Disease relevance of Optic Chiasm

• We studied a patient with spontaneous intracranial hypotension whose gadolinium-enhanced MRI revealed an extraordinary degree of dural enhancement and striking displacement of the optic chiasm, flattening of the pons, and downward displacement of the cerebellar tonsils [1].
• The proportion of uncrossed retinal ganglion cells expressing beta-galactosidase was found to be identical to the proportion that did not express it, indicating that the albino mutation associated with axonal behavior at the optic chiasm must affect ganglion cells in a cell-extrinsic manner [2].
• PURPOSE: To evaluate techniques for anatomical and physiological imaging of the intracranial optic nerve (ON), optic chiasm (OC), and optic tract (OT) at 3T with the aim of visualizing axonal damage in multiple sclerosis (MS) [3].
• Carboplatin for the treatment of children with newly diagnosed optic chiasm gliomas: a phase II study [4].
• The formation of the head of the optic nerve and the optic chiasm require ligand-receptor interactions between netrin-1 and the deleted in colorectal cancer receptor, and Slit proteins and Robo receptors, respectively [5].

High impact information on Optic Chiasm

• Pathfinding of retinal ganglion cell (RGC) axons at the midline optic chiasm determines whether RGCs project to ipsilateral or contralateral brain visual centers, critical for binocular vision [6].
• Loss- and gain-of-function analyses indicate that Zic2 is necessary and sufficient to regulate RGC axon repulsion by cues at the optic chiasm midline [7].
• Thus, the GAP-43 protein is not essential for axonal outgrowth or growth cone formation per se, but is required at certain decision points, such as the optic chiasm [8].
• Ephrin-B2 and EphB1 mediate retinal axon divergence at the optic chiasm [9].
• Our results indicate that Slit proteins repel retinal axons in vivo and cooperate to establish a corridor through which the axons are channeled, thereby helping define the site in the ventral diencephalon where the optic chiasm forms [10].

Chemical compound and disease context of Optic Chiasm

• A case of steroid-responsive malignant lymphoma of the optic chiasm is reported in a 58-year-old woman presenting with subacute vision loss, headaches, and decreased hearing [11].
• A 3-month-old infant with optic chiasm glioma developed hypopituitarism and inappropriate secretion of antidiuretic hormone with plasma hypo-osmolality [12].

Biological context of Optic Chiasm

• Here, we show that the zinc finger transcription factor Zic2, a vertebrate homolog of the Drosophila gene odd-paired, is expressed in RGCs with an uncrossed trajectory during the period when this subpopulation grows from the ventrotemporal retina toward the optic chiasm [7].
• We show that bel(Ihx2) function is required for patterning in the ventral forebrain and eye, and that loss of bel function leads to alterations in regulatory gene expression, perturbations in axon guidance factors, and the absence of an optic chiasm and forebrain commissures [13].
• As much of the increased ipsilateral projection in Foxg1-/- embryos arises from temporal RGCs that are unlikely to have an autonomous requirement for Foxg1, we propose that the phenotype reflects at least in part a requirement for Foxg1 outwith the RGCs themselves, most likely at the optic chiasm [14].
• METHODS: A 34-year-old woman with a history of strabismus and absent cutaneous pigment underwent comprehensive ophthalmic examination, visual-evoked potentials to detect altered optic decussation, and molecular analysis [15].

Anatomical context of Optic Chiasm

• Previous studies have shown that RGC axons in GAP-43-deficient mice initially fail to grow from the optic chiasm to form optic tracts and are delayed temporarily in the midline region [16].
• PDGF-alpha R+ cells in the optic nerve first appear near the optic chiasm and subsequently spread to the retinal end of the nerve; these PDGF-alpha R+ cells are probably oligodendrocyte precursors (Pringle et al., 1992) [17].
• Neurons and dendrites exhibiting specific VIP immunoreactivity are concentrated in the ventral half of the nucleus, with the greatest concentration of immunoreactive perikarya occurring in the ventral SCN immediately adjacent to and within the optic chiasm (OC) [18].
• Substantial quantities of TRH also were detected in the medulla oblongata (0.26 +/- 0.08), mammillary bodies (0.33 +/- 0.25), and optic chiasm (0.14 +/- 0.07) [19].
• Frontal sections at the level of the optic chiasm and arcuate nucleus were examined for the colocalization of TH and PR [20].

Associations of Optic Chiasm with chemical compounds

• Evidence from labeling growing retinal axons with the carbocyanine dye Dil in mouse embryos indicates that the two subpopulations diverge at a zone along the midline of the optic chiasm [21].
• Axon routing at the optic chiasm after enzymatic removal of chondroitin sulfate in mouse embryos [22].
• An extensive network of 5-HT neurones appeared gradually, with a substantial subset crossing to the opposite side of the brain through the developing optic chiasma [23].
• Using the whole-cell patch technique, we first demonstrated that AMPA currents elicited by either local AMPA application or optic chiasm stimulation were augmented by aniracetam in the neurons of the SCN [24].
• Basal hypothalamic deafferentation extending from the posterior border of the optic chiasm to the mid-mammillary bodies resulted in depression of plasma TSH, thyroxine (T4), and triiodothyronine (T3) concentration to 50% of normal controls within 7 days [25].

Gene context of Optic Chiasm

• Foxg1 is also expressed at the optic chiasm [14].
• Foxd1 is required for proper formation of the optic chiasm [26].
• Six6 expression was detected in the neural retina, the optic chiasma and optic stalk, but not in the lens [27].
• The suprachiasmatic preoptic nucleus (PSCh), a small group of cells located ventral to the AVPv just dorsal to the optic chiasm, contained high densities of alpha-MSH- and ACTH-immunoreactive fibers, as well as substantial numbers of fibers containing catecholamines or NPY [28].
• Hybridization histochemistry revealed the presence of both TGF alpha and EGFR mRNAs in cells scattered throughout the hypothalamus, but more predominantly in the median eminence, suprachiasmatic nuclei, optic chiasm and cells along the wall of the third ventricle [29].

Analytical, diagnostic and therapeutic context of Optic Chiasm

• The administration of kynurenate suppressed responses elicited by electrical stimulation of the dorsal lateral geniculate nucleus (LGN) and optic chiasm (OX) of 65% of the cells tested [30].
• CONCLUSION: The Bagolini Striated Glasses Test can be used as a simple differential diagnostic test for lesions of the optic chiasm [31].

References