Quantification and analysis of apoptosis in embryonic atrioventricular endocardial cushions of the Ts65Dn mouse model for Down syndrome
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Gotlieb, Naomi R.
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The Ts65Dn mouse model for Down syndrome (DS) has triplication of more than half of the mouse genes orthologous to those on human chromosome 21, and exhibits many phenotypes characteristic of human DS. Previous gross anatomical examinations have shown that some trisomic neonates have cardiovascular abnormalities similar to the congenital heart defects affecting 50% of children born with DS. Some of these defects may be due to reduced levels of programmed cell death (apoptosis) identified in the atrioventricular (AV) endocardial cushions of trisomic versus euploid 13.5 days post coitum (dpc) embryonic hearts. To determine the spatiotemporal origins of such differences, trisomic and euploid embryos were collected at 12.5 dpc. Apoptosis was identified in 8 µm sagittal embryonic sections every 40 µm through the entire AV endocardial cushion region using the fluorometric Terminal deoxynucleotidyl Transferase fluorescein-12-dUTP Nick End Labeling (TUNEL) assay with DAPI nuclear counterstain. The stained tissues were examined by fluorescence microscopy to quantify the proportion of apoptotic nuclei. At 12.5 dpc, the total percentage of apoptosis in the AV cushion region of each embryo was quantified and the average percentage was found to be 2.39 ± 2.09% in euploid embryos (n = 4) versus 0.87 ± 0.24% in the trisomics (n = 4), suggesting that a defect in the regulation of an apoptotic pathway may represent one contributing factor in the development of cardiac abnormalities in the Ts65Dn mice that model human DS.
Franklin and Marshall College Archives, Undergraduate Honors Thesis 2009
- F&M Theses Collection