Table 3.

Quantification of neuron positioning defects in genetic chimeras composed of wild-type and cxcr7b^−/− embryos

Genotype	Position relative to MHB			n (neurons)	Ectopic
	Anterior (ectopic)	Adjacent (ectopic)	Posterior (correct)
					%
Wild type into TgSN-less wild type	0	11	154	165	6.70
Wild-type into TgSN-less cxcr7b−/−	94	81	20	195	89.70
cxcr7b−/− into TgSN-less wild type	7	48	328	383	14.40
cxcr7b−/− into TgSN-less cxcr7b−/−	55	50	16	121	86.80

Neurons were categorized according to their position with respect to the MHB at the 12-somite stage as diagrammed in Fig. 5 U.