Gene therapy for glycogen storage diseases

The focus of this review is the development of gene therapy for glycogen storage diseases (GSDs). GSD results from the deficiency of specific enzymes involved in the storage and retrieval of glucose in the body. Broadly, GSDs can be divided into types that affect liver or muscle or both tissues. For example, glucose-6-phosphatase (G6Pase) deficiency in GSD type Ia (GSD Ia) affects primarily the liver and kidney, while acid α-glucosidase (GAA) deficiency in GSD II causes primarily muscle disease. The lack of specific therapy for the GSDs has driven efforts to develop new therapies for these conditions. Gene therapy needs to replace deficient enzymes in target tissues, which has guided the planning of gene therapy experiments. Gene therapy with adeno-associated virus (AAV) vectors has demonstrated appropriate tropism for target tissues, including the liver, heart and skeletal muscle in animal models for GSD. AAV vectors transduced liver and kidney in GSD Ia and striated muscle in GSD II mice to replace the deficient enzyme in each disease. Gene therapy has been advanced to early phase clinical trials for the replacement of G6Pase in GSD Ia and GAA in GSD II (Pompe disease). Other GSDs have been treated in proof-of-concept studies, including GSD III, IV and V. The future of gene therapy appears promising for the GSDs, promising to provide more efficacious therapy for these disorders in the foreseeable future.

Prevalence of mutations responsible for glycogen storage disease type-II and congenital myasthenic syndrome in Brazilian Brahman cattle

ABSTRACT: Glycogen storage disease type II (GSD-II) and congenital myasthenic syndrome (CMS) are important autosomal recessive disorders in Brahman cattle. The objective of this study was to investigate the presence of mutations responsible for GSD II (E7, c.1057_1058delTA; and E13, c.1783C>T) and CMS (c.470del20) in purebred Brazilian Brahman cattle and in purebred Brahman bulls that were routinely used in breeding programs in Brazil. A total of 276 purebred Brahman cattle (167 females and 109 males, with ages ranging from 12-24 months) and 35 frozen semen samples taken from purebred Brahman bulls (22 bulls from the USA, 11 Brazilian bulls, one Argentine bull and one Australian bull) were used in this study. Genomic DNA was purified from hair root samples and from semen samples. Purified DNA was used in PCR genotyping to mutations c.1057_1058delTA (E7) and c.1783C>T (E13) in the GAA gene and c.470del20 in the CHRNE gene. The PCR products were purified and sequenced. The genotypic frequencies per polymorphism were estimated separately. Of the 276 Brahman cattle tested, 7.3% were identified as heterozygous for E7. All Brahman cattle studied were homozygous for the wild-type E13 allele. The E7 mutations was identified as heterozygous in 8.6% (3/35) of the commercial semen samples, whereas the E13 mutations was not identified. The c.470del20 mutation was identified as heterozygous in 0.73% of the hair root samples, but this mutation was not present in any semen sample assessed. No study had previously evaluated the prevalence of mutations responsible for GSD II or CMS in Brazilian Brahman cattle. In summary, the E7 and c.470del20 mutations are present in the Brazilian Brahman herd, and control measures should be adopted to prevent an increase in the incidence of GSD-II and CMS in Brahman cattle in Brazil.

Glycogen Storage Disorders

Glucose is the body’s major energy source, and carbohydrate serves as fuel—particularly during high-intensity exercise that requires rapid energy release. A deficiency of any of the enzymes involved in the catabolism of glycogen to glucose may cause symptoms, with hypoglycemia and exercise intolerance as the most common presentations. Glycogen storage disorders (GSD) affect muscle, liver, and brain. The most common GSDs affecting muscle are GSD II (Pompe disease) and GSD V (McArdle disease). GSDs affecting mainly the liver are GSD I, III, IV, VI, IX, XI. Most liver-GSDs present during infancy, with symptoms of hypoglycemia, impressive hepatomegaly, and retarded growth. Adult presentations have been reported for GSD Ia, III, IV, and IX.Adult polyglucosan body disease (APBD) is the main GSD affecting primarily the brain and mainly characterized by spastic paraplegia, axonal neuropathy and leukodystrophy. APBD is a subtype of GSD IV and is due to a deficiency of glycogen branching enzyme (GBE). Besides GSD IV, other GSDs have been reported to have CNS effects in some patients—notably GSD II and GSD III.

Rapid Ultraperformance Liquid Chromatography–Tandem Mass Spectrometry Assay for a Characteristic Glycogen-Derived Tetrasaccharide in Pompe Disease and Other Glycogen Storage Diseases

BACKGROUND Urinary excretion of the tetrasaccharide 6-α-D-glucopyranosyl-maltotriose (Glc4) is increased in various clinical conditions associated with increased turnover or storage of glycogen, making Glc4 a potential biomarker for glycogen storage diseases (GSD). We developed an ultraperformance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) assay to detect Glc4 in urine without interference of the Glc4 isomer maltotetraose (M4). METHODS Urine samples, diluted in 0.1% ammonium hydroxide containing the internal standard acarbose, were filtered, and the filtrate was analyzed by UPLC-MS/MS. RESULTS We separated and quantified acarbose, M4, and Glc4 using the ion pairs m/z 644/161, 665/161, and 665/179, respectively. Response of Glc4 was linear up to 1500 μmol/L and the limit of quantification was 2.8 μmol/L. Intra- and interassay CVs were 18.0% and 18.4% (10 μmol/L Glc4), and 10.5% and 16.2% (200 μmol/L Glc4). Glc4 in control individuals (n = 116) decreased with increasing age from a mean value of 8.9 mmol/mol to 1.0 mmol/mol creatinine. M4 was present in 5% of urine samples. Mean Glc4 concentrations per age group in untreated patients with Pompe disease (GSD type II) (n = 66) were significantly higher, ranging from 39.4 to 10.3 mmol/mol creatinine (P < 0.001–0.005). The diagnostic sensitivity of Glc4 for GSD-II was 98.5% and the diagnostic specificity 92%. Urine Glc4 was also increased in GSD-III (8 of 9), GSD-IV (2 of 3) and GSD-IX (6 of 10) patients. CONCLUSIONS The UPLC-MS/MS assay of Glc4 in urine was discriminative between Glc4 and M4 and confirmed the diagnosis in >98% of GSD-II cases.

Caracterização das habilidades simbólicas de crianças com síndrome de Down

OBJETIVO: Caracterizar as habilidades simbólicas de um grupo de crianças com síndrome de Down. MÉTODOS: Participaram do estudo 26 crianças com idades entre 12 e 36 meses, divididas em dois grupos: grupo síndrome de Down (GSD) e grupo controle (GC) - crianças com desenvolvimento normal. Os grupos foram subdivididos de acordo com a idade: GSD I e GC I, compostos por crianças de 12 a 24 meses; GSD II e GC II, com crianças de 25 a 36 meses. Os dados foram coletados por meio da interação com a examinadora em situação lúdica, durante 30 minutos o GSD e 20 minutos o GC, de acordo com a proposta do protocolo de observação comportamental. RESULTADOS: Comparando ambos os grupos controle encontramos diferença (p<0,05) para as formas de manipulação dos objetos, para o nível de desenvolvimento do simbolismo e para o desempenho geral no protocolo. Em ambos os grupos síndrome de Down houve diferença para o nível de desenvolvimento do simbolismo. Na comparação inter-grupos de acordo com as faixas etárias encontramos diferenças quanto à forma de manipulação dos objetos, nível de desenvolvimento do simbolismo e desempenho geral no protocolo. A imitação sonora e gestual não se diferenciou significativamente nessa pesquisa. CONCLUSÃO: Os resultados confirmaram a hipótese de atraso do desenvolvimento das habilidades simbólicas para crianças com síndrome de Down. O exame da linguagem e simbolismo em contexto funcional possibilitou a confrontação das manifestações observadas neste grupo e as descritas para crianças com desenvolvimento linguístico e simbólico considerados normais, sendo o nível de desenvolvimento simbólico o melhor parâmetro de análise e acompanhamento para o grupo.