeletal deformities. Since the mother of
461
the propositus does not exhibit mosaicism in either blood or skin, the event most likely occurred prezygotically in gametogenesis of either one of the grandparents. However, one cannot rule out the possibility that the occurrence of the chromosomal and skeletal anomalies is coincidental. We appreciate the excellent technical assistance of Mrs. Clara Lockwood, Mrs. Claudia Hastings, and Miss Pamela Borchert. REFERENCES
1. Lele, K. P., Dent, J., and Delhanty, J. D. A.: Chromosome studies in 5 cases of coloboma of the iris, Lancet 1: 576, 1965. 2. Carr, D. H.: Chromosome anomalies, Trans. Amer. Ass. Genitourin. Surg. 54" 9, 1962. 3. Grouchy, J., Emerit, I., Corone, P., Vernant, P., Lamy, M., and Soulie, P.: Inversion pericentrique probable du chromosome no. 2 et malformations congenitales chez un garcon, Ann. Genet. 6: 21, 1963. 4. Hooft, C., Coetsier, H., and Oyre, H.: Syndrome de Turner et inversion pericentrique dn chromosome no. 2 [45,X,2(p+q-)], Ann. Genet. ll" I81, 1968. 5. Weitkamp, L. R., Janzen, M. K., Guttoremsen, S. A., and Gershowitz, H.: Inherited pericentric inversion of chromosome number two: A linkage study, Ann. Hum. Genet. 33: 53, 1969. 6. Mikelsaar, A. V. N., Ananjer, E. V., and Gindlis, V. M.: Probable pericentric inversion in chromosome number 1 in a female child [46,XX,inv(lp+q-)], Humangenetik 9: 316-324, 1970. 7. Morishima, A., Liu, N., and Grumbach, M. M.: Multiple congenital anomalies associated with probable pericentrie inversion of number 4 and mosaicism in an asymptomatie mother, J. PEmAT. 65: 1096, 1964. 8. Grouchy, J., Frezal, J., Bitan, A., Jammer, M. L., and Lamy, M.: Ramaniement d'un chromosome X, 6-12 chez nn trisomique 21, Ann. Genet. 8: 67, 1965. 9. Jacobs, P. A., Cruickshank, G., Faed, M. J. W., Frackiewicz, A., Robson, E. B., Harris, H., and Sutherland, I.: Pericentric inversion of a group C autosome: A study of three families, Ann. Hum. Genet. 31: 219, 1967. 10. Keutel, J., and Schubert, W.: Strukturanomalie [inv(t>-q+) ?] eines chromosoms der gruppe C + X bei einem jungen mit multiplen dysplasien und dissozlationen der psychischen entwicklung, Humangenetik 7: 119, 1969. 11. Chandra, H. S., and Hungerford, D. A.: An aberrant autosome (I3-15) in a human female and her father, both apparently normal, Cytogenetics 2: 34, 1963. 12. Cohen, M. M., Capraro, V. J., and Takagi', N.: Pericentric inversion in a group D ehro-
462
Cohen and Davidson
mosome (13-15) associated with amenorrhea and gonadal dyspenesls, Amer. Hum. Genet. 30: 313, 1967. 13. Crandall, B. F., and Sparkes, R. S.: Pericentrie inversion of a number 15 chromosome in nine members of one family, Cytogenetics 9: 307, 1970. 14. Schmid, W.: Pericentric inversions: Report on two malformation cases suggestive of parental inversion heterozygosity, J. Genet. Hum. 16: 89, 1967. 15. Soudek, D., Laxova, R., and Adawek, R.: Pericentric inversion in a family with a 21/22 translocation, Cytogenetics 7: 108, 1968.
The Journal of Pediatrics September 1971
16. Moorhead, P. S., Mowell, P. G., Mellman, W. J., Battips, D. M., and Hungerford, D. A.: Chromosome preparations of leukocytes cultured from human peripheral blood, Exp. Cell Res. 20: 613, 1960. 17. Schmid, W.: DNA replication patterns of human chromosomes, Cytogenetlcs 2: 175, 1963. 18. Cohen, M. M , Shaw, M. W., and MacCluer, J. W.: Racial differences in the length of the human Y chromosome, Cytogenetics 5: 34, 1966. 19. German, J. L.: DNA synthesis in human chromosomes, Trans. N. Y. Acad. Sci. 24: 395, 1962.
September, 1971 T h e J o u r n a l o[ P E D I A T R I C S
An inherited pericentric chromosomal inversion (46, inv3 [p-q+]) associated with skeletal anomalies A [amily is described in which the propositus and his mother possess identical skeletal anomalies of the fingers and toes. Cytogenetic investigation revealed an abnormal No. 3 chromosome in both peripheral lymphocytes and fibroblasts o[ these individuals. On the basis of morphologic, autoradiographic, and measurement data, this chromosome is interpreted as representing a pericentric inversion o/ a No. 3.
Maimon M. Cohen and Ronald G. Davidson BUFFALO~ N. Y.
A M o N G the structural chromosome rearrangements, pericentric inversions are relatively infrequent. Nonetheless, the published cases of autosomal pericentric inversions have involved chromosome groups A, ~-G B, 7 Cff "10 D, ~-~:~ a n d G14-1~ a n d include both sporadic and familial cases. This paper describes a family in which both mother a n d son were afflicted with identical skeletal anomalies of the extremities and show the first reported instance of a pericentric inversion in chromosome No. 3 (46, inv3 [p-q+]) 9
CASE REPORTS The propositus was a 3-1nonth-old, Caucasian male infant referred to the Division of Human From the Division o[ H u m a n Genetics, Department o[ Pediatrics, State University o[ New York at Buffalo School o[ Medicine, and Children's Hospital o[ Buffalo. Supported in part by a grant [rorn the United States Children's Bureau (Project No. 417). Reprint address: Mabnon M. Cohen, M.D., 86 Hodge Ave., Buffalo, N. Y. 14222. Vol. 79, No. 3, pp. 4.56-462
Genetics because of the presence of multiple malformations and a positive family history for deformities of the extremities. The infant's mother had a full-term, normal pregnancy preceded by several years of irregular menstrual periods and apparent sterility. She was treated with various hormone preparations during the year prior to conception, and from conception through the first few weeks of pregnancy she took clomiphene citrate (Clomid). Labor was complicated by premature rupture of the membranes followed by slow irregular labor and delivery by cesarean section 5 days later. There were no problems in the neonatal period. Physical examination at birth and at 3 months of age revealed the following anomalies: bilateral inferior colobomata of the irides, a high-arched palate, a thin upper lip with absent philtrum, low-set ears, a midline prominence of the forehead, a sclerosing capillary hemangioma on the anterior aspect of the left leg (less than one square inch in size), and marked anomalies of the hands and feet (Figs. l and 2). When the infant was 3 months of age, height and weight were between the fiftieth and seventyfifth percentiles, but the head circumference was
Volume 79 Number 3
Chromosomal inversion with skeletal anomalies
45 7
Fig. 1. Photographs of the hands and feet of the propositus and his mother~ illustrating syndactyly and absence of digits. A and B, Dorsal and palmar aspects of the infant's right hand. C and D, Dorsal and palmar aspects of the infant's left hand. E and F, The infant's feet. G and H. The mother's hands and feet. between the tenth and twenty-fifth percentiles. In addition, head control was absent and the infant was abnormally placid during the examination. Prognosis for normal mental development is guarded. Family history revealed the mother to have congenital anomalies of the hands and feet similar to those of the propositus (Fig. 1). She had no other detectable defects and seemed to be of normal intelligence. Other maternal relatives had minimal anomalies of the extremities:
A paternal first cousin of the mother was reported to have had polydactyly and a great aunt to have had 2 webbed toes; 2 of the mother's 3 sisters had unilateral clinodaetyly of the fi~th finger. The propositus is an only child. The father was raised in an orphanage and knows nothing about his family history. MATERIALS
AND METHODS
Cytogenetie studies. Cytogenetic studies were performed on 8 family members; the
458
Cohen and Davidson
The ]ournal o[ Pediatrics September 1971
Fig. 2. Radiographs of the hands and feet of the propositus. propositus, his parents and maternal grandparents, and his mother's 3 sisters. Chromosome preparations were obtained by means of a micromethod (Chromosome Medium 1A, Grand Island Biological Co., Grand Island, N. Y.) using 4 to 5 drops of whole blood as inoculum. At least 30 cells per individual were microscopically and/or photographically studied in detail. In addition, fibroblast cultures were propagated from skin biopsies obtained from the propositus and his mother. Cultures were harvested and slides prepared by slight modification of the method of Moorhead and associates? 6 Autoradiographic studies were performed on leukocyte cultures of the mother of the propositus. Tritiated thymidine (Schwartz Bioresearch Corporation, specific activity 3C per milIimole) was added to the cultures, at
a final concentration of 1 /xc per milliliter, for the final 5 hours of culture. Colcemide (0.05 /xg per milliliter) was added for the last 2 hours of incubation. Prepared slides were dipped in Kodak Nuclear Tract (NTB3) emulsion and incubated at 4 ~ C. for 10 days. After development and staining, 17 cells with moderate labeling and informative patterns were located and photographed. The silver grains were then reduced by using a 10 per cent solution of potassium ferricyanide (30 minutes) followed by 24 per cent sodium thiosulfate (severaI dips) and rinsing in distilled water. Those cells previously photographed were located and rephotographed without the overlying silver grains. In this way, a direct comparison was possible and the labeled chromosomes could be identified. Chromosome measurement. Chromosomal
Volume 79 Number 3
Chromosomal inversion with skeletal anomalies
459
Table I. Chromosomal measurement ratios and tests of significance based on data from 25 cells of both the propositus and his mother A. Derived ratios Length
..
Arm ratio
Subject
Normal 3/2
Inverted 3/2
Average B/2
Normal 3/2
Inverted 3/2
Average B/2
Prop*situs Mean S.D.
0.8457 0.0048
0.8569 0.0006
0.8059 0.0032
1.136 0.005
2.022 0.047
2.220 0.027
Mother Mean S.D.
0.8597 0.0054
0.8581 0.0006
0.8067 0.0025
1.138 0.001
2.058 0.124
2.247 0.256
B. t Tests . Test 3/2 vs. inverted 3/2 Inverted 3/2 vs. average B/2 ~Denotes
statistical significance
Length Propositus 0.76 - N.S. 4.10 ~
I
Arm ratio
Mother 0.01 - N.S. 4.634
Propositus 19.43 ~ 3.654
[
Mother 39.48 ~ 10.53 ~
at the 0.01 level of probability.
measurements were obtained from 25 cells of both the propositus and his mother. Length and a r m ratio measurements were derived as described by Cohen and associates ~8 from positive photographic prints (8 x 10 inches). T h e chromosomes measured included pairs No. 2 and 3 and the 4 to 5 (B) group. Length values were obtained for each chromatid arm of each chromosomal pair per cell. An average of the four B group chromosomes in the cell was taken to yield a representative 4-5 element. T o obviate intercell contraction differences, all values obtained were divided by the average length of chromosome No. 2 in that cell. T h e No. 2 pair was chosen since it is large, accurately identifiable in every cell, and possesses no obvious secondary constriction which might affect its length. RESULTS
K a r y o t y p i c findings. All 8 family members examined had a modal n u m b e r of 46 chromosomes. However, in the propositus and his mother, only one metacentric member of the No. 3 pair could be found (Fig. 3). I n addition, an extra chromosome with an arm ratio simulating a B group element was seen. This chromosome, however, appeared larger than the other B group chromosomes and
f17-TS)
'k _ ':i
~EXCHrOMOSOMeS
Fig. 3. Karyotype of the propositus. All chromosomes appear normal except for one member of the number 3 pair representing a pericentric inversion (arrow). A similar chromosome was present in the mother's karyotype. Note the small Y chromosome which was also observed in the father's karyotype. approximated the over-all length of the missing No. 3. This "marker" chromosome was considered to represent a pericentric inversion of the missing No. 3. A similar karyotypic abnormality was observed in the
460
Cohen and Davidson
Fig. 4. Autoradiographs and partial karyotypes of the group A and B chromosomes in 3 cells from the mother. The inversion chromosome (arrow) has a pattern similar to that of the normal No. 3 except that the late-labeling centrorneric area has been shifted. fibroblast cultures derived from the skin biopsies in both the propositus and his mother. Since this anomaly was present in all cells examined from both tissues (125 cells in each person), mosiacism is unlikely. All other family members examined had normal karyotypes. Also, the propositus possessed an inordinately small Y chromosome, approximately one half the length of the G group chromosome (Fig. 3). This small Y chromosome was also present in his father. Chromosome measurements. Statistical evaluation of the mensuration data (Table I) supported the concept of a pericentric inversion. The measurements for these chromosomes in both the propositus and his mother were not significantly different from each other. The statistical analyses (t test) indicate that, in both cases, there were no significant differences between the over-all length of the no~mal No. 3 chromosome and
The Journal o[ Pediatrics September 1971
the inverted No. 3 (t = 0.76 and 0.01 for propositus and mother, respectively). However, highly significant values (p < 0.01) were obtained when testing for: (1) length of the inversion chromosome versus the average of the B group chromosomes, (2) arm ratios of the normal and inversion No. 3's, and (3) arm ratio between the inversion and the average of the B(4-5) chromosomes. Therefore, although the total length of the inversion chromosome could not be distinguished from the normal No. 3, it was easily separated by arm ratio differences. In addition, this chromosome was discernible from the B group chromosomes both on the basis of length and arm ratio. Therefore, it appeared as a unique element in the karyotypes of both the propositus and his mother. Autoradiography. Autoradiographic findings of 20 informatively labeled cells derived from the mother's leukocytes also indicate that the marker is indeed an inverted No. 3. Fig. 4 illustrates partial karyotypes of 3 cells showing chromosomes of the A and B groups (Nos. 1-5). These late replication patterns indicate that only one normal No. 3, as described by Schmid 1~ and German, ~9 is present in each cell. The amount of label present over both the normal No. 3 and the inversion chromosome is quite comparable in all cells and falls within the limits of replication asynchrony observed within a pair of homologues. However, the intrachromosomal distribution of silver grains differs in the 2 chromosomes. The No. 3 pair usually has a concentration of grains over the centromere region which is apparently one of the last areas to replicate its DNA. Additionally, the distal portions of the arms are sometimes "hot." The inversion chromosome also illustrates this pattern, but even though the centromere has been shifted from its median position by the inversion, it is still late replicating. The distal portion of the 2 No. 3's, however, have similar labeling patterns. DISCUSSION'
Pericentric inversion is a chromosomal rearrangement not frequently encountered in
Volume 79 Number 3
Chromosomal inversion with skeletal anomalies
man. la Since almost all chromosomal groups have been involved in inversions, a wide range of phenotypic deviation has been associated with this type of aberration. The family described in this report represents the first in which the No. 3 pair is involved; it is also the first instance in which a striking skeletal abnormality, limited only to the carriers of the anomaly, has been reported. T h a t the abnormal chromosome observed indeed represents a pericentric inversion is supported by evidence from morphology, mensuration, and autoradiography. T h e karyotypes of both the propositus and his mother, although possessing a modal n u m b e r of 45 chromosomes, are obviously missing one m e m b e r of the No. 3 pair. It is fortunate that No. 3 is easily identifiable in all cells and that the chromosome involved in the inversion is discernible. T h e inversion chromosome is the same length as a normal No. 3, but its arm ratio is aberrant. This identification is borne out by the measurement data on both the propositus and his mother. T h e total length of the abnormal No. 3 is not distinguishable from that of the normal No. 3, but is significantly greater than the length of the B group chromosomes. W h e n the parameter of arm ratio is used, the inverted chromosome is distinctive from all other elements measured. T h e autoradiographs indicate maintenance of the latereplicating areas of a normal No. 3 in the centromere and distal regions, but in an inverted order. Therefore, the fact that the over-all length of this chromosome has not been altered, but the centromere position and arm ratio have been changed, as documented by morphology, mensuration, and autoradiography, strongly supports the concept that the abnormal chromosome represents a pericentric inversion. The problem of causality is raised since the propositus and his mother have identical skeletal abnormalities and the chromosomal aberration. It is tempting to speculate that since no other relatives of the family are similarly affected, either clinically or chromosomally, the inversion is responsible for the skeletal deformities. Since the mother of
461
the propositus does not exhibit mosaicism in either blood or skin, the event most likely occurred prezygotically in gametogenesis of either one of the grandparents. However, one cannot rule out the possibility that the occurrence of the chromosomal and skeletal anomalies is coincidental. We appreciate the excellent technical assistance of Mrs. Clara Lockwood, Mrs. Claudia Hastings, and Miss Pamela Borchert. REFERENCES
1. Lele, K. P., Dent, J., and Delhanty, J. D. A.: Chromosome studies in 5 cases of coloboma of the iris, Lancet 1: 576, 1965. 2. Carr, D. H.: Chromosome anomalies, Trans. Amer. Ass. Genitourin. Surg. 54" 9, 1962. 3. Grouchy, J., Emerit, I., Corone, P., Vernant, P., Lamy, M., and Soulie, P.: Inversion pericentrique probable du chromosome no. 2 et malformations congenitales chez un garcon, Ann. Genet. 6: 21, 1963. 4. Hooft, C., Coetsier, H., and Oyre, H.: Syndrome de Turner et inversion pericentrique dn chromosome no. 2 [45,X,2(p+q-)], Ann. Genet. ll" I81, 1968. 5. Weitkamp, L. R., Janzen, M. K., Guttoremsen, S. A., and Gershowitz, H.: Inherited pericentric inversion of chromosome number two: A linkage study, Ann. Hum. Genet. 33: 53, 1969. 6. Mikelsaar, A. V. N., Ananjer, E. V., and Gindlis, V. M.: Probable pericentric inversion in chromosome number 1 in a female child [46,XX,inv(lp+q-)], Humangenetik 9: 316-324, 1970. 7. Morishima, A., Liu, N., and Grumbach, M. M.: Multiple congenital anomalies associated with probable pericentrie inversion of number 4 and mosaicism in an asymptomatie mother, J. PEmAT. 65: 1096, 1964. 8. Grouchy, J., Frezal, J., Bitan, A., Jammer, M. L., and Lamy, M.: Ramaniement d'un chromosome X, 6-12 chez nn trisomique 21, Ann. Genet. 8: 67, 1965. 9. Jacobs, P. A., Cruickshank, G., Faed, M. J. W., Frackiewicz, A., Robson, E. B., Harris, H., and Sutherland, I.: Pericentric inversion of a group C autosome: A study of three families, Ann. Hum. Genet. 31: 219, 1967. 10. Keutel, J., and Schubert, W.: Strukturanomalie [inv(t>-q+) ?] eines chromosoms der gruppe C + X bei einem jungen mit multiplen dysplasien und dissozlationen der psychischen entwicklung, Humangenetik 7: 119, 1969. 11. Chandra, H. S., and Hungerford, D. A.: An aberrant autosome (I3-15) in a human female and her father, both apparently normal, Cytogenetics 2: 34, 1963. 12. Cohen, M. M., Capraro, V. J., and Takagi', N.: Pericentric inversion in a group D ehro-
462
Cohen and Davidson
mosome (13-15) associated with amenorrhea and gonadal dyspenesls, Amer. Hum. Genet. 30: 313, 1967. 13. Crandall, B. F., and Sparkes, R. S.: Pericentrie inversion of a number 15 chromosome in nine members of one family, Cytogenetics 9: 307, 1970. 14. Schmid, W.: Pericentric inversions: Report on two malformation cases suggestive of parental inversion heterozygosity, J. Genet. Hum. 16: 89, 1967. 15. Soudek, D., Laxova, R., and Adawek, R.: Pericentric inversion in a family with a 21/22 translocation, Cytogenetics 7: 108, 1968.
The Journal of Pediatrics September 1971
16. Moorhead, P. S., Mowell, P. G., Mellman, W. J., Battips, D. M., and Hungerford, D. A.: Chromosome preparations of leukocytes cultured from human peripheral blood, Exp. Cell Res. 20: 613, 1960. 17. Schmid, W.: DNA replication patterns of human chromosomes, Cytogenetlcs 2: 175, 1963. 18. Cohen, M. M , Shaw, M. W., and MacCluer, J. W.: Racial differences in the length of the human Y chromosome, Cytogenetics 5: 34, 1966. 19. German, J. L.: DNA synthesis in human chromosomes, Trans. N. Y. Acad. Sci. 24: 395, 1962.