Late onset Alexander’s disease presenting as cerebellar ataxia associated with a novel mutation in the GFAP gene

Identification of a novel de novo pathogenic variant in GFAP in an Iranian family with Alexander disease by whole-exome sequencing

Background

Alexander disease (AxD) is a rare leukodystrophy with an autosomal dominant inheritance mode. Variants in GFAP lead to this disorder and it is classified into three distinguishable subgroups: infantile, juvenile, and adult-onset types.

Objective

The aim of this study is to report a novel variant causing AxD and collect all the associated variants with juvenile and adult-onset as well.

Methods

We report a 2-year-old female with infantile AxD. All relevant clinical and genetic data were evaluated. Search strategy for all AxD types was performed on PubMed. The extracted data include total recruited patients, number of patients carrying a GFAP variant, nucleotide and protein change, zygosity and all the clinical symptoms.

Results

A novel de novo variant c.217A > G: p. Met73Val was found in our case by whole-exome sequencing. In silico analysis categorized this variant as pathogenic. Totally 377 patients clinically diagnosed with juvenile or adult-onset forms were recruited in these articles, among them 212 patients were affected with juvenile or adult-onset form carrier of an alteration in GFAP. A total of 98 variants were collected. Among these variants c.262C > T 11/212 (5.18%), c.1246C > T 9/212 (4.24%), c.827G > T 8/212 (3.77%), c.232G > A 6/212 (2.83%) account for the majority of reported variants.

Conclusion

This study highlighted the role of genetic in AxD diagnosing. It also helps to provide more information in order to expand the genetic spectrum of Iranian patients with AxD. Our literature review is beneficial in defining a better genotype–phenotype correlation of AxD disorder.

Juvenile Alexander Disease: A Rare Leukodystrophy

Alexander disease is an uncommon autosomal dominant leukodystrophy that influences the white matter of the central nervous system (CNS), predominantly affecting the frontal lobe bilaterally. The most obvious pathogenic hallmark is the extensive deposition of cytoplasmic inclusions known as "Rosenthal fibers" in perivascular, subpial, and subependymal astrocytes throughout the CNS. The hereditary cause is mutations in the glial fibrillary acidic protein (GFAP) gene. Infantile, adult, and juvenile onsets are the three subtypes. Psychomotor retardation, mile-stone regression, spastic paresis, brain stem symptoms (swallowing, speech, etc.), and seizures define the juvenile variety, which emerges between the ages of three and 10 years. Macrocephaly has a lower likelihood of being a juvenile type. It is generally diagnosed based on clinical and magnetic resonance imaging findings. A five-year-old girl is presented as a case of juvenile Alexander disease, with typical clinical and MRI features.

Decoding epigenetic codes: new frontiers in exploring recovery from spinal cord injury

Spinal cord injury that results in severe neurological disability is often incurable. The poor clinical outcome of spinal cord injury is mainly caused by the failure to reconstruct the injured neural circuits. Several intrinsic and extrinsic determinants contribute to this inability to reconnect. Epigenetic regulation acts as the driving force for multiple pathological and physiological processes in the central nervous system by modulating the expression of certain critical genes. Recent studies have demonstrated that post-SCI alteration of epigenetic landmarks is strongly associated with axon regeneration, glial activation and neurogenesis. These findings not only establish a theoretical foundation for further exploration of spinal cord injury, but also provide new avenues for the clinical treatment of spinal cord injury. This review focuses on the epigenetic regulation in axon regeneration and secondary spinal cord injury. Together, these discoveries are a selection of epigenetic-based prognosis biomarkers and attractive therapeutic targets in the treatment of spinal cord injury.

Aggregation-prone GFAP mutation in Alexander disease validated using a zebrafish model

Background

Alexander disease (AxD) is an astrogliopathy that predominantly affects the white matter of the central nervous system (CNS), and is caused by a mutation in the gene encoding the glial fibrillary acidic protein (GFAP), an intermediate filament primarily expressed in astrocytes and ependymal cells. The main pathologic feature of AxD is the presence of Rosenthal fibers (RFs), homogeneous eosinophilic inclusions found in astrocytes. Because of difficulties in procuring patient’ CNS tissues and the presence of RFs in other pathologic conditions, there is a need to develop an in vivo assay that can determine whether a mutation in the GFAP results in aggregation and is thus disease-causing.

Methods

We found a GFAP mutation (c.382G > A, p.Asp128Asn) in a 68-year-old man with slowly progressive gait disturbance with tendency to fall. The patient was tentatively diagnosed with AxD based on clinical and radiological findings. To develop a vertebrate model to assess the aggregation tendency of GFAP, we expressed several previously reported mutant GFAPs and p.Asp128Asn GFAP in zebrafish embryos.

Results

The most common GFAP mutations in AxD, p.Arg79Cys, p.Arg79His, p.Arg239Cys and p.Arg239His, and p.Asp128Asn induced a significantly higher number of GFAP aggregates in zebrafish embryos than wild-type GFAP.

Conclusions

The p.Asp128Asn GFAP mutation is likely to be a disease-causing mutation. Although it needs to be tested more extensively in larger case series, the zebrafish assay system presented here would help clinicians determine whether GFAP mutations identified in putative AxD patients are disease-causing.

Familial Adult-onset Alexander Disease: Clinical and Neuroradiological Findings of Three Cases

The adult-onset Alexander disease (AOAD) dramatically differs from the early onset AD with respect to clinical and neuroradiological findings. Herein we report the detailed clinical and neuroradiological findings of a Turkish family with AOAD. In all three cases, magnetic resonance imaging revealed marked atrophy of the mesencephalon, bulbus, and cervical spinal cord accompanied with signal abnormalities in the same regions along with supratentorial white matter. Basal ganglia were affected in two cases. Molecular genetic analysis revealed heterozygous mutation in the 8th exon of the glial fibrillary acidic protein gene M451I (c.1245G>A), leading to the diagnosis of AOAD in all cases.

Familial adult-onset Alexander disease with a novel mutation (D78N) in the glial fibrillary acidic protein gene with unusual bilateral basal ganglia involvement

In this report, we describe the case of a new Japanese family (32 to 64 years old; 2 females and 1 male) affected by adult-onset Alexander disease. Clinically, one member (age at onset, 56 years old) developed cerebellar ataxia, another (age at onset, 55 years old) showed cerebellar ataxia and pseudobulbar signs, and one member (32 years old) was asymptomatic. Marked atrophy of the medulla oblongata and spinal cord was detected in the two symptomatic patients by magnetic resonance imaging (MRI). However, in the asymptomatic patient, cervicomedullary atrophy was mild. Hyperintensity signals in the medulla oblongata were detected in the two symptomatic patients, but not in the asymptomatic patient. In addition, there are symmetrical hyperintensity signals in the posterior part of the globus pallidus on T2-weighted images in the two symptomatic patients, which are rarely observed in adult-onset Alexander disease. Molecular genetic analysis revealed a novel missense mutation (p. D78N) in the glial fibrillary acidic protein (GFAP) gene in this family. The typical atrophy of the medulla oblongata and upper cervical cord detected by MRI is the diagnostic feature of adult-onset Alexander disease. Genetic analysis of the GFAP gene is recommended for all patients with late-onset progressive ataxia and suspected of having adult-onset Alexander disease on the basis of MRI findings. Additionally, these characteristic MRI patterns might even lead to the identification of asymptomatic cases, as in one of our cases.