Eye Movements, Strabismus, Amblyopia, and Neuro-Ophthalmology Differences in Gene Expression between Strabismic and Normal Human Extraocular Muscles

PURPOSE. Strabismic extraocular muscles (EOMs) differ from normal EOMs in structural and functional properties, but the gene expression profile of these two types of EOM has not been examined. Differences in gene expression may inform about causes and effects of the strabismic condition in humans. METHODS. EOM samples were obtained during corrective surgery from patients with horizontal strabismus and from deceased organ donors with normal EOMs. Microarrays and quantitative PCR identified significantly up-and down-regulated genes in EOM samples. Analysis was performed on probe sets with more than 3-fold differential expression between normal and strabismic samples, with an adjusted P value of 0.05. RESULTS. Microarray analysis showed that 604 genes in these samples had significantly different expression. Expression predominantly was upregulated in genes involved in extracellular matrix structure, and down-regulated in genes related to contractility. Expression of genes associated with signaling, calcium handling, mitochondria function and biogenesis, and energy homeostasis also was significantly different between normal and strabismic EOM. Skeletal muscle PCR array identified 22 (25%) of 87 muscle-specific genes that were significantly down-regulated in strabismic EOMs; none was significantly upregulated. CONCLUSIONS. Differences in gene expression between strabismic and normal human EOMs point to a relevant contribution of the peripheral oculomotor system to the strabismic condition. Decreases in expression of contractility genes and increases of extracellular matrix-associated genes indicate imbalances in EOM structure. We conclude that gene regulation of proteins fundamental to contractile mechanics and extracellular matrix structure is involved in pathogenesis and/or consequences of strabismus, suggesting potential novel therapeutic targets. (Invest Ophthalmol Vis Sci. 2012;53:5168-5177

Altered Protein Composition and Gene Expression in Strabismic Human Extraocular Muscles and Tendons

PURPOSE: To determine whether structural protein composition and expression of key regulatory genes are altered in strabismic human extraocular muscles. METHODS: Samples from strabismic horizontal extraocular muscles were obtained during strabismus surgery and compared with normal muscles from organ donors. We used proteomics, standard and customized PCR arrays, and microarrays to identify changes in major structural proteins and changes in gene expression. We focused on muscle and connective tissue and its control by enzymes, growth factors, and cytokines. RESULTS: Strabismic muscles showed downregulation of myosins, tropomyosins, troponins, and titin. Expression of collagens and regulators of collagen synthesis and degradation, the collagenase matrix metalloproteinase (MMP)2 and its inhibitors, tissue inhibitor of metalloproteinase (TIMP)1 and TIMP2, was upregulated, along with tumor necrosis factor (TNF), TNF receptors, and connective tissue growth factor (CTGF), as well as proteoglycans. Growth factors controlling extracellular matrix (ECM) were also upregulated. Among 410 signaling genes examined by PCR arrays, molecules with downregulation in the strabismic phenotype included GDNF, NRG1, and PAX7; CTGF, CXCR4, NPY1R, TNF, NTRK1, and NTRK2 were upregulated. Signaling molecules known to control extraocular muscle plasticity were predominantly expressed in the tendon rather than the muscle component. The two horizontal muscles, medial and lateral rectus, displayed similar changes in protein and gene expression, and no obvious effect of age. CONCLUSIONS: Quantification of proteins and gene expression showed significant differences in the composition of extraocular muscles of strabismic patients with respect to important motor proteins, elements of the ECM, and connective tissue. Therefore, our study supports the emerging view that the molecular composition of strabismic muscles is substantially altered

Slit-Robo signals regulate pioneer axon pathfinding of the tract of the postoptic commissure in the mammalian forebrain

11 p., 5 figures and references.During early vertebrate forebrain development, pioneer axons establish a symmetrical scaffold descending longitudinally through the rostral forebrain, thus forming the tract of the postoptic commissure (TPOC). In mouse embryos, this tract begins to appear at embryonic day 9.5 (E9.5) as a bundle of axons tightly constrained at a specific dorsoventral level. We have characterized the participation of the Slit chemorepellants and their Robo receptors in the control of TPOC axon projection. In E9.5-E11.5 mouse embryos, Robo1 and Robo2 are expressed in the nucleus origin of the TPOC (nTPOC), and Slit expression domains flank the TPOC trajectory. These findings suggested that these proteins are important factors in the dorsoventral positioning of the TPOC axons. Consistently with this role, Slit2 inhibited TPOC axon growth in collagen gel cultures, and interfering with Robo function in cultured embryos induced projection errors in TPOC axons. Moreover, absence of both Slit1 and Slit2 or Robo1 and Robo2 in mutant mouse embryos revealed aberrant TPOC trajectories, resulting in abnormal spreading of the tract and misprojections into both ventral and dorsal tissues. These results reveal that Slit-Robo signaling regulates the dorsoventral position of this pioneer tract in the developing forebrain.Contract grant sponsor: The Wellcome Trust; Contract grant number: GR071174; Contract grant sponsor: CONACYT; Contract grant number: 101433 (to A.V.-E.); Contract grant sponsor: CONACYT (to I.R.-C. and C.M.G.-P.); Contract grant sponsor: Program Ramón y Cajal-2004, Spanish Ministry of Health, Instituto de Salud Carlos III-CIBERSAM; Contract grant sponsor: MEC; Contract grant number: SAF2008-01004; Contract grant sponsor: NIH; Contract grant number: P20 RR-016464; Contract grant sponsor: INBRE Program of the National Center for Research Resources; Contract grant number: HD38069; Contract grant number: NS054740; Contract grant sponsor: March of Dimes; Contract grant number: 1-FY06-387 (to G.S.M.); Contract grant sponsor: DGAPA-UNAM (to A.M.).Peer reviewe

Longitudinal axons are guided by Slit/Robo signals from the floor plate

Longitudinal axons grow long distances along precise pathways to connect major CNS regions. However, during embryonic development, it remains largely undefined how the first longitudinal axons choose specific positions and grow along them. Here, we review recent evidence identifying a critical role for Slit/Robo signals to guide pioneer longitudinal axons in the embryonic brain stem. These studies indicate that Slit/Robo signals from the floor plate have dual functions: to repel longitudinal axons away from the ventral midline, and also to maintain straight longitudinal growth. These dual functions likely cooperate with other guidance cues to establish the major longitudinal tracts in the brain