a, Differentially expressed genes in E14.5 brains of SPF, ABX, and Sp dams (Two-tailed Wald, n=3 dams). b, NTNG1 and LRRC4C expression in E14.5 brains (Two-way ANOVA+Tukey’s, n=9, 13, 8 offspring from different dams). c, Netrin-G1a (magenta) and L1 (cyan) in E14.5 Sp brain sections. Scale=500μm. d, Netrin-G1a fluorescence per matched ROI in E14.5 brain sections. (Two-way ANOVA+Tukey’s, n=5 offspring from different dams). e, L1 fluorescence per matched ROI in E14.5 brain sections (Two-way ANOVA+Tukey’s, n= 5 offspring from different dams). f, Netrin-G1a in whole E14.5 brains from Sp dams. Scale=100μm. g, Volume of Netrin-G1a axons in whole E14.5 brains. (One-way ANOVA+Tukey’s; n= 5 offspring from different dams). h, Length of Netrin-G1a axons in whole E14.5 brains. (One-way ANOVA+Tukey’s; n= 5 offspring from different dams). i, Distance from distal tip of Netrin-G1a axons to cortex in whole E14.5 brains. (One-way ANOVA+Tukey’s; n= 5 offspring from different dams). j, Circumference of Netrin-G1a axonal bundle at the internal capsule (IC) in whole E14.5 brains. (One-way ANOVA+Tukey’s; n= 5 offspring from different dams). k, Force filament to induce 50% paw withdrawal in adult offspring (One-way ANOVA+Tukey’s, n = 5, 7, 7 dams). l, Forepaw sensitivity, as latency to contact the adhesive tape, in adult offspring (left) (One-way ANOVA+Tukey’s, n = 6, 6, 7 dams). Forepaw motor dexterity, as latency to remove the adhesive tape after first contact, in adult offspring (right) (One-way ANOVA+Tukey’s, n = 6, 6, 7 dams). Mean±SEM. SPF and ABX data are as displayed in Figure 1, 2 and Extended Figure 2, 3, 4. *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001, n.s.=not statistically significant