Tay-Sachs Disease
Hexosaminidase A
beta-N-Acetylhexosaminidases
Lipidoses
Hexosaminidase B
G(M2) Ganglioside
Sandhoff Disease
Gangliosidoses
Gangliosidoses, GM2
Gangliosidosis, GM1
Adenoviral gene therapy of the Tay-Sachs disease in hexosaminidase A-deficient knock-out mice. (1/158)
The severe neurodegenerative disorder, Tays-Sachs disease, is caused by a beta-hexosaminidase alpha-subunit deficiency which prevents the formation of lysosomal heterodimeric alpha-beta enzyme, hexosaminidase A (HexA). No treatment is available for this fatal disease; however, gene therapy could represent a therapeutic approach. We previously have constructed and characterized, in vitro, adenoviral and retroviral vectors coding for alpha- and beta-subunits of the human beta-hexosaminidases. Here, we have determined the in vivo strategy which leads to the highest HexA activity in the maximum number of tissues in hexA -deficient knock-out mice. We demonstrated that intravenous co-administration of adenoviral vectors coding for both alpha- and beta-subunits, resulting in preferential liver transduction, was essential to obtain the most successful results. Only the supply of both subunits allowed for HexA overexpression leading to massive secretion of the enzyme in serum, and full or partial enzymatic activity restoration in all peripheral tissues tested. The enzymatic correction was likely to be due to direct cellular transduction by adenoviral vectors and/or uptake of secreted HexA by different organs. These results confirmed that the liver was the preferential target organ to deliver a large amount of secreted proteins. In addition, the need to overexpress both subunits of heterodimeric proteins in order to obtain a high level of secretion in animals defective in only one subunit is emphasized. The endogenous non-defective subunit is otherwise limiting. (+info)Sialidase-mediated depletion of GM2 ganglioside in Tay-Sachs neuroglia cells. (2/158)
Tay-Sachs disease is a severe, inherited disease of the nervous system caused by accumulation of the brain lipid GM2 ganglioside. Mouse models of Tay-Sachs disease have revealed a metabolic bypass of the genetic defect based on the more potent activity of the enzyme sialidase towards GM2. To determine whether increasing the level of sialidase would produce a similar effect in human Tay-Sachs cells, we introduced a human sialidase cDNA into neuroglia cells derived from a Tay-Sachs fetus and demonstrated a dramatic reduction in the accumulated GM2. This outcome confirmed the reversibility of GM2 accumulation and opens the way to pharmacological induction or activation of sialidase for the treatment of human Tay-Sachs disease. (+info)Structure of the GM2A gene: identification of an exon 2 nonsense mutation and a naturally occurring transcript with an in-frame deletion of exon 2. (3/158)
Deficiency of the GM2 activator protein, encoded by GM2A, results in the rare AB-variant form of GM2 gangliosidosis. Four mutations have been identified, but the human gene structure has been only partially characterized. We report a new patient from a Laotian deme whose cells are deficient in both GM2-activator mRNA and protein. However, reverse transcription (RT)-PCR detected some normal-sized cDNA and a smaller cDNA species, which was not seen in the RT-PCR products from normal controls. Sequencing revealed that, although the patient's normal-sized cDNA contained a single nonsense mutation in exon 2, his smaller cDNA was the result of an in-frame deletion of exon 2. Long PCR was used to amplify introns 1 and 2 from patient and normal genomic DNA, and no differences in size, in 5' and 3' end sequences, or in restriction-mapping patterns were observed. From these data we developed a set of four PCR primers that can be used to identify GM2A mutations. We use this procedure to demonstrate that the patient is likely homozygous for the nonsense mutation. Other reports have associated nonsense mutations with dramatically reduced levels of mRNA and with an increased level of skipping of the exon containing the mutation, thus reestablishing an open reading frame. However, a recent article has concluded that, in some cases, the latter observation is caused by an artifact of RT-PCR. In support of this conclusion, we demonstrate that, if the competing, normal-sized cDNA is removed from the initial RT-PCR products, from both patient and normal cells, by an exon 2-specific restriction digest; a second round of PCR produces similar amounts of exon 2-deleted cDNA. (+info)Biochemical consequences of mutations causing the GM2 gangliosidoses. (4/158)
The hydrolysis of GM2-ganglioside is unusual in its requirements for the correct synthesis, processing, and ultimate combination of three gene products. Whereas two of these proteins are the alpha- (HEXA gene) and beta- (HEXB) subunits of beta-hexosaminidase A, the third is a small glycolipid transport protein, the GM2 activator protein (GM2A), which acts as a substrate specific co-factor for the enzyme. A deficiency of any one of these proteins leads to storage of the ganglioside, primarily in the lysosomes of neuronal cells, and one of the three forms of GM2-gangliosidosis, Tay-Sachs disease, Sandhoff disease or the AB-variant form. Studies of the biochemical impact of naturally occurring mutations associated with the GM2 gangliosidoses on mRNA splicing and stability, and on the intracellular transport and stability of the affected protein have provided some general insights into these complex cellular mechanisms. However, such studies have revealed little in the way of structure-function information on the proteins. It appears that the detrimental effect of most mutations is not specifically on functional elements of the protein, but rather on the proteins' overall folding and/or intracellular transport. The few exceptions to this generalization are missense mutations at two codons in HEXA, causing the unique biochemical phenotype known as the B1-variant, and one codon in both the HEXB and GM2A genes. Biochemical characterization of these mutations has led to the localization of functional residues and/or domains within each of the encoded proteins. (+info)Isoenzymes of N-acetyl-beta-hexosaminidase. (5/158)
Biological significance, structure and posttranslational processing of N-acetyl-beta-hexosaminidase isoenzymes are described. Clinical application of N-acetyl-beta-hexosaminidase is also reviewed. (+info)Primer system for single cell detection of double mutation for Tay-Sachs disease. (6/158)
PURPOSE: Nearly 100% of infantile Tay-Sachs disease is produced by two mutations occurring in the alpha chain of the lysosomal enzyme beta-N-acetylhexosaminidase (HEXA) in the Ashkenazi Jewish population. Although others have described primer systems used to amplify both sites simultaneously, few discuss the allele dropout problems inherent in this test. Our goal was to construct a more robust test enabling stronger signal generation for single cell preimplantation genetic diagnosis and to investigate the occurrence of allele dropout. METHODS: New nested primers were designed to optimize detection of both major Tay-Sachs mutations. Four hundred fifty-seven single cells, including normal cells and those carrying mutations of either the 4bp insertion exon 11 or splice-site intron 12 defects, were used to screen a new primer system. RESULTS: Based on PCR amplified product analysis, total efficiency of amplification was 85.3%, (390/457). The allele dropout rate for the 4bp insertion mutation in exon 11 and splice-site mutation in intron 12 was 4.8% and 5.8%, respectively. CONCLUSIONS: Multiple mutation detection and analysis within the Tay-Sachs disease gene (HEXA) is possible using single cells for clinical preimplantation genetic diagnosis. Alternative PCR primers and conditions offer various methods for developing systems compatible to specific program requirements. (+info)Gangliosides as modulators of dendritogenesis in normal and storage disease-affected pyramidal neurons. (7/158)
Pyramidal cells initiate the formation of dendritic arbors in a prolific burst of neurite outgrowth during early cortical development. Although morphologically mature pyramidal neurons do not normally sprout additional primary dendrites, the discovery of ectopic dendritogenesis in neuronal storage diseases has revealed that these cells do retain this ability under appropriate stimulation. The capacity for renewal of dendritogenesis has been found to exhibit a species gradient with human > cat, dog, sheep > mouse. A consistent metabolic feature of ectopic dendrite-bearing pyramidal neurons is a heightened intracellular expression of GM2 ganglioside. Elevated expression of this same glycosphingolipid has also been found to correlate with normal dendritogenesis. Immature neurons in developing cat and ferret cortex exhibit high levels of GM2 ganglioside immunoreactivity coincident with normal dendritic sprouting and a similar relationship has now been shown for human cortical development. Ultrastructural studies of all three species revealed GM2 localized to vesicles in a manner consistent with Golgi synthesis and exocytic trafficking to the somatic-dendritic plasmalemma. We propose that GM2 ganglioside functions in glycosphingolipid-enriched microdomains (lipid rafts) in the plasmalemma to promote dendritic initiation through modulation of specific membrane proteins and/or their associated second messenger cascades. (+info)Screening for genetic disorders among Jews: how should the Tay-Sachs screening program be continued? (8/158)
The screening program in Israel for Tay-Sachs disease has proven very successful, giving Jewish couples a choice not to have affected children. The technology of carrier detection is now possible in several other severe genetic diseases that are relatively frequent among Jews. Due to the current confusion, a policy is needed to determine how the TSD screening program should be continued in the Israeli Jewish population. We propose that such a screening program include only mutations agreed by consensus as causing a disease severe enough to warrant the possibility of therapeutic abortion. We also propose that general screening include only mutations that are relatively frequent, taking into account the carrier frequencies in the Israeli Jewish population. (+info)Yarrowia is a genus of fungi that belongs to the family of Dipodascaceae. It is a type of yeast that is often found in various environments, including plants, soil, and water. One species, Yarrowia lipolytica, has gained attention in biotechnology applications due to its ability to break down fats and oils, produce organic acids, and express heterologous proteins. It's also known to be an opportunistic pathogen in humans, causing rare but serious infections in individuals with weakened immune systems.
Tay-Sachs Disease is a rare, inherited autosomal recessive disorder that affects the nervous system's functioning. It results from the deficiency of an enzyme called hexosaminidase A (Hex-A), which is necessary for breaking down gangliosides, a type of fatty substance found in nerve cells. When Hex-A is absent or insufficient, gangliosides accumulate abnormally in the nerve cells, leading to their progressive destruction and severe neurological deterioration.
The classic infantile form of Tay-Sachs Disease manifests within the first six months of life with symptoms such as loss of motor skills, seizures, paralysis, dementia, blindness, and eventually death, usually by age four. Late-onset forms of the disease also exist, which may present in childhood or adulthood with milder symptoms.
Tay-Sachs Disease is more prevalent among individuals of Ashkenazi Jewish, French Canadian, and Cajun descent. Genetic counseling and prenatal testing are recommended for couples at risk of passing on the disease.
Hexosaminidase A is an enzyme that is responsible for breaking down certain complex molecules in the body, specifically gangliosides. This enzyme is composed of two subunits, alpha and beta, which are encoded by the genes HEXA and HEXB, respectively.
Deficiency or mutation in the HEXA gene can lead to a genetic disorder called Tay-Sachs disease, which is characterized by an accumulation of gangliosides in the nerve cells, leading to progressive neurological degeneration. The function of hexosaminidase A is to break down these gangliosides into simpler molecules that can be eliminated from the body. Without sufficient levels of this enzyme, the gangliosides build up and cause damage to the nervous system.
Beta-N-Acetylhexosaminidases are a group of enzymes that play a role in the breakdown and recycling of complex carbohydrates in the body. Specifically, they help to break down gangliosides, which are a type of molecule found in cell membranes.
There are several different isoforms of beta-N-Acetylhexosaminidases, including A, B, and S. These isoforms are formed by different combinations of subunits, which can affect their activity and substrate specificity.
Mutations in the genes that encode for these enzymes can lead to a variety of genetic disorders, including Tay-Sachs disease and Sandhoff disease. These conditions are characterized by an accumulation of gangliosides in the brain, which can cause progressive neurological deterioration and death.
Treatment for these conditions typically involves managing symptoms and providing supportive care, as there is currently no cure. Enzyme replacement therapy has been explored as a potential treatment option, but its effectiveness varies depending on the specific disorder and the age of the patient.
Lipidoses are a group of genetic disorders characterized by abnormal accumulation of lipids (fats or fat-like substances) in various tissues and cells of the body due to defects in lipid metabolism. These disorders include conditions such as Gaucher's disease, Tay-Sachs disease, Niemann-Pick disease, Fabry disease, and Wolman disease, among others. The accumulation of lipids can lead to progressive damage in multiple organs, resulting in a range of symptoms and health complications. Early diagnosis and management are essential for improving the quality of life and prognosis of affected individuals.
Hexosaminidase B is a type of enzyme that is involved in the breakdown of complex lipids called gangliosides in the body. These enzymes are found in lysosomes, which are structures inside cells that break down and recycle various materials.
Hexosaminidase B specifically helps to break down a particular type of ganglioside called GM2 ganglioside, which is abundant in the nervous system. Mutations in the gene that provides instructions for making this enzyme can lead to a condition called Tay-Sachs disease, which is characterized by the accumulation of GM2 gangliosides in the nerve cells, leading to progressive neurological deterioration.
In summary, Hexosaminidase B is an essential enzyme for breaking down certain types of lipids in the body, and its deficiency can lead to serious health consequences.
Sandhoff disease is a rare inherited disorder that affects the nervous system. It's a type of GM2 gangliosidosis, which is a group of conditions characterized by the body's inability to break down certain fats (lipids) called gangliosides.
In Sandhoff disease, deficiencies in the enzymes hexosaminidase A and B lead to an accumulation of GM2 ganglioside in various cells, particularly in nerve cells of the brain. This accumulation results in progressive damage to the nervous system.
The symptoms of Sandhoff disease typically appear between 6 months and 2 years of age and can include developmental delay, seizures, an exaggerated startle response, muscle weakness, loss of motor skills, and vision and hearing loss. The condition is often fatal by around age 3. It's caused by mutations in the HEXB gene, and it's inherited in an autosomal recessive manner, meaning an individual must inherit two copies of the mutated gene (one from each parent) to develop the disease.
Gangliosidoses are a group of inherited metabolic disorders caused by the accumulation of certain complex lipids called gangliosides in the brain and nervous system. This buildup is due to a deficiency of specific enzymes needed to break down these substances. The three main types of gangliosidoses are:
1. Type 1 - Infantile Neurovisceral or Tay-Sachs Disease: Characterized by the absence of the enzyme hexosaminidase A, leading to severe neurological symptoms such as muscle weakness, blindness, and developmental delay in early infancy, with rapid progression and death usually occurring before age 4.
2. Type 2 - Juvenile or Subacute GM1 Gangliosidosis: Caused by a deficiency of the enzyme beta-galactosidase, resulting in progressive neurological symptoms such as motor and cognitive decline, beginning between ages 6 months and 2 years. Affected individuals may survive into adolescence or early adulthood.
3. Type 3 - Adult or Chronic GM1 Gangliosidosis: Characterized by a deficiency of beta-galactosidase, leading to milder neurological symptoms that appear in late childhood, adolescence, or even adulthood. The progression is slower compared to the other types, and life expectancy varies widely.
Gangliosidoses are autosomal recessive disorders, meaning an individual must inherit two copies of the defective gene (one from each parent) to develop the condition.
GM2 gangliosidoses are a group of inherited metabolic disorders caused by the accumulation of harmful amounts of GM2 gangliosides in the body's cells, particularly in the nerve cells of the brain. There are three main types of GM2 gangliosidoses: Tay-Sachs disease, Sandhoff disease, and AB variant of GM2 gangliosidosis. These conditions are characterized by progressive neurological degeneration, which can lead to severe physical and mental disabilities, and ultimately death in childhood or early adulthood.
The underlying cause of GM2 gangliosides is a deficiency in the enzyme hexosaminidase A (Tay-Sachs and AB variant) or both hexosaminidase A and B (Sandhoff disease), which are responsible for breaking down GM2 gangliosides. Without sufficient enzyme activity, GM2 gangliosides accumulate in the lysosomes of cells, leading to cell dysfunction and death.
Symptoms of GM2 gangliosidoses can vary depending on the specific type and severity of the disorder, but often include developmental delay, muscle weakness, loss of motor skills, seizures, blindness, and dementia. There is currently no cure for GM2 gangliosidoses, and treatment is focused on managing symptoms and improving quality of life.
GM1 gangliosidosis is a rare inherited lysosomal storage disorder caused by the deficiency of an enzyme called β-galactosidase. This enzyme is responsible for breaking down certain complex fats (gangliosides) in the body. When this enzyme is lacking or not working properly, these gangliosides accumulate in various cells, particularly in nerve cells of the brain, leading to progressive neurological deterioration.
The condition can present at different ages and with varying severity, depending on the amount of functional β-galactosidase enzyme activity. The three main types of GM1 gangliosidosis are:
1. Early infantile (type I): This is the most severe form, with symptoms appearing within the first few months of life. Infants may appear normal at birth but then develop rapidly progressing neurological problems such as developmental delay, muscle weakness, seizures, and cherry-red spots in the eyes. Life expectancy is typically less than 2 years.
2. Late infantile/juvenile (type II): Symptoms begin between ages 1 and 3 years or later in childhood. Affected individuals may have developmental delay, motor difficulties, muscle weakness, and cognitive decline. Some individuals with this form may also develop corneal clouding and bone abnormalities.
3. Adult/chronic (type III): This is the least severe form of GM1 gangliosidosis, with symptoms appearing in late childhood, adolescence, or adulthood. Symptoms can include neurological problems such as muscle weakness, tremors, and difficulties with coordination and speech.
Currently, there is no cure for GM1 gangliosidosis, and treatment is primarily supportive to manage symptoms and improve quality of life.