CYP7B1: novel mutations and magnetic resonance spectroscopy abnormalities in hereditary spastic paraplegia type 5A.

UNLABELLED: The SPG5A subtype of Hereditary Spastic Paraplegia (HSP) is a rare autosomal recessive neurodegenerative disorder caused by mutations in the CYP7B1 gene, which encodes a steroid cytochrome P450 7α-hydroxylase. This enzyme provides the primary metabolic route for neurosteroids. Clinically, SPG5A has been characterized as a pure form of HSP with a variable age of onset, but recently a broader spectrum of phenotypes has been described. OBJECTIVE: This study characterizes four unrelated SPG5A patients through clinical evaluation. METHODS: The investigations included blood biochemistry, electrophysiology, brain MRI and MR spectroscopy. RESULTS: One patient had saccadic pursuit eye movements in addition to a pure HSP phenotype. Motor evoked potential (MEP) examinations revealed prolonged central conduction time. MRI of the brain showed white matter hyperintensities (WMH) in one patient. MRS showed elevated mI/Cr ratio in white matter in two patients; in the one patient with WMH and in one patient with normal MRI. Four novel mutations were identified; one frameshift (c.509 delT p.L170fs), one premature stop codon (c.334 C>T p.R112X), one amino acid changing (c.440 G>A p.G147D) and one duplication (c.945_947 dupGGC p.A316AA). CONCLUSION: SPG5A could be characterized as a predominantly pure HSP. MRS showing elevated mI/Cr ratio in the white matter may be indicative of SPG5A.

Hereditary spastic paraplegia is not associated with C9ORF72 repeat expansions in a Danish cohort.

OBJECTIVES: Hereditary spastic paraplegia (HSP) is a heterogeneous group of neurodegenerative disorders characterized by a progressive gait disorder, lower limb spasticity, hyper-reflexia, weakness and extensor plantar responses. Recently, large intronic hexanucleotide repeat expansions (GGGGCC) in C9ORF72 have been found to cause frontotemporal dementia (FTD), amyotrophic lateral sclerosis and FTD with motor neuron disease. Owing to the overlapping phenotypes among HSP, amyotrophic lateral sclerosis and FTD with motor neuron disease along with shared pathological findings, we hypothesized that C9ORF72 expansions might be a genetic risk factor or modifier of HSP. METHODS: Clinically characterized HSP patients were investigated for elongations in the hexanucleotide repeat of C9ORF72. RESULTS: Upon analyses of the repeat lengths in the C9ORF72 gene in a Danish cohort of HSP patients, we found no expansions. CONCLUSION: We conclude that HSP is most likely not associated with repeat expansions in C9ORF72.

Corticobasal and ataxia syndromes widen the spectrum of C9ORF72 hexanucleotide expansion disease.

Recently, a hexanucleotide (GGGGCC) repeat expansion in the first intron of C9ORF72 was reported as the cause of chromosome 9p21-linked frontotemporal dementia-amyotrophic lateral sclerosis (FTD-ALS). We here report the prevalence of the expansion in a hospital-based cohort and associated clinical features indicating a wider clinical spectrum of C9ORF72 disease than previously described. We studied 280 patients previously screened for mutations in genes involved in early onset autosomal dominant inherited dementia disorders. A repeat-primed polymerase chain reaction amplification assay was used to identify pathogenic GGGGCC expansions. As a potential modifier, confirmed cases were further investigated for abnormal CAG expansions in ATXN2. A pathogenic GGGGCC expansion was identified in a total of 14 probands. Three of these presented with atypical clinical features and were previously diagnosed with clinical olivopontocerebellar degeneration (OPCD), atypical Parkinsonian syndrome (APS) and a corticobasal syndrome (CBS). Further, the pathogenic expansion was identified in six FTD patients, four patients with FTD-ALS and one ALS patient. All confirmed cases had normal ATXN2 repeat sizes. Our study widens the clinical spectrum of C9ORF72 related disease and confirms the hexanucleotide expansion as a prevalent cause of FTD-ALS disorders. There was no indication of a modifying effect of the ATXN2 gene.

Novel mutation in ATP13A2 widens the spectrum of Kufor-Rakeb syndrome (PARK9).

Kufor-Rakeb syndrome (KRS) is a rare autosomal recessive inherited juvenile parkinsonian syndrome caused by mutations in ATP13A2. We describe six patients from a consanguineous Greenlandic Inuit family, homozygous for a novel frame-shift mutation in exon 22 of ATP13A2 (c.2473C>AA, p.Leu825AsnfsX32). Disease onset varied from 10 to 29 years of age, the latest reported, and the clinical features were highly variable within a wide spectrum of an extrapyramidal-pyramidal syndrome with cognitive/psychiatric features. Ataxia was seen in two patients and axonal neuropathy in one, features not previously related to KRS. Dopamine transporter scans showed symmetrical, severely reduced uptake in striatum in two patients. Magnetic resonance imaging was without atrophy in one patient despite disease duration of 17 years, and cerebral and cerebellar atrophy was seen in another patient after 4 years of disease duration. The molecular pathogenic mechanisms of ATP13A2 mutations are discussed. The observation that the mutant transcript is not degraded by nonsense-mediated RNA decay and the fact that none of the eight heterozygous carriers from the family have KRS symptoms suggest that the mutant protein does not interfere and destroy the function of the wild-type ATP13A2 protein.

NIPA1 mutation in complex hereditary spastic paraplegia with epilepsy.

BACKGROUND AND PURPOSE: Hereditary spastic paraplegia (HSP) is a group of clinically and genetically heterogeneous neurodegenerative disorders characterized in the 'pure' phenotype by progressive spasticity and weakness of the lower limbs. In the 'complex' phenotype, additional neurologic symptoms or signs are found. Mutations in the NIPA1 gene have been reported to cause spastic paraplegia type 6 (SPG6) in 10 families. SPG6 is a rare form of autosomal dominantly inherited HSP associated with a pure phenotype; however, in one complex SPG6 family, idiopathic generalized epilepsy (IGE) has been described and in addition, recurrent microdeletions at 15q11.2 including NIPA1 have been identified in patients with IGE. The purpose was to identify NIPA1 mutations in patients with pure and complex HSP. METHODS: Fifty-two patients with HSP were screened for mutations in NIPA1. RESULTS: One previously reported missense mutation c.316G>A, p.Gly106Arg, was identified in a complex HSP patient with spastic dysarthria, facial dystonia, atrophy of the small hand muscles, upper limb spasticity, and presumably IGE. The epilepsy co-segregated with HSP in the family. CONCLUSION: NIPA1 mutations were rare in our population of patients with HSP, but can be found in patients with complex HSP. Epilepsy might be more common in SPG6 than in other forms of HSP because of a genetic risk factor closely linked to NIPA1.

Frontotemporal dementia linked to chromosome 3 (FTD-3)--current concepts and the detection of a previously unknown branch of the Danish FTD-3 family.

BACKGROUND: Among patients with onset of dementia below the age of 65 years, frontotemporal dementia (FTD) is the second most prevalent cause, secondary only to Alzheimer's disease. Recent advances in understanding the heterogeneous genetic background for different clinical and neuropathological entities of FTD have involved identification of several new causative genes. METHODS AND RESULTS: We report the finding of a truncating mutation in the CHMP2B gene (c.532-1G>C) in a patient with early onset dementia. The patient was previously not known to be related to the single Danish pedigree known to have this specific mutation. Subsequently he has turned out to represent a new branch of the family with several affected individuals. DISCUSSION: Our findings highlight the need for awareness of the CHMP2B mutation and associated clinical phenotype for neurological assessment in Denmark. Further, we discuss recent advances and current concepts in the understanding of CHMP2B-related dementia.

Double-blind crossover trial of gabapentin in SPG4-linked hereditary spastic paraplegia.

Patients with hereditary spastic paraplegia (HSP) are often treated with antispastic drugs to relieve symptoms but documentation is lacking. In this study, gabapentin was tested in a double-blind crossover trial on a group of patients with HSP and linkage to the SPG4 locus. There was no difference between periods with gabapentin and placebo treatment in clinical assessment, self-reported parameters or paired transcranial magnetic stimulation evaluation of motor cortical excitability.

Improved glucose tolerance and acinar dysmorphogenesis by targeted expression of transcription factor PDX-1 to the exocrine pancreas.

The homeodomain protein PDX-1 is critical for pancreas development and is a key regulator of insulin gene expression. PDX-1 nullizygosity and haploinsufficiency in mice and humans results in pancreatic agenesis and diabetes, respectively. At embryonic day (e) 10.5, PDX-1 is expressed in all pluripotential gut-derived epithelial cells destined to differentiate into the exocrine and endocrine pancreas. At e15, PDX-1 expression is downregulated in exocrine cells, but remains high in endocrine cells. The aim of this study was to determine whether targeted overexpression of PDX-1 to the exocrine compartment of the developing pancreas at e15 would allow for respecification of the exocrine cells. Transgenic (TG) mice were generated in which PDX-1 was expressed in the exocrine pancreas using the exocrine-specific elastase-1 promoter. These mice exhibited a marked dysmorphogenesis of the exocrine pancreas, manifested by increased rates of replication and apoptosis in acinar cells and a progressive fatty infiltration of the exocrine pancreas with age. Interestingly, the TG mice exhibited improved glucose tolerance, but absolute beta-cell mass was not increased. These findings indicate that downregulation of PDX-1 is required for the proper maintenance of the exocrine cell phenotype and that upregulation of PDX-1 in acinar cells affects beta-cell function. The mechanisms underlying these observations remain to be elucidated.

Unbiased estimation of total beta-cell number and mean beta-cell volume in rodent pancreas.

We describe a method for unbiased assumption-free estimation of the total number of beta-cells and the mean beta-cell volume in mouse and rat pancreas based on light microscopy. Such a method, which takes advantage of one of the most recent developments in stereology, the fractionator, has not previously been described. It relies on repeated fractionation of the tissue using systematic uniform random sampling combined with an unbiased counting principle. The method was applied to eight BALB/cBom male mice (56 days) and six Lewis/MOL male rats (47 days). In mice, the total number of beta-cells was 1.06 +/- 0.07 x 10(6) (mean +/- SEM) per pancreas with a mean beta-cell volume of 1280 +/- 17 microm3, while in rats the total beta-cell number was 2.76 +/- 0.42 x 10(6) per pancreas with a mean beta-cell volume of 1170 +/- 65 microm3. Furthermore, the results showed that in both species the biological variability in the total beta-cell volume is due to differences in the number of beta-cells rather than variability of the mean beta-cell volume. The method can be used to give a precise description of number and volume of beta-cells at different ages, and will make it possible to estimate the contributions of hyper/hypotrophia and hyper/hypoplasia to a given induced or spontaneous change in the total beta-cell mass.