An additional human chromosome 21 causes suppression of neural fate of pluripotent mouse embryonic stem cells in a teratoma model.
BACKGROUND
Down syndrome (DS), caused by trisomy of human chromosome 21 (HSA21), is the most common genetic cause of mental retardation in humans. Among complex phenotypes, it displays a number of neural pathologies including smaller brain size, reduced numbers of neurons, reduced dendritic spine density and plasticity, and early Alzheimer-like neurodegeneration. Mouse models for DS show behavioural and cognitive defects, synaptic plasticity defects, and reduced hippocampal and cerebellar neuron numbers. Early postnatal development of both human and mouse-model DS shows the reduced capability of neuronal precursor cells to generate neurons. The exact molecular cause of this reduction, and the role played by increased dosage of individual HSA21 genes, remain unknown.


RESULTS
We have subcutaneously injected mouse pluripotent ES cells containing a single freely segregating supernumerary human chromosome 21 (HSA21) into syngeneic mice, to generate transchromosomic teratomas. Transchromosomic cells and parental control cells were injected into opposite flanks of thirty mice in three independent experiments. Tumours were grown for 30 days, a time-span equivalent to combined intra-uterine, and early post-natal mouse development. When paired teratomas from the same animals were compared, transchromosomic tumours showed a three-fold lower percentage of neuroectodermal tissue, as well as significantly reduced mRNA levels for neuron specific (Tubb3) and glia specific (Gfap) genes, relative to euploid controls. Two thirds of transchromosomic tumours also showed a lack of PCR amplification with multiple primers specific for HSA21, which were present in the ES cells at the point of injection, thus restricting a commonly retained trisomy to less than a third of HSA21 genes.


CONCLUSIONS
We demonstrate that a supernumerary chromosome 21 causes Inhibition of Neuroectodermal DIfferentiation (INDI) of pluripotent ES cells. The data suggest that trisomy of less than a third of HSA21 genes, in two chromosomal regions, might be sufficient to cause this effect.
Mensah
Afua
A
Centre for Haematology, Institute of Cell and Molecular Science, Barts & The London, Queen Mary's School of Medicine, University of London, 4 Newark Street, London E1 2AT, UK. afua.mensah@irb.unisi.ch
Mulligan
Claire
C
Linehan
Jackie
J
Ruf
Sandra
S
O'Doherty
Aideen
A
Grygalewicz
Beata
B
Shipley
Janet
J
Groet
Juergen
J
Tybulewicz
Victor
V
Fisher
Elizabeth
E
Brandner
Sebastian
S
Nizetic
Dean
D
D000818:Animals; D001253:Astrocytes / Q000378:metabolism / Q000473:pathology; D002454:Cell Differentiation; D002460:Cell Line; D002891:Chromosomes, Human, Pair 21 / Q000235:genetics*; D005455:Fluorescent Antibody Technique; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D009374:Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D054258:Neural Plate / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D039904:Pluripotent Stem Cells / Q000378:metabolism* / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013724:Teratoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D014404:Tubulin / Q000235:genetics / Q000378:metabolism
D005904:Glial Fibrillary Acidic Protein; D014404:Tubulin