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Figure 3.

Figure 3. From: Human Genetic Disorders of Axon Guidance.

Schematic representation of gene products implicated in human disorders of axon guidance. KAL1 (anosmin) and PROK2 are shown as secreted ligands. ROBO3, L1, and PROKR2 are shown as transmembrane receptors on the growth cone. CHN1 is depicted with 3 green domains (SH2, C1, RacGAP), responding to an unknown activated receptor and altering a microtubule, which is depicted as a brown line. KIF21A dimers are depicted walking down MTs. The OCA/OA and JSRD gene products are not depicted. Note: these gene products are not necessarily expressed in the same neurons or function in the same pathways.

Elizabeth C. Engle. Cold Spring Harb Perspect Biol. 2010 March;2(3):a001784.
Figure 2.

Figure 2. From: Human Genetic Disorders of Axon Guidance.

Tractography studies in patients with partial agenesis of the corpus callosum (pACC). T1-weighted anatomic images and DTI tractography of six subjects with pACC (top panels) and two representative controls (bottom panel). Axial (left) and midline sagittal (middle) T1 sections are shown for each subject. Callosal fragments are identified with yellow arrows, and heterotopic fibers visible on T1-weighted images are denoted by red arrows. Midline sagittal DTI color maps are shown with segmented callosal fibers (right). For subjects with pACC, connectivity ranged from anterior frontal connections (subject 3) to only posterior frontal and occipitotemporal connections (subject 4). One individual (subject 5) displayed a discontinuous set of homotopic callosal connections, with anterior frontal and occipitotemporal connectivity without any posterior frontal or parietal connections. Control subjects (bottom panel) display normal callosal morphology and tractography results. Tracts are segmented and colored according to their cortical projections: homotopic anterior frontal, blue; homotopic posterior frontal, orange; homotopic parietal, pink; homotopic occipitotemporal, green; heterotopic left anterior-right posterior, yellow; heterotopic right anterior-left posterior, red. (Reprinted, with permission, from Wahl et al. 2009 [© AJNR].)

Elizabeth C. Engle. Cold Spring Harb Perspect Biol. 2010 March;2(3):a001784.
Figure 1.

Figure 1. From: Human Genetic Disorders of Axon Guidance.

Ocular synkinesis. (A) Child with CFEOM1 and Marcus Gunn jaw-winking phenomenon harboring a KIF21A mutation. His superior branch of the oculomotor nerve is hypoplastic/absent, resulting in bilateral ptosis from lack of appropriate innervation of the levator palpebrae superioris (LPS) muscle, and a downward position of each eye from absent innervation of the superior rectus muscle (left). Marcus Gunn phenomenon (right) is seen as the synkinetic elevation of the left eyelid with a subtle change in jaw position associated with a volitional increase in pterygoid muscle tension. This results from aberrant innervation of the LPS by axons from the motor branch of the trigeminal nerve that also innervates the intended ipsilateral pterygoid muscle. (B) Adult with Duane retraction syndrome harboring a CHN1 mutation. Central gaze reveals mild exotropia (middle). On attempted right gaze (left) and left gaze (right), there is limited horizontal excursion with globe retraction and secondary palpebral fissure narrowing of the adducting eye. Globe retraction results from synkinesis of the medial and lateral recti muscles. (A) Modified with permission from Yamada et al. 2005. Copyright © (2005) American Medial Association. All rights reserved. (B) Modified from Demer et al. 2007. Copyright © (2007) Association for Research in Vision and Ophthalmology. All rights reserved.

Elizabeth C. Engle. Cold Spring Harb Perspect Biol. 2010 March;2(3):a001784.

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