SHORT COMMUNICATIONS DEGENERATION OF THE ADRENAL X-ZONE IN
Tfm MICE
WITH INHERITED INSENSITIVITY TO ANDROGENS J. G. M. SHIRE Institute
of Genetics, University of Glasgow, Glasgow,
Gli 5JS
(Received 5 April 1976) In house mice the
juxtamedullary
X-zone of the adrenal cortex involutes
rapidly at puberty in
males, and during their first pregnancy in females (Chester Jones, 1957). In virgin females the zone degenerates more slowly, at a rate dependent on genotype (Shire & Spickett, 1968). It is
generally considered that these developmental changes are brought about by androgens secreted by the gonads or by the zona fasciculata (Chester Jones, 1957; Chirvan-Nia, 1967). Consequently the X-zone should persist in Tfm mutant mice, whose cells are insensitive to androgens because of defects in their steroid receptors (Lyon & Hawkes, 1970; Bardin, Bullock, J\l=a"\nne& Jacob, 1975). The mutant is sex-linked. Tfm/Y mice are externally female in phenotype, lack a reproductive tract, but have abdominal testes (Bardin, Bullock, Sherins, Mowszowicz & Blackburn, 1973). Carrier females (Tfm/+) are fully fertile. Such females were crossed to males of normal phenotype. The presence, in repulsion, of a closely-linked coat-colour gene, Tabby (Ta), in these females enabled their offspring to be divided into four, equally frequent,
classes. These were: normal males (++/Y), normal females (+Ta/++), females for Tfm (Tfm +/++), and feminized males (Tfm+/Y). After weighing the mice, the adrenals of all the offspring which had the external appearance of females were fixed in formol\p=n-\saline.Frozen sections stained with Sudan Blue were scored for the extent of fatty degeneration of the X-zone (Shire & Spickett, 1968). The litters measured were from 5 to 18 weeks old. Since body weight was found to be a better indicator of developmental status than age in an earlier study of the X-zone of mice (Shire & Spickett, 1968), the mice of each genotype were divided into groups of similar weight. Figure 1 shows the mean extent of degeneration for each group. The genetic constitution of the stock of mice resulted in the early onset of degeneration of the X-zone in the normal females. Heterozygous carriers of Tfm were similar to normal females in the onset and progression of X-zone degeneration. Fatty degeneration of the X-zone occurred in the adrenals of the Tfm/Y mice, despite their insensitivity to androgen. Thus androgens are not essential for X-zone degeneration in phenotypic females, and other mechanisms, such as the withdrawal of trophic stimuli, must be involved. Since degeneration did not occur as rapidly in Tfm/Y as in their androgen-sensitive sibs, androgens may play an accessory role in degeneration in normal females. In all three genotypes the X-zone eventually degenerated com¬ pletely. Amongst 11 mice, aged between 22 and 34 weeks, from the cross Tfm +/++ x ++/Y, the mean extent of degeneration was 98+4 (S.E.M.) % in five feminized mice and 100% in six female mice. Degeneration was as evenly distributed throughout the X-zone in female Tfm/+ hétérozy¬ gotes as it was in +/+ homozygotes and Tfm hemizyotes. This suggests that either X-inactivation clones (Tettenborn, Dofuku & Ohno, 1971; Lyon, 1972) in the adrenal cortex contain very few cells or that androgen does not act directly on the X-zone but elsewhere, perhaps in the hypothalamus. A few Tfm/+ hétérozygotes were bred which were also hétérozygotes for the sex-reversing gene, Sxr (Cattanach, Pollard & Hawkes, 1971). Such mice have testes and a male phenotype,
phenotypic
heterozygous
'
100-1
75
4
50
4
(2) (4)
(2)0)
(2)
25 H
oJ
32
36
40
44
Body weight (g) Fig. 1. The extent ot tatty degeneration of the X-zone in mice of three genotypes. Open bars, normal females; stippled bars, Tfm/+ hétérozygotes; solid bars, Tfm/Y feminized males. Each bar represents the mean value for mice whose body weights were within 2 g of the indicated weight. The S.E.M. is indicated by a vertical line. Numbers of mice in each group in parentheses. two X
chromosomes and no Y chromosome. The adrenals of these animals, Tfm/+ female hétérozygotes, are mosaics of cells sensitive and insensitive to testosterone. However, after puberty, their adrenals lacked an X-zone completely; only a capsule separated the medulla from the zona fasciculata. Thus in phenotypic males, as well as in phenotypic females, degeneration of the X-zone is not directly dependent on androgens, otherwise half the cells in the X-zone should have remained intact in the hétérozygotes.
despite having
like those of the
REFERENCES
Bardin, C. W., Bullock, L. P., Jänne, O. & Jacob, S. T. (1975). Journal of Steroid Biochemistry 6, 515-520. Bardin, C. W., Bullock, L. P., Sherins, R. J., Mowszowicz, I. & Blackburn, W. R. (1973). Recent Progress in
Hormone Research 29, 65-110. Cattanach, B. M., Pollard, C. E. & Hawkes, S. G. (1971). Cytogenetics 10, 318-337. Chester Jones, I. (1957). The Adrenal Cortex, Ch. 1. Cambridge University Press. Chirvan-Nia, P. (1967). Annales de la Faculté des Sciences de l'Université de Clermont 34, 1-235. Lyon, M. F. (1972). Biological Reviews 47,1-36. Lyon, M. F. & Hawkes, S. G. (1970). Nature 227, 1217-1219. Shire, J. G. M. & Spickett, S. G. (1968). General and Comparative Endocrinology 11, 355-365. Tettenborn, U., Dofuku, R. & Ohno, S. (1971). Nature New Biology 234, 37-40.
Tfm MICE
WITH INHERITED INSENSITIVITY TO ANDROGENS J. G. M. SHIRE Institute
of Genetics, University of Glasgow, Glasgow,
Gli 5JS
(Received 5 April 1976) In house mice the
juxtamedullary
X-zone of the adrenal cortex involutes
rapidly at puberty in
males, and during their first pregnancy in females (Chester Jones, 1957). In virgin females the zone degenerates more slowly, at a rate dependent on genotype (Shire & Spickett, 1968). It is
generally considered that these developmental changes are brought about by androgens secreted by the gonads or by the zona fasciculata (Chester Jones, 1957; Chirvan-Nia, 1967). Consequently the X-zone should persist in Tfm mutant mice, whose cells are insensitive to androgens because of defects in their steroid receptors (Lyon & Hawkes, 1970; Bardin, Bullock, J\l=a"\nne& Jacob, 1975). The mutant is sex-linked. Tfm/Y mice are externally female in phenotype, lack a reproductive tract, but have abdominal testes (Bardin, Bullock, Sherins, Mowszowicz & Blackburn, 1973). Carrier females (Tfm/+) are fully fertile. Such females were crossed to males of normal phenotype. The presence, in repulsion, of a closely-linked coat-colour gene, Tabby (Ta), in these females enabled their offspring to be divided into four, equally frequent,
classes. These were: normal males (++/Y), normal females (+Ta/++), females for Tfm (Tfm +/++), and feminized males (Tfm+/Y). After weighing the mice, the adrenals of all the offspring which had the external appearance of females were fixed in formol\p=n-\saline.Frozen sections stained with Sudan Blue were scored for the extent of fatty degeneration of the X-zone (Shire & Spickett, 1968). The litters measured were from 5 to 18 weeks old. Since body weight was found to be a better indicator of developmental status than age in an earlier study of the X-zone of mice (Shire & Spickett, 1968), the mice of each genotype were divided into groups of similar weight. Figure 1 shows the mean extent of degeneration for each group. The genetic constitution of the stock of mice resulted in the early onset of degeneration of the X-zone in the normal females. Heterozygous carriers of Tfm were similar to normal females in the onset and progression of X-zone degeneration. Fatty degeneration of the X-zone occurred in the adrenals of the Tfm/Y mice, despite their insensitivity to androgen. Thus androgens are not essential for X-zone degeneration in phenotypic females, and other mechanisms, such as the withdrawal of trophic stimuli, must be involved. Since degeneration did not occur as rapidly in Tfm/Y as in their androgen-sensitive sibs, androgens may play an accessory role in degeneration in normal females. In all three genotypes the X-zone eventually degenerated com¬ pletely. Amongst 11 mice, aged between 22 and 34 weeks, from the cross Tfm +/++ x ++/Y, the mean extent of degeneration was 98+4 (S.E.M.) % in five feminized mice and 100% in six female mice. Degeneration was as evenly distributed throughout the X-zone in female Tfm/+ hétérozy¬ gotes as it was in +/+ homozygotes and Tfm hemizyotes. This suggests that either X-inactivation clones (Tettenborn, Dofuku & Ohno, 1971; Lyon, 1972) in the adrenal cortex contain very few cells or that androgen does not act directly on the X-zone but elsewhere, perhaps in the hypothalamus. A few Tfm/+ hétérozygotes were bred which were also hétérozygotes for the sex-reversing gene, Sxr (Cattanach, Pollard & Hawkes, 1971). Such mice have testes and a male phenotype,
phenotypic
heterozygous
'
100-1
75
4
50
4
(2) (4)
(2)0)
(2)
25 H
oJ
32
36
40
44
Body weight (g) Fig. 1. The extent ot tatty degeneration of the X-zone in mice of three genotypes. Open bars, normal females; stippled bars, Tfm/+ hétérozygotes; solid bars, Tfm/Y feminized males. Each bar represents the mean value for mice whose body weights were within 2 g of the indicated weight. The S.E.M. is indicated by a vertical line. Numbers of mice in each group in parentheses. two X
chromosomes and no Y chromosome. The adrenals of these animals, Tfm/+ female hétérozygotes, are mosaics of cells sensitive and insensitive to testosterone. However, after puberty, their adrenals lacked an X-zone completely; only a capsule separated the medulla from the zona fasciculata. Thus in phenotypic males, as well as in phenotypic females, degeneration of the X-zone is not directly dependent on androgens, otherwise half the cells in the X-zone should have remained intact in the hétérozygotes.
despite having
like those of the
REFERENCES
Bardin, C. W., Bullock, L. P., Jänne, O. & Jacob, S. T. (1975). Journal of Steroid Biochemistry 6, 515-520. Bardin, C. W., Bullock, L. P., Sherins, R. J., Mowszowicz, I. & Blackburn, W. R. (1973). Recent Progress in
Hormone Research 29, 65-110. Cattanach, B. M., Pollard, C. E. & Hawkes, S. G. (1971). Cytogenetics 10, 318-337. Chester Jones, I. (1957). The Adrenal Cortex, Ch. 1. Cambridge University Press. Chirvan-Nia, P. (1967). Annales de la Faculté des Sciences de l'Université de Clermont 34, 1-235. Lyon, M. F. (1972). Biological Reviews 47,1-36. Lyon, M. F. & Hawkes, S. G. (1970). Nature 227, 1217-1219. Shire, J. G. M. & Spickett, S. G. (1968). General and Comparative Endocrinology 11, 355-365. Tettenborn, U., Dofuku, R. & Ohno, S. (1971). Nature New Biology 234, 37-40.
