Fig. 6
From: Analysis of structural variation among inbred mouse strains
BTBR mice have a non-functional Draxin protein that contributes to the absence of its corpus collosum (CC). A) BTBR has an 8 bp deletion at the 3’ end of exon 2 of Draxin, which is not present in 52 other strains. B) The full length draxin protein has 343 amino acids, but this frameshift deletion generates a termination codon at amino acid 160; this eliminates the Netrin and DCC binding domains from BTBR Draxin that are essential for its neurodevelopmental function. C) The CC is partially restored in BTBR mice with a heterozygous knockin (KI) that reverted the 8 bp Draxin deletion to wild type (BTBRDraxin WT/− KI mice). Coronal (rows 1–2) and horizontal (row 3) images of adult female C57BL/6, BTBR and BTBRDraxin WT/− KI mice obtained with a Bruker 11.7-T MRI. Each row represents aligned brain sections obtained from these mice. The CC is within the areas indicated by the red dotted lines. BTBR mice have a complete agenesis of the CC (as indicated by the disconnection between the left and right hemispheres), the CC of C57BL/6 mice is intact, and the CC in BTBRDraxin WT/− KI mice was partially restored. D) The length of the CC was quantitated along the rostro-caudal axis by analysis of serial aligned coronal sections (n = 3 mice per group). The red dotted lines shown in the top two rows of Fig. 6C outline the CC. The CC length is determined by an automated measurement of the distance between the outer two ends of the CC (excluding gaps) that are shown in the outline. The sites where the BTBR Draxin WT/− KI measurements significantly differ from BTBR (Tukey’s multiple comparison test) are indicated (*, p < 0.05; and **, p < 0.01.The partial correction of the CC in BTBRDraxin WT/− KI mice is indicated by the significantly increased length of the CC relative to that in aligned sections from BTBR mice; however, the inter-hemispheric connections in the more rostral and caudal sections of BTBRDraxin WT/− KI mice are below those in C57BL/6 mice