Exp. Anim. 35(1), 109-115, 1986

Note

Prolongation of the Life of a -deficient Mouse, the Reeler

Masaharu TOGO*, Atsushi NUMAZAWA**, Seigo SHUMIYA and Minoru OSANAI

Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo 173, Japan

(Received 24 May 1985/Accepted 3 September 1985)

Although the reeler, an autosomal recessive mutant mouse with the abnormality of lamination in the central nervous system, died about 3 weeks of age when fed ordinary laboratory chow, this mouse could grow up normally and prolong its destined, short lifespan to 50 weeks and more when given assistance in taking paste food and water from the weaning period. Histopathological examinations of the brain of this mutant mouse revealed no significant age-related difference, suggesting that this mutation does not fundamentally obstruct the spontaneous growth despite the abnormality of the central nervous systems. This mutant mouse is advantageous for investigations on influences of the central nervous system on the aging process and longevity.

The reeler (gene symbol rl) is an autosomal laboratory chow (CRF-1; Oriental Yeast Co.,) recessive mutation occurring spontaneously in and given water ad libituna. The homozygous mice [4]. It gives rise to malposition of neurons mutant mice (rl/rl) were prepared according in all cortical structures of the forebrain exept to Mariani et al. [6]. All new born mice of the olfactory bulb. The cell position is also a litter were weaned from the mother at 21 abnormal in the cerebellar cortex [1, 3]. days of age. Thereafter, normal child mice

Because of these abnormalities the mutant were fed the same laboratory chow as their mouse is unable to keep its hindquarters uplight parents, while the homozygous affected ones and frequently stumbles during walking or were reared in other cages separately from running. This mutant mouse which has a those for the phenotypically normal littermates.

C57BL/6 background is less active than normal They were fed paste prepared from minced littermates and dies at about 3 weeks of age chow and water (1: 1) and allowed to take

[2, 6, 7]. In this paper the cause of the prema- water ad libitum from a extended suction tube ture death of reeler mice was investigated to of a water bottle (1 to 1.5 cm above the cage examine the possibility of its application in floor) until the 8 th weeks after birth. Body weight of both groups of mice were measured gerontological researches. Heterozygous (ri/+) , phenotypically normal everyday until the 4 th week after birth and breeding pairs were purchased from The then twice a week.

Jackson Laboratory (Bar Harbor, Maine), where When the mutant mice were reared with the mutation had been maintained on a hybrid the same laboratory chow as normal littermates,

background (C57BL/ 6•~C3H ; [2] ), fed their body weight reached a maximum at about * Present address: Nippon Institute for Biological Science, 2221-1, Shinmachi, Ome, Tokyo 198 Japan. ** Present address: Tsumura Research; Institute for Pharmacology, Ami-cho, 3586 Yoshiwara, Ibaraki, Japan. 110

Fig. 1. Growth curves of reeler mice and their Fig. 2. Growth curves of reeler mice fed paste food littermates, when fed ordinary laboratory chow. and their littermates fed laboratory chow.

14 days of age, followed by a gradual decrease, 12 months of age were fixed in 10 per cent resulted in a short mean survival time (22.7 neutral buffered formalin, embedded in paraffin days in males and 21.0 days in females, Fig. 1). and sectioned into slices 5 microns thick. The However, When the mutant mice were kept sections were stained with hematoxilin and on paste, their body weight decrease soon before eosin, followed by a comparison with sections weaning increased again : they survived for prepared from the brains of 3-week-old animals. over 30th days after birth, as shown in Fig. 2, In reeler mice the was much smaller since they could take sufficient food and water than that of normal mice, and its molecular despite muscular convulsions caused by a de- layer was greatly diminished. Purkinje's cells ficiency in the central nervous system. were found mostly in the central mass of the Such long-surving mutant mice at 8 weeks cerebellum with a few distributed in the of age were again kept together with their molecular layer and granular layer (Fig. 5). normal littermates and fed the laboratory chow. In the of reeler mice, The body weight of normal littermates reached absence of a well-defined molecular layer was a plateau at about 30 weeks of age whereas the most striking histological feature. The that of the mutant mice had already plateaued cortical layer of the reeler cerebrum which lies at about 20 weeks of age : the latter level was directly below the surface of the cerebral cortex, 62.6% of the former one in males and 57.4% was crowded with cells of diverse sizes and in females. Reeler mice then maintained their various shapes. Several cell types in the cortex body weight level constantly in the same way of normal mice could also be recognized in the as their normal siblings (Figs. 3 and 4). cortex of reeler mice, but not typical lamination Both brains of normal and mutant mice at of the cortex was observed in the mutant mice 111

Fig. 3. Growth curves of long-surviving reeler mice and their siblings. I. Males.

Fig. 4. Growth curves of long-surviving reeler mice and their siblings. II. Females. 112

Fig. 5. Sagittal sections of the cerebellum of (a) 3-week-old reeler mouse, (b) 12-month-old

reeler mouse, (c) 3-week-old normal littermate and (d) 12-month-old normal littermate. •~100. Reeler cerebellum shows a thin molecular layer (M), much diminished cell density in the granular

layer (G) and Purkinje's cells (P). Purkinje's cells are scattered mostly in the granular layer. There are no significant differences between 3-week-old and 12-month-old mice. 113

Fig. 6. Sagittal sections through the cerebral hemisphere of (a) 3-week-old reeler mouse, (b) 12- month-old reeler mouse, (c) 3-week-old normal littermate and (d) 12-month-old normal litter-

mate.•~40. The reeler cerebrum lack a well-defined molecular layer (M). Typical lamination of the cortex

(C) is obscured in the mutant mouse. The hippocampal cortex (H) seen in the normal cerebrum as a horseshoe shape is not found in reelers as a result of the failure of lamination. 114

(Fig. 6). Furthermore, the of laminar structures in the brain between young reeler mice showed failure of lamination of the and old reeler mutants suggests that the develop- horseshoe-shaped hippocampal cortex which ment of the reeler brain including abnormal consist of mostly of so-called pyramidal cells. structure formation is finished by the 3rd week In the reeler mutant, the pyramidal cells were after birth. The brain abnormality seems not scattered in the hippocampus (Fig. 6). to disturb their fundamental body growth. Between the brain of young and adult However, early termination of growth and reeler mutants there were no significant histolo- very light adult body weight reveal the major gical differences, meaning that the lamination- effects of abnormalities of the central nervous deficiency in the brain established in the late system. embryonal stages is not changed, at least Since the lifespan of an animal can be morphorogically. decided by manifestation and development of Since all three long-surviving male mutant the life program prescribed by genes, it is mice failed to breed, although kept with their certain that the central nervous system, which normal female littermates in the same cage for regulates physiological conditions of other about half a year, they appeared to be com- organs via the endocrine systems to maintain pletely sterile. However, no histological differ- homeostasis, greatly influences senescence and ences in the testis between reeler mutants and also longevity. Therefore, the reeler mutant their littermates were found, suggesting that mouse must be advantageous for investigating the sterility of male reelers might be due to the effects of the central nervous system on some physical difficulty in copulation or more aging. probably to the inability to perform normal sexual behavior. The majority of female reeler References mice could not become pregnant when kept with normal males, probably for the same [1] Caviness, V. S., Jr., and Sidman, R. L. (1972). reason as in the males. Although only one J. Comp. Neurol., 145, 85-104. [2] Caviness, VS., Jr., So, D.K., and Sidman, R. L. female mutant mouse succeeded in breeding, (1972). J. Hered., 63, 241-246. she did not nurse her young. The reason for [3] Devor, M., Caviness, V. S., Jr., and Derer, P. this is not clear, but may be related to the (1975). J. Comp. Neur., 164, 471-482. mental deficiency of this mutant [4]. [4] Falconer, D. S. (1951). J. Genet., 50, 192-201. [5] Hamburgh, M. (1968). Dev. Biol., 8, 165-185. Although it has been reported that reeler [6] Mariani, J., Crepel, F., Mikoshiba, K., Changeux, mutant mice die within 3 weeks after birth J. P., and Sotelo, C. (1977). Phil. Trans. Royal Soc. London, Ser. B, 281, 1-28. [2, 6, 7], they survived for over 12 months [7] Meier, H., and Hoag, W. G. (1962). J. Neuro- when given assistance in taking food and water, pathol. Exp. Neurol., 21, 649-654. suggesting that the premature death of the [8] Mikoshiba, K., Kohsaka, S., Takamatsu, K., mutant mice must result from a type of star- Aoki, E., and Tsukada, Y. (1980). J. Neurochem. 34, 835-844. vation due to difficulties in eating and drinking [9] Mikoshiba, K., Nagaike, K., Kohsaka, S., Taka- because of their ataxia. matsu, K., Aoki, E., and Tsukada, Y. (1980). The lack of significant differences in Develop. Biol., 79, 64-80. 115

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(財)東京都老人総合研究所

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