Anticipation in familial amyotrophic lateral sclerosis with SOD1-G93S mutation

Anticipation Can Be More Common in Hereditary Spastic Paraplegia with SPAST Mutations Than It Appears

BACKGROUND AND OBJECTIVE

Hereditary spastic paraplegia (HSP) is a heterogeneous neurodegenerative disorder with lower-limb spasticity and weakness. Different patterns of inheritance have been identified in HSP. Most autosomal-dominant HSPs (AD-HSPs) are associated with mutations of the SPAST gene (SPG4), leading to a pure form of HSP with variable age-at-onset (AAO). Anticipation, an earlier onset of disease, as well as aggravation of symptoms in successive generations, may be correlated to SPG4. Herein, we suggested that anticipation might be a relatively common finding in SPG4 families.

METHODS

Whole-exome sequencing was done on DNA of 14 unrelated Iranian AD-HSP probands. Data were analyzed, and candidate variants were PCR-amplified and sequenced by the Sanger method, subsequently checked in family members to co-segregation analysis. Multiplex ligation-dependent probe amplification (MLPA) was done for seven probands. Clinical features of the probands were recorded, and the probable anticipation was checked in these families. Other previous reported SPG4 families were investigated to anticipation.

RESULTS

Our findings showed that SPG4 was the common subtype of HSP; three families carried variants in the KIF5A, ATL1, and MFN2 genes, while five families harbored mutations in the SPAST gene. Clinical features of only SPG4 families indicated decreasing AAO in affected individuals of the successive generations, and this difference was significant (p-value <0.05).

CONCLUSION

It seems SPAST will be the first candidate gene in families that manifests a pure form of AD-HSP and anticipation. Therefore, it may be a powerful situation of genotype-phenotype correlation. However, the underlying mechanism of anticipation in these families is not clear yet.

SOD1-related ALS with anticipation in a large family from Martinique

Amyotrophic Lateral Sclerosis (ALS) is a rare neurological disorder that causes degeneration of upper and lower motor neurons and their axons. ALS is mostly sporadic, but there are familial forms. In more than half of the familial forms, a pathogenic variant is found in one of the following genes: C9ORF72, SOD1, TDP-43, FUS, and VCP. SOD1 is the 2nd most common gene involved in genetic forms of ALS. Genotype-phenotype relationships are occasionally established in genetic forms of ALS associated with SOD1 mutations pathogenic variants. The c.281G > T (p.[G93V]) variant in SOD1 is associated with a rarely described and unexplained anticipation phenomenon. We report a large family from Martinique in whom ALS is associated with a c.281G > T (p.[G93V]) pathogenic variant in SOD1 and a statistically suggested anticipation. A whole-exome study and detection of CNVs (CoDESeq) from 3 affected members of this family revealed the presence of variants of uncertain signification (VUS) in other ALS genes. VUS in DCTN1 and NEFH were present in patients of the 2nd generation, and CNVs involving UBQLN2 and C21orf2 were found in the youngest case of the family.

LMNA-associated partial lipodystrophy: anticipation of metabolic complications

Background

Type-2 familial partial lipodystrophy (FPLD2) is a rare autosomal dominant lipodystrophic disorder due to mutations inLMNAencoding lamin A/C, a key epigenetic regulator. FPLD2 severity is determined by the occurrence of metabolic complications, especially diabetes and hypertriglyceridaemia. We evaluated the disease history and severity over generations.

Methods

This retrospective study of the largest cohort of patients with FPLD2 reported to date investigates 85 patients from 24 families comprising three generations (G1: n=39; G2: n=41; G3: n=5).

Results

Lipodystrophy appears with the same characteristics and at the same age in first generation (G1;18.6±1.5 years) and second generation (G2;15.9±0.8 years). Despite similar body mass index (23.7±0.6 vs 23.8±0.6 kg/m2), the mean delay between the onset of lipodystrophy and diabetes was far shorter in G2 (10.5±2.4 years) than in G1 (29.0±3.5 years) (p=0.0002). The same is true for the delay preceding hypertriglyceridaemia (G2: 4.5±1.4; G1: 19.3±3.2 years) (p=0.002), revealing an anticipation phenomenon. Observations in G3, and analysis within each family of disease history and diagnostic procedures, confirmed this result.

Conclusions

This study is a rare example of anticipation unrelated to a trinucleotide expansion. Discovery of this early occurrence of metabolic complications in young generations underlines the utility of presymptomatic genetic diagnosis, with careful metabolic screening and preventive lifestyle in all at-risk individuals.

Familial amyotrophic lateral sclerosis with an I104F mutation in the SOD1 gene: Multisystem degeneration with neurofilamentous aggregates and SOD1 inclusions

We previously reported familial amyotrophic lateral sclerosis (FALS) of 11 years duration in a 57-year-old woman, who received artificial ventilation for 5 years prior to death and exhibited widespread multisystem degeneration and neurofilamentous aggregates, so-called conglomerate inclusions (CIs). In the present study, we re-evaluated this autopsied patient (proband) with further immunohistochemical observation as well as mutational analysis of the superoxide dismutase 1 (SOD1) gene. A review of the clinical features of the proband's family revealed five affected members (including the proband) over two successive generations who showed marked variability in clinical presentation, such as the age at onset. The proband was found to harbor a heterozygous missense mutation in exon 4 (I104F) of the SOD1 gene. In the brain and spinal cord, SOD1-positive neuronal cytoplasmic inclusions (NCIs) were found to be more widely distributed than CIs, the latter being weakly positive for SOD1. No Lewy body-like hyaline inclusions were found. This is considered to be the first description of an autopsy case of FALS with an I104F SOD1 gene mutation, suggesting that combination of marked intra-familial clinical variability and multisystem degeneration with occurrence of CIs and SOD1-positive NCIs is a characteristic feature of FALS with this SOD1 gene mutation.

Next-generation sequencing of 28 ALS-related genes in a Japanese ALS cohort

We investigated the frequency and contribution of variants of the 28 known amyotrophic lateral sclerosis (ALS)-related genes in Japanese ALS patients. We designed a multiplex, polymerase chain reaction-based primer panel to amplify the coding regions of the 28 ALS-related genes and sequenced DNA samples from 257 Japanese ALS patients using an Ion Torrent PGM sequencer. We also performed exome sequencing and identified variants of the 28 genes in an additional 251 ALS patients using an Illumina HiSeq 2000 platform. We identified the known ALS pathogenic variants and predicted the functional properties of novel nonsynonymous variants in silico. These variants were confirmed by Sanger sequencing. Known pathogenic variants were identified in 19 (48.7%) of the 39 familial ALS patients and 14 (3.0%) of the 469 sporadic ALS patients. Thirty-two sporadic ALS patients (6.8%) harbored 1 or 2 novel nonsynonymous variants of ALS-related genes that might be deleterious. This study reports the first extensive genetic screening of Japanese ALS patients. These findings are useful for developing genetic screening and counseling strategies for such patients.

Apparent phenotypic anticipation in autosomal dominant connexin 26 deafness

BACKGROUND

Connexin 26 (GJB2) mutations are associated with various types of hearing loss, either without associated symptoms or with skin disease, constituting a form of syndromic hearing loss. These mutations can lead to deafness in either a recessive or a dominant autosomal form of inheritance.

METHODS

Ascertainment of a Jewish Ashkenazi family with nonsyndromic hearing loss led to the construction of a pedigree for a four-generation family, with hearing loss detected in three successive generations. The entire coding region of the GJB2 gene was amplified and sequenced by Sanger sequencing.

RESULTS

Audiological analysis revealed that the age of onset and severity of hearing loss were earlier and more severe, respectively, in each successive generation of an Ashkenazi Jewish family. A mutation, c.224G>A, leading to missense p.Arg75Gln was detected only in the affected members of the family.

CONCLUSIONS

The entire coding region of GJB2 should be checked in hearing-impaired patients by Sanger sequencing, rather than examination only of the two most prevalent mutations, regardless of mode of inheritance or ethnicity. Furthermore, predictions regarding phenotype based on genotype can be difficult to make due to clinical variability in multigenerational families, as demonstrated in the family presented in this study.

Phenotypic heterogeneity in hereditary motor neuropathy type V: a new case report series

Previous studies have revealed a wide phenotypic heterogeneity in hereditary motor neuropathy type V in which upper and lower motor neurons and peripheral motor axons are variously affected, even within the same family. In this case series, we describe the genetic, clinical and electrophysiological features of patients belonging to a four-generation Italian family. Because of a possible anticipation phenomenon, the disorder became apparent at an earlier age as it passed to the next generation, with a median age of onset of 65 years for the first 2 generations, 32 for the third, and 13.5 for the fourth. The symptoms at onset varied considerably among the sufferers, with a predominant impairment of the hands in seven cases, the impairment of the four limbs in one patient and only of the lower limbs in another. Also muscle atrophy was variable, from very mild to severe (wasting of the distal muscles of the limbs). Moreover, electrophysiological results were heterogeneous, including cases with isolated and with diffuse axonal motor neuropathy, and one case of motor sensory polyneuropathy. A novel polymorphism G→T was also found in the Berardinelli-Seip congenital lipodystrophy 2 gene on intron 4. This broad phenotypic and genotypic spectrum calls the clinician attention to this rare and still insufficiently known disease.

High-Resolution Melting (HRM) Analysis of the Cu/Zn Superoxide Dismutase (SOD1) Gene in Japanese Sporadic Amyotrophic Lateral Sclerosis (SALS) Patients

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder, and the majority of ALS are sporadic (SALS). Recently, several causative genes for familial ALS (FALS) were identified, but the cause of the SALS is still unknown. This time, we aimed to identify the genetic background of SALS. First, we applied the new sensitive screening methods: high-resolution melting (HRM) analysis. HRM analysis detected 18 out of 19 known SOD1 gene mutations (94.7% sensitivity). Next, we screened SOD1, three novel mutations (C6Y, Q22H, and S134T) were identified in our own 184 SALS cases (1.63% prevalence), and four mutations in another 255 SALS cases (1.56% prevalence) registered from all over Japan. The patients with SOD1 mutations suggested a relatively young onset and limb involvement at onset. The HRM analysis is a sensitive and easy screening method; we will use this method for screening other ALS causative genes and revealing the genetic background of SALS.

Protein aggregation and protein instability govern familial amyotrophic lateral sclerosis patient survival

The nature of the "toxic gain of function" that results from amyotrophic lateral sclerosis (ALS)-, Parkinson-, and Alzheimer-related mutations is a matter of debate. As a result no adequate model of any neurodegenerative disease etiology exists. We demonstrate that two synergistic properties, namely, increased protein aggregation propensity (increased likelihood that an unfolded protein will aggregate) and decreased protein stability (increased likelihood that a protein will unfold), are central to ALS etiology. Taken together these properties account for 69% of the variability in mutant Cu/Zn-superoxide-dismutase-linked familial ALS patient survival times. Aggregation is a concentration-dependent process, and spinal cord motor neurons have higher concentrations of Cu/Zn-superoxide dismutase than the surrounding cells. Protein aggregation therefore is expected to contribute to the selective vulnerability of motor neurons in familial ALS.

Anticipation and phenotypic heterogeneity in korean familial amyotrophic lateral sclerosis with superoxide dismutase 1 gene mutation

Background and purpose

Different mutations in the Cu/Zn superoxide dismutase 1 (SOD1) gene have been reported in approximately 10% of cases of familial amyotrophic lateral sclerosis (ALS). The aim of this study was to analyze for mutations in the SOD1 gene and clinical characteristics in Korean family of ALS.

Methods

A subpopulation of the family reported here has been described previously. In the present study, we analyzed the SOD1 gene in the proband and his immediate family members, who were not reported on previously. Genomic DNA was isolated from the leukocytes of whole blood samples and the coding region of the SOD1 gene was analyzed by PCR and direct sequencing.

Results

The genetic alterations were a GGC-to-GTT transition at codon 10 in exon 1 and [IVS4+15_16insA; IVS4+42delG; IVS4+59_60insT] in intron 4. Patients with these mutations exhibit diverse clinical onset symptoms and acceleration of the age at onset in successive generations, which is called anticipation.

Conclusions

We have described a family with familial ALS that showed autosomal-dominant inheritance and two distinct genetic alterations in Cu/Zn-SOD1. The affected family members had different phenotypes and anticipation.

Equilibrium Thermodynamic Analysis of Amyotrophic Lateral Sclerosis-Associated Mutant Apo Cu,Zn Superoxide Dismutases,

The folding and thermodynamic properties of metal free (apo) superoxide dismutases (SODs) are systematically analyzed using equilibrium guanidinium chloride (GdmCl) curves and differential scanning calorimetry (DSC). Chemically and structurally diverse amyotrophic lateral sclerosis (ALS)-associated mutations (G85R, G93R, E100G, I113T) are introduced into a pseudo-wild-type background that has no free cysteines, resulting in highly reversible unfolding. Analysis of the protein concentration dependence of GdmCl curves reveals formation of a monomer intermediate in equilibrium with native dimer and unfolded monomer. Global fitting of the data enables quantitative measurement of free energy changes for both dimer dissociation and monomer intermediate stability. All the mutations decrease protein stability, mainly by destabilizing the monomer intermediate, but also by tending to weaken dimerization, even for mutations far from the dimer interface. Thus, the effects of mutations seem to propagate through the apo protein, and result in increased population of both intermediate and unfolded monomers. This may underlie increased formation of toxic aggregates by mutants in ALS. Analysis of DSC data for apo SODs is consistent with stability measurements from GdmCl curves and provides further evidence for increased aggregation by mutant proteins through increased ratios of van't Hoff to calorimetric enthalpies of unfolding.

Calorimetric Analysis of Thermodynamic Stability and Aggregation for Apo and Holo Amyotrophic Lateral Sclerosis-associated Gly-93 Mutants of Superoxide Dismutase

Differential scanning calorimetry was used to measure changes in thermodynamic stability and aggregation for glycine 93 mutants of human copper, zinc-superoxide dismutase (SOD). Glycine 93 is a conserved residue at position i + 3 of a tight turn and has been found to be a mutational hot spot in familial amyotrophic lateral sclerosis (fALS). The fALS-associated mutations, G93A, G93S, G93R, G93D, and G93V, were made in a pseudo wild-type background containing no free cysteines, which prevented the formation of aberrant disulfide bonds upon thermal unfolding, and enabled quantitative thermodynamic analysis of the effects of the mutations. Thermal unfolding was highly reversible for all the SODs in both the fully metallated (holo) and metal-free (apo) forms. The data for all the holo-SODs and for the apo-pseudo-wild-type SOD were well fit by a 2-state unfolding model for native dimer (N2) to two unfolded monomers (2U), N2 <--> 2U. The holo- and apo-forms of the mutants are significantly destabilized (by 1.5-3.5 kcal mol(-1) monomer) relative to the corresponding forms of pseudo wild-type, with the relative stabilities being correlated with statistical preferences for amino acids in this structural context. Although van't Hoff (DeltaHvH) to calorimetric (DeltaHcal) enthalpy ratios are close to unity for all the holo-SODs and for apo-pseudo-wild-type, consistent with a 2-state transition, DeltaHvH is considerably larger than DeltaHcal for all the apo-mutants. This suggests that the mutations cause apo-SOD to have an increased propensity to misfold or aggregate, which may be linked to increased toxic mutant SOD aggregation in fALS.

CADASIL with NOTCH3 S180C presenting anticipation of onset age and hallucinations

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited disease leading to strokes and vascular dementia. The average age of onset for stroke is 45 years with a range of about 30 to 70 years. We describe a Japanese CADASIL family showing S180C in the exon 4 of NOTCH3, presenting an anticipation of the onset age for stroke. MRI demonstrated a similar extent of white matter involvement in younger and older individuals, supporting the presence of anticipation. In addition, hallucinations in 71% of affected patients, and delusions in 57% were also described. Our findings in this family suggest that a specific NOTCH3 mutation was related to unique clinical features, although such correlations have seldom been encountered in CADASIL.