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

sanatorium@pronatal.cz

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