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B Boulay

Publications and source records attributed to B Boulay.

7 recordsLinked to original sources
PubMed1992

The intron 7 donor splice site transition: a second Tay-Sachs disease mutation in French Canada.

Mutations at the hexosaminidase A (HEXA) gene which cause Tay-Sachs disease (TSD) have elevated frequency in the Ashkenazi Jewish and French-Canadian populations. We report a novel TSD allele in the French-Canadian population associated with the infantile form of the disease. The mutation, a G-->A transition at the +1 position of intron 7, abolishes the donor splice site. Cultured human fibroblasts from a compound heterozygote for this transition (and for a deletion mutation) produce no detectable HEXA mRNA. The intron 7 + 1 mutation occurs in the base adjacent to the site of the adult-onset TSD mutation (G805A). In both mutations a restriction site for the endonuclease EcoRII is abolished. Unambiguous diagnosis, therefore, requires allele-specific oligonucleotide hybridization to distinguish between these two mutant alleles. The intron 7 + 1 mutation has been detected in three unrelated families. Obligate heterozygotes for the intron 7 + 1 mutation were born in the Saguenay-Lac-St-Jean region of Quebec. The most recent ancestors common to obligate carriers of this mutation were from the Charlevoix region of the province of Quebec. This mutation thus has a different geographic centre of diffusion and is probably less common than the exon 1 deletion TSD mutation in French Canadians. Neither mutation has been detected in France, the ancestral homeland of French Canada.

Base Sequence↗
PubMed1991

Allele-specific amplification of genomic DNA for detection of deletion mutations: identification of a French-Canadian Tay-Sachs mutation.

A rapid and efficient method for the detection of a 7.6-kb deletion in the beta-hexosaminidase A alpha-subunit gene, a mutant allele causing Tay-Sachs disease in French Canadians, is described. The protocol involves PCR (polymerase chain reaction) amplification of target sequences on normal and mutant chromosomes. Three amplification primers, a single 5' primer complementary to normal and mutant DNA templates and two 3' primers specific for normal and mutant DNA templates are required. The primers direct amplification of two unique fragments (normal and mutant) that are easily separated by gel electrophoresis. Allele-specific oligonucleotide hybridization using normal and mutant probes to genomic DNA samples from normal, heterozygous and homozygous individuals confirms these results and is consistent with results of genotypic classification of individuals using Southern analysis. The method is applicable to detection of deletion mutations in cases where some deletion-flanking sequence is known.

Alleles↗
PubMed1990

More than one mutant allele causes infantile Tay-Sachs disease in French-Canadians.

Two Tay-Sachs disease (TSD) patients of French-Canadian origin were shown by Myerowitz and Hogikyan to be homozygous for a 7.6-kb deletion mutation at the 5' end of the hexosaminidase A alpha-subunit gene. In order to determine whether all French-Canadian TSD patients were homozygotes for the deletion allele and to assess the geographic origins of TSD in this population, we ascertained 12 TSD families of French-Canadian origin and screened for occurrence of mutations associated with infantile TSD. DNA samples were obtained from 12 French-Canadian TSD families. Samples were analyzed using polymerase-chain-reaction (PCR) amplification followed by hybridization to allele-specific oligonucleotides (ASO) or by restriction analysis of PCR products. In some cases Southern analysis of genomic DNA was performed. Eighteen of the 22 independently segregating mutant chromosomes in this sample carried the 7.6-kb deletion mutation at the 5' end of the gene. One chromosome carried the 4-nucleotide insertion in exon 11 (a "Jewish" mutation). In this population no individuals were detected who had the substitution at the splice junction of exon 12 previously identified in Ashkenazi Jews. One chromosome carried an undescribed B1 mutation; this allele came from a parent of non-French-Canadian origin. Patients in three families carried TSD alleles different from any of the above mutations. The 5' deletion mutation clusters in persons originating in southeastern Quebec (Gaspé) and adjacent counties of northern New Brunswick.

Alleles↗
PubMed1989

The mutation mechanism causing juvenile-onset Tay-Sachs disease among Lebanese.

Expression of the hexosaminidase isozymes was evaluated in fibroblast cell lines obtained from two sibs of Lebanese-Christian origin who presented with juvenile-onset Tay-Sachs disease. In the normal control fibroblasts the alpha subunit of hexosaminidase A (hex A) is synthesized as a 67 KD precursor which is cleaved in lysosomes to a mature 54 KD peptide. The patients' fibroblasts were capable of synthesizing the 67 KD precursor but failed to convert it to the mature subunit. The alpha subunit precursor synthesized by patients' cells could not be phosphorylated, nor was the patients' alpha subunit precursor secreted into the medium in response to NH4Cl, which caused accumulation of both alpha and beta subunit precursor in the medium of the normal control fibroblasts. The measurement of residual enzyme activity in the fibroblasts of patients which best correlated with the onset of the illness was the ion exchange chromatographic separation of Hex A-associated hydrolysis of the synthetic substrate 4-methylumbelliferyl N-acetyl-beta-D-glucosamine-6-sulfate (4MUGS). The patients had 0.32% and 0.36% of Hex A-associated 4MUGS cleaving activity compared to normal control fibroblasts as compared to less than 0.016% for infantile Tay-Sachs disease fibroblasts. The residual Hex A activity in patients' cells had a pH optimum identical with normal enzyme (pH 3.9-4.0), a reduced specific activity for 4MUGS (relative to hydrolysis of unsulfated synthetic substrate), and a greatly enhanced thermal stability. The occurrence of this form of Tay-Sachs disease in Lebanon, the fact that the condition has been described in three unrelated Lebanese immigrant families in Canada, together with the fact that the grandparents of the unrelated probands come from villages in both the northern and southern regions of Lebanon, leads us to speculate that a gene causing juvenile-onset Tay-Sachs disease may not be infrequent in Lebanon.

Alleles↗
PubMedDate not supplied

[Bullosis in diabetics. Apropos of a new case].

Idiopathic bullae occurring in diabetics constitute an uncommon condition which may reveal the diabetes, announce its decompensation or represent a mere epiphenomenon. The authors report the case of a woman who experienced two episodes of idiopathic bullae: the first one disclosed the diabetes, the second one heralded its decompensation. Both episodes were preceded by painful paraesthesia. The bullae contained a clear and serous fluid and the separation was intradermal. Direct immunofluorescence with anti-fibrin serum only showed fluorescence in the lumen of the bulla and in subjacent dermal areas. Electron microscopy demonstrated that the tissue separation was at the base of the stratum corneum. Other clinical cases and pathogenetic theories found in the literature are reported. In contrast with other bullous diseases occurring in diabetics and often of poor prognosis, idiopathic bullae is a benign condition requiring no more than a symptomatic treatment.

Adult↗
PubMedDate not supplied

A chronic GM2 gangliosidosis variant with a HEXA splicing defect: quantitation of HEXA mRNAs in normal and mutant fibroblasts.

Over 72 mutations have been identified in the HEXA gene of which only four (T538C, A590C, G805A, and C1495T) are believed to cause a chronic form of Tay-Sachs disease (TSD). We identified a novel HEXA mutation (IVS7, -7 G-->A) leading to chronic TSD in a Canadian patient of English ancestry. The second allele in this patient was the exon 11 4-bp insertion mutation (/1277TATC), which is the most frequent TSD allele in Ashkenazi Jews. The IVS7, -7 G-->A mutation introduces a new 3' splice acceptor site 5 bp upstream of the normal intron 7 splice acceptor site. The mutation leads to reduction of steady-state levels of HEXA mRNA by more than 80%. Two mRNA species are produced by the IVS7, -7 G-->A allele; a normal nRNA species and an mRNA lacking exon 8. No mRNA species that was spliced at the upstream 3' splice acceptor site was detected. We used competitive PCR to quantitate mRNA species in fibroblasts obtained from this patient. We compared the amounts of three identified mRNA species to HEXA mRNA levels in cells from normal individuals and from individuals heterozygous for /1277TATC. The steady-state level of HEXA mRNA in cells from a normal individual was 17.3 pg/microg RNA. An individual heterozygous for /1277TATC produced 8.7 pg of normal HEXA mRNA/microg RNA. The HEXA mRNA species with the insertion mutation was present in patient cells at 4.8% of the level of normal HEXA nRNA in homozygous normal cells. In fibroblasts from the patient carrying the IVS7, -7 G-->A mutation, the steady-state level of exon 8-deleted HEXA mRNA was 5.9% the level of that produced by homozygous normal cells. The level of normal HEXA nRNA in this patient's cells was 10.4%.

Alleles↗