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in fairly large areas t h a t are n o t a l w a y s m o n t a i n o u s , b u t , as in t h e case of t h e CB p o p u l a t i o n , t h e 2 2 - c h r o m o s o m e mice s p r e a d to t h e plains of N o r t h e r n Puglia. This c i r c u m s t a n c e a s s u m e s a c e r t a i n t h e o r e t i c a l interest, since we 12 h a d p r e v i o u s l y a t t r i b u t e d an i m p o r t a n t r61e in s e t t i n g u p t h e h o m o z y g o u s R o b e r t s o n i a n p o p u l a t i o n s , to t h e c o m p a r t m e n t a l i z a t i o n of t h e m o n t a i n o u s e n v i r o n m e n t , on a c c o u n t of t h e possible g e o g r a p h i c isolations into small a n i m a l c o m m u n i t i e s , a n d c o n s e q u e n t l y of genetic drift. Y e t a n o t h e r difference c o n c e r n s t h e t a x o n o m i c aspect. T h e Alpine p o p u l a t i o n s b e l o n g to 2 d i f f e r e n t species, Mus m u s c u l u s t h e mice of Val Mesolecina, a n d Mus p o s c h i a v i n u s Fatio, t h o s e of t h e P o s c h i a v o Valley. All t h e A p e n n i n e mice, on t h e o t h e r h a n d , belong t o t h e Mus m u s c u l u s species. This c i r c u m s t a n c e , h o w e v e r , b e c o m e s i r r e l e v a n t d u e t o t h e f a c t t h a t t h e v a l i d i t y of t h e F a t i o ' s species ~3, i.e. Mus p o s c h i a v i n u s , was r e - e v a l u a t e d solely on t h e basis of t h e cytological difference (2n -- 26), whereas from a purely morphological and taxonomical p o i n t of viewS% it was c o n s i d e r e d s y n o n y m u s w i t h Mus m u s c u l u s L. But, a t p r e s e n t , as m o r e a n d m o r e e v i d e n c e emerges a b o u t a n e x t r a o r d i n a r y R o b e r t s o n i a n v a r i a b i l i t y of t h e m o u s e k a r y o t y p e , t h i s t a x o n o m i c a l s e p a r a t i o n loses a n y logical j u s t i f i c a t i o n . Nonetheless, t h e p r o b l e m of t h e s y s t e m a t i c e v a l u a t i o n of each house m o u s e p o p u l a -
175
t i o n a p p e a r s v e r y c o m p l e x . T h e i n t e r p r e t a t i o n of e a c h R o b e r t s o n i a n p o p u l a t i o n of h o u s e m o u s e as a 'species i n c i p i e n t e s ' 15 w o u l d be too e a s y a solution of a p u z z l i n g e v o l u t i o n a r y p r o b l e m . All t h e biological c h a r a c t e r i s t i c s of t h e s e m o u s e p o p u l a t i o n s h a v e to be carefully e v a l u a t e d before s u c h an e x p l i c a t o r y h y p o t h e s i s can be p r o p o s e d .
7 The symbols given to the Robertsonian inetacentrics are according to the recommendations of the Committee on Standardized Genetic Nomenclature for Mice, meetings of 2, 9 and 20 November at Howell. 8 A. Gropp and L. Zech, Nobel Syrup. 23, 118 (1973). 9 E. P. Evans, G. Breckon and C. E. Ford, Cytogenetics 3, 289 (1964). 10 A. Gropp, U. Tettenborn and E. yon Lehmann, Cytogeneties 9, 9 (t970). 11 A. Gropp, H. Winking, L. Zech anti H. MfilIer, Chromosoma 39, 265 (1972). 12 E. Capanna, M. V. Civitelli and M. Cristaldi, Theriologia (in press). 13 A. Fatio, in: Faune des vert6br6s de la Suisse.Io Histoire naturelle des mammif~res. Ed. H. Georg. Geneva 1869. 14 G. S. Miller, in: Catalogue of the Mammals of Western Europe. Br. Mus. (Nat. History). London 1912. 15 E. Mayr, in: Population Species and Evolution. Harvard Univ. Press, Cambridge (Mass.) 1970.
S p o n t a n e o u s R o b e r t s o n i a n f u s i o n l e a d i n g to k a r y o t y p e v a r i a t i o n i n t h e h o u s e m o u s e first report from Asia S. C h a k r a b a r t i a n d A. C h a k r a b a r t i
Department o/Zoology, Hooghly Mohsin Govt. College, Chinsurah 712 707 (W. 13., India), and Department o[ Turnout 13iology, C. N. C. R. C., Calcutta 700 026 (W. 13., India), 5 M a y 1976 Summary. The occurrence of s p o n t a n e o u s R o b e r t s o n i a n fusion leading to 2n -- 39 c h r o m o s o m e s (NF -- 40) in t h e house mouse (Mus m u s c u l u s domesticus) has b e e n r e p o r t e d for t h e first t i m e f r o m Asia. 3 p h e n o t y p i c a l l y n o r m a l female mice collected from 2 d i s t a n t l y l o c a t e d p o p u l a t i o n s of I n d i a (Tripura a n d Calcutta) s h o w centric fusion in s o m a t i c c h r o m o somes b e t w e e n pairs 2 and 16, a n d 8 a n d 14 respectively. C - b a n d i n g analysis revealed t h a t t h e ( s u b ) m e t a c e n t r i c has been o r i g i n a t e d b y fusion b e t w e e n t h e b r o k e n / e r o d e d c e n t r o m e r e s of 2 telocentric c h r o m o s o m e s . T h o u g h t h e analysis of k a r y o t y p e of d i f f e r e n t l a b o r a t o r y s t r a i n s of m o u s e has b e e n t h e s u b j e c t of a large n u m b e r of studies, t h e house mouse, Mus m u s c u l u s d o m e s t i c u s h a s received as y e t v e r y little a t t e n t i o n in t b e karyological l i t e r a t u r e of m a m m a l s . R e c e n t l y , in course of our inv e s t i g a t i o n s on t h e k a r y o t y p e of t h e c o m m o n house m o u s e 1, 3, an i n t e r e s t i n g incidence of s p o n t a n e o u s c e n t r i c fusion h a s b e e n n o t i c e d in 3 female mice. 2 of t h e s e 3 females were collected f r o m our h o u s e a t C a l c u t t a , W e s t Bengal, a n d one f r o m Agartala, Tripura. These 2 I n d i a n s t a t e s are w i d e l y s e p a r a t e d f r o m each o t h e r b y Bangladesh. The s o m a t i c c h r o m o s o m e s of t h e female s p e c i m e n s (weighing a b o u t 18-20 g) were p r e p a r e d f r o m b o n e m a r r o w b y following t h e colchicine-citrate-acetic alcoholair d r y i n g t e c h n i q u e a n d were s t a i n e d in Giemsa b y using t h e p h o s p h a t e buffer of a p H of 7.23, 4. The n o r m a l diploid c o m p l e m e n t of Mus m u s c u l u s dom e s t i c u s consists of 40 rod-like t e l o c e n t r i c e l e m e n t s of w h i c h t h e first pair m a y be d e s i g n a t e d as ' m a r k e r c h r o m o somes' due t o t h e i r r e m a r k a b l e l e n g t h in c o m p a r i s o n w i t h o t h e r e l e m e n t s 1,2 (figure 1). A f t e r a critical e x a m i n a t i o n of 50 m e t a p h a s e c o m p l e m e n t s f r o m each of t h e 3 p h e n o t y p i c a l l y n o r m a l individuals, it was c o n f i r m e d t h a t t h e s e 3 females are a c t u a l l y h e t e r o z y g o u s for a centric fusion w i t h a 3 9 - c h r o m o s o m e k a r y o t y p e (NF ~ 40).
Of these, 38 are original t e l o c e n t r i c a n d one is s u b m e t a c e n t r i c (figures 2-4). The l a t t e r o r i g i n a t e d b y c e n t r i c fusion of 2 telocentrics b e l o n g i n g to groups I I a n d III'~-8 or m o r e precisely a) b e t w e e n c h r o m o s o m e s belonging to pairs 2 a n d 16 in t h e s p e c i m e n collected f r o m T r i p u r a (figure 4), a n d b) b e t w e e n c h r o m o s o m e s belonging to pairs 8 a n d 14 in t h e females collected f r o m C a l c u t t a (figures 2 a n d 3). Several r e p o r t s o n s p o n t a n e o u s c e n t r i c fusion in l a b o r a t o r y m o u s e s t r a i n s h a v e b e e n p u b l i s h e d f r o m t i m e to t i m e b y
1 S. Chakrabarti, Proc. 2nd All India Cong. Cytol. Genet., p. 23 (1975). 2 S. Chakrabarti and A. Chakrabarti, Proe. 63rd Session Indian Science Cong., pt. III, p. 155 (1976). 3 K. H. Rothfels and L. L. Siminovltch, Stain Teehnol. 33, 73 (1958). 4 G. K. Manna and S. Chakrabarti, The Nucieus 13, 167 (1970). 5 M. Crippa, Chromosoma 15, 301 (1964). 6 S. Chakrabarti, Proc. 1st All India Cong. Cytol. Genet., p. 127 (1971). 7 S. Chakrabarti, C. I. S. 17, 7 (1974). 8 S. Chakrabarti, Genen Phaenen 16, 1 (1973).
176
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Species
Localities
Mus musculus domesticus Mus musculus domesticus Mus museulus
Mus nmsculus
Tripura, 39 India CMeutta, 39 India Central Apenine; 22 Italy Rhaetian Alps, 28 Switzerland Rhaetian Prealps, 35 Switzerland Rhaetian Alps, 38 Albula, Switzerland Rhaetian Alps, 26 Val Poschiavo, Switzerland Lab. strain 39
Mus musculus
Lab. strain
39
Mus museulus
Lab. strain
39
Mus musculus
Lab. strain
39
Mus museulus
Lab. strain
39
Mus museulus Mus musculus Mus musculus Mus poschiavinus
2n
EXPERIENTIA 33/2
Total number of fusion metacentrics (no. of chromosomes involved ill centric fusion)
References
I (2 + 16) I (8 + 14) I II III IV V VI VII VIII IX (6+1) (8+3) (11+7) (15+4) (10+9) (18+2) (17+5) (14+12) (16+13) I II III IV V VI (3+1) (14+2) (12+4) (8+7) (11+10) (16+13) I II III (17 + 16) (11 + 10) (12 +4) (12+4)
Present paper Present paper Capanna et al. 19 Gropp et al.18 Gropp et al. TM Gropp et al. 18
I II III IV V VI VII (3+1) (6+4) (15+5) (13+11) (12+8) (14+9) (17+16)
Gropp et a l ) 5
I (16 + 6) I (19+9) I (17+8) I (19+5) I (17+4)
L~onard and Deknudt 9 Evans et al. 1~ Baranov and Dyban 12 White and Tijo 11 Chakrabarti ~4
Fig. 1-5. Photomicrographs of somatic metaphases of female house mice (Mus musculus domesticus). 1 Normal metaphase with 40 telocentric chromosomes. 2-4 Metaphases of 3 heterozygous females each with 38 telocentrics and one submetacentrie chromosome (arrowed). 5 Cbanding of a metaphase of a heterozygous female showing the fused centromere of the submetaeentric chromosome (arrowed).
15.2. 1977
177
Specialia
d i f f e r e n t i n v e s t i g a t o r s 9-14. A d i v e r g e n t finding on t h e occurrence of 7 pairs of m e t a c e n t r i c s d u e t o R o b e r t s o n i a n fusions h a s also b e e n r e p o r t e d in t o b a c c o mouse, Mus p o s c h i a v i n u s f r o m S w i t z e r l a n d 15. P r e v i o u s l y it was generally a c c e p t e d t h a t t h e wild p o p u l a t i o n s of house m o u s e h a v e a fairly u n i f o r m k a r y o t y p e of 40 t e l o c e n t r i c c h r o m o somes ~6 B u t r e c e n t l y t h e occurrence of v a r i a b l e m e t a c e n trics (2-9) due t o R o b e r t s o n i a n fusions has b e e n r e p o r t e d f r o m d i f f e r e n t regions of Switzerland~7,~s a n d R o m e l g . So far as we are aware, t h e r e is no r e p o r t on t h e occurrence of R o b e r t s o n i a n fusion in a n y of t h e h o u s e m o u s e p o p u l a t i o n s of Asia. This first r e p o r t on k a r y o t y p e variation due to R o b e r t s o n i a n fusion in h o u s e m o u s e f r o m t w o widely s e p a r a t e d localities of E a s t e r n I n d i a will a d d f u r t h e r cytological d a t a to t h e p r o b l e m of c h r o m o s o m e p o l y m o r p h i s m of t h e species a n d t h e p r o b a b l e t r e n d of its evolution. I t is s o m e w h a t difficult a t p r e s e n t to suggest w i t h confidence w h e t h e r t h e occurrence of R o b e r t s o n i a n fusion in t h e s e t h r e e s p e c i m e n s collected f r o m 2 d i s t a n t l y l o c a t e d p o p u l a t i o n s is a c c i d e n t a l or has a n y e v o l u t i o n a r y significance. B u t it is e v i d e n t f r o m d i f f e r e n t r e s e a r c h r e p o r t s p u b l i s h e d in r e c e n t years t h a t , like l a b o r a t o r y strains, t h e wild p o p u l a t i o n s of house m o u s e also t e n d to u n d e r g o centric fusion r e l a t i v e l y easily. Moreover, t h e d a t a compiled in t h e t a b l e also i n d i c a t e t h a t in m o s t cases t h e fusion has t a k e n place b e t w e e n c h r o m o s o m e s belonging to groups I I a n d I V ~-s in l a b o r a t o r y s t r a i n s a n d b e t w e e n groups I and I V 1, 2 in wild p o p u l a t i o n s of mouse. R e c e n t l y an e x t e n s i v e review on t h e causes and consequences of R o b e r t s o n i a n e x c h a n g e has been p u b l i s h e d b y J o h n and F r e e m a n ~0. B u t it is n o t v e r y easy to conclude h o w t h e s e fusion ( s u b ) m e t a c e n t r i c s h a v e o r i g i n a t e d in our material. A l t h o u g h t h e rods of m o u s e h a v e b e e n
v a r i o u s l y c h r i s t e n e d as acro- or telocentrics, a c c o r d i n g t o t h e choice of i n d i v i d u a l a u t h o r s , y e t b y whole m o u n t E M studies Comings a n d O k a d a 21 h a v e c o n f i r m e d t h a t t h e rods of m o u s e are t e l o c e n t r i c in n a t u r e w i t h no e v i d e n c e of a s h o r t arm. I t is, therefore, q u i t e plausible t h a t t h e ( s u b ) m e t a c e n t r i c in t h e s e 3 female s p e c i m e n s h a s orig i n a t e d e i t h e r b y a simple b r e a k a g e r e u n i o n e v e n t w i t h i n t h e c e n t r o m e r e itself, or else is due t o fusion b e t w e e n 2 e r o d e d c e n t r o m e r e s . T h e results of our C - b a n d i n g a n a l y s i s (figure 5), b y following t h e t e c h n i q u e suggested b y S u m n e r a n d E v a n s ~, a n d t h e absence of a n y m i n u t e s or a n y s u p e r n u m e r a r y like e l e m e n t s are also in s u p p o r t of t h i s view.
9 A. L6onard and G. H. Deknudt, Experientia 22, 715 (1966). 10 g. P. Evans, M. L. Layon and M. Daglish, Cytogenetics 6, 105 (1967). 11 B. J. White and J. H. Tijo, Hereditas 58, 284 (1967). 12 V. S. Baranov and A. P. Dyban, Ontogenez 2, 1.64 (1971). 13 G. K. Manna, S. Bardhan, S. Chakrabarti, S. Gupta and A. B. Mitra, Experientia 30, 1412 (1974). 14 S. Chakrabarti, Ge~en Phaenen t8, 65 (1975). 15 A. Gropp, U. Tettenborn and yon Lehmann, Cytogenetics 9, 9 (1970). 16 T. C. ttsu and K. Benirschke, in: An Atlas of Mamm. Chr., vol. 1, folio 17. Springer-Verlag, New York 1967. 17 A. Gropp and H. Winking, MCN 72, 4 (1971). 18 A. Gropp, H. Winking, L. Zech and H. Mfiller, Chromosoma 39, 265 (1972). 19 E. Capan~a, M. Cristaldi, P. Partieone and M. Rizzoni, Experientia 31, 294 (1975). 20 B. John and M. Freeman, Chromosoma 52, 123 (1975). 21 D. E. Comings and T. A. Okada, Cytogeneties 9, 436 (1970). 22 A. T. Sumner and H. J. Evans, Exp. Cell Res. 81, 223 (1973).
O n the l o c a t i o n of the t e t r a p y r r o l e m a c r o c y c l e of c h l o r o p h y l l a in p h o s p h o l i p i d v e s i c l e s a n d in hexadecane M. F r a g a t a 1
Biophysics Research Grou,p and Department o/ Chemistry and Biology, University o/ Oudbec at Trois-Rivigres, Trois-Rivi~res, Qudbec (Canada), 17 August 1976 Summary. T h e s t a t e of c h l o r o p h y l l a in p h o s p h a t i d y l c h o l i n e vesicles was e x a m i n e d . The results i n d i c a t e t h a t t h e chlorophylls are p r e s e n t in m o n o m e r i c form. A kinetic s t u d y of c h l o r o p h y l l r e a c t i o n s w i t h K2S208 a n d p i p e r i d i n e showed t h a t t h e s e s u b s t a n c e s r e a c t w i t h t h e p o r p h y r i n rings of p i g m e n t s l o c a t e d on b o t h vesicle faces, m o s t p r o b a b l y w i t h i n t h e polar h e a d g r o u p region. Artificial m e m b r a n e s c o n t a i n i n g c h l o r o p h y l l h a v e b e e n used as m o d e l s for t h e s t u d y of p h o t o s y n t h e s i s 2 - 4 Since the membranes reproduced certain spectroscopic characteristics a n d p h o t o c h e m i c a l r e a c t i o n s of in vivo s y s t e m s , i n v e s t i g a t i o n s were u n d e r t a k e n t o w a r d s t h e e l u c i d a t i o n of t h e c h l o r o p h y l l s a r r a n g e m e n t in t h e lipid layers. S t e i n e m a n n e t al. ~ r e p o r t e d t h e p r e p a r a t i o n of a lipid b i l a y e r (BLM) c o n t a i n i n g c h l o r o p h y l l a (Chl-a) a n d suggested t h a t t h e p i g m e n t s are localized on b o t h m e m b r a n e faces w i t h t h e t e t r a p y r r o l e m a c r o c y c l e e i t h e r a) in t h e 2 m e m b r a n e - s o l u t i o n i n t e r f a c e s in c o n t a c t w i t h t h e a q u e o u s phase, or b) i n s e r t e d into t h e p h o s p h o l i p i d core. The locat i o n of Chl-a in a bilayer as it is p r e d i c t e d b y t h e first m o d e l is t h e r m o d y n a m i c a l l y u n s t a b l e . I t suffices to n o t e t h a t one edge only of t h e m a c r o c y c l e (figure 1) m a y event u a l l y h a v e c o n t a c t w i t h a layer of w a t e r K R e c e n t l y , a spin label s t u d y of 0 t t m e i e r et al. 7 on chlorop h y l l - c o n t a i n i n g p h o s p h o l i p i d vesicles f a v o u r e d t h e pres-
ence of Chl-a p o r p h y r m w i t h i n t h e polar h e a d g r o n p region; a n d K a t z e t alY r e m a r k e d t h a t t h e b e s t l o c a t i o n for a n t e n n a a n d special p a i r c h l o r o p h y l l a g g r e g a t e s in t h e 1 2 3 4 5 6 7 8
Acknowledgments. This work was supported by the Research Comnfittee and the Biophysics Research Group, University of Quebec at Trois-Rivithres. D.W. Deamer, R. C. Prince and A. R. Crofts, Bioehim. biophys. Aeta 27d, 323 (1972). P. Nicholls, J. West and A. D. Bangham, Biochim. biophys. Acta 363, 190 (1974). W. 0ttmeier, J. R. Norris and J. J. Katz, Z. Naturforsch. 31c, 163 (1976). A. Steinemann, O. Stark and P. L/iuger, J. Membrane Biol. 9, 177 (1972). J. P'ranek, Daedalus 86, 17 (1955). W. 0ttmeier, J. R. Norris and J. J. Katz, in : Book of Abstracts, I 9. Brookhaven Syrup. Biol. No. 28 (1976}. J . J . Katz, W. ()ttmeier and J. R. Norris, Phil. Trans. R. Soc. Lond. B 273, 227 (1976)..]
Specialia
in fairly large areas t h a t are n o t a l w a y s m o n t a i n o u s , b u t , as in t h e case of t h e CB p o p u l a t i o n , t h e 2 2 - c h r o m o s o m e mice s p r e a d to t h e plains of N o r t h e r n Puglia. This c i r c u m s t a n c e a s s u m e s a c e r t a i n t h e o r e t i c a l interest, since we 12 h a d p r e v i o u s l y a t t r i b u t e d an i m p o r t a n t r61e in s e t t i n g u p t h e h o m o z y g o u s R o b e r t s o n i a n p o p u l a t i o n s , to t h e c o m p a r t m e n t a l i z a t i o n of t h e m o n t a i n o u s e n v i r o n m e n t , on a c c o u n t of t h e possible g e o g r a p h i c isolations into small a n i m a l c o m m u n i t i e s , a n d c o n s e q u e n t l y of genetic drift. Y e t a n o t h e r difference c o n c e r n s t h e t a x o n o m i c aspect. T h e Alpine p o p u l a t i o n s b e l o n g to 2 d i f f e r e n t species, Mus m u s c u l u s t h e mice of Val Mesolecina, a n d Mus p o s c h i a v i n u s Fatio, t h o s e of t h e P o s c h i a v o Valley. All t h e A p e n n i n e mice, on t h e o t h e r h a n d , belong t o t h e Mus m u s c u l u s species. This c i r c u m s t a n c e , h o w e v e r , b e c o m e s i r r e l e v a n t d u e t o t h e f a c t t h a t t h e v a l i d i t y of t h e F a t i o ' s species ~3, i.e. Mus p o s c h i a v i n u s , was r e - e v a l u a t e d solely on t h e basis of t h e cytological difference (2n -- 26), whereas from a purely morphological and taxonomical p o i n t of viewS% it was c o n s i d e r e d s y n o n y m u s w i t h Mus m u s c u l u s L. But, a t p r e s e n t , as m o r e a n d m o r e e v i d e n c e emerges a b o u t a n e x t r a o r d i n a r y R o b e r t s o n i a n v a r i a b i l i t y of t h e m o u s e k a r y o t y p e , t h i s t a x o n o m i c a l s e p a r a t i o n loses a n y logical j u s t i f i c a t i o n . Nonetheless, t h e p r o b l e m of t h e s y s t e m a t i c e v a l u a t i o n of each house m o u s e p o p u l a -
175
t i o n a p p e a r s v e r y c o m p l e x . T h e i n t e r p r e t a t i o n of e a c h R o b e r t s o n i a n p o p u l a t i o n of h o u s e m o u s e as a 'species i n c i p i e n t e s ' 15 w o u l d be too e a s y a solution of a p u z z l i n g e v o l u t i o n a r y p r o b l e m . All t h e biological c h a r a c t e r i s t i c s of t h e s e m o u s e p o p u l a t i o n s h a v e to be carefully e v a l u a t e d before s u c h an e x p l i c a t o r y h y p o t h e s i s can be p r o p o s e d .
7 The symbols given to the Robertsonian inetacentrics are according to the recommendations of the Committee on Standardized Genetic Nomenclature for Mice, meetings of 2, 9 and 20 November at Howell. 8 A. Gropp and L. Zech, Nobel Syrup. 23, 118 (1973). 9 E. P. Evans, G. Breckon and C. E. Ford, Cytogenetics 3, 289 (1964). 10 A. Gropp, U. Tettenborn and E. yon Lehmann, Cytogeneties 9, 9 (t970). 11 A. Gropp, H. Winking, L. Zech anti H. MfilIer, Chromosoma 39, 265 (1972). 12 E. Capanna, M. V. Civitelli and M. Cristaldi, Theriologia (in press). 13 A. Fatio, in: Faune des vert6br6s de la Suisse.Io Histoire naturelle des mammif~res. Ed. H. Georg. Geneva 1869. 14 G. S. Miller, in: Catalogue of the Mammals of Western Europe. Br. Mus. (Nat. History). London 1912. 15 E. Mayr, in: Population Species and Evolution. Harvard Univ. Press, Cambridge (Mass.) 1970.
S p o n t a n e o u s R o b e r t s o n i a n f u s i o n l e a d i n g to k a r y o t y p e v a r i a t i o n i n t h e h o u s e m o u s e first report from Asia S. C h a k r a b a r t i a n d A. C h a k r a b a r t i
Department o/Zoology, Hooghly Mohsin Govt. College, Chinsurah 712 707 (W. 13., India), and Department o[ Turnout 13iology, C. N. C. R. C., Calcutta 700 026 (W. 13., India), 5 M a y 1976 Summary. The occurrence of s p o n t a n e o u s R o b e r t s o n i a n fusion leading to 2n -- 39 c h r o m o s o m e s (NF -- 40) in t h e house mouse (Mus m u s c u l u s domesticus) has b e e n r e p o r t e d for t h e first t i m e f r o m Asia. 3 p h e n o t y p i c a l l y n o r m a l female mice collected from 2 d i s t a n t l y l o c a t e d p o p u l a t i o n s of I n d i a (Tripura a n d Calcutta) s h o w centric fusion in s o m a t i c c h r o m o somes b e t w e e n pairs 2 and 16, a n d 8 a n d 14 respectively. C - b a n d i n g analysis revealed t h a t t h e ( s u b ) m e t a c e n t r i c has been o r i g i n a t e d b y fusion b e t w e e n t h e b r o k e n / e r o d e d c e n t r o m e r e s of 2 telocentric c h r o m o s o m e s . T h o u g h t h e analysis of k a r y o t y p e of d i f f e r e n t l a b o r a t o r y s t r a i n s of m o u s e has b e e n t h e s u b j e c t of a large n u m b e r of studies, t h e house mouse, Mus m u s c u l u s d o m e s t i c u s h a s received as y e t v e r y little a t t e n t i o n in t b e karyological l i t e r a t u r e of m a m m a l s . R e c e n t l y , in course of our inv e s t i g a t i o n s on t h e k a r y o t y p e of t h e c o m m o n house m o u s e 1, 3, an i n t e r e s t i n g incidence of s p o n t a n e o u s c e n t r i c fusion h a s b e e n n o t i c e d in 3 female mice. 2 of t h e s e 3 females were collected f r o m our h o u s e a t C a l c u t t a , W e s t Bengal, a n d one f r o m Agartala, Tripura. These 2 I n d i a n s t a t e s are w i d e l y s e p a r a t e d f r o m each o t h e r b y Bangladesh. The s o m a t i c c h r o m o s o m e s of t h e female s p e c i m e n s (weighing a b o u t 18-20 g) were p r e p a r e d f r o m b o n e m a r r o w b y following t h e colchicine-citrate-acetic alcoholair d r y i n g t e c h n i q u e a n d were s t a i n e d in Giemsa b y using t h e p h o s p h a t e buffer of a p H of 7.23, 4. The n o r m a l diploid c o m p l e m e n t of Mus m u s c u l u s dom e s t i c u s consists of 40 rod-like t e l o c e n t r i c e l e m e n t s of w h i c h t h e first pair m a y be d e s i g n a t e d as ' m a r k e r c h r o m o somes' due t o t h e i r r e m a r k a b l e l e n g t h in c o m p a r i s o n w i t h o t h e r e l e m e n t s 1,2 (figure 1). A f t e r a critical e x a m i n a t i o n of 50 m e t a p h a s e c o m p l e m e n t s f r o m each of t h e 3 p h e n o t y p i c a l l y n o r m a l individuals, it was c o n f i r m e d t h a t t h e s e 3 females are a c t u a l l y h e t e r o z y g o u s for a centric fusion w i t h a 3 9 - c h r o m o s o m e k a r y o t y p e (NF ~ 40).
Of these, 38 are original t e l o c e n t r i c a n d one is s u b m e t a c e n t r i c (figures 2-4). The l a t t e r o r i g i n a t e d b y c e n t r i c fusion of 2 telocentrics b e l o n g i n g to groups I I a n d III'~-8 or m o r e precisely a) b e t w e e n c h r o m o s o m e s belonging to pairs 2 a n d 16 in t h e s p e c i m e n collected f r o m T r i p u r a (figure 4), a n d b) b e t w e e n c h r o m o s o m e s belonging to pairs 8 a n d 14 in t h e females collected f r o m C a l c u t t a (figures 2 a n d 3). Several r e p o r t s o n s p o n t a n e o u s c e n t r i c fusion in l a b o r a t o r y m o u s e s t r a i n s h a v e b e e n p u b l i s h e d f r o m t i m e to t i m e b y
1 S. Chakrabarti, Proc. 2nd All India Cong. Cytol. Genet., p. 23 (1975). 2 S. Chakrabarti and A. Chakrabarti, Proe. 63rd Session Indian Science Cong., pt. III, p. 155 (1976). 3 K. H. Rothfels and L. L. Siminovltch, Stain Teehnol. 33, 73 (1958). 4 G. K. Manna and S. Chakrabarti, The Nucieus 13, 167 (1970). 5 M. Crippa, Chromosoma 15, 301 (1964). 6 S. Chakrabarti, Proc. 1st All India Cong. Cytol. Genet., p. 127 (1971). 7 S. Chakrabarti, C. I. S. 17, 7 (1974). 8 S. Chakrabarti, Genen Phaenen 16, 1 (1973).
176
Specialia
Species
Localities
Mus musculus domesticus Mus musculus domesticus Mus museulus
Mus nmsculus
Tripura, 39 India CMeutta, 39 India Central Apenine; 22 Italy Rhaetian Alps, 28 Switzerland Rhaetian Prealps, 35 Switzerland Rhaetian Alps, 38 Albula, Switzerland Rhaetian Alps, 26 Val Poschiavo, Switzerland Lab. strain 39
Mus musculus
Lab. strain
39
Mus museulus
Lab. strain
39
Mus musculus
Lab. strain
39
Mus museulus
Lab. strain
39
Mus museulus Mus musculus Mus musculus Mus poschiavinus
2n
EXPERIENTIA 33/2
Total number of fusion metacentrics (no. of chromosomes involved ill centric fusion)
References
I (2 + 16) I (8 + 14) I II III IV V VI VII VIII IX (6+1) (8+3) (11+7) (15+4) (10+9) (18+2) (17+5) (14+12) (16+13) I II III IV V VI (3+1) (14+2) (12+4) (8+7) (11+10) (16+13) I II III (17 + 16) (11 + 10) (12 +4) (12+4)
Present paper Present paper Capanna et al. 19 Gropp et al.18 Gropp et al. TM Gropp et al. 18
I II III IV V VI VII (3+1) (6+4) (15+5) (13+11) (12+8) (14+9) (17+16)
Gropp et a l ) 5
I (16 + 6) I (19+9) I (17+8) I (19+5) I (17+4)
L~onard and Deknudt 9 Evans et al. 1~ Baranov and Dyban 12 White and Tijo 11 Chakrabarti ~4
Fig. 1-5. Photomicrographs of somatic metaphases of female house mice (Mus musculus domesticus). 1 Normal metaphase with 40 telocentric chromosomes. 2-4 Metaphases of 3 heterozygous females each with 38 telocentrics and one submetacentrie chromosome (arrowed). 5 Cbanding of a metaphase of a heterozygous female showing the fused centromere of the submetaeentric chromosome (arrowed).
15.2. 1977
177
Specialia
d i f f e r e n t i n v e s t i g a t o r s 9-14. A d i v e r g e n t finding on t h e occurrence of 7 pairs of m e t a c e n t r i c s d u e t o R o b e r t s o n i a n fusions h a s also b e e n r e p o r t e d in t o b a c c o mouse, Mus p o s c h i a v i n u s f r o m S w i t z e r l a n d 15. P r e v i o u s l y it was generally a c c e p t e d t h a t t h e wild p o p u l a t i o n s of house m o u s e h a v e a fairly u n i f o r m k a r y o t y p e of 40 t e l o c e n t r i c c h r o m o somes ~6 B u t r e c e n t l y t h e occurrence of v a r i a b l e m e t a c e n trics (2-9) due t o R o b e r t s o n i a n fusions has b e e n r e p o r t e d f r o m d i f f e r e n t regions of Switzerland~7,~s a n d R o m e l g . So far as we are aware, t h e r e is no r e p o r t on t h e occurrence of R o b e r t s o n i a n fusion in a n y of t h e h o u s e m o u s e p o p u l a t i o n s of Asia. This first r e p o r t on k a r y o t y p e variation due to R o b e r t s o n i a n fusion in h o u s e m o u s e f r o m t w o widely s e p a r a t e d localities of E a s t e r n I n d i a will a d d f u r t h e r cytological d a t a to t h e p r o b l e m of c h r o m o s o m e p o l y m o r p h i s m of t h e species a n d t h e p r o b a b l e t r e n d of its evolution. I t is s o m e w h a t difficult a t p r e s e n t to suggest w i t h confidence w h e t h e r t h e occurrence of R o b e r t s o n i a n fusion in t h e s e t h r e e s p e c i m e n s collected f r o m 2 d i s t a n t l y l o c a t e d p o p u l a t i o n s is a c c i d e n t a l or has a n y e v o l u t i o n a r y significance. B u t it is e v i d e n t f r o m d i f f e r e n t r e s e a r c h r e p o r t s p u b l i s h e d in r e c e n t years t h a t , like l a b o r a t o r y strains, t h e wild p o p u l a t i o n s of house m o u s e also t e n d to u n d e r g o centric fusion r e l a t i v e l y easily. Moreover, t h e d a t a compiled in t h e t a b l e also i n d i c a t e t h a t in m o s t cases t h e fusion has t a k e n place b e t w e e n c h r o m o s o m e s belonging to groups I I a n d I V ~-s in l a b o r a t o r y s t r a i n s a n d b e t w e e n groups I and I V 1, 2 in wild p o p u l a t i o n s of mouse. R e c e n t l y an e x t e n s i v e review on t h e causes and consequences of R o b e r t s o n i a n e x c h a n g e has been p u b l i s h e d b y J o h n and F r e e m a n ~0. B u t it is n o t v e r y easy to conclude h o w t h e s e fusion ( s u b ) m e t a c e n t r i c s h a v e o r i g i n a t e d in our material. A l t h o u g h t h e rods of m o u s e h a v e b e e n
v a r i o u s l y c h r i s t e n e d as acro- or telocentrics, a c c o r d i n g t o t h e choice of i n d i v i d u a l a u t h o r s , y e t b y whole m o u n t E M studies Comings a n d O k a d a 21 h a v e c o n f i r m e d t h a t t h e rods of m o u s e are t e l o c e n t r i c in n a t u r e w i t h no e v i d e n c e of a s h o r t arm. I t is, therefore, q u i t e plausible t h a t t h e ( s u b ) m e t a c e n t r i c in t h e s e 3 female s p e c i m e n s h a s orig i n a t e d e i t h e r b y a simple b r e a k a g e r e u n i o n e v e n t w i t h i n t h e c e n t r o m e r e itself, or else is due t o fusion b e t w e e n 2 e r o d e d c e n t r o m e r e s . T h e results of our C - b a n d i n g a n a l y s i s (figure 5), b y following t h e t e c h n i q u e suggested b y S u m n e r a n d E v a n s ~, a n d t h e absence of a n y m i n u t e s or a n y s u p e r n u m e r a r y like e l e m e n t s are also in s u p p o r t of t h i s view.
9 A. L6onard and G. H. Deknudt, Experientia 22, 715 (1966). 10 g. P. Evans, M. L. Layon and M. Daglish, Cytogenetics 6, 105 (1967). 11 B. J. White and J. H. Tijo, Hereditas 58, 284 (1967). 12 V. S. Baranov and A. P. Dyban, Ontogenez 2, 1.64 (1971). 13 G. K. Manna, S. Bardhan, S. Chakrabarti, S. Gupta and A. B. Mitra, Experientia 30, 1412 (1974). 14 S. Chakrabarti, Ge~en Phaenen t8, 65 (1975). 15 A. Gropp, U. Tettenborn and yon Lehmann, Cytogenetics 9, 9 (1970). 16 T. C. ttsu and K. Benirschke, in: An Atlas of Mamm. Chr., vol. 1, folio 17. Springer-Verlag, New York 1967. 17 A. Gropp and H. Winking, MCN 72, 4 (1971). 18 A. Gropp, H. Winking, L. Zech and H. Mfiller, Chromosoma 39, 265 (1972). 19 E. Capan~a, M. Cristaldi, P. Partieone and M. Rizzoni, Experientia 31, 294 (1975). 20 B. John and M. Freeman, Chromosoma 52, 123 (1975). 21 D. E. Comings and T. A. Okada, Cytogeneties 9, 436 (1970). 22 A. T. Sumner and H. J. Evans, Exp. Cell Res. 81, 223 (1973).
O n the l o c a t i o n of the t e t r a p y r r o l e m a c r o c y c l e of c h l o r o p h y l l a in p h o s p h o l i p i d v e s i c l e s a n d in hexadecane M. F r a g a t a 1
Biophysics Research Grou,p and Department o/ Chemistry and Biology, University o/ Oudbec at Trois-Rivigres, Trois-Rivi~res, Qudbec (Canada), 17 August 1976 Summary. T h e s t a t e of c h l o r o p h y l l a in p h o s p h a t i d y l c h o l i n e vesicles was e x a m i n e d . The results i n d i c a t e t h a t t h e chlorophylls are p r e s e n t in m o n o m e r i c form. A kinetic s t u d y of c h l o r o p h y l l r e a c t i o n s w i t h K2S208 a n d p i p e r i d i n e showed t h a t t h e s e s u b s t a n c e s r e a c t w i t h t h e p o r p h y r i n rings of p i g m e n t s l o c a t e d on b o t h vesicle faces, m o s t p r o b a b l y w i t h i n t h e polar h e a d g r o u p region. Artificial m e m b r a n e s c o n t a i n i n g c h l o r o p h y l l h a v e b e e n used as m o d e l s for t h e s t u d y of p h o t o s y n t h e s i s 2 - 4 Since the membranes reproduced certain spectroscopic characteristics a n d p h o t o c h e m i c a l r e a c t i o n s of in vivo s y s t e m s , i n v e s t i g a t i o n s were u n d e r t a k e n t o w a r d s t h e e l u c i d a t i o n of t h e c h l o r o p h y l l s a r r a n g e m e n t in t h e lipid layers. S t e i n e m a n n e t al. ~ r e p o r t e d t h e p r e p a r a t i o n of a lipid b i l a y e r (BLM) c o n t a i n i n g c h l o r o p h y l l a (Chl-a) a n d suggested t h a t t h e p i g m e n t s are localized on b o t h m e m b r a n e faces w i t h t h e t e t r a p y r r o l e m a c r o c y c l e e i t h e r a) in t h e 2 m e m b r a n e - s o l u t i o n i n t e r f a c e s in c o n t a c t w i t h t h e a q u e o u s phase, or b) i n s e r t e d into t h e p h o s p h o l i p i d core. The locat i o n of Chl-a in a bilayer as it is p r e d i c t e d b y t h e first m o d e l is t h e r m o d y n a m i c a l l y u n s t a b l e . I t suffices to n o t e t h a t one edge only of t h e m a c r o c y c l e (figure 1) m a y event u a l l y h a v e c o n t a c t w i t h a layer of w a t e r K R e c e n t l y , a spin label s t u d y of 0 t t m e i e r et al. 7 on chlorop h y l l - c o n t a i n i n g p h o s p h o l i p i d vesicles f a v o u r e d t h e pres-
ence of Chl-a p o r p h y r m w i t h i n t h e polar h e a d g r o n p region; a n d K a t z e t alY r e m a r k e d t h a t t h e b e s t l o c a t i o n for a n t e n n a a n d special p a i r c h l o r o p h y l l a g g r e g a t e s in t h e 1 2 3 4 5 6 7 8
Acknowledgments. This work was supported by the Research Comnfittee and the Biophysics Research Group, University of Quebec at Trois-Rivithres. D.W. Deamer, R. C. Prince and A. R. Crofts, Bioehim. biophys. Aeta 27d, 323 (1972). P. Nicholls, J. West and A. D. Bangham, Biochim. biophys. Acta 363, 190 (1974). W. 0ttmeier, J. R. Norris and J. J. Katz, Z. Naturforsch. 31c, 163 (1976). A. Steinemann, O. Stark and P. L/iuger, J. Membrane Biol. 9, 177 (1972). J. P'ranek, Daedalus 86, 17 (1955). W. 0ttmeier, J. R. Norris and J. J. Katz, in : Book of Abstracts, I 9. Brookhaven Syrup. Biol. No. 28 (1976}. J . J . Katz, W. ()ttmeier and J. R. Norris, Phil. Trans. R. Soc. Lond. B 273, 227 (1976)..]
