Ten novel mutations in the HEXA gene in non-Jewish Tay-Sachs patients.
The heterogeneity of mutations causing Tay-Sachs disease in non-Jewish populations requires efficient techniques allowing the simultaneous screening for both known and novel mutations. beta-hexosaminidase mRNA isolated from cultured fibroblasts of 19 Tay-Sachs patients (7 with adult or late onset form of the disease and 12 with infantile Tay-Sachs disease) was amplified by cDNA-PCR in two overlapping segments spanning the entire coding sequence. We used chemical mismatch cleavage (CMC), denaturing gradient gel electrophoresis (DGGE) and direct sequencing of amplified fragments displaying a cleaved product or an altered melting behavior to screen the HEX A gene for mutations and to determine their distribution and frequency in the non-Jewish Tay-Sachs patients. These methods allowed us to identify 31 out of 38 alleles studied (82%). In addition to 9 previously described mutations (the 4 bp insertion in exon 11, G to A transitions at codons 170, 269, 482, 499 and 504, C to T transition at codon 499 and 504 and a GT to AT transition at the donor site of intron 9), we have identified 10 novel mutations. These include 1 donor splice site defect in intron 6, 8 missense mutations at non-randomly distributed conserved residues and a 2 bp deletion in exon 4. These results confirm the extreme molecular heterogeneity of mutations causing Tay-Sachs disease in non-Jewish population. The strategy used should be profitable for identifying mutations in large genes and for diagnostic purposes.
Akli
S
S
Institut Cochin de Génétique Moléculaire (ICGM), Institut National de la Santé et de la Recherche Médicale, U129, Paris, France.
Chomel
J C
JC
Lacorte
J M
JM
Bachner
L
L
Kahn
A
A
Poenaru
L
L
D000328:Adult; D000595:Amino Acid Sequence; D001483:Base Sequence; D002478:Cells, Cultured; D005006:Ethnicity; D005091:Exons; D005347:Fibroblasts / Q000201:enzymology; D005787:Gene Frequency; D054818:Hexosaminidase A; D006801:Humans; D007223:Infant; D007438:Introns; D007585:Jews; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D017354:Point Mutation; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000235:genetics / Q000302:isolation & purification; D013661:Tay-Sachs Disease / Q000201:enzymology* / Q000235:genetics*; D001619:beta-N-Acetylhexosaminidases / Q000235:genetics*
D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D054818:Hexosaminidase A; D001619:beta-N-Acetylhexosaminidases