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Neurol Genet. 2019 Jan 24;5(1):e305. doi: 10.1212/NXG.0000000000000305. eCollection 2019 Feb.

Genomic deletions upstream of lamin B1 lead to atypical autosomal dominant leukodystrophy.

Author information

1
Department of Human Genetics (B.N., Q.S.P.), Graduate School of Public Health, University of Pittsburgh; Department of Medical Sciences (E.G., A.B.), University of Torino, Italy; Department of Radiology (R.R.), Uppsala University, Sweden; Department of Medical Genetics (A.L.), British Columbia Children's Hospital, Vancouver, Canada; Department of Genome Sciences (M. Spielmann), University of Washington, Seattle; Department of Pediatrics (M.K.K., R.A., M.K.), McGovern Medical School, University of Texas, Houston; Departments of Clinical Genomics and Neurology (R.G.), Mayo Clinic, Rochester, MN; Department of Pathology (M.A.), King Abdulaziz University, Jeddah, Saudi Arabia; Department of Medical Imaging (M. Sharma), Western University, London, Canada; Departments of Pathology and Clinical Neurological Sciences (R.H.), Western University and London Health Sciences Centre, Canada; Office of the Clinical Director (W.A.G., C.T.), NHGRI; and NIH Undiagnosed Diseases Program (W.A.G., C.T.), Office of the Director, NIH, Bethesda, MD.

Abstract

Objective:

Clinical, radiologic, and molecular analysis of patients with genomic deletions upstream of the LMNB1 gene.

Methods:

Detailed neurologic, MRI examinations, custom array comparative genomic hybridization (aCGH) analysis, and expression analysis were performed in patients at different clinical centers. All procedures were approved by institutional review boards of the respective institutions.

Results:

Five patients from 3 independent families presented at ages ranging from 32 to 52 years with neurologic symptoms that included progressive hypophonia, upper and lower limb weakness and spasticity, and cerebellar dysfunction and MRIs characterized by widespread white matter alterations. Patients had unique nonrecurrent deletions upstream of the LMNB1, varying in size from 250 kb to 670 kb. Deletion junctions were embedded in repetitive elements. Expression analysis revealed increased LMNB1 expression in patient cells.

Conclusions:

Our findings confirmed the association between LMNB1 upstream deletions and leukodystrophy previously reported in a single family, expanding the phenotypic and molecular description of this condition. Although clinical and radiologic features overlapped with those of autosomal dominant leukodystrophy because of LMNB1 duplications, patients with deletions upstream of LMNB1 had an earlier age at symptom onset, lacked early dysautonomia, and appeared to have lesser involvement of the cerebellum and sparing of the spinal cord diameter on MRI. aCGH analysis defined a smaller minimal critical region required for disease causation and revealed that deletions occur at repetitive DNA genomic elements. Search for LMNB1 structural variants (duplications and upstream deletions) should be an integral part of the investigation of patients with autosomal dominant adult-onset leukodystrophy.

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