Common HEXB polymorphisms reduce serum HexA and HexB enzymatic activities, potentially masking Tay-Sachs disease carrier identification.

A DNA-proven Tay-Sachs disease (TSD) carrier and his brother were found to have serum percent Hexosaminidase A (%HexA) enzymatic activities in the non-carrier range, while the leukocyte %HexA profiles clearly identified them as TSD heterozygotes. Both their serum HexA and HexB enzymatic activities were below reference range, suggesting inheritance of mutations in both the HEXA (alpha-subunit) and HEXB (beta-subunit) genes. DNA sequencing revealed that both individuals, carried the common HEXA 1277_1278insTATC mutation, and two common HEXB polymorphisms: [619A>G (+) delTG].

Eight novel mutations in the HEXA gene.

Purpose: To characterize novel mutations in the HEXA gene (alpha-subunit beta-hexosaminidase A).

Methods: Subjects included participants in the California Tay-Sachs disease prevention program. DNA samples from 49 subjects (47 enzymatically defined carriers and 2 disease afflicted) who were negative for the four common disease-associated and the two pseudodeficient mutations, were subjected to single-strand conformation polymorphism (SSCP) analysis over 14 exons.

A second mutation associated with apparent beta-hexosaminidase A pseudodeficiency: identification and frequency estimation.

Deficient activity of beta-hexosaminidase A (Hex A), resulting from mutations in the HEXA gene, typically causes Tay-Sachs disease. However, healthy individuals lacking Hex A activity against synthetic substrates (i.e.

Tay-Sachs disease--carrier screening, prenatal diagnosis, and the molecular era. An international perspective, 1970 to 1993. The International TSD Data Collection Network.

Objectives: To provide an update of the international experience with carrier screening and prenatal diagnosis for Tay-Sachs disease (TSD), to assess the impact of these efforts, and to review the recent developments in DNA technology with application to TSD carrier detection and screening.

Design: Through the International TSD Testing, Quality Control, and Data Collection Center, all testing centers in the world were surveyed annually to assess overall experience with carrier testing and prenatal diagnosis. Quality control and laboratory surveillance of testing centers were performed through an annual assessment, using samples provided by the center.

Further investigation of the HEXA gene intron 9 donor splice site mutation frequently found in non-Jewish Tay-Sachs disease patients from the British Isles.

In a previous study we found that a Tay-Sachs disease (TSD) causing mutation in the intron 9 donor splice site of the HEXA gene occurs at high frequency in non-Jewish patients and carriers from the British Isles. It was found more frequently in subjects of Irish, Scottish, and Welsh origin compared with English origin (63% and 31% respectively). We have now tested, in a blind study, 26 American TSD carriers and 28 non-carriers who have British ancestry for the intron 9 splice site mutation.