Cytogenetic and histological features of a human embryo with homogeneous chromosome 8 trisomy.
BACKGROUND
Homogeneous and complete trisomy 8 is extremely rare. With one recent neonatal exception, all reported cases have been mosaic, due to mitotic non-disjunction during early zygotic development. We report a case of chromosome 8 trisomy in a human embryo examined at Carnegie stage 11 (25 days post-fertilization). It presented severe cardiovascular and central nervous system malformations.


METHODS
The unusual bifid heart in this embryo spurred a detailed histological examination, karyotyping of a chorionic villus sample and subsequent FISH on inter-phase nuclei of intra-embryonic sections.


RESULTS
Trophoblast cells had a karyotype of 47,XX, +8. Within the embryo proper, FISH demonstrated that the trisomy 8 was homogeneous in embryonic as well as extra-embryonic tissues. FQ-PCR supports a meiosis I origin of non-disjunction. In sections, the pharyngeal arches (including cardiac outflow tract), forebrain, mesonephros and liver were absent. Somites and yolk sac blood vessels were irregularly shaped.


CONCLUSIONS
We show that homogeneous, intra-embryonic trisomy 8 is compatible with implantation and early human development. Molecular pathways that may be compromised and their impact on organogenesis are discussed.
Golzio
Christelle
C
INSERM U781, Hôpital Necker - Enfants Malades, 149 rue de Sèvres, 75743 Paris Cedex 15, France.
Guirchoun
Jessica
J
Ozilou
Catherine
C
Thomas
Sophie
S
Goudefroye
Géraldine
G
Morichon-Delvallez
Nicole
N
Vekemans
Michel
M
Attié-Bitach
Tania
T
Etchevers
Heather C
HC
D000015:Abnormalities, Multiple; D000025:Abortion, Eugenic; D018376:Cardiovascular Abnormalities / Q000235:genetics* / Q000473:pathology; D015193:Chorionic Villi Sampling; D002898:Chromosomes, Human, Pair 8; D004622:Embryo, Mammalian / Q000002:abnormalities*; D005819:Genetic Markers / Q000235:genetics; D006801:Humans; D009421:Nervous System Malformations / Q000235:genetics* / Q000473:pathology; D032681:Spectral Karyotyping; D014314:Trisomy; D014327:Trophoblasts / Q000473:pathology
D005819:Genetic Markers