Increased nuchal translucency in the human fetus is associated with chromosomal abnormalities, enlarged jugular lymphatic sacs, cardiac defects and changed flow through the ductus venosus. The developmental background of this nuchal edema in relation to the associated anomalies remains elusive. We studied the morphologic correlation between neurogenesis and vasculogenesis in neck, heart, and ductus venosus region of wild type and trisomy 16 mice embryos (E10-E18), using an antibody against Neural Cell Adhesion Molecule (NCAM). Trisomy 16 mice are a model for the above described human phenotype. From E12 trisomy 16 mice showed an altered arrangement of cranial nerves IX, X and XI, which are positioned between the carotid artery, jugular vein and enlarged lymphatic sac. The vagal nerve was significantly smaller, compared with wild type embryos. NCAM was over expressed in both neuronal and cardiovascular structures in trisomy 16 mice, being particularly prominent in the 4 th and 6 th pharyngeal arch arteries, and the ductus venosus. In the 4 th and 6 th pharyngeal arch arteries, NCAM over expression was located to the part of the vessel wall that is closely related to the vagal and recurrent nerve. In case of 4 th pharyngeal arch artery abnormalities NCAM expression, on the other hand, was reduced. In conclusion, the interaction between neurogenesis and vasculogenesis is disturbed in the trisomy 16 mouse model, and might be a common denominator in the spectrum of anomalies associated with increased nuchal translucency. Ultrasonographic measurement of nuchal translucency (NT) in the human fetus at gestational age between 10 to 14 wk is a common screening method to detect trisomy 21. Increased NT is associated with a spectrum of anomalies, including aneuploidy, isolated cardiac defects, and changed flow velocities through the ductus venosus (1,2).The developmental background of increased NT and associated findings is still insufficiently understood. Recently, a disturbed lymphangiogenesis has been suggested as a basis for the nuchal edema because of the concomitant abnormal enlargement and persistence of the jugular lymphatic sacs (JLS) in both human fetuses and mouse embryos with nuchal edema (3,4). This theory explains both the regional accumulation of the fluid in the neck region and the temporary character of the NT enlargement. Other suggested theories, like temporary cardiac failure (5,6) and the alteration of extracellular matrix components (7) might be part of the causal pathway, but fail to completely elucidate this phenomenon.A study (3) of trisomy 16 embryos showed that the endothelium of the enlarged JLS was abnormally thickened. Also, there was a very close correlation of nerves with the JLS and other vascular structures. A mutual influence of nerves and endothelium could play a role in the development of nuchal translucency, since vessels and nerves are known to share many developmental genes (8).The hypothesis for this study was that a disturbance in the interaction between neurogenesis and vasculogene...
