Biomaterial Database

Prenatal Diagnosis of Tay-Sachs Disease. 2019

Jinglan Zhang, and Hongjie Chen, and Ruth Kornreich, and Chunli Yu

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.

Tay-Sachs disease (TSD) is an autosomal recessive lysosomal storage disorder caused by mutations of the HEXA gene resulting in the deficiency of hexosaminidase A (Hex A) and subsequent neuronal accumulation of GM2 gangliosides. Infantile TSD is a devastating and fetal neurodegenerative disease with death before the age of 3-5 years. A small proportion of TSD patients carry milder mutations and may present juvenile or adult onset milder disease. TSD is more prevalent among Ashkenazi Jewish (AJ) individuals and some other genetically isolated populations with carrier frequencies of approximately ~1:27 which is much higher than that of 1:300 in the general population. Carrier screening and prenatal testing for TSD are effective in preventing the birth of affected fetuses greatly diminishing the incidence of TSD. Testing of targeted HEXA mutations by genotyping or sequencing can detect 98% of carriers in AJ individuals; however, the detection rate is much lower for most other ethnic groups. When combined with enzyme analysis, above 98% of carriers can be reliably identified regardless of ethnic background. Multiplex PCR followed by allele-specific primer extension is one method to test for known and common mutations. Sanger sequencing or other sequencing methods are useful to identify private mutations. For prenatal testing, only predefined parental mutations need to be tested. In the event of unknown mutational status or the presence of variants of unknown significance (VUS), enzyme analysis must be performed in conjunction with DNA-based assays to enhance the diagnostic accuracy. Enzymatic assays involve the use of synthetic substrates 4-methylumbelliferyl-N-acetyl-β-glucosamine (4-MUG) and 4-methylumbelliferyl-6-sulfo-2-acetamido-2-deoxy-β-D-glucopyranoside (4-MUGS) to measure the percentage Hex A activity (Hex A%) and specific Hex A activity respectively. These biochemical and molecular tests can be performed in both direct specimens and cultured cells from chorionic villi sampling or amniocentesis.

UI	MeSH Term	Description	Entries
D009154	Mutation	Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.	Mutations
D011296	Prenatal Diagnosis	Determination of the nature of a pathological condition or disease in the postimplantation EMBRYO; FETUS; or pregnant female before birth.	Diagnosis, Prenatal,Fetal Diagnosis,Fetal Imaging,Fetal Screening,Intrauterine Diagnosis,Antenatal Diagnosis,Antenatal Screening,Diagnosis, Antenatal,Diagnosis, Intrauterine,Prenatal Screening,Antenatal Diagnoses,Antenatal Screenings,Diagnosis, Fetal,Fetal Diagnoses,Fetal Imagings,Fetal Screenings,Imaging, Fetal,Intrauterine Diagnoses,Prenatal Diagnoses,Prenatal Screenings,Screening, Antenatal,Screening, Fetal,Screening, Prenatal
D004252	DNA Mutational Analysis	Biochemical identification of mutational changes in a nucleotide sequence.	Mutational Analysis, DNA,Analysis, DNA Mutational,Analyses, DNA Mutational,DNA Mutational Analyses,Mutational Analyses, DNA
D005820	Genetic Testing	Detection of a MUTATION; GENOTYPE; KARYOTYPE; or specific ALLELES associated with genetic traits, heritable diseases, or predisposition to a disease, or that may lead to the disease in descendants. It includes prenatal genetic testing.	Genetic Predisposition Testing,Genetic Screening,Predictive Genetic Testing,Predictive Testing, Genetic,Testing, Genetic Predisposition,Genetic Predictive Testing,Genetic Screenings,Genetic Testing, Predictive,Predisposition Testing, Genetic,Screening, Genetic,Screenings, Genetic,Testing, Genetic,Testing, Genetic Predictive,Testing, Predictive Genetic
D005838	Genotype	The genetic constitution of the individual, comprising the ALLELES present at each GENETIC LOCUS.	Genogroup,Genogroups,Genotypes
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000483	Alleles	Variant forms of the same gene, occupying the same locus on homologous CHROMOSOMES, and governing the variants in production of the same gene product.	Allelomorphs,Allele,Allelomorph
D013661	Tay-Sachs Disease	An autosomal recessive neurodegenerative disorder characterized by the onset in infancy of an exaggerated startle response, followed by paralysis, dementia, and blindness. It is caused by mutation in the alpha subunit of the HEXOSAMINIDASE A resulting in lipid-laden ganglion cells. It is also known as the B variant (with increased HEXOSAMINIDASE B but absence of hexosaminidase A) and is strongly associated with Ashkenazic Jewish ancestry.	G(M2) Gangliosidosis, Type I,Gangliosidosis G(M2), Type I,Gangliosidosis GM2, B Variant,Hexosaminidase A Deficiency Disease,Tay-Sachs Disease, B Variant,Amaurotic Familial Idiocy,B Variant GM2 Gangliosidosis,B Variant GM2-Gangliosidosis,Deficiency Disease Hexosaminidase A,Familial Amaurotic Idiocy,GM2 Gangliosidosis, B Variant,GM2 Gangliosidosis, Type 1,GM2 Gangliosidosis, Type I,GM2-Gangliosidosis, Type I,Gangliosidosis GM2 , Type 1,Gangliosidosis GM2, Type I,HexA Deficiency,Hexosaminidase A Deficiency,Hexosaminidase alpha-Subunit Deficiency (Variant B),Sphingolipidosis, Tay-Sachs,Amaurotic Idiocy, Familial,B Variant GM2-Gangliosidoses,Deficiency, Hexosaminidase A,Deficiency, Hexosaminidase alpha-Subunit (Variant B),GM2-Gangliosidosis, B Variant,Hexosaminidase alpha Subunit Deficiency (Variant B),Sphingolipidosis, Tay Sachs,Tay Sachs Disease,Tay Sachs Disease, B Variant,Tay-Sachs Sphingolipidosis,Type I GM2-Gangliosidosis
D016133	Polymerase Chain Reaction	In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.	Anchored PCR,Inverse PCR,Nested PCR,PCR,Anchored Polymerase Chain Reaction,Inverse Polymerase Chain Reaction,Nested Polymerase Chain Reaction,PCR, Anchored,PCR, Inverse,PCR, Nested,Polymerase Chain Reactions,Reaction, Polymerase Chain,Reactions, Polymerase Chain
D054820	beta-Hexosaminidase alpha Chain	The alpha subunit of hexosaminidase A. Mutations in the gene that encodes this protein can result in loss of hexosaminidase A activity and are linked to TAY-SACHS DISEASE.	Hexosaminidase A, alpha Chain,beta-N-Acetylhexosaminidase alpha Chain,alpha Chain, beta-Hexosaminidase,alpha Chain, beta-N-Acetylhexosaminidase,beta Hexosaminidase alpha Chain,beta N Acetylhexosaminidase alpha Chain