HERITABLE VARIATION IN THE LENGTH OF THE Y CHROMOSOME

18

HERITABLE VARIATION IN THE LENGTH OF THE Y CHROMOSOME C. E. BLANK Wales, Ph.D. Lond.

AUDREY BISHOP B.Sc. Brist.

M.B.

LECTURER IN MEDICAL GENETICS

SCIENTIFIC OFFICER DEPARTMENT OF

GENETICS,

THE

UNIVERSITY, SHEFFIELD

H. HUNTER M.B.

Lond.,

D.P.M.

MEDICAL SUPERINTENDENT BALDERTON

HOSPITAL,

NR.

NEWARK, NOTTINGHAM

THE normal Y chromosome in man has been described shorter than, the same size as, or longer than the autosomes of the 21-22 group (Chu and Giles 1959, Levan and Hsu 1959, Human Chromosome Study Group 1960). A long Y chromosome in a phenotypically normal male has been reported by Bender and Gooch (1961). Jacobs and Harnden (cited by Penrose 1961) have observed a long Y chromosome in an otherwise unremarkable as

mongol. Heritable variation in the length of the Y chromosome exists in several organisms without causing phenotypic abnormality (Swanson 1958) and the same may be true in man. If variations in the length of the Y chromosome are inherited, it might be expected that Y chromosomes derived from a common ancestor would tend to be of the same length. This would be especially noticeable where extremes of length were involved.

findings in a male mongol, his phenobrother, and a father and son, also phenotypically normal, who were said to be distant relatives of the propositus. We report our typically normal

Material and Methods

Family Data The propositus.-A 47-year-old male mongol with most of the classical signs of mongolism (fig. 1), of asthenic build, and with frontal balding. Chest, axillary, and pubic hair was sparse, but of male distribution. The right testicle was very small and

Fig. 2-Karyotype of the propositus. There

The extra chromosome is con47 chromosomes. ventionally referred to as an extra 21, although it is usually not possible to distinguish between chromosome pair 21 and chromosome pair 22. The Y chromosome is very long. are

tion of the method of Moorhead et al. (1960) and skin-biopsy specimens were cultured by the method of Harnden (1960). We chose for analysis metaphase and prophase plates which clearly showed the Y chromosome’s characteristic shape with its long arms lying parallel to each other. The cells were photographed and the chromosomes measured. A control series was derived from males without demonstrable chromosome

abnormality.

the left testicle undescended. He had an i.Q. of less than 30 (Terman and Merrill) and was hallucinated. A.-56 years old and a brother of the propositus. There was early frontal balding and chest, back, abdomen, and limbs were thickly covered with long dark hair. His physique was otherwise unremarkable. He was thought to be of average intelligence and was unmarried. B.-B. was said (by A.) to be a distant relative of the propositus; each had the same surname, andhad ancestors living in the same parish and working in the same trade. We have, however, not been able to obtain documentary proof of this relationship. B. was a well-

preserved 78-year-old hair

was

not

man.

excessive.

Body

He had

and a daughter. C.-47 years old and a son of B. Body hair was not excessive and his physique was unremarkable. He had two sons. two sons

Methods Fig. 1-The propositus: male mongol.

a

from peripheral cultured by a modifica-

Leucocytes blood

were

Fig. 3-Karyotype of A., A long Y chromosome is

a

brother of the propositus.

again apparent.

19

Results of The karyotype the propositus (fig. 2) is that of a male mongol with the standard trisomic condition. The karyotypes of A. (fig. 3), B., and C. are those of normal

males. Measurements of the Y chromosome in this family are a control series in the A was present Y chromosome table. long accompanying

summarised and compared with

COMPARISON OF RELATIVE LENGTHS OF THE Y CHROMOSOME IN THE FAMILY DESCRIBED IN THE TEXT WITH THOSE IN A CONTROL SERIES

individual

with

Y chromosome whose chromatin content noticeably different from the The normal. family described by us may fall into this studied by Chu and category. Possibly in the Giles, Levan and Hsu, and the Human Chromosome Study Group, there were different frequencies of chromosomes with differing chromatin content. Nevertheless, some, if not all, of the reported variation in length may be due to differences of technique and of

(or family)

a

was

populations

interpretation. Extreme variation in chromatin

content

of this chromo-

occasionally abnormal fcetal developevidence of this has yet to be ment, although unequivocal put forward. In this connection it is significant that the patient, described by Hauschka et al. (1962), who was reported to have two Y chromosomes was a fertile male without serious physical defect. Conen et al. (1961) described an extremely small Y chromosome in a patient with both testicular and ovarian tissue and presumed XO/X" y " mosaicism. This patient had clinical features similar to those described by Hirschhorn et al. (1960) in an XO/XY mosaic. The abnormalities of sexual development in these patients can be attributed to sexsome

cause

may

to Y chromosomes deficient in chromatin. Vaharu et al. (1961) described a patient with failure of growth, developmental retardation, and an enlarged clitoris. Her karyotype was believed to be 45 chromosomes plus a " fragment ", and contained a normal complement of autosomes with only The fragment of chromatin may one X chromosome. a of the Y chromosome. In this represent portion case, the gonads were not examialed, and a mosaic state cannot be excluded since only the one tissue was studied. Of three males with oligospermia or azoospermia studied by Wijck et al. (1962), one was reported to have a short Y chromosome, another a long Y chromosome, and the third to be a mosaic with some cells containing a normal Y chromosome and others containing a long one. Unfortunately, there was no report on the male relatives of these three patients. In a family described by Muldal and Ockey (1961), three of the four members thought to have a " deleted " Y chromosome also had hypospadias. On this evidence alone, it is not possible to be sure that the short Y chromosome contributed to the origin of the hypospadias; the association may have been fortuitous. Variation in the relative length of a chromosome may reflect differences in chromatin content, in chromosomal behaviour, or in both. Little attention has yet been paid to differences in human chromosomal behaviour during cell division. In some of the cases mentioned above, the variation in Y-chromosome length may reflect differences simply in chromosomal behaviour and not in chromatin content. Preliminary analysis suggests that, in the family we have described, the increased length of the Y chromosome at metaphase may be due, partly or wholly, to a difference in the degree of contraction of the chromosome during cell division. This possibility is being more fully

chromosomal mosaicism rather than

in

peripheral blood taken from the Y chromosome was also present in a culture derived from his brother. Long Y chromosomes were also seen in cultures of peripheral blood and skin obtained from B. and C. B. and C., father and son, were believed to be related to the propositus and to possess a Y chromosome derived from an ancestor common to both branches of the family; but this had not been proved. Therefore, in tests of significance (see table) B. and C. are considered separately from A. and the two

cultures of

propositus. A long

propositus. Several factors affect the length and shape of chromoin tissue-culture-e.g., the particular stage in metaphase in which they are examined, the method of pretreatment, and the method of preparation for cytological study. Because the Y chromosome shows differential contraction (allocycly) the length of this chromosome relative to that of the total chromosome complement is particularly variable, even between cells of the same preparation. Nevertheless, in the family described above, long Y chromosomes have been consistently demonstrated on different occasions, in different tissues, and in specimens from related individuals. It is concluded that, in this family, the length of this chromosome is a heritable somes

characteristic. Discussion The Y chromosome in man is heterochromatic. Deficiencies or duplications of heterochromatic segments are thought to have far less harmful effects than deficiencies or duplications of euchrQmatic segments of the same size (Pontecorvo 1944). It would therefore not be surprising to find an occasional phenotypically normal

investigated. Summary A

long mongol,

Y chromosome has been described in a male his phenotypically normal brother, and a

father and

believed children.

to

son

(also phenotypically normal) who

be related

to

them.

These last

two

were

had

20 It has been shown that Y-chromosome length is variable and heritable. A long Y chromosome is not necessarily associated with developmental anomaly. We are grateful to the members of this family for their kind cooperation. We are also indebted to Dr. Michael Casey and Dr. Mary Lord for their help in obtaining samples of blood from members of the family and for selecting suitable preparations for a control series. This work is assisted by a grant from the Medical Research Council. Some of the equipment was lent to us by Messrs. Smith, Kline, & French, and other equipment was obtained with a grant from the Mental Health Research Fund. REFERENCES

Bender, M. A., Gooch, P. C. (1961) Lancet, ii, 463. Chu, E. H. Y., Giles, N. H. (1959) Amer. J. hum. Genet. 11, 63. Conen, P. E., Bailey, J. D., Allemang, W. H., Thompson, D. W., Ezrin, C. (1961) Lancet, ii, 294. Harnden, D. G. (1960) Brit. J. exp. Path. 41, 31. Hauschka, T. S., Hasson, J. E., Goldstein, M. N., Koepf, G. F., Sandberg, A. A. (1962) Amer. J. hum. Genet. 14, 22. Hirschhorn, K., Decker, W. H., Cooper, H. L. (1960) New Engl. J. Med. 263, 1044. Human Chromosome Study Group (1960) J. Hered. 51, 214. Levan, A., Hsu, T. C. (1959) Hereditas, Lund. 45, 665. Moorhead, P. S., Nowell, P. C., Mellman, W. J., Battips, D. M., Hungerford, D. A. (1960) Exp. Cell Res. 20, 613. Muldal, S., Ockey, C. H. (1961) Lancet, ii, 601. Penrose, L. S. (1961) Brit. med. Bull. 17, (no. 3), 184. Pontecorvo, G. (1944) Nature, Lond. 153, 365. Swanson, C. P. (1958) Cytology and Cytogenetics. New York. Vaharu, T., Patton, R. G., Voorhess, M. L., Gardner, L. I. (1961) Lancet, i, 1351. van Wijck, J. A. M., Tijdink, G. A. J., Stolte, L. A. M. (1962) ibid. i, 218.

ABSENCE OF THE Y CHROMOSOME

(XO SEX-CHROMOSOME CONSTITUTION) IN A HUMAN INTERSEX WITH AN EXTRA-ABDOMINAL TESTIS

LEONARD ATKINS M.D. Johns Hopkins ERIC ENGEL M.D. Geneva

With the technical assistance of DAVID A. FLORY, B.A. Harvard, and MIREILLE ENGEL From the Departments of Pathology and Medicine of Harvard Medical School, and the James Homer Wright Pathology Laboratories and the Department of Medicine (Endocrine and Thyroid Units) of the Massachusetts General Hospital, Boston, Mass.

To date, at least ten examples of a testis in patients without a demonstrable Y chromosome have been These include seven true hermaphrodites described. (Hungerford et al. 1959, Harnden and Armstrong 1959, Ferguson-Smith et al. 1960b, de Assis et al. 1960, Gordon et al. 1960, Sasaki and Makino 1960) and a male pseudohermaphrodite (Shah et al. 1961). In addition, Bloise et al. (1960) have reported a patient with an XO sex-chromosome constitution who had a rudimentary uterus, an intra-abdominal embryonic testis, and other congenital defects; and Oikawa and Blizzard (1961) studied a phenotypical male with features of Turner’s syndrome, an intra-abdominal testis, and an abnormal female karyotype in which 1 of the 2 Xs was probably an isochromosome for the long arm of an X chromosome. Our present report concerns a phenotypical intersex with a testis and an XO sex-chromosome constitution.

Case-report The propositus, a Negress, was born illegitimately in 1936 of a father aged 16 and a mother aged 15. The family history is sketchy, but as far as is known there are no other siblings, and there is no familial genital disorder. Abnormal genitalia were noted at birth, and the child, who appeared " mostly female ", was brought up as a girl. She sat up at 6-7 months, walked at 14 months, and talked at 1 year. She was withdrawn, preferred to play with boys, and was

somewhat slow in her schoolwork. A 13 she was admitted to the Massachusetts General Hospital because the phallus had grown larger during the previous 5 or 6 years. At the time of admission to hospital the patient was

small, measuring 4

ft.

5

in.

and

weighing 4 st. 91/ 21b. (651/2 lb.). No breast

tissue was There was

palpable. no

axillary hair, and

only a little pubic The hands hair. and feet were large Fig. i-View of phallus and gonad in left labial fold after biopsy of the gonad and The and long. before removal. which phallus, measured 4 cm. long and 1-1-5 cm. in diameter, resembled a penis, with a definite glans and prepuce adherent to its undersurface by a chordee. Extending from beneath the glans was a mucosalined groove that passed posteriorly in the midline for 2-5 cm., and ended in a semilunar urethral orifice measuring 0-5 cm. in diameter. Labial folds partially overlapped the phallus. A gonad that could be easily moved upward into the inguinal canal was present in the left labial fold (fig. 1), and there was a small vagina. The cervix could not be seen. Rectal examination did not reveal a prostate gland. X-ray films of the ’hands showed bone development corresponding to 103/4 years (Todd’s standards for females); the metacarpals and proximal phalanges were unusually long, the cortices were thin, and the trabeculations were coarse. A film of the pelvis showed a spina bifida occulta of the sacrum. An intravenous pyelogram was normal; and the urinary bladder and the distal portions of the ureters appeared normal. The i.Q. was 55, and psychological testing indicated a female role. Exploratory laparotomy revealed a small prepubertal uterus and a right-sided fallopian tube, with a well-developed round ligament on the right. There was no gonad near the right tube. No structure resembling a gonad could be found on the left side, and the left round ligament was rudimentary. A thorough search revealed nothing that could be identified as a vas deferens on either side. The kidneys and ureters were normal. The adrenal glands were not palpable. There was incomplete rotation of the ascending colon; the cxcum lay high and was completely bound down. Incision into the left labium revealed a tunica vaginalis enveloping a testis that measured 2 cm. in its longest diameter; it was attached to some fimbriated tubal tissue. No vasa or epididymis was identified, but the testis was grossly normal. Incision into the other labium showed only a pea-sized nodule of fat. It seemed best for the patient to emphasise the female characteristics, and to remove the testis before androgen production started. The phallus was cosmetically resected. Microscopic examination showed a partially mature testis with definitely recognisable germ-cells, and no spermatogenesis. In some tubules the Sertoli cells were fully developed, whereas in others they were immature. Well-developed interstitial cells, some of which were highly vacuolated, were readily found (figs. 2 and 3). After operation the patient was given no oestrogen therapy for 8 months, at the end of which the urinary gonadotropin excretion was raised to 52 mouse units per 24 hours. Nevertheless, no gonadal response was evident. Breast tissue was entirely lacking, and vaginal smears showed no cestrin effect. The 17-ketosteroid excretion, which had been 1-9 mg. per no