preimplantation genetic diagnosis (pgd) in couples with reciprocal and robertsonian translocations...
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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
www.pronatal.cz Antalya 2011
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
• Carriers of translocations have reduced fertility and are at risk of recurrent miscarriages and unbalanced offspring.
• Translocations
- reciprocal
- Robertsonian
• 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
Reciprocal translocationsReciprocal translocations
• exchange of material between nonhomologous chromosomes
Robertsonian translocationsRobertsonian 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 abortionsCancer (acute and chronic myelogenous
leukemia)
Chr.1Chr.144
Chr.1Chr.133
Chr.1Chr.144Chr.1Chr.133
Material and methodsMaterial and methods
• 94 couples (first IVF-PGD cycles) with chromosomal translocation treated in Institute Pronatal 2004-2010
• Robertsonian translocation : 44x • Reciprocal translocation: 50x
• PGD method: FISH on interphase blastomere nucleus
Material Material (Robertsonian translocations)(Robertsonian translocations)
Most frequent: t(13;14) – 70%
Material Material (reciprocal translocations)(reciprocal translocations)
• 50 couples• Chromosomes affected:
1, 2, 3, 4, 5, 9, 10, 11,12, 13, 14, 15, 16, 17, 18, 19, 21
MethodsMethods
• 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
Genetic examination – Genetic examination – testing of probes before testing of probes before
PGDPGD
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)
Results (1)Results (1)
TranslocationMean
age
No. of fixed blastomeres per couple
No. of diagnosedembryos per couple (%)
Robertsonian 33,2 7,4 7,2 (97,4)
Reciprocal 32,8 6,7 6,3 (97,0)
Results (2)Results (2)
TranslocationNo. 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)
Results (3)Results (3)
TranslocationCPR/ 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)
Results (4)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
Discussion – summary resultsDiscussion – summary results
No. cycles Cycles with ET (%)
CPR / ET (%)
Pronatal 94 57 (60,6) 24 (42,1)
Verlinsky
RBMonline 2005183 126 (68,9) 45 (35,7)
ESHRE PGD Consortium
2270 1465
(64,5)
357
(24,4)
Discussion – results according to the Discussion – results according to the type of translocationtype of translocation
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
Pronatal
ESHRE PGD Consortium
50
1505
27 (54)
900 (59,8)
359
9843
58 (16,4)
1974 (20,1)
Discussion – Discussion – baby take home ratebaby take home rate
BTHR% before PGD
BTHR % after PGD
Pronatal - 91,7
Verlinsky 2005 18,6 81,4
Munné 2010 11,5% 87
DiscussionDiscussion
Preimplantation analysis of interphase blastomere nucleus using FISH cannot discriminate between
„normal“
(with normal chromosomal arrangement)
and „balanced“ blastomeres
(with balanced translocation)
Discussion – results according to the type Discussion – results according to the type of translocationof 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
Robertsonian translocation
Chr.1Chr.133
Chr.1Chr.144
Chr.1Chr.133 Chr.1Chr.144
Normal Balanced translocati
on
Trisomy chr.13
Trisomy chr.14
Monosomy
chr.13
Monosomy chr.14
normal balanced U n b a l a n c e d
16
bla
sto
mer
es
gam
ete
s
Chromosomal segregation Chromosomal segregation in gametes in a carrier of in gametes in a carrier of reciprocal balanced reciprocal balanced translocationtranslocation
Conclusion (1)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
Conclusion (2)Conclusion (2)
Couples with Robertsonian translocation have a higher chance for succesful treatment (PR/cycle) compared to couples with reciprocal translocations
AcknowledgementAcknowledgement
J.Vobořil
J.Slámová
D.Kult
R.Středa
T.Mardešić
V.Sobotka
L.Jelínková
Š. Vilímová
J.Mádrová
M.Mašata
I.Hamplová
D.Hlinka
Gynaecology Embryology Genetics
M.Kosařová
D. Zudová
T. Brachtlová
E. Bürgerová
K. Slabá
V. Gregor