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Impaired riboflavin transport due to missense mutations in SLC52A2 causes Brown-Vialetto-Van Laere syndrome.

ABSTRACT: Brown-Vialetto-Van Laere syndrome (BVVLS [MIM 211530]) is a rare neurological disorder characterized by infancy onset sensorineural deafness and ponto-bulbar palsy. Mutations in SLC52A3 (formerly C20orf54), coding for riboflavin transporter 2 (hRFT2), have been identified as the molecular genetic correlate in several individuals with BVVLS. Exome sequencing of just one single case revealed that compound heterozygosity for two pathogenic mutations in the SLC52A2 gene coding for riboflavin transporter 3 (hRFT3), another member of the riboflavin transporter family, is also associated with BVVLS. Overexpression studies confirmed that the gene products of both mutant alleles have reduced riboflavin transport activities. While mutations in SLC52A3 cause decreased plasma riboflavin levels, concordant with a role of SLC52A3 in riboflavin uptake from food, the SLC52A2-mutant individual had normal plasma riboflavin concentrations, a finding in line with a postulated function of SLC52A2 in riboflavin uptake from blood into target cells. Our results contribute to the understanding of human riboflavin metabolism and underscore its role in the pathogenesis of BVVLS, thereby providing a rational basis for a high-dose riboflavin treatment.

SUBMITTER: Haack TB

PROVIDER: S-EPMC3470687 | biostudies-literature | 2012 Nov

REPOSITORIES: biostudies-literature

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Impaired riboflavin transport due to missense mutations in SLC52A2 causes Brown-Vialetto-Van Laere syndrome.

Haack Tobias B TB Makowski Christine C Yao Yoshiaki Y Graf Elisabeth E Hempel Maja M Wieland Thomas T Tauer Ulrike U Ahting Uwe U Mayr Johannes A JA Freisinger Peter P Yoshimatsu Hiroki H Inui Ken K Strom Tim M TM Meitinger Thomas T Yonezawa Atsushi A Prokisch Holger H

Journal of inherited metabolic disease 20120803 6

Brown-Vialetto-Van Laere syndrome (BVVLS [MIM 211530]) is a rare neurological disorder characterized by infancy onset sensorineural deafness and ponto-bulbar palsy. Mutations in SLC52A3 (formerly C20orf54), coding for riboflavin transporter 2 (hRFT2), have been identified as the molecular genetic correlate in several individuals with BVVLS. Exome sequencing of just one single case revealed that compound heterozygosity for two pathogenic mutations in the SLC52A2 gene coding for riboflavin transpo ...[more]

PMID: 22864630

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Project description:The Brown-Vialetto-Van Laere syndrome (BVVL) is a rare neurological disorder characterized by progressive pontobulbar palsy associated with sensorineural deafness. Fifty-eight cases have been reported in just over 100 years. The female to male ratio is approximately 3:1. The age of onset of the initial symptom varies from infancy to the third decade. The syndrome most frequently presents with sensorineural deafness, which is usually progressive and severe. Lower cranial nerve involvement and lower and upper motor neuron limb signs are common neurological features. Other features include respiratory compromise (the most frequent non-neurological finding), limb weakness, slurring of speech, facial weakness, and neck and shoulder weakness. Optic atrophy, retinitis pigmentosa, macular hyperpigmentation, autonomic dysfunction, epilepsy may occur. The etiopathogenesis of the condition remains elusive. Approximately 50% of cases are familial, of which autosomal recessive is suggested. The remaining cases are sporadic. The diagnosis is usually based on the clinical presentation. Investigations (neurophysiological studies, magnetic resonance imaging of the brain, muscle biopsy, cerebrospinal fluid examination) are done to exclude other causes or to confirm the clinical findings. The differential diagnoses include the Fazio-Londe syndrome, amyotrophic lateral sclerosis, Nathalie syndrome, Boltshauser syndrome and Madras motor neuron disease. Treatment with steroids or intravenous immunoglobulin may result in temporary stabilization of the syndrome. However, the mainstays of management are supportive and symptomatic treatment, in particular assisted ventilation and maintenance of nutrition via gastrostomy. The clinical course of BVVL is variable and includes gradual deterioration (almost half of cases), gradual deterioration with stable periods in between (a third of cases) and deterioration with abrupt periods of worsening (just under a fifth of cases). After the initial presentation, one third of patients survive for ten years or longer.

Project description:The Brown-Vialetto-Van Laere syndrome is a rare neurological disorder which may present at all ages with sensorineural deafness, bulbar palsy and respiratory compromise. Fazio-Londe syndrome is considered to be the same disease entity. Recently it was demonstrated that in some patients the disease is caused by mutations in the SLC52A3 gene which encodes the intestinal (hRFT2) riboflavin transporter. In these patients riboflavin deficiency is the cause of the BVVL/FL syndrome and supplementation of riboflavin proved a life saving treatment. Mutations in the SLC52A2 gene and the SLC52A1 (GPR172B) gene, coding for human riboflavin transporters hRFT3 and hRFT1 have been associated with the BVVL syndrome as well. We performed a review of the literature, with emphasis on the natural history and the effects of treatment in these patients. A total of 35 publications were traced reporting on the clinical presentation of 74 patients who presented before age 18. The most prevalent symptoms were bulbar palsy, hearing loss, facial weakness and respiratory compromise. Death was reported in 28 of the 61 untreated patients, with a very low survival in patients presenting before age 4. All 13 patients who were treated with riboflavin survived, with a strong clinical improvement after days to months of treatment in eight patients. Three patients demonstrated a stable clinical course and treatment was stopped early in two patients. Abnormalities in plasma flavin levels and/or plasma acylcarnitine profiles were observed in some but not in all patients, and also patients with normal plasma flavin levels and acylcarnitine profiles demonstrated a striking clinical improvement on riboflavin supplementation. It is now clear that proper diagnosis requires mutation analysis of all three transporter genes and treatment should be started immediately without first awaiting results of molecular analysis. Clinical improvement may be rapid or gradual over a period of more than 12 months.

Dataset Information

Impaired riboflavin transport due to missense mutations in SLC52A2 causes Brown-Vialetto-Van Laere syndrome.

Publications

Impaired riboflavin transport due to missense mutations in SLC52A2 causes Brown-Vialetto-Van Laere syndrome.

Similar Datasets

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