Trisomy 16 in a mid-trimester IVF foetus with multiple abnormalities.

An 18 week foetus with multiple system abnormalities was found to have full trisomy 16. This appears to be only the third reported case surviving into mid-gestation; typically, this common aneuploidy dies post-implantation. Similarities exist in the abnormalities found in the three cases suggesting that there is a 'surviving' trisomy 16 phenotype. It is characterised by: absent hemidiaphragm, pulmonary hypoplasia/aplasia, major cardiac defect, small chest, vertebral and rib defects, cystic kidneys, absent gall bladder, multiple spleens and imperforate anus, together with cleft palate, nuchal webbing/cystic hygroma, microcephaly, marked dysmorphic facial features and dorsiflexed great toe.

A trisomy 2 fetus with severe neural tube defects and other abnormalities.

Examination of an abortus from a 13 week miscarriage revealed a fetus of around 9 weeks developmental age with multiple abnormalities including microcephaly, iniencephaly and encephalocele continuous with cervical and thoracic spina bifida, whose karyotype was subsequently shown to be 47,XY, + 2.

Microdeletion 22q11.2, Kousseff syndrome and spina bifida.

A fetus was diagnosed on ultrasound scan as having sacral spina bifida and a ventricular septal defect in the heart. At postmortem examination the cardiac defect was found to be a conotruncal abnormality, and there was a cleft palate, some facial dysmorphism as well as the spina bifida. A diagnosis of Kousseff syndrome was made, but detailed cytogenetics subsequently revealed a 22q11.2 deletion. In the light of these findings, and on review of the literature, we suggest that spina bifida is recognized as a feature of the variable phenotype associated with this microdeletion.

Multicolor banding detects a complex three chromosome, seven breakpoint unbalanced rearrangement in an ICSI-derived fetus with multiple abnormalities.

We describe a fetus from an intracytoplasmic sperm injection (ICSI) pregnancy with severe facial clefts, receding jaw, preauricular skin tags, postaxial hexadactyly, bi-lobed right lung, supernumerary cranial bone, and dilated lateral ventricles of the brain. Using a combination of G-banding, fluorescence in situ hybridization (FISH), whole chromosome paints (WCPs), subtelomere probes, and multicolor banding (MCB), the karyotype was found to include a de novo unbalanced highly complex chromosome rearrangement (hCCR) involving chromosomes 3, 12, and 15 with seven breakpoints, and including monosomy for two separate regions of chromosome 12.

Six1 and Six4 homeoproteins are required for Pax3 and Mrf expression during myogenesis in the mouse embryo.

In mammals, Six5, Six4 and Six1 genes are co-expressed during mouse myogenesis. Six4 and Six5 single knockout (KO) mice have no developmental defects, while Six1 KO mice die at birth and show multiple organ developmental defects. We have generated Six1Six4 double KO mice and show an aggravation of the phenotype previously reported for the single Six1 KO. Six1Six4 double KO mice are characterized by severe craniofacial and rib defects, and general muscle hypoplasia. At the limb bud level, Six1 and Six4 homeogenes control early steps of myogenic cell delamination and migration from the somite through the control of Pax3 gene expression. Impaired in their migratory pathway, cells of the somitic ventrolateral dermomyotome are rerouted, lose their identity and die by apoptosis. At the interlimb level, epaxial Met expression is abolished, while it is preserved in Pax3-deficient embryos. Within the myotome, absence of Six1 and Six4 impairs the expression of the myogenic regulatory factors myogenin and Myod1, and Mrf4 expression becomes undetectable. Myf5 expression is correctly initiated but becomes restricted to the caudal region of each somite. Early syndetomal expression of scleraxis is reduced in the Six1Six4 embryo, while the myotomal expression of Fgfr4 and Fgf8 but not Fgf4 and Fgf6 is maintained. These results highlight the different roles played by Six proteins during skeletal myogenesis.

The human embryo: a scientist's point of view.

...Thus, my judgement is that a human embryo is not a human person, and so we may do experiments on it which involve killing it. But my judgement is also that a human embryo has the potential to become a human being. The consequence of this attribute is that it imposes limits on the kinds of experiments which may be performed on human embryos. It is this which sets the boundaries. Experiments which may harm the embryo while still allowing it subsequently to realise its potential, and become a person, should not be permitted. It is the potentiality of the human embryo which governs our behaviour towards it. Its potential makes it special, and radically different from any other human tissue. This potential which the early embryo has means that great respect must always be accorded it, and great thought and care must surround any dealings with it....