No. 2] Proc. Japan Acad., 53 (1977) 79
22. Banding Analyses o f Pericentric Inversion, mv (9), in Two Families
By Yukimasa SHIRAISHI*> and Sajiro MAKING, M. J. A.**) (Communicated Feb. 12, 1977)
Pericentric inversion in chromosome No. 9 has been noted as one of polymorphic variations of the human chromosomes (Jacobs et al.
1967 ; Wahrman et al. 1972 ; De la Chapelle et al. 1974 ; Hansmann 1976) . It was shown that morphologically the cytogenetic profile of this anomaly was almost identical in all individuals described so far, without showing interfamilial differences. Based on the G-banding analysis, De la Chapelle et al. (1974) described the presumptive break points as inv (9) (p1 q13). Thus, the exact point of breakage in the short arm has remained uncertain, while the break point in the long arm was difinitely identified as q13. We have chanced to study two patients with Pericentric inversion No. 9 who had experienced several spontaneous abortions. The present study deals with banding analyses of the chromosomes in cultured lymphocytes in the two patients and their mothers, utilizing G- and C-banding techniques.
Patients and methods. Two cases (24- and 36-year-old females) from two different families carrying pericentric inversion of No. 9 concerned here were phenotypically normal but had experienced abortions several times. Their mothers who were healthy and had no experience of abortion, were found to carry a morphologically similar anomaly, inv (9). Heparinized blood cultures (72-hr) with PHA-containing RPMI 1640 medium and 10% fetal calf serum provided chromosomal samples. Trypsin G-banding technique accord- ing to Shiraishi and Yosida (1973), and the BSG method by Sumner
(1972) were applied to G- and C-bands analyses.
Results and discussion. The pictures of the No. 9 chromosome pair obtained from the two families according to the conventional staining and C- and G-band techniques are shown in Fig. 1. So far as the banding patterns presented by us are shown, the morphologi- cal appearance of the Pericentric inv (9) was identical in the four subjects involving two daughters and their mothers. Cells displaying long and narrow chromosomes were most suitable for analysis of bands in the inv (9) chromosome. Evidence was provided that breaks
*' Department of Anatomy, School of Medicine, Kanazawa University, Kanazawa.
**' Chromosome Research Institute
, Hokkaido University, Sapporo.
80 Y. SHIRAISHI and S. MAKING [Vol. 53,
occurred in the region of p11 of the short arm and q13 of the long arm of the No. 9, and that the part of the chromosome between these two bands (p11 and q13) was inverted resulting in the formation of
pericentric inv (9) (Figs. 1 and 2). De la Chapelle et al. (1974) failed to determine the exact break-point in the short arm, showing the presumptive break-point as p13, whereas our Figs. 1 and 2 clearly demonstrated that the band 9p12 did not lie in the long arm but was present in the short arm. This has led us to conclude that pen- centric inv (9) is to be described as inv (9) (p11 q13). Patient I
appeared to show occasional chromosome breaks (7%), as well as a Robertsonian translocation-type isochromosome of the long arm of the inverted chromosome, inv (9). Since one homologue of the pair No. 9 is normal, that isochromosome seems to be produced as a result of duplication of the long arm of the inverted chromosome. Fig. 3 did not show the p12 band in the long arm of the inverted chromo- some. This finding is also important for the present conclusion as inv (9) (p11 q13). The other three subjects concerned showed no such chromosomal changes.
Fig. 1. Conventional staining, and C- and G-banding pictures of chromo- some pair No. 9 with pericentric inversion, observed in two patients.
a: patient I, b: patient II.
Fig. 2. Diagramatic representation of pericentric inv (9).
Fig. 3. Isochromosome of long arm of the inverted chromosome inv (9), from patient I.
No. 2] Banding Analyses of Pericentric Inversion, Inv (9) 81 The measuremental data given in Table I indicate the absence of intercellular, interindividual, or interfamilial differences in length or centromere index between the normal No. 9 chromosome and its inverted homologue. Furthermore, the length of the inverted ._chromo- some was apparently identical with that of its normal homologue, and this suggests no loss of material. The measurements resulted in a mean centromere index as 34.64±0.27 for the normal No. 9, and as 46.19±0.26 for its inverted homologue. This finding is compatible with the break points indicated in the diagram (Fig. 2). On this respect, our feature agrees with that of De la Chapelle et al. (1974).
Many cases studied by banding techniques indicate that the localization of break points of breaks and rearrangements is non- random : weakly staining areas are involved rather often in the break points in contrast to deeply staining bands. A corresponding feature was observed in the present cases.
Phenotypically, the cases with pericentric inv (9) demonstrated in familial studies are apparently normal, though there are some who carry clinical abnormalities. The patients with similar types of in- version in chromosome No. 10 have been known to show different phenotypic anomalies (De la Chapelle et al. 1974). Our two patients had several spontaneous abortions, while their mothers had no such experiences. Further investigations of inv (9) with sufficient sam- ples are needed in order to assess a certain correlation between pheno- typic or clinical constitutions and chromosome aberrations.
This work was supported in part by grants from the Ministry of Education of Japan (No. 854138).
Table I. Measuremental data of chromosome pair No. 9
References
De la Chapelle, A., Schroder, K., Stenstrand, K., Fellman, J., Herva, R., Saarni, M., Anttolainen, I., Tallila, I., Tervila, L., Husa, L., Tallqvist, G., Robson, E. B.,
Cook, P. J. L., and Sanger, R. (1974) : Am. J. Hum. Genet., 2'6, 746-766.
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82 Y. SHIRAISHI and S. MAKINO [Vol. 53, Hansmann, I. (1976) : Human Genet., 31, 247-262.
Shiraishi, Y., and Yosida, T. H. (1973) : Jap. J. Genet., 4$, 11-17.
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Cytogenetics,
