A GM1 gangliosidosis mutant mouse model exhibits activated microglia and disturbed autophagy.

GM1 gangliosidosis is a rare lysosomal storage disease caused by a deficiency of ß-galactosidase due to mutations in the GLB1 gene. We established a C57BL/6 mouse model with Glb1G455R mutation using CRISPR/Cas9 genome editing. The ß-galactosidase enzyme activity of Glb1G455R mice measured by fluorometric assay was negligible throughout the whole body. Mutant mice displayed no marked phenotype at eight weeks. After 16 weeks, GM1 ganglioside accumulation in the brain of mutant mice was observed by immunohistochemical staining. Meanwhile, a declining performance in behavioral tests was observed among mutant mice from 16 to 32 weeks. As the disease progressed, the neurological symptoms of mutant mice worsened, and they then succumbed to the disease by 47 weeks of age. We also observed microglia activation and proliferation in the cerebral cortex of mutant mice at 16 and 32 weeks. In these activated microglia, the level of autophagy regulator LC3 was up-regulated but the mRNA level of LC3 was normal. In conclusion, we developed a novel murine model that mimicked the chronic phenotype of human GM1. This Glb1G455R murine model is a practical in vivo model for studying the pathogenesis of GM1 gangliosidosis and exploring potential therapies.

A duplication in the canine beta-galactosidase gene GLB1 causes exon skipping and GM1-gangliosidosis in Alaskan huskies.

GM(1)-gangliosidosis is a lysosomal storage disease that is inherited as an autosomal recessive disorder, predominantly caused by structural defects in the beta-galactosidase gene (GLB1). The molecular cause of GM(1)-gangliosidosis in Alaskan huskies was investigated and a novel 19-bp duplication in exon 15 of the GLB1 gene was identified. The duplication comprised positions +1688-+1706 of the GLB1 cDNA. It partially disrupted a potential exon splicing enhancer (ESE), leading to exon skipping in a fraction of the transcripts. Thus, the mutation caused the expression of two different mRNAs from the mutant allele. One transcript contained the complete exon 15 with the 19-bp duplication, while the other transcript lacked exon 15. In the transcript containing exon 15 with the 19-bp duplication a premature termination codon (PTC) appeared, but due to its localization in the last exon of canine GLB1, nonsense-mediated RNA decay (NMD) did not occur. As a consequence of these molecular events two different truncated GLB1 proteins are predicted to be expressed from the mutant GLB1 allele. In heterozygous carrier animals the wild-type allele produces sufficient amounts of the active enzyme to prevent clinical signs of disease. In affected homozygous dogs no functional GLB1 is synthesized and G(M1)-gangliosidosis occurs.

Central nervous system inflammation is a hallmark of pathogenesis in mouse models of GM1 and GM2 gangliosidosis.

Mouse models of the GM2 gangliosidoses [Tay-Sachs, late onset Tay-Sachs (LOTS), Sandhoff] and GM1 gangliosidosis have been studied to determine whether there is a common neuro-inflammatory component to these disorders. During the disease course, we have: (i) examined the expression of a number of inflammatory markers in the CNS, including MHC class II, CD68, CD11b (CR3), 7/4, F4/80, nitrotyrosine, CD4 and CD8; (ii) profiled cytokine production [tumour necrosis factor alpha (TNF alpha), transforming growth factor (TGF beta 1) and interleukin 1 beta (IL1 beta)]; and (iii) studied blood-brain barrier (BBB) integrity. The kinetics of apoptosis and the expression of Fas and TNF-R1 were also assessed. In all symptomatic mouse models, a progressive increase in local microglial activation/expansion and infiltration of inflammatory cells was noted. Altered BBB permeability was evident in Sandhoff and GM1 mice, but absent in LOTS mice. Progressive CNS inflammation coincided with the onset of clinical signs in these mouse models. Substrate reduction therapy in the Sandhoff mouse model slowed the rate of accumulation of glycosphingolipids in the CNS, thus delaying the onset of the inflammatory process and disease pathogenesis. These data suggest that inflammation may play an important role in the pathogenesis of the gangliosidoses.

Mancha mongólica generalizada en un niño con gangliosidosis GM1 tipo 1 / Extensive mongolian spot in a child with GM1, type 1 gangliosidosis

Se presenta el caso de un niño de raza blanca, de 9 meses de edad, con gangliosidosis GM1 tipo 1 que presentaba una mancha mongólica generalizada. Los casos informados con esta asociación bien pueden apoyar una relación causal entre ambas enfermedades o bien puede considerarse que la mancha mongólica generalizada sea una manifestación de la gangliosidosis GM1 (AU)

[GM1-gangliosidosis knockout mouse].

We generated a beta-galactosidosis mouse by gene targeting in an embryonic stem cell. Clinical, pathological, and biochemical analyses revealed that this mouse is a useful animal model to study the pathogenesis and therapy of human GM1-gangliosidosis.

[beta-galactosidosis--GM1 gangliosidosis and Morquio B disease].

beta-galactosidosis is a lysosomal storage disorder caused by a deficiency of acid beta-galactosidase, including to autosomal recessive diseases; GM1-gangliosidosis (neurovisceral form) and Morquio B disease (skeletal form). To date, 26 different mutations in the beta-galactosidase gene have been identified in patients with beta-galactosidosis from various ethnic groups. Transient expression of the mutant genes has confirmed that mutant enzymes responsible for infantile GM1-gangliosidosis have almost no detectable beta-galactosidase activity. But the other three forms (late infantile/juvenile, adult/chronic GM1-gangliosidosis and Morquio B disease) are characterized by specific mutant enzymes with significant residual enzyme activity. Heterogeneous patterns of post-translational processing and maturation in these mutant enzymes are closely related to the phenotypic variations in beta-galactosidosis.

Lysosomal storage diseases presenting as transient or persistent hydrops fetalis.

Two cases of beta-glucuronidase deficiency (mucopolysaccharidosis VII), presented with fetal hydrops at 20 and 26 weeks of gestation. The enzyme deficiency was observed in cultured amniotic fluid cells and in fetal plasma from cord-blood and was confirmed after termination of pregnancy. A third case presented with transient ascites at 6.5 months of gestation. Mild dysmorphic features at birth and gradual neurological deterioration were observed. Deficiency of beta-galactosidase was documented confirming a GM1 gangliosidosis. Evidence has accumulated that fetuses affected by lysosomal diseases, may present with transient or persistent hydrops fetalis. The exact frequency is however not known. Further diagnostic studies in persistent or transient hydrops fetalis, looking for lysosomal and other metabolic diseases, whenever major causes of hydrops fetalis have been excluded, are therefore indicated. Amniocentesis and cordocentesis should always be performed.