Chromosome abnormalities in chicken ( Gallus domesticus ) embryos: Types, frequencies and phenotypic effects PDF

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Chromosoma (Berl.) 37, 309--326 (1972) 9 by Springer-Verlag 1972 Chromosome Abnormalities in Chicken (Gallus domesticus) Embryos: Types, Frequencies and Phenotypic Effects Stephen E. Bloom Department of Poultry Science, Cornell University, Ithaca, New York Received January 11, 1972 / Accepted Februa...

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Chromosoma (Berl.) 37, 309--326 (1972) 9 by Springer-Verlag 1972

Chromosome Abnormalities in Chicken (Gallus domesticus) Embryos: Types, Frequencies and Phenotypic Effects Stephen E. Bloom Department of Poultry Science, Cornell University, Ithaca, New York Received January 11, 1972 / Accepted February 18, 1972

Abstract. Cytological screening of 4182 chick embryos from 10 strains and 5 strain crosses was performed to determine the types and frequencies of chromosome abnormalities. Gross phenotypic effects, such as growth retardation and malformation, were noted. Clues to the etiology of such chromosome aberrations were also sought. The following euploid series was observed: Haploid mosaics (A-Z/2A-ZZ, A-Z/2A-ZZ/3A-ZZZ, A-Z/A.W/2A-ZW/2A-ZZ,

A-Z/A-W/2A-ZW/

3A-Z ?), diploid (2A-ZZ and 2A-ZW), triploid (3A-ZWW, 3A-ZZW, 3A-ZZZ, 3A-ZZZW) and tetraploid (4A-ZZWW and 4A-ZZZZ). Aneuploidy was observed as follows: Trisomy for chromosome numbers 1, 2, 3, 4 and double trisomy 2/5. Trisomy-4 with deletion of 50% of the long arm of one member of the trisomie triplet was observed. A 3A-ZWW embryo was found with two cell populations: one, disomic for chromosome 2 and 6; the other, tetrasomic for 2 and 6. Of the 4182 embryos sampled 1.4% were haploids, 97.5 % diploids, 0.8% triploids, 0.1% tetraploids and 0.2% trisomics. On the average 10.8% of the early dead embryos were euploid (excluding diploid) oz" aneuploid. However, the range for euploidy and aneuploidy among strains was 2.3-23.7% of early deads. Haploid embryos were consistently underdeveloped at 4 days of incubation (D.I.), and died by 5-7 D.I. About 90% of (36) triploid embryos died at or before 4 D.I. The remaining 10% (normal embryos) died prior to hatching. Trisomic embryos were dead or underdeveloped at 4 D.I. Tetraploidy appeared to be lethal at a very early stage. The various strains examined had different overall rates of chromosome aberrations (0.4-8.9%), and also showed different varieties of such aberrations. The modes and possible causes of meiotic, mitotic and fertilization errors are considered. Genetic control of chromosome abnormalities, particularly haploidy, is postulated.

Introduction I d e n t i f i c a t i o n of various types of chromosome abnormalities (aneuploidy, polyploidy, translocations, inversions, deletions, breaks) i n higher a n i m a l s has proceeded with increasing precision in the last decade. Less is k n o w n a b o u t the basic causes of meiotic, mitotic a n d fertilization errors. A n i m a l models p e r m i t the testing of such variables as genotype, physiological state, infection b y bacteria and/or vh'uses, n u t r i t i o n a l variables a n d e n v i r o n m e n t a l pollutants. The chicken offers a test system for i n v e s t i g a t i n g the effects of the above m e n t i o n e d variables

310

S.E. Bloom:

on meiosis, mitosis and fertilization as reflected in the chromosome constitution and developmental p a t t e r n of the embryo (Bloom, 1971) as well as in the growing bird (Bloom, 1970a; Bloom, Buss, and Strother, 1970). The development of a cytogenetic model began in 1966 (Bloom and Buss) with the observation of a phenotypically abnormal chick e m b r y o having tI~ploid-diploid mosaieism. This observation stimulated further studies on the possible association between chromosome abnormalities and early embryonic mortality. A sampling of 115 embryos revealed six additional cases of chromosome defects, all appearing in early deads (Bloom, 1969). Cytogenetic d a t a on over 4000 embryos have been collected since 1966, and are herein reported. The types, frequencies and phenotypie effects of chromosome aberrations are defined for ten strains and five strain crosses. Two m a j o r conclusions emerge: Fh'st, a significant portion of early dead embryos (up to 24%) are aneuploid and euploid (excluding diploid) ; second, embryos with a b n o r m a l numbers of chromosomes usually die prior to hatching. As a result of these studies estimates can be made of the types a n d frequencies of meiotic errors occurring during m a t u r a t i o n of the male and female gametes, errors at fertilization a n d early cleavage defects. Materials and Methods Pedigree matings involving ten strains and five strain crosses were made. Obese (Cole, 1966), Araucana (Bruckner and Hurt, 1939), Jungle Fowl (Hurt, 1949), Low Line (Lamoreux, Hurt, and Hall, 1943) and S-strMn (Cole, 1967) chickens were pen mated with 6-10 females per male. K-strain (C01e, 1967), ]~iboflavin Deficient (Maw, 1954), Naked (Hurt, 1949), Diabetes Insipidus (Dunson and Buss, 1968) and C-strain (Cole, 1967) chickens were individually caged and mated by artificial insemination (A.I.) with one male per three females. Males were shifted periodically and 5 strain crosses made in an effort to identify the parents responsible for producing progeny with aberrant chromosomes. Of the ten strains, the Jungle Fowl was the closest relative of the ancestral or wild-type chicken. Data on reproductive performance (fertility, hatchability, egg production) were collected for each chicken. An attempt was made to correlate these data with the occurrence of chromosome abnormalities. An average of 250 embryos were examined from each strain and strain cross. The handling of embryos and preparation of cells for cytogenetie studies were performed as previously described (Bloom, 1969; Bloom, 1971; Bloom, Povar, and Peakall, 1972). A minimum of 25 metaphases were examined per embryo, and 150~250 metaphases were studied if a chromosome aberration was discovered in the initial 25 cells.

Results Of 4182 embryos examined in this s t u d y , 103 or 2.5% had aberrant chromosome complements (Table ]). The following euploid series was observed: Haploid mosaics (A-Z/2A-ZZ and A-Z/2A-ZZ/3A-ZZZ),

Chromosome Abnormalities in Chicken Embryos

3it

Table 1. Types and frequencies of chromosome abnormalities in four-d~y chick embryos a Euploid Haploid mosaics

Diploid

Triploid

A:2A

A:YA:3A

ZZ or ZW

ZWW ZZW Z Z Z

Tetraploid

51

8

4079

15

7

9

?

2

ZZWW

ZZZZ

1

1

Aneuploid Chromosome number

Trisomie I

2

Totals 3

4

2-5

Number with abnormal

Grand total

chromosoInes 2

2

2

2

1

4 I82

103

a This table includes data on 313 embryos not given in Tables 3 and 4.

Table 2. Types and percentages of chromosome abnormalities observed in four-day chick-embryos Euploid

AbnormaI~ ( % ) Total b (%)

Haploid

Diploid

Triploid

Tetraploid

57.3 1.4

-97.5

32.0 0.8

1.9 0.1

Trisomic

Totals

8.7 0.2

% with abnormal chromosomes (103/4182) = 2.5 %

Aneuploid

Abnormala (%) Total b ( % )

a Abnormal (%) = number of euploid or aneuploid embryos/103 (total number of chromosomally ~bnormal embryos). b Total ( % ) ~ number of euploid or aneuploid embryos/4182 (total number of embryos).

diploid (2A-ZZ a n d 2A-ZW), triploid (3A-ZWW, 3A-ZZW, 3A-ZZZ, 3A-ZZZW) a n d t e t r a p l o i d (4A-ZZWW a n d 4A-ZZZZ). A n e u p l o i d y was observed as follows: T r i s o m y for chromosomes 1, 2, 3, 4 a n d double t r i s o m y 2/5. Of the 4182 embryos sampled 1.4% were haploids, 97.5% diploids, 0.8% triploids, 0.1% tetraploids a n d 0.2% trisomics. Of the

312

S.E. Bloom: Table 3. Chromosome aberration rates in various strains and strain crosses

Strains

Aberration rates for: All embryos

Fhenotypically normal embryos (%)

Total number embryos

(%)

Phenotypically abnormal embryos (%)

Obese K Riboflavin deficient (rd) Naked (n) Diabetes insipidus Araucana Jungle Fowl C Low Line S

0.4 1.0 1.4 1.9 2.6 2.7 2.8 3.5 5.7 7.1

2.3 4.5 5.2 8.6 18.0 9.1 4.5 17.0 19.5 23.7

0 0 0.4 0 0.8 0 1.0 0 0.8 1.0

558 309 357 154 265 186 214 429 319 140

K • C n• K • S rd • C n• C

1.1 1.9 2.1 4.3 8.9

2.6 2.9 7.1 15.7 21.5

0 1.5

267 103

0.5

240

1.2 0

]14 214

Ranges

0.4-8.9

2.3-23.7

0-1.5

103 e m b r y o s w i t h a b n o r m a l chromosomes 57.3 % were haploids, 32.0% triploids, 1.9% t e t r a p l o i d s a n d 8.7% trisomics ( T a b l e 2 ) . C h r o m o s o m e a b e r r a t i o n r a t e s v a r i e d f r o m 0 . 4 - 8 . 9 % for t h e t e n s t r a i n s a n d five s t r a i n crosses (Table 3). The J u n g l e F o w l h a d a n interm e d i a t e r a t e of 2.8%. A b e r r a t i o n r a t e s were also c a l c u l a t e d a c c o r d i n g to e m b r y o p h e n o t y p e (Table 3). Of t h e p h e n o t y p i e a l l y a b n o r m a l (early deaths, gross malformations) e m b r y o s a t 4 - 5 d a y s of i n c u b a t i o n (D.I.), 2.3-23.7% were e u p l o i d (excluding diploid) a n d a n e u p l o i d (mean ~ 10.8 %), a n d 0 - l . 5 % of n o r m a l e m b r y o s were euploid (excluding diploid) a n d a n e u p l o i d (mean =: 0.5 % ). The 10 strains showed different v a r i e t i e s of c h r o m o s o m e a b e r r a t i o n s (Table 4). T h e J u n g l e F o w l p r o d u c e d o n l y t r i p l o i d e m b r y o s ( 3 A - Z W W or 3A-ZZZ), i n d i c a t i n g diploid egg cell p r o d u c t i o n in this w i l d - t y p e p o p u l a t i o n . H a p l o i d y occurred in 12 of t h e 15 strains (80%), t r i p l o i d y in 11 of 15 (73%), t e t r a p l o i d y in 2 of 15 (13%) a n d t r i s o m y in 7 of 15 (47%). Multiple occurrences of a b e r r a t i o n s were c o m m o n , w i t h 73% o~ strains h a v i n g t w o or m o r e t y p e s of aberrations.

Chromosome Abnormalities in Chicken Embryos

313

Table 4. Chromosome aberration types and frequencies in various strains and strain crosses Strains

Aberration rates for Haploid

Triloloid

Trisomic

(%)

Tetraploid (%)

(%)

Total number embryos

(%) Araucana rd • C

2.7 4.3

0 0

0 0

0 0

186 114

Jungle Fowl Obese

0 0

2.8 0.4

0 0

0 0

214 558

C S Diabetes inspidus n• K

2.3 5.0 0.8 1.0

1.2 2.1 1.9 1.0

0 0 0 0

0 0 0 0

429 140 265 103

K Naked

0.6 1.3

0 0

0 O

0.3 0.6

309 154

Low line K • C K • S

2.8 0.4 0.4

1.9 0.4 1.3

0 0 0

0.9 0.4 0.4

319 267 240

Riboflavin deficient 0

0.8

0.3

0.3

357

n• C

0.9

0.5

0.5

214

7.0

I n six strains, chromosome a b e r r a t i o n s p r o d u c e d b y i n d i v i d u a l m a t i n g c o m b i n a t i o n s were s t u d i e d (Table 5). F r o m 12-67 % of the d a m s t e s t e d p r o d u c e d euploid (except diploid) a n d a n e u p l o i d progeny. The p r o d u c t i o n of h a p l o i d e m b r y o s was female d e p e n d e n t . This was demons t r a t e d with C-strain hens 12, 17 a n d 18, where shifting to u n r e l a t e d sires d i d n o t stop h a p l o i d production. Males from previous h a p l o i d p r o d u c i n g pairs failed to induce h a p l o i d y with females t h a t were n o t h a p l o i d producing. The h a p l o i d p r o d u c i n g hens 12, 17 a n d 18 were full sisters d e r i v e d from hen 61. The r e p e a t e d p r o d u c t i o n of t r i p l o i d e m b r y o s from certain hens was also n o t e d (hens 31, 51, 20, 31, 36). These e m b r y o s were either 3 A - Z W W or 3A-ZZZ, i n d i c a t i n g diploid egg cell p r o d u c t i o n . All e m b r y o s were e x a m i n e d a t 4 - 5 D.I. for the presence of gross a n a t o m i c a l m a l f o r m a t i o n s a n d classified as given in Table 6. The g r e a t m a j o r i t y (92 %) of h a p l o i d mosaic e m b r y o s achieved only early developmen~. A n occasional e m b r y o achieved n e a r n o r m a l d e v e l o p m e n t . This was associated with either a high p r o p o r t i o n of diploid or t r i p l o i d cells. The one n o r m a l e m b r y o in Table 6 was A-Z (39%), 2A-ZZ (15%) a n d 3A-ZZZ (46%). Considerable v a r i a t i o n in d e v e l o p m e n t was o b s e r v e d for t r i p l o i d e m b r y o s (Table 7). Only 3A-ZZZ e m b r y o s a c h i e v e d n o r m a l 22

Chromosoma (Berl.), Bd. 37

314

S . E . Bloom:

Table 5. Chromosome aberrrations produced b y individual m a t i n g combinations Strain

Number 99

Number ~

Dam numher

Sire number

:K

25

12

31 33 67 68 70

390 375 703 703 1099

83 86

5089 5093 1091

51

3986 3981 3969 3982 3969 3981

Naked

9

Diabetes insipidus

10

C

36

4

7

56 58

17

12 13 17 18 19 20 21 23 26 28 60 61 65 66

Ribo: flavin deficient

Araueana

12

10

31

37 38 42

32 390 4171 4171 4174 4174 399 415 415 Y-9-6 Y-9-6

475 481 482 486 620

1 2 2 2 3

32 34 35 36

42

12

299 X1029 299 373 299 373 299 299 299 1091 319 365 374 374 720 703 275 720 720

Number haploid

Number triploid

Number trisomic

Mumber tetraploid

% afleered dams

2 1 1 1 1

1 1 1

1

20 22

4 1 2

30

7 1 8 19 1 1 1

1 2 39

2 1

3

1 1 1 2 1 1

67

12

Chromosome Abnormalities in Chicken Embryos

315

Table 6. Gross phenotypic descriptions of haploid mosaic embryos after four to five days of incubation Macroscopic phenotypes Haploid type

BM a

Early b

Early dead c

Small aa

Small dead bb

Norreal ce

Number of embryos

A : 2A A:2A:3A

19 1

31 6

0 0

2 1

1 0

0 1

53 9

BM = blood and membrane only. b Early = development equivalent to a 2 to 3 day embryo. c Early dead = death at 2-3 days. aa Small ~ development equivalent to 3-4 day embryo. bb Small d e a t h - - d e a t h at 3 4 days. cc Normal ~ normal development at 4-5 days of incubation.

Table 7. Gross phenotypic descriptions of triploid embryos after four to five days of incubation Macroscopic phenotypes Triploid type

BM

Early

Early dead

Small

Small dead

Normal Number of embryos

ZWW

5

7

4

3

0

0

19

ZZW ZZZ ZZZW

0 1 0

2 1 0

1 1 0

4 2 0

0 1 0

0 3 1

7 9 1

Table 8. Gross phenotypic descriptions of trisomic embryos after four to five days of incubation Macroscopic phenotypes Trisomy

BM

Early

Early dead

1

1

1

0

2 3 4 2/5

0 0 1 o

1 0 0 o

1 0 0 1

Small

Small dead

Normal

Number of embryos

0

0

0

2

0 0 1 o

0 2 0 o

0 0 0 o

2 2 2 1

development at 4 5 D.I. Also an occasional 3A-ZZZ embryo had a very small or missing pair of eyes. Trisomie embryos exhibited a broad spectrum in development (Table 8). No organ specific malformations were seen. An inverse relationship between size of trisomic chromosome 22*

316

S . E . Bloom:

Table 9. Incidence of triploidy (ZWW, ZZZ) during a one year egg laying period Dam nmnber

Date of first egg

Number of triploid embryos

Occurrence of triploid embryos (Days from first egg)

31 (Riboflavin)

9/25/70

3

14, 24, 173

34 (Riboflavin)

10/4/70

1

227

36 (Riboflavin)

9/26/70

2

74, 333

51 (DI)

2/7/71

4

37, 54, 78, 197

56 (DI)

1/19/71

1

206

58 (DI)

1/25/71

1

174

Table 10. Incidence of haploidy during a one year egg laying period for one C-strain hen m a t e d sequentially with two males Month

Number of eggs

Fertility (%)

Number of haploid embryos

Percentage of haploid embryos a

March April May June July August September October November December January February

29 28 25 22 24 26 23 24 19 18 21 19

59 64 68 68 46 4 0 79 63 50 33 26

0 4 2 2 3 0 0 3 3 0 1 1

0 22 12 13 27 0 0 16 25 0 14 20

Totals Means Ranges

278 23.2 18-29

--0-79

19 1.6 0-4

-14.5 0-27

a N u m b e r of haploid embryos/number of fertile eggs • 100. and growth achieved was noted, but the data were obtained from only 9 embryos. I n t w o s t r a i n s , t h e i n c i d e n c e of t r i p l o i d y ( Z W W , Z Z Z ) w a s o b s e r v e d r e l a t i v e t o t h e p o s i t i o n of t h e egg i n a o n e y e a r l a y i n g c y c l e ( T a b l e 9).

Chromosome Abnormalities in Chicken Embryos

317

Fig. l a and b. Colehieinized metaphases from squashed embryonic membranes of a developing mosaic embryo, a Haploid (A-Z) cell. b Haploid (A-W) cell. See Fig. 2 for karyotypes

Fig. 2a and b. Karyotypes of the largest ten chromosomes in haploid cells of a single embryo, a Haploid A-Z karyotype from cell in Fig. l a. b Haploid A-W karyotype from cell in Fig. l b

I n t h e R i b o f l a v i n Deficient strain, t r i p l o i d y occurred a t various p o i n t s in t h e cycle including two weeks...