A family with autosomal dominant leukodystrophy linked to 5q23.2-q23.3 without lamin B1 mutations.

BACKGROUND AND PURPOSE: Duplications of lamin B1 (LMNB1) at 5q23 are implicated in adult-onset autosomal dominant leukodystrophy (ADLD) having been described in six families with diverse ethnic background but with a homogeneous phenotype. In a large Italian family, we recently identified a variant form of ADLD characterized clinically by absence of the autonomic dysfunction at onset described in ADLD and, on MRI, by milder cerebellar involvement with sparing of hemispheric white matter. Aim of this study was to investigate the genetic basis of this variant form of ADLD. METHODS: We carried out a genome-wide linkage analysis using microsatellite markers, and the genes in the candidate region were screened for point mutations. LMNB1 was also screened for deletions/duplications by real-time PCR, multiplex ligation-dependent probe amplification and Southern blot. RESULTS: We mapped the variant ADLD locus to 5q23.2-q23.3, a genomic region containing 11 genes including LMNB1. Neither gene copy-number defects nor point mutations in the LMNB1 gene were found. We also excluded point mutations in the coding exons of the other ten genes in the candidate region. However, expression of lamin B1 evaluated in lymphoblastoid cells was higher in patients than in healthy controls, and was similar to the lamin B1 expression levels found in a patient with LMNB1 duplication. CONCLUSIONS: This observation suggests that a mutation in an LMNB1 regulatory sequence underlies the variant ADLD phenotype. Thus, adult forms of ADLD linked to 5q23 appear to be more heterogeneous clinically and genetically than previously thought.

Mutations in the lamin B1 gene are not present in multiple sclerosis.

BACKGROUND: Whole gene duplication of the lamin B1 gene (LMNB1), encoding for a protein of the nuclear lamina, causes an adult-onset autosomal dominant leukodystrophy (ADLD). Clinical features of ADLD (onset in adult life, dysautonomic symptoms, followed by pyramidal and cerebellar dysfunctions) partially resemble those of multiple sclerosis (MS), particularly the primary-progressive form. Our aim was to test whether LMNB1 gene mutations were present amongst patients with a diagnosis of MS. METHODS: One hundred eighty-two MS patients were screened for copy number variations of the LMNB1 gene using a qPCR assay. Point mutations in the LMNB1 gene were searched by denaturing high-performance liquid chromatography and direct sequencing in a subgroup of 16 patients with familial MS. RESULTS: No duplication/deletion of the lamin B1 gene was found amongst MS patients, and no point mutation was identified in the familial cases. CONCLUSION: Our work indicates that lamin B1 defects are probably not responsible for signs and symptoms resembling multiple sclerosis.

Investigating the genetic role of aquaporin4 gene in migraine.

Aquaporin4 (AQP4) has an important role in water homeostasis of human brain and a dysfunction of AQP4 could induce pathological conditions in neuronal activity. The purpose of our work was to evaluate the association of polymorphisms in the AQP4 gene with the risk and the clinical features of migraine. A total of 293 migraineurs and 249 controls were involved in the study. They were genotyped for four single nucleotide polymorphisms (SNPs) of AQP4 gene. No significant difference in the distribution of AQP4 genotypic and allelic frequencies between cases and controls was found. In addition, haplotype analysis did not show any significant difference. Comparison of the clinical features of the disease according to different AQP4 genotypes showed no significant difference. Our data do not support the hypothesis that the AQP4 gene could represent a genetic susceptibility factor for migraine.

A novel family with Lamin B1 duplication associated with adult-onset leucoencephalopathy.

BACKGROUND AND AIMS: Duplication of the lamin B1 gene (LMNB1) has recently been described in a rare form of autosomal dominant adult-onset leucoencephalopathy. The aim of the study was to evaluate the presence of LMNB1 gene defects in a series of eight patients with diffuse adult-onset hereditary leucoencephalopathy. METHODS: Clinical features of tested patients included a variable combination of pyramidal, cerebellar, cognitive and autonomic dysfunction. Neuroradiological data (MRI) showed symmetrical and diffuse white-matter lesions in six cases, and multifocal confluent lesions in two. LMNB1 full gene deletion/duplication and point mutations were searched using a TaqMan real-time PCR assay and direct sequencing of all coding exons. RESULTS: One patient carried a 140-190 kb duplication involving the entire LMNB1 gene, the AX748201 transcript and the 3' end of the MARCH3 gene. Clinical and neuroimaging data of this proband and an affected relative overlapped with the features already described in patients with LMNB1 duplication. Lamin B1 expression was found increased in lymphoblasts. No LMNB1 gene defect was identified in the remaining seven probands. CONCLUSIONS: LMNB1 gene duplication appears characteristic of a subset of adult-onset autosomal dominant leucoencephalopathies, sharing autonomic dysfunction at onset, diffuse T2-hyperintensity of supra- and infratentorial white matter, sparing of U-fibres and optic radiations. The variable phenotypes in the remaining cases lacking LMNB1 defects (five with autosomal dominant transmission) suggest that adult-onset leucoencephalopathies are genetically heterogeneous.

Association of the C677T polymorphism in the MTHFR gene with migraine: a meta-analysis.

There are conflicting data concerning the association between migraine and C677T polymorphism of the MTHFR gene. The C677T polymorphism reduces enzymatic capability by 50% and causes hyperhomocysteinaemia. We performed a meta-analysis of all published studies investigating the association between the MTHFR gene and migraine. Pooled odds ratios (OR) were estimated using random (RE) and fixed effects (FE) models. Among the overall 2961 migraineurs there was no significant difference compared with controls. Only in migraine with aura was the TT genotype associated with a higher risk of disease compared with the CC genotype [FE OR 1.30, 95% confidence interval (CI) 1.06, 1.58; RE OR 1.66, 95% CI 1.06, 2.59]. In the same subgroup a significant difference was observed in the comparison between TT and CT + CC genotypes (FE OR 1.32, 95% CI 1.10, 1.59; RE OR 1.63, 95% CI 1.10, 2.43). This study provides evidence for an association of the MTHFR gene only in migraine with aura.

The 1246G-->A polymorphism of the HCRTR2 gene is not associated with migraine.

Studies in experimental animals have suggested that the hypocretin/orexin system may be involved in migraine pathophysiology. Using a case-control design study, we genotyped 246 migraine patients and 239 healthy controls for the 1246G-->A polymorphism of the hypocretin receptor 2 (HCRTR2) gene. Genotypic and allelic frequencies of the examined polymorphism were similarly distributed between cases and controls (chi2 = 2.22, P = 0.14 and chi2 = 2.45, P = 0.29, respectively). When different migraine subgroups were compared (migraine with aura vs. migraine without aura and episodic vs. chronic migraine) no significant difference was found. Comparison of the clinical features of the disease with the 1246G-->A genotypes showed no significant difference. Our data suggest that the HCRTR2 gene is not a genetic risk factor in migraine.

Association between the interleukin-1alpha gene and Alzheimer's disease: a meta-analysis.

Inflammatory processes are involved in the pathogenesis of Alzheimer's disease (AD). Several studies have addressed the effects of interleukin-1 (IL-1) genes polymorphisms on the risk of developing AD. The results are not in full agreement on whether these polymorphisms are associated with the disease. To clarify this issue, we performed a meta-analysis of all the association studies between IL-1 genes and AD. Due to the relatively small number of published articles, the meta-analysis was restricted to the association of the IL-1alpha -889 C/T gene polymorphism and AD. Under a random effects model, the risk for the disease was significantly higher in subjects with the T/T genotype in comparison with both C/T (OR: 1.51; 95% C.I.: 1.15-1.99) and C/C (OR: 1.49; 95% C.I.: 1.09-2.03) subjects. There was modest heterogeneity for these effect estimates. Analysis of subgroups showed a significant association in patients with early-onset AD but not in late-onset AD. Our data support a significant but modest association between the T/T genotype of the IL-1alpha gene and AD.

Neurophysiological study in an Italian family with autosomal dominant late-onset leukodystrophy.

Evoked potentials (EPs) and nerve conduction velocities (NCV) were evaluated in 8 affected and 10 asymptomatic members of a new Italian family with an adult-onset autosomal dominant leukodystrophy of uncertain nosography. NCV studies did not show anomalies. Various EPs abnormalities were found in all the symptomatic patients (increase of interpeak latency and/or loss of cortical responses), according with a myelin disorder. Among the asymptomatic subjects 3/10 (30%) showed similar anomalies at auditory brainstem EPs (increase of I-III/I-V/III-V interval). Two of these patients had normal brain MRI. This datum require further confirms (very low penetrance of the disease?), but it remarks the importance of a functional study of SNC in order to obtain elements not usually given from clinical and neuroradiological study.

MRI and CT in an autosomal-dominant, adult-onset leukodystrophy.

We report MRI findings in a family with an autosomal-dominant, adult-onset neurological disorder. The clinical picture, the white matter changes detected on MRI and the absence of any laboratory abnormality suggested the diagnosis of leukodystrophy with an unknown biochemical defect. Autosomal-dominant inheritance is extremely rare in this kind of disease, and most reported families have not undergone MRI. We performed MRI and clinical examination of 17 members of our family; 9 affected subjects, at different stages of the disease, were detected. The most characteristic MRI findings were initially symmetrical areas of signal change in the white matter of the trigonal region; demyelination extending thereafter to the frontal and parietal regions, partially involving subcortical white matter; the temporal lobe and optic radiations were less involved; the internal capsule and corpus callosum were involved later, in a dorsoventral direction; patchy demyelination was evident in the late stages in the brain stem; the cerebellum was spared even in the latest stages of the disease. While pathological examination is essential to characterise and classify these kinds of diseases, MRI can make substantial contributions to understanding their natural history, and to detect early signs of the disease.

Autosomal dominant late-onset leukoencephalopathy. Clinical report of a new Italian family.

The adult-onset autosomal dominant leukoencephalopathies are rare disorders. Very few pedigrees have been extensively described and no biochemical or genetic marker has been identified so far. The present study was aimed to characterized an autosomal dominant late-onset leukoencephalopathy occurring in a large Italian kindred. A genealogic method was adopted to ascertain 51 affected individuals among nearly 400 subjects in 8 generations. Medical records were obtained from 11 deceased patients. We personally examined 8 symptomatic and 9 asymptomatic at-risk individuals who underwent a standardized clinical, biochemical, radiological and neurophysiological study. The mean age at onset of the disease was 46.6 years and the mean duration of disease 9.9 years. The clinical picture was characterized by progressive pyramidal and pseudobulbar signs, urinary incontinence and, sometimes, action tremor of the head and/or hands. No relevant mental deterioration was noted. In all the symptomatic and in 1 asymptomatic subject, brain MRI showed marked symmetrical hyperintensity on T2-weighted images of the white matter of the cerebral hemispheres, with constant sparing of the cerebellum. In these subjects, evoked potentials revealed altered central neural conduction. Nerve conduction velocity, biochemical (including lysosomal enzymatic activities) and biopsy (peripheral tissue specimens) examination were normal. The clinical and neuroradiological data are consistent with an autosomal dominant adult-onset leukoencephalopathy whose features are unusual when compared to those previously reported.

Analysis of the functional effects of a mutation in SOD1 associated with familial amyotrophic lateral sclerosis.

Mutations in the Cu, Zn superoxide dismutase (SOD1) gene have been reported in some pedigrees with Familial Amyotrophic Lateral Sclerosis (FALS). We have investigated the functional and structural effects of a Gly-->Ser mutation at codon 41 of SOD1 in a pedigree with FALS and the topography of SOD1 expression in the mammalian CNS. These analyses show that the 41Gly-->Ser mutation causes a 27% reduction in Cu, Zn SOD activity. SOD1 is transcribed at high levels in rat motoneurons and four other types of neurons homologous to upper motoneurons that degenerate in human ALS. However, SOD1 is transcribed at lower levels in other types of neurons, such as cerebellar Purkinje cells, which are not usually involved significantly in human ALS. On the other hand, immunocytochemical studies indicate that most types of rat neurons contain similar levels of Cu, Zn SOD immunoreactive protein. Nevertheless, these results suggest that the essential feature causing this subtype of ALS is either a reduction in Cu, Zn SOD activity in cell types that presumably critically require Cu, Zn SOD for protection against oxidative damage or the fact that the mutation in SOD1 associated with FALS results in a novel gain of function that is particularly deleterious to those cell types expressing SOD1 at high levels.

Assessment of genetic polymorphisms in DNA from formalin fixed neurological tissues.

The ability to analyze the genotype of deceased affected members of pedigrees segregating inherited neurological diseases considerably augments the informativeness of such pedigrees. This information has direct application in attempts to isolate disease genes by positional cloning strategies, and for genetic counselling. We show that the genotype at polymorphic simple sequence repeat loci can be determined from genomic DNA isolated from 10 micron thick paraffin embedded, formalin fixed neurological tissues. The critical constraint on this method is the size of the template target bearing the simple sequence repeat, which should ideally be less than 165 base pairs.

Protein-DNA interactions in the promoter region of the amyloid precursor protein (APP) gene in human neocortex.

We have investigated protein-DNA interactions in the proximal promoter of the human amyloid precursor protein (APP) gene in temporal lobe neocortical nuclei isolated from control and Alzheimer disease (AD) affected brains. We report that the human APP 5' promoter sequence from -203 to +55 bp, which has been previously reported to contain essential regulatory elements for APP gene transcription, lies in a deoxyribonuclease I, micrococcal nuclease- and restriction endonuclease-sensitive, G+C-rich nucleosome-free gap flanked both 5' and 3' by typical nucleosome structures. As analyzed by electrophoretic mobility shift assay, this extended internucleosomal linker DNA is heavily occupied by nuclear protein factors, and interacts differentially with nuclear protein extracts obtained from HeLa and human brain neocortical nuclei. This suggests that the chromatin conformation of the APP gene promoter may vary in different cell types, and may correlate with differences in APP gene expression. Human recombinant transcription factors AP1, SP1 and TFIID (but not AP2 or brain histones H1, H2B and H4) interact with the -203 to +55 bp of the human APP promoter sequence. Only minor differences were observed in the chromatin structure of the immediate APP promoter between non-AD and AD affected neocortical nuclei, suggesting either that post-transcriptional processes, or that regulatory elements lying elsewhere in the APP gene may be important in the aberrant accumulation of the APP gene product.

SOD1 missense mutation in an Italian family with ALS.

We have discovered a new Italian pedigree with autosomal-dominant ALS. The pedigree, at present, comprises 75 members distributed in five generations. ALS was diagnosed in eight patients. The mean +/- SD age of onset of the disease was 46.8 +/- 13.5 years, with a range of 29 to 63 years. The mean +/- SD duration of the disease was 11.6 +/- 1.7 months. Molecular genetic studies showed a missense mutation (Gly-->Ser, codon 41) in exon 2 of the Cu/Zn superoxide dismutase gene (SOD1) on chromosome 21 in the available affected member and in 45% of the at-risk subjects of the pedigree. This study confirms the presence of SOD1 point mutations in families with autosomal-dominant ALS and suggests that additional genetic or environmental factors may be involved in the full expression of the disease.

A new Italian pedigree with early-onset Alzheimer's disease.

We have recently discovered in Torino (Italy) a new pedigree with early-onset Alzheimer's disease. The index patient is a woman who, at the age of 43 years, showed progressive memory impairment and ideomotor apraxia. Several relatives of the patient have had a history of dementia. The ancestors of the patient were from Calabria (southern Italy) and members of the family emigrated to the north of Italy, to France, and to the United States. Up to now, the new kindred comprises 1950 members, distributed in eight generations. Thirty members affected with Alzheimer's disease have been identified. Neuropathologic confirmation of antemortem clinically diagnosed Alzheimer's disease has been achieved for one patient. The pedigree is consistent with autosomal dominant inheritance. The clinical course of the disease is fairly uniform: the first symptom is memory loss, beginning around age 40 years. Psychiatric symptoms like hallucinations and delusions follow. At a later stage of the disease, several patients developed myoclonus and generalized epileptic seizures and eventually died with profound dementia. The "Torino family" shows several genealogic and clinical similarities with other large multigenerational familial Alzheimer's disease pedigrees originating from the Calabria region.

Analysis of the c-FOS gene on chromosome 14 and the promoter of the amyloid precursor protein gene in familial Alzheimer's disease.

The c-FOS gene product, a putative transacting transcriptional regulator of the amyloid precursor protein (APP) gene, is a candidate locus for the familial Alzheimer's disease (FAD) mutation on chromosome 14 (FAD14). In light of this functional relationship, we investigated the nucleotide sequence and segregation of c-FOS and the nucleotide sequence of the 5' APP promoter. Single-stranded conformational polymorphisms (SSCPs) in the c-FOS gene revealed that c-FOS closely cosegregates with the FAD14 gene but does not show allelic association with FAD. A conservative third-position T-->C mutation was demonstrated in exon 2 (codon 84) of c-FOS, and a C-->G substitution was detected at -209 bp in the 5' promoter of APP. Neither were unique to FAD and are unlikely to be pathogenic or secondary modifiers of the FAD phenotype. We conclude that the c-FOS open reading frame is probably not the site of the FAD14 locus, but we cannot exclude the existence of modifier loci on chromosome 21.

Genetic evidence for a novel familial Alzheimer's disease locus on chromosome 14.

Familial Alzheimer's disease (FAD) has been shown to be genetically heterogeneous, with a very small proportion of early onset pedigrees being associated with mutations in the amyloid precursor protein (APP) gene on chromosome 21, and some late onset pedigrees showing associations with markers on chromosome 19. We now provide evidence for a major early onset FAD locus on the long arm of chromosome 14 near the markers D14S43 and D14S53 (multipoint lod score z = 23.4) and suggest that the inheritance of FAD may be more complex than had initially been suspected.