Characterization of a novel founder MSH6 mutation causing Lynch syndrome in the French Canadian population

We identified an MSH6 mutation (c.10C>T, p.Gln4*) causing Lynch syndrome (LS) in 11 French Canadian (FC) families from the Canadian province of Quebec. We aimed to investigate the molecular and clinical implications of this mutation among FC carriers and to assess its putative founder origin. We studied 11 probands and 27 family members. Additionally 6433 newborns, 187 colorectal cancer (CRC) cases, 381 endometrial cancer (EC) cases and 179 additional controls, all of them from Quebec, were used. Found in approximately 1 of 400 newborns, the mutation is one of the most common LS mutations described. We have found that this mutation confers a greater risk for EC than for CRC, both in the 11 studied families and in the unselected cases: EC [odds ratio (OR) = 7.5, p < 0.0001] and CRC (OR = 2.2, p = 0.46). Haplotype analyses showed that the mutation arose in a common ancestor, probably around 430-656 years ago, coinciding with the arrival of the first French settlers. Application of the results of this study could significantly improve the molecular testing and clinical management of LS families in Quebec.

Clinical spectrum of infantile free sialic acid storage disease

Infantile free sialic acid storage disease (ISSD) is a rare autosomal recessive metabolic disorder caused by a lysosomal membrane transport defect, resulting in accumulation of free sialic acid within lysosomes. Only a few cases have been described. We report on three new cases of ISSD with different modes of presentation: an infant with nephrotic syndrome, a case of fetal and neonatal ascites with heart failure, and a case of fetal ascites with esophageal atresia type III. From these patients and a review of the literature (27 cases total) we draw the following conclusions. 1) "Coarse facies," fair complexion, hepatosplenomegaly, and severe psychomotor retardation are constant findings in this disorder. 2) Nephrotic syndrome occurred in most cases (four in seven) in which renal evaluation was performed. Therefore, ISSD is an important cause of nephrosis in infants with a storage disorder phenotype. 3) Fetal/neonatal ascites or hydrops was the mode of presentation in 13 (60%) of 21 cases. Thus, ISSD enters in the differential diagnosis of hydrops fetalis with a storage disease phenotype. 4) Cardiomegaly was evident in nine cases. 5) Corneae were always clear, and albinoid fundi were reported in five cases. 6) Dysostosis multiplex was not prominent. 7) Bone marrow aspiration could be negative. 8) Death ensued in early infancy with a mean age of 13.1 months. All reported deaths were caused by respiratory infections.

A case of tyrosinaemia type I with normal level of succinylacetone in the amniotic fluid

Prenatal diagnosis of tyrosinaemia type I can be achieved in cultured amniotic cells and in chorionic villus material by testing the activity of fumarylacetoacetate hydrolase and by DNA analysis, and in amniotic fluid by succinylacetone measurement. This specific metabolite can be measured either by gas chromatography-mass spectrometry or by delta-aminolevulinate dehydratase inhibition assay. In a series of 65 at-risk cases tested with the enzyme inhibition assay, one case out of the 18 with the disease had a normal level of succinylacetone. This case is presented.

A biochemically distinct form of cytochrome oxidase (COX) deficiency in the Saguenay-Lac-Saint-Jean region of Quebec

We report the results of biochemical and molecular investigations on a group of patients from the Saguenay-Lac-Saint-Jean region of Quebec who have an unusual form of cytochrome oxidase deficiency and Leigh disease. This group can be distinguished from the classical presentation of cytochrome oxidase deficiency with Leigh disease, by the severity of the biochemical defect in different tissues. The activity in skin fibroblasts, amniocytes, and skeletal muscle of cytochrome oxidase is 50% of normal, while in kidney and heart it is close to normal values. Brain and liver, on the other hand, have very low activities. The defect in activity appears to result from a failure of assembly of the cytochrome oxidase complex in liver, but levels of mRNA for both mitochondrially encoded and nuclear-encoded subunits in liver and skin fibroblasts were found to be the same as those in controls. The cDNA sequence of the liver-specific cytochrome oxidase subunits VIa and VIIa were determined in samples from patient liver and skin fibroblasts and showed normal coding sequence.

Definition of a small chromosomal rearrangement on chromosome 11p14 by molecular cytogenetics in situ hybridization

Chromosomal in situ hybridization allows the detection and the definition of single copy DNA segments of very small size. In a particular case, we demonstrate the inactivity of this molecular cytogenetic technique. In this case, karyotype analysis revealed a chromosome 11p+. In situ hybridization of probes PBGD, D11S29, NCAM, and ETSI located at 11q23-qter shows that the extra chromosomal material on chromosome 11p+ is a duplication of the 11q23-qter region.

Assignment of the gene encoding the catalytic subunit C beta of cAMP-dependent protein kinase to the p36 band on chromosome 1

A cDNA for the human catalytic subunit (C beta) of cAMP-dependent protein kinase (PKA) has been cloned from a testis cDNA library. In the present study, we have determined the chromosomal localization of this gene using a cDNA for C beta as a probe. Southern blot analysis of genomic DNA from human/mouse cell hybrids revealed that the presence or absence of a 20-kb XbaI fragment, which hybridized with the C beta probe, was concordant with the presence of human chromosome 1. In situ hybridization to metaphase chromosome confirmed the somatic cell hybrid data and regionally mapped the C beta gene of PKA to the p36 band on chromosome 1.

Localization of the catalytic subunit C gamma of the cAMP-dependent protein kinase gene (PRKACG) to human chromosome region 9q13

A cDNA for a new catalytic subunit (C gamma) of the cAMP-dependent protein kinase (PKA) was recently isolated from a human testis cDNA library. This subunit was shown to be expressed only in testis, and has so far not been demonstrated in other species. In the present study, we have determined the chromosomal localization of this gene employing a cDNA for C gamma as a probe. Southern blot analysis of genomic DNA from human x mouse somatic cell hybrids allowed us to assign this gene (PRKACG) to human chromosome 9. In situ hybridization to metaphase chromosomes confirmed the somatic cell hybrid data and regionally mapped the C gamma gene of PKA to human chromosome 9q13.

Localization of the human gene for the type I cyclic GMP-dependent protein kinase to chromosome 10

We have recently characterized cDNAs and genomic DNA fragments for human type I cGMP-dependent protein kinase (cGK). By probing human x hamster hybrid cell lines with a 1.2-kb intron fragment from the human type I cGK gene, we identified a 5.9-kb BglII restriction fragment and localized it to human chromosome 10. In situ hybridization analyses using 3H-labeled cDNA and genomic DNA probes for the human type I cGK to human metaphase chromosomes supported the somatic cell hybrid data and indicated that the gene (PRKG1B; protein kinase, cGMP-dependent) maps to 10p11.2----q11.2.

The human corticosteroid binding globulin gene is located on chromosome 14q31-q32.1 near two other serine protease inhibitor genes

Human corticosteroid binding globulin (CBG) cDNA fragments were radiolabeled and hybridized in situ to metaphase chromosome preparations. The results localized the CBG gene to the q31-q32.1 region of human chromosome 14. This location also contains the genes for two closely related serine protease inhibitors: alpha 1-proteinase inhibitor and alpha 1-antichymotrypsin. It is therefore likely that these genes evolved by duplication events, and it would appear that this region contains a series of functionally related genes.

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.

11p13 deletion, Wilms' tumour, and aniridia: unusual genetic, non-ocular and ocular features of three cases

Three cases of Wilms' tumour and sporadic aniridia were followed up for periods ranging from 32 months to seven years. All had a deletion of the short arm of the eleventh chromosome 11p13, including one case with mosaicism, a cytogenetic feature that has not been previously described in the Wilms' tumour and sporadic aniridia association. Unusual non-ocular features found in all patients included tracheomalacia and delayed closure of the anterior fontanelle. In two cases tracheomalacia was responsible for respiratory distress after general anaesthesia. Wilms' tumour developed bilaterally in one patient and on the isthmus of a horseshoe kidney in another patient. In addition to the more commonly observed ocular features the presence of a corneal pannus was noted before 38 months of age in all patients and as early as 17 months in one case. An iridocorneal adherence with an overlying corneal opacity (presumably related to abnormal developmental cleavage of the anterior segment) was noted in one eye only of the mosaicism case.

Oral loading of homogentisic acid in controls and in obligate heterozygotes for hereditary tyrosinemia type I

Homogentisic acid (HGA) (50 mg/kg) was given orally to 22 obligate heterozygotes for hereditary tyrosinemia type 1 (HT) and to 11 controls. After 1 h the mean +/- standard error (SE) plasma level of HGA was 30.42 +/- 1.41 micrograms/ml in carriers and 19.29 +/- 1.62 in controls. Mean +/- SE fasting delta-amino-levulinate dehydratase (delta-ALD) was 40.05 +/- 1.79 m microM/min/g Hb in carriers, much lower than the 60.81 +/- 5.11 found in controls. After 3 h this difference in levels of delta-ALD remained, with mean +/- SE values of 25.70 +/- 2.89 m microM/min/g Hb in carriers, compared with 48.83 +/- 5.37 in controls. Three-hour mean +/- SE excretion of fumarylacetone "equivalent" [FAc] in urine in carriers, 51.597 +/- 5.580 micrograms/mg/creatinine, was significantly higher than the 27.941 +/- 5.916 in controls. Three-hour excretion of succinylacetone "equivalent" [SAc] was also significantly higher in the urine of carriers. FAc in 3-h urine was identified by thin-layer chromatography and confirmed by gas chromatography/mass spectrometry. Multivariate stepwise discriminant analysis showed that the inclusion order of significant variables was as follows: HGA levels at 1 hr, fasting level of delta-ALD, residual level of HGA at 3 h, and 3-h excretion of [FAc]. Non-significant variables were HGA tolerance, levels of delta-ALD at 3 h, sex, and 3-h excretion of [SAc].(ABSTRACT TRUNCATED AT 250 WORDS)

Exonuclease digestion of human chromosomes for in situ hybridization and R-banding

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Fine mapping of the long arm of human chromosome 11 by in situ hybridization using different translocations, including the t(11;22) of Ewing sarcoma

The progesterone receptor gene (PGR), the gene coding for porphobilinogen deaminase (PBGD), the gene coding for a neural cell adhesion molecule (NCAM), the oncogene ETS1, and the anonymous genomic sequence D11S29 have been previously located on the long arm of chromosome 11. However, gene localizations obtained with different gene-mapping procedures have led to occasional discrepancies. To localize these genes more precisely, we hybridized five human DNA sequences with different chromosomal rearrangements, including four balanced and one unbalanced translocations. We show here that the order of these five sequences is cen-PGR-PBGD-DIIS29/NCAM/ETS1-tel.

Localization of the human sex hormone-binding globulin gene (SHBG) to the short arm of chromosome 17 (17p12----p13)

Human sex hormone-binding globulin (SHBG) is a plasma steroid transport protein which is known to be encoded by an autosomal gene. We have hybridized two separate cDNA probes, corresponding to the 5' and 3' portions of the coding sequence for SHBG, to human metaphase chromosomes in situ. In this way, the SHBG gene has been localized to the p12----p13 bands of chromosome 17.

Characterization of cDNAs for human estradiol 17 beta-dehydrogenase and assignment of the gene to chromosome 17: evidence of two mRNA species with distinct 5'-termini in human placenta

Human placenta estradiol 17 beta-dehydrogenase (E2DH) cDNA clones were isolated from a lambda gt11 expression library by screening with 33 mer synthetic oligonucleotides derived from the amino acid sequence of the catalytic site of E2DH and with polyclonal antibodies raised against the enzyme purified from human placenta. Using 32P-labeled fragments from the coding and 5'-untranslated regions, two mRNA species have been identified in poly(A)+ RNA from human placenta, a major species migrating at 1.3 kilobases (kb) while a minor one is found at 2.2 kb. Primer extension analysis identifies the major mRNA as starting 9-10 nucleotides upstream from the in-frame ATG initiating codon while the longer mRNA has at least 814 noncoding nucleotides at its 5'-terminus. Sequence analysis of the longest cDNA clone (2092 base pairs) shows that this clone possesses identical coding and noncoding sequences in the regions of overlap with the shorter cDNA clones. The 32P-labeled 5'-noncoding fragment hybridized only to the 2.2 kb band, thus providing additional evidence for the existence of two distinct mRNA species which differ only in their 5'-noncoding regions. Using hpE2DH36 cDNA as a probe for in situ hybridization, the human E2DH gene was localized to the q11-q12 region of chromosome 17. The cloned cDNAs encode E2DH, a 327-amino acid protein having a calculated molecular weight of 34,853. Since E2DH is the enzyme required for the formation of 17 beta-estradiol, the availability of the cDNA encoding the enzyme should permit a detailed investigation of the factors regulating the expression and activity of this crucial enzyme, in both normal and malignant tissues, especially breast cancer.

Leukocyte and plasma N-laurylsphingosine deacylase (ceramidase) in Farber disease

Severe deficiency of acid ceramidase activity (4-5% of normal) was demonstrated in cultured skin fibroblasts, leukocytes and plasma from a 1-year-old boy who was diagnosed as being affected with Farber disease. Determination of ceramidase activity in plasma was achieved by a highly sensitive assay employing a ceramide substrate containing radiolabeled C12 N-acyl moiety (N-lauryl). The enzyme activity in the parents' leukocytes and plasma was found to be reduced to 18-47% of the respective normal values, and that determined in a plasma specimen from a patient with I-cell disease was about 4 times elevated above the normal level.

Characterization of two mRNA species encoding human estradiol 17 beta-dehydrogenase and assignment of the gene to chromosome 17

Using two 33-mer synthetic oligonucleotides derived from the amino acid sequence of the catalytic site of estradiol 17 beta-dehydrogenase (E2DH) and polyclonal antibodies raised against the enzyme purified from human placenta, clones were isolated from a lambda gt11 human placental cDNA library. A 327-amino acid sequence was deduced from cDNA sequencing. Two mRNA species have been identified in poly(A)+ RNA from human placenta, a major species migrating at 1.3 kb while a minor one is found at approx. 2.2 kb. Primer extension and S1 nuclease analysis indicate that the major mRNA species starts 9-10 nucleotides while the minor mRNA starts 971 nucleotides upstream from the ATG initiating codon, respectively. Sequence analysis of the longest cDNA clone (2092 bp) shows that it possesses identical coding and non-coding sequences in the regions of overlap with the shorter cDNA clones. The 32P-labeled 5' non-coding fragment hybridizes only to the 2.2 kb band, thus providing evidence for the existence of two distinct mRNA species which differ in their 5' noncoding regions. Using hp E2DH-36 cDNA as a probe for in situ hybridization of translocated chromosomes, the human E2DH gene was localized to the q11-q12 region of chromosome 17.

Assignment of the human 3 beta-hydroxysteroid dehydrogenase gene (HSDB3) to the p13 band of chromosome 1

Three-beta-hydroxysteroid dehydrogenase (HSDB3) is the enzyme which catalyses the oxidative conversion of delta 5-3 beta-hydroxy steroids to the delta 4-3-keto configuration and is therefore involved in the biosynthesis of all classes of hormonal steroids, namely progesterone, glucocorticoids, mineralocorticoids, androgens, and estrogens. Deficiency of the enzyme is associated with congenital adrenal hyperplasia and is usually lethal in early life. Despite its crucial role, chromosome assignment of the gene for this enzyme has not been reported. Using in situ hybridization, we report that hybridization with labeled human HSDB3-specific cDNA yielded 27% of silver grains associated with chromosome 1 with a maximal concentration in the p13 band.

[" When I'm sad " Activities for adolescents living with different losses.]

In this article, the author relates an activity carried out with 209 adolescents. They were invited to write about circumstances surrounding sorrowful events. The adolescents mentioned events concerning mainly family and friends that made them very sad. Those who identified several sorrowful events at a time, namely family arguments, tend to be still affected when the author's survey tookplace. The author discusses in which way these events are related to loss, and how reactions are related to sorrow. Finally, the author suggests preventive assistance to young girls and boys in sorrow, with the help of peers, parents and the adolescent's own strengths.

Detection of succinylacetone and the use of its measurement in mass screening for hereditary tyrosinemia

A technique designed to measure quantitatively succinylacetone (4,6-dioxoheptanoic acid) is presented. It essentially involves the inhibition of delta-aminolevulinate dehydratase (EC 4.2.1.24) by succinylacetone. Prior to their use in the assay, the samples are heated at 100 degrees C for 30 min in order to transform all succinylacetoacetate (3,5-dioxooctanedioic acid) to succinylacetone. By this transformation of the first abnormal metabolite specific to hereditary tyrosinemia to the second and last one, which is a powerful inhibitor of delta-aminolevulinate dehydratase, we determine in one sensitive assay the total amount of both. Succinylacetone was measured in sera and urines from 19 patients with hereditary tyrosinemia. All sera and urines contained succinylacetone at concentrations ranging, respectively, from 2 to 100 mumol/l and from 190 to 6000 mumol/g creatinine. The technique was also adapted to dried blood spots on paper and was used as a test complementary to blood tyrosine determination in mass screening for hereditary tyrosinemia. A total of 2412 samples having concentrations of 60 mg/l or more of tyrosine were assayed, and ten showed the presence of succinylacetone. These were all from newborns with hereditary tyrosinemia. The test has proven to virtually eliminate false positives, and, thereby, much clerical work and parental anxiety.

Prenatal diagnosis of hereditary tyrosinaemia: measurement of succinylacetone in amniotic fluid

A method is proposed for prenatal diagnosis in pregnancies at risk of hereditary tryosinaemia. Affected fetuses were detected on the basis of the abnormal presence in the amniotic fluid of succinylacetone, a metabolite previously identified in sera and urines of patients suffering from hereditary tyrosinaemia. Our data show that the forty amniotic control samples had no detectable succinylacetone, while succinylacetone was found in three out of the thirteen cases at risk. Following the parents' decision, these three fetuses were aborted. The ten other mothers who brought their pregnancies to term had normal infants. Enzymatic analysis from two of their aborted fetuses' livers revealed an absence or a low activity of fumarylaceto-acetate hydrolase (EC 3.7.1.2) compared with control fetal livers of the same age.

Constitutive heterochromatin and micronucleoli in the human oocyte at the diplotene stage

In the diplotene stage of the human oocyte, the processes of elaboration of the nucleolar material are amplified. The principal nucleoli are more voluminous but their relations with the secondary constrictions and the satellites of the D and G chromosomes are not modified. Numerous micronucleoli, frequently to the number of 15-20 this stage. The most remarkable point is their association to various segments of constitutive heterochromatin: centromeric regions, secondary constrictions of the C9 and probably of the A1 and E16. These observations reveal that the human oocyte at the diplotene stage shows an amplification of the ribosomal cistrons. This phenomenon is homologous, to a more reduced scale, of this described from the inferior vetebrates. Besides, the role of heterochromatin in the synthesis of nucleolar material without the intervention of the classic nucleolar organizers is suggested.