Mutations in FRMD7, a newly identified member of the FERM family, cause X-linked idiopathic congenital nystagmus

Idiopathic congenital nystagmus (ICN) is characterised by involuntary, periodic, predominantly horizontal, oscillations of both eyes. We identified 22 mutations in FRMD7 in 26 families with X-linked idiopathic congenital nystagmus. Screening of 42 ICN singleton cases (28 male, 14 females) yielded three mutations (7%). We found restricted expression of FRMD7 in human embryonic brain and developing neural retina suggesting a specific role in the control of eye movement and gaze stability

Mutations in A Human Robo Gene Disrupt Hindbrain Axon Pathway Crossing and Morphogenesis

The mechanisms controlling axon guidance are of fundamental importance in understanding brain development. Growing corticospinal and somatosensory axons cross the midline in the medulla to reach their targets and thus form the basis of contralateral motor control and sensory input. The motor and sensory projections appeared uncrossed in patients with horizontal gaze palsy with progressive scoliosis (HGPPS). In patients affected with HGPPS, we identified mutations in the ROBO3 gene, which shares homology with roundabout genes important in axon guidance in developing Drosophila, zebrafish, and mouse. Like its murine homolog Rig1/Robo3, but unlike other Robo proteins, ROBO3 is required for hindbrain axon midline crossing.Wo

Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance

We report that eight heterozygous missense mutations in TUBB3, encoding the neuron-specific beta-tubulin isotype III, result in a spectrum of human nervous system disorders that we now call the TUBB3 syndromes. Each mutation causes the ocular motility disorder CFEOM3, whereas some also result in intellectual and behavioral impairments, facial paralysis, and/or later-onset axonal sensorimotor polyneuropathy. Neuroimaging reveals a spectrum of abnormalities including hypoplasia of oculomotor nerves and dysgenesis of the corpus callosum, anterior commissure, and corticospinal tracts. A knock-in disease mouse model reveals axon guidance defects without evidence of cortical cell migration abnormalities. We show that the disease-associated mutations can impair tubulin heterodimer formation in vitro, although folded mutant heterodimers can still polymerize into microtubules. Modeling each mutation in yeast tubulin demonstrates that all alter dynamic instability whereas a subset disrupts the interaction of microtubules with kinesin motors. These findings demonstrate that normal TUBB3 is required for axon guidance and maintenance in mammals.Max A. Tischfield, Hagit N. Baris, Chen Wu, Guenther Rudolph, Lionel Van Maldergem, Wei He, Wai-Man Chan, Caroline Andrews, Joseph L. Demer, Richard L. Robertson, David A. Mackey, Jonathan B. Ruddle, Thomas D. Bird, Irene Gottlob, Christina Pieh, Elias I. Traboulsi, Scott L. Pomeroy, David G. Hunter, Janet S. Soul, Anna Newlin, Louise J. Sabol, Edward J. Doherty, Clara E. de Uzca´ tegui, Nicolas de Uzca´ tegui, Mary Louise Z. Collins, Emin C. Sener, Bettina Wabbels, Heide Hellebrand, Thomas Meitinger, Teresa de Berardinis, Adriano Magli, Costantino Schiavi, Marco Pastore-Trossello, Feray Koc, Agnes M. Wong, Alex V. Levin, Michael T. Geraghty, Maria Descartes, Maree Flaherty, Robyn V. Jamieson, H.U. Møller, Ingo Meuthen, David F. Callen, Janet Kerwin, Susan Lindsay, Alfons Meindl, Mohan L. Gupta, Jr., David Pellman, and Elizabeth C. Engl