Autosomal-recessive complicated spastic paraplegia with a novel lysosomal trafficking regulator gene mutation.

BACKGROUND: Autosomal-recessive hereditary spastic paraplegias (AR-HSP) consist of a genetically diverse group of neurodegenerative diseases characterised by pyramidal tracts dysfunction. The causative genes for many types of AR-HSP remain elusive. We tried to identify the gene mutation for AR-HSP with cerebellar ataxia and neuropathy. METHODS: This study included two patients in a Japanese family with their parents who are first cousins. Neurological examination and gene analysis were conducted in the two patients and two normal family members. We undertook genome-wide linkage analysis employing single nucleotide polymorphism arrays using the two patients' DNAs and exome sequencing using one patient's sample. RESULTS: We detected a homozygous missense mutation (c.4189T>G, p.F1397V) in the lysosomal trafficking regulator (LYST) gene, which is described as the causative gene for Chédiak-Higashi syndrome (CHS). CHS is a rare autosomal-recessive syndrome characterised by hypopigmentation, severe immune deficiency, a bleeding tendency and progressive neurological dysfunction. This mutation was co-segregated with the disease in the family and was located at well-conserved amino acid. This LYST mutation was not found in 200 Japanese control DNAs. Microscopic observation of peripheral blood in the two patients disclosed large peroxidase-positive granules in both patients' granulocytes, although they had no symptoms of immune deficiency or bleeding tendency. CONCLUSIONS: We diagnosed these patients as having adult CHS presenting spastic paraplegia with cerebellar ataxia and neuropathy. The clinical spectrum of CHS is broader than previously recognised. Adult CHS must be considered in the differential diagnosis of AR-HSP.

A homozygous mutation of C12orf65 causes spastic paraplegia with optic atrophy and neuropathy (SPG55).

BACKGROUND: Autosomal recessive hereditary spastic paraplegias (AR-HSP) constitute a heterogeneous group of neurodegenerative diseases involving pyramidal tracts dysfunction. The genes responsible for many types of AR-HSPs remain unknown. We attempted to identify the gene responsible for AR-HSP with optic atrophy and neuropathy. METHODS: The present study involved two patients in a consanguineous Japanese family. Neurologic examination and DNA analysis were performed for both patients, and a skin biopsy for one. We performed genome-wide linkage analysis involving single nucleotide polymorphism arrays, copy-number variation analysis, and exome sequencing. To clarify the mitochondrial functional alteration resulting from the identified mutation, we performed immunoblot analysis, mitochondrial protein synthesis assaying, blue native polyacrylamide gel electrophoresis (BN-PAGE) analysis, and respiratory enzyme activity assaying of cultured fibroblasts of the patient and a control. RESULTS: We identified a homozygous nonsense mutation (c.394C>T, p.R132X) in C12orf65 in the two patients in this family. This C12orf65 mutation was not found in 74 Japanese AR-HSP index patients without any mutations in previously known HSP genes. This mutation resulted in marked reduction of mitochondrial protein synthesis, followed by functional and structural defects in respiratory complexes I and IV. CONCLUSIONS: This novel nonsense mutation in C12orf65 could cause AR-HSP with optic atrophy and neuropathy, resulting in a premature stop codon. The truncated C12orf65 protein must lead to a defect in mitochondrial protein synthesis and a reduction in the respiratory complex enzyme activity. Thus, dysfunction of mitochondrial translation could be one of the pathogenic mechanisms underlying HSPs.

A novel adult case of juvenile-onset Alexander disease: complete remission of neurological symptoms for over 12 years, despite insidiously progressive cervicomedullary atrophy.

We present here a 25-year-old woman with genetically confirmed (p.R276L mutation in the GFAP gene) juvenile-onset AxD. Episodic vomiting appeared at age nine, causing anorexia and insufficient growth. Brain MRI at age 11 showed a small nodular lesion with contrast enhancement in the left dorsal portion of the cervicomedullary junction. Her episodic vomiting improved spontaneously at age 13, and she became neurologically asymptomatic. The enhancement of the lesion disappeared simultaneously, although the plaque remained. Longitudinal MRI observations, however, revealed insidiously progressive cervicomedullary atrophy without a signal change. This case broadens our knowledge of AxD: (1) molecular analysis of the GFAP gene is warranted in patients with MRI evidence of tumor-like lesions in the brainstem, particularly if they present with isolated episodic vomiting and/or anorexia; (2) the disease can be self-remitting for at least 12 years; (3) cervicomedullary atrophy, characteristic of the adult form, can be insidiously progressive without a signal change before the clinical symptoms appear.