Annals of neurology
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Annals of neurology · May 2004
Case ReportsPOLG mutations associated with Alpers' syndrome and mitochondrial DNA depletion.
Alpers' syndrome is a fatal neurogenetic disorder first described more than 70 years ago. It is an autosomal recessive, developmental mitochondrial DNA depletion disorder characterized by deficiency in mitochondrial DNA polymerase gamma (POLG) catalytic activity, refractory seizures, neurodegeneration, and liver disease. In two unrelated pedigrees of Alpers' syndrome, each affected child was found to carry a homozygous mutation in exon 17 of the POLG locus that led to a Glu873Stop mutation just upstream of the polymerase domain of the protein. In addition, each affected child was heterozygous for the G1681A mutation in exon 7 that led to an Ala467Thr substitution in POLG, within the linker region of the protein.
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The histogenetic origin and the basis of the distribution of central nervous system (CNS) hemangioblastomas in the von Hippel-Lindau (VHL) tumor suppressor gene syndrome, VHL disease, are unknown. To better understand hemangioblastoma histogenesis, we analyzed postmortem CNS tissues from four patients with well-established diagnosis of VHL disease including development of characteristic tumors and positive family history. Numerous angiomesenchymal tumorlets, which resembled hemangioblastoma, but which also consistently showed distinct histological features, were distributed in the nerve roots, spinal cord, and cerebellum. ⋯ In analogy to the wide morphological spectrum of lesions known to exist in VHL kidneys, nerve roots appear to harbor more wide-spread and morphologically heterogeneous changes than previously appreciated. The abundance of tumorlets, associated with highly consistent morphology and topography, suggests a developmental origin of hemangioblastoma. Therefore, in VHL disease, inactivation of the VHL wild-type allele appears necessary, but not sufficient, for the formation of tumor that produces symptoms and neurological disability.
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Annals of neurology · May 2004
Comparative StudyUnilateral nerve injury produces bilateral loss of distal innervation.
There are no known anatomical connections between neurons that innervate homologous right and left body parts. Nevertheless, some patients develop bilateral abnormalities after unilateral injury, a phenomenon often unrecognized and not yet characterized. Therefore, we examined in rats the effects of ligating and cutting one tibial nerve on sensory function and on density of innervation in hind paws contralaterally as well as ipsilaterally to the injury, at times between 1 day and 5 months after surgery. ⋯ Contralesional sural-innervated skin had neither neurite loss nor sprouting. These results imply that unilateral nerve injury can cause profound, long lasting, nerve-branch-specific loss of distal innervation contralaterally as well as ipsilaterally. They discredit the practice of using tissues contralateral to an injury to provide normative controls and suggest the possibility of rapid, transmedian postinjury signals between homologous mirror-image neurons.