Table 1. The amount, but not the source of Endoglycan matters.

Treatment	No of embryos	No of inj. sites	% inj sites normal PT	p-Value	% inj sites stalling	% inj sites no turn
Untreated	14	111	85.3 ± 2.6	0.999	0.8 ± 0.8	14.6 ± 2.7
EGFP	14	85	80.5 ± 6.7	1	5.1 ± 2.4	18.6 ± 7.4
dsEndo	21	161	30.2 ± 4.4	<0.0001	31.6 ± 5	50.1 ± 3.9
β-actin::EndoOE	16	91	49.1 ± 5.4	0.0177	20 ± 5.1	30 ± 5
Hoxa1::Endo-L	25	234	38.5 ± 5.7	<0.0001	24.1 ± 4.8	44.5 ± 5
Hoxa1::Endo-M	18	136	60.3 ± 6.7	0.3686	10.9 ± 4.2	32.1 ± 5
Hoxa1::Endo-H	7	72	24.6 ± 10.1	<0.0001	40.0 ± 11.3	44.1 ± 7
Math1::Endo-L	15	157	59.6 ± 6.8	0.3738	12.3 ± 3.5	30.9 ± 5.4
Math1::Endo-M	7	86	35 ± 10.7	0.0031	31.7 ± 7.2	42.4 ± 9.3
Math1::Endo-H	8	86	26.3 ± 6.5	<0.0001	50.8 ± 6.4	40.5 ± 6.1

Concomitant expression of Endoglycan could rescue the aberrant axon guidance phenotype induced by the downregulation of Endoglycan throughout the spinal cord. It did not matter whether Endoglycan was expressed under the Hoxa1 enhancer for specific expression in floor-plate cells, or under the Math1 enhancer for specific expression in dI1 neurons. However, the rescue effect was dose-dependent. Too little, or too much Endoglycan was inducing axon guidance defects. For rescue, Endoglycan cDNA under the control of the Hoxa1 enhancer (Hoxa1::Endo) or the Math1 enhancer (Math1::Endo) were injected at 150 ng/µl (low, L), 300 ng/µl (medium, M), or 750 ng/µl (high, H). The same criteria for quantification were applied as for the results shown in Figure 2. There was no fundamental difference between too much or too little stickiness. In both conditions, we found stalling in the floor plate and failure to turn into the longitudinal axis. The only difference was that we did not find any ‘corkscrew’ phenotypes after overexpression of Endoglycan. The number of embryos and the number of DiI injection sites analyzed per group are indicated. The average % of injection sites with normal axon guidance phenotypes (± standard error of the mean) and the p-value for the comparison between the respective group and the control-treated (EGFP-expressing) group are given. The last two columns list the average values for injection sites with the majority of axons stalling in the floor plate and the majority of axons not turning into the longitudinal axis. Because some injection sites can have both phenotypes, the values do not add up to 100%.