1. Preimplantation genetic diagnosis (PGD)
in couples with reciprocal and Robertsonian
translocations – limitations and results
Mardesic,T., Kosarova,M., Zudova,D.,Jelinkova,L.,
Voboril,J., Sobotka,V.
Institute Pronatal, Prague
Antalya 2011

2. Chromosome translocation is a structural chromosomal abnormity caused by rearrangement of parts between nonhomologous chromosomes. Translocations can be balanced (in an even exchange of material with no genetic information extra or missing) or unbalanced (where the exchange of chromosome material is unequal resulting in extra or missing genes). Genetic examination of preimplantation embryos (PGD) can select chromosomal normal (or balanced) embryos suitable for embryotransfer

3. Carriers of translocations have reduced fertility and are at risk of recurrent miscarriages and unbalanced offspring.
Translocations
- reciprocal
- Robertsonian

4. In couples with recurrent miscarriage the incidence of either of the partners being a carrier of a structural chromosomal abnormity is 3-4%, mainly consisting of reciprocal translocations (61%) and Robertsonian translocations (16%)
Clifford et al. , Hum Reprod, 1994
Franssen et al., BMJ, 2005

5. Reciprocal translocations
exchange of material between nonhomologous chromosomes

6. Robertsonian translocations
rearrangement involving centromeric fusion of two acrocentric chromosome with loss of the short arms.
Karyotype leaves only 45 chromosomes since two chromosomes have fused together
The most common translocation in human involves chromosomes 13 and 14
Risks:
Infertility (unbalanced gametes)
Repeated abortions
Cancer (acute and chronic myelogenous leukemia)
Chr.14
Chr.13
Chr.13
Chr.14

7. Material and methods
94 couples (first IVF-PGD cycles) with chromosomal translocation treated in Institute Pronatal
Robertsonian translocation : 44x
Reciprocal translocation: x
PGD method: FISH on interphase blastomere nucleus

8. Material (Robertsonian translocations)
Most frequent: t(13;14) – 70%

9. Material (reciprocal translocations)
50 couples
Chromosomes affected:
1, 2, 3, 4, 5, 9, 10, 11,12, 13, 14, 15, 16, 17, 18, 19, 21

10. Methods Biopsy of 1 blastomere (72 h) Nucleus fixation
Genetic analysis (translocated chromosomes + 13, 18, 21, X, Y)
ET max. 2 blastocysts (120 h) with normal chromosomal arrangement or with balanced translocation

11. Genetic examination – testing of probes before PGD
Robertsonian translocation:
DNA probes for subtelomeric regions of translocated chromosomes
(Cytocell, Kreatech Biotechnology)
Reciprocal translocations:
2 DNA probes for regions distal to breaks+ 1 DNA probe for proximal part (or vice versa), optimum are 2 distal and 2 proximal probes
(Vysis, Cytocell, Kreatech Biotechnology)

12. Results (1) Robertsonian 33,2 7,4 7,2 (97,4) Reciprocal 32,8 6,7
Translocation
Mean
age
No. of fixed blastomeres per couple
No. of diagnosed
embryos per couple (%)
Robertsonian
33,2
7,4
7,2 (97,4)
Reciprocal
32,8
6,7
6,3 (97,0)

13. Results (2) Robertsonian 44 30 (68,2) 270 68 (25,2) Reciprocal 50
Translocation
No. cycles
Cycles with ET (%)
No. embryos with biopsy
No. norm. embryos (%)
Robertsonian 44
30 (68,2)
270
68 (25,2)
Reciprocal 50
27 (54,0)
359
58 (16,4)
Total 94
57 (60,6)
629
126 (21,9)

14. Results (3) Translocation CPR/ started cycle (%) CPR/ ET (%)
Robertsonian
15 (34,1)
15 (50,0)
Reciprocal
9 (18,0)
9 (33,0)
Total
24 (25,5)
24 (42,1)

15. Results (4) Translocation Pregnant Ab. (%) BTHR % Robertsonian 15
1 (6,7)
93,3
Reciprocal 9
1 (11,1)
88,9
Total 24
2 (8,3)
91,7

16. Discussion – summary results
No. cycles
Cycles with ET (%)
CPR / ET (%)
Pronatal 94
57 (60,6)
24 (42,1)
Verlinsky
RBMonline 2005
183
126 (68,9)
45 (35,7)
ESHRE PGD Consortium
2270
1465
(64,5)
357
(24,4)

17. Discussion – results according to the type of translocation
No.of cycles
Cycles with ET (%)
No. of diagnosed embryos
No of normal embryos (%)
Robertsonian
Pronatal
ESHRE PGD Consortium 44
765
30 (68,2)
565 (73,8)
270
4217
68 (25,2)
1457 (34,6)
Reciprocal 50
1505
27 (54)
900 (59,8)
359
9843
58 (16,4)
1974 (20,1)

18. Discussion – baby take home rate
BTHR% before PGD
BTHR % after PGD
Pronatal -
91,7
Verlinsky 2005
18,6
81,4
Munné 2010
11,5% 87

19. Discussion
Preimplantation analysis of interphase blastomere nucleus using FISH cannot discriminate between
„normal“
(with normal chromosomal arrangement)
and „balanced“ blastomeres
(with balanced translocation)

20. Discussion – results according to the type of translocation
in couples with reciprocal translocations more abnormal gametes (and embryos) are created compared to couples with Robertsonian translocation
Couples with Robertsonian translocation have a higher chance for succesful treatment (PR/cycle) compared to couples with reciprocal translocations

21. Robertsonian translocation
Chr.14
Chr.13
Chr.14
Chr.13
Normal
Balanced translocation
Trisomy chr.13
Monosomy
chr.13
Monosomy chr.14
Trisomy chr.14

22. Chromosomal segregation in gametes in a carrier of reciprocal balanced translocation
blastomeres
normal
balanced
U n b a l a n c e d 16

23. Conclusion (1)
PGD can benefit translocation carrier couples with a history of infertility or repeated pregnancy losses to conceive and deliver a healthy child in a short period of time

24. Conclusion (2)
Couples with Robertsonian translocation have a higher chance for succesful treatment (PR/cycle) compared to couples with reciprocal translocations

25. Acknowledgement Gynaecology Embryology Genetics J.Vobořil J.Slámová
D.Kult
R.Středa
T.Mardešić
V.Sobotka
L.Jelínková
Š. Vilímová
J.Mádrová
M.Mašata
I.Hamplová
D.Hlinka
M.Kosařová
D. Zudová
T. Brachtlová
E. Bürgerová
K. Slabá
V. Gregor