A case of 21q-syndrome with normal SOD-1 activity

Summary A female infant with del(21)(pterq22.1-2:) constitution identified by G, Q, and R banding is reported. She had marked mental and physical retardation, generalized hypertonia, microphthalmia with persistent hypoplastic primary vitreous, blepharochalasia, high nasal bridge, micrognathia, malformed ears with preauricular pits, and overlying fingers. The assay for superoxide dismutase-1 (SOD-1) activity in the patient revealed a normal value and it was suggested that the gene locus for SOD-1 in 21q22.2qter is not compatible with the presence of the gene dosage effect in the monosomic state.     

Dosage effects for superoxide dismutase-1 in nucleated cells aneuploid for chromosome 21.

Assays of the activity of chromosome 21 determined superoxide dismutase-1 (SOD-1) in lymphocytes and polymorphonuclear granulocytes have demonstrated 38% and 40% increases, respectively, in cells from individuals with trisomy 21. Similarly, SOD-1 activity in trisomic fibroblasts is increased by 81%, while cells monosomic for chromosome 21 have only 60% of normal activity. Taken together with the data on SOD-1 activities in trisomic erythrocytes and platelets, the present results firmly confirm the existence of a true dosage effect for this enzyme in cells aneuploid for chromosome 21. However, the results of assays of the activity of glutathione peroxidase in trisomic fibroblasts did not confirm the possibility previously reported of a chromosome 21 related dosage effect for this enzyme.     

A case of 21q-syndrome with half normal SOD-1 activity

A male Japanese infant was found to have a chromosomal aberration of del(21)(qter leads to q22.1-2) and decreased superoxide dismutase (SOD) activity in erythrocytes and polymorphonuclear and mononuclear leukocytes. The cuprozinc enzyme (SOD-1) level was 40-50% of normal, while the cyanide-insensitive manganese enzyme (SOD-2) activity was within the normal range. Determination of SOD activity in blood cells is a valuable method of classification of the syndrome.     

Maternally transmitted extra ring(21) chromosome in a boy with Down's syndrome

Summary An 11-month-old boy with typical Down's syndrome is presented. His karyotype was 47,XY,+r(21); the erythrocyte superoxide dismutase-1 (SOD-1) activity was elevated. His phenotypically normal mother showed 46,XX,r(21) karyotype and normal SOD-1 activity. Analysis of chromosomal heteromorphism revealed that in addition to the ring, a normal chromosome 21 was transmitted from the mother.     

A linkage map of three anonymous human DNA fragments and SOD-1 on chromosome 21

Using DNA polymorphisms adjacent to single-copy genomic fragments derived from human chromosome 21, we initiated the construction of a linkage map of human chromosome 21. The probes were genomic EcoRI fragments pW228C, pW236B, pW231C and a portion of the superoxide dismutase gene (SOD-1). DNA polymorphisms adjacent to each of the probes were used as markers in informative families to perform classical linkage analysis. No crossing-over was observed between the polymorphic sites adjacent to genomic fragments pW228C and pW236B in 31 chances for recombination. Therefore, these fragments are closely linked to one another (theta = 0.00, lod score = 6.91, 95% confidence limits = 0-10 cM) and can be treated as one 'locus' with four high-frequency markers. There is a high degree of non-random association of markers adjacent to each of these two probes which suggests that they are physically very close to one another in the genome. The pW228C - pW236B 'locus' was also linked to the SOD-1 gene (theta = 0.07, lod score = 4.33, 95% confidence limits = 1-20 cM). On the other hand, no evidence for linkage was found between the pW228C-pW236B 'locus' and the genomic fragment pW231C (theta = 0.5, lod score = 0.00). Based on the fact that pW231C maps to 21q22.3 and SOD-1 to 21q22.1, we suggest that the pW228C-pW236B 'locus' lies in the proximal long arm of chromosome 21. These data provide the outline of a linkage map for the long arm of chromosome 21, and indicate that the pW228C-pW236B 'locus' is a useful marker system to differentiate various chromosome 21s in a population.     

SOD-1 expression in pig coronary arterioles is increased by exercise training

Coronary arterioles of exercise-trained (EX) pigs have enhanced nitric oxide (NO.)-dependent dilation. Evidence suggests that the biological half-life of NO. depends in part on the management of the superoxide anion. The purpose of this study was to test the hypothesis that expression of cytosolic copper/zinc-dependent superoxide dismutase (SOD)-1 is increased in coronary arterioles as a result of exercise training. Male Yucatan pigs either remained sedentary (SED, n = 4) or were EX (n = 4) on a motorized treadmill for 16-20 wk. Individual coronary arterioles ( approximately 100-microm unpressurized internal diameter) were dissected and frozen. Coronary arteriole SOD-1 protein (via immunoblots) increased as a result of exercise training (2.16 +/- 0.35 times SED levels) as did SOD-1 enzyme activity (measured via inhibition of pyrogallol autooxidation; approximately 75% increase vs. SED). In addition, SOD-1 mRNA levels (measured via RT-PCR) were higher in EX arterioles (1.68 +/- 0.16 times the SED levels). There were no effects of exercise training on the levels of SOD-2 (mitochondrial), catalase, or p67(phox) proteins. Thus chronic aerobic exercise training selectively increases the levels of SOD-1 mRNA, protein, and enzymatic activity in porcine coronary arterioles. Increased SOD-1 could contribute to the enhanced NO.-dependent dilation previously observed in EX porcine coronary arterioles by improving management of superoxide in the vascular cell environment, thus prolonging the biological half-life of NO.     

Abnormal localization of proto-oncogene c-ets 1 in acute leukemia with translocation t(1: 11)(q21: q23)

The chromosome localization of a 5.4 kb DNA genomic probe of proto-oncogene c-ets 1 has been analysed in an acute monocytic leukemia with t (1; 11) (q21; q23) translocation. The c-ets probe has been translocated onto the rearranged chromosome 1, suggesting the involvement of the proto-oncogene in leukemias with chromosome rearrangements at band 11 q23.     

Genes for two autosomal recessive forms of chronic granulomatous disease assigned to 1q25 (NCF2) and 7q11.23 (NCF1).

Chronic granulomatous disease (CGD) is a heterogeneous group of inherited disorders of impaired superoxide production in phagocytes. The most common X-linked recessive form involves the CYBB locus in band Xp21.1 that encodes the membrane-bound beta subunit of the cytochrome b558 complex. Two autosomal recessive forms of CGD result from defects in cytosolic components of the phagocyte NADPH oxidase system, p47phox (NCF1) and p67phox (NCF2). By using human cDNA probes we have mapped the genes for these proteins to chromosomal sites. The combined data from Southern analysis of somatic cell hybrid lines and chromosomal in situ hybridization localize NCF1 to 7q11.23 and NCF2 to band 1q25. The NCF1 localization corrects an erroneous preliminary assignment to chromosome 10. In the mouse, the locus corresponding to NCF2 (Ncf-2) was mapped with somatic cell hybrid panels and recombinant inbred strains to mouse chromosome 1 near Xmv-21 within a region of conserved homology with human chromosome 1 region q21-q32. A second site, probably a processed pseudogene, was identified on mouse chromosome 13.     

SOD-1 inhibits FAS expression in cortex of APP transgenic mice

Peptides derived from proteolytic processing of the amyloid precursor protein (APP) are important for the pathogenesis of Alzheimers disease (AD). In the present study, we found that transgenic mice overexpressing wild-type human APP gene (hAPP/+) displayed a much higher expression of FAS, one of the death receptor subfamily. This FAS overexpression was significantly reduced in the cortex of mice overexpressing both wild-type hAPP gene and wild-type human superoxide dismutase-1 gene (hSOD-1). Moreover hSOD-1 transgenic expression was associated with an increase of Glial fibrillary acidic protein (GFAP) production. This study indicates that SOD-1 overexpression can inhibit FAS expression, which may be beneficial in AD.     

Tissue-specific developmental regulation of superoxide dismutase (SOD-1 and SOD-2) activities in genetic strains of mice

The activity levels of CuZn superoxide dismutase (SOD) (SOD-1) and Mn SOD (SOD-2) in liver, kidney, and lung were assessed in newborn and 3-, 10-, 25-, and 70-week-old females from seven genetic strains (BALB/c, Cs^b, C3H/HeSnJ, C3H/S, C57BL/6J, Swiss-Webster, and 129/ReJ) of mice. Total SOD enzyme activity was high at birth and declined somewhat with old age (70 weeks) in the liver and increased in both kidney and lung from newborn to 25 weeks. The activity level of SOD-1 was found to be highly variable among strains at different ages in liver, with little change associated with aging in the kidney, and showed a strain-specific increase during aging in the lung. In general, SOD-2 activity was lower than SOD-1 activity in liver and lung but levels of the two forms of this enzyme were similar in the kidney. The SOD-2 activity increased with age with little variation among strains in kidney. The increase in this form of the enzyme with age was relatively small and strain specific in lung and highly variable among strains in the liver. The Cs^b genotype (acatalasemic) at age 70 weeks showed an exceptionally high SOD-1 activity associated with an exceptionally low SOD-2 activity in the liver. Changes in enzyme activity with age in different tissues associated with differences in activity level among genotypes (of the type reported here for SOD-1 and SOD-2) may be indicative of a complex system of enzyme regulation. Further studies are needed to explain fully the genetic/molecular mechanism(s) for SOD regulation.This study was financially supported by an NSERC operating grant to S.M.S. N.J.S. was the recipient of a postgraduate scholarship from the NSERC during this period.     

Localization of human c-mos to chromosome band 8q11 in leukemic cells with the t(8;21) (q22;q22)

Summary Chromosome in situ hybridization studies locate c-mos to chromosome band 8q11 in leukemic cells carrying the t(8;21) (q22;q22). This amends the previous assignment of c-mos to chromosome band 8q22 and conforms with its recent assignment to 8q11 in normal cells and in a cell line with a structurally abnormal chromosome 8. C-mos lies proximally to, and distant from, the breakpoint at 8q22 in the t(8;21) and is unlikely to have a role in the onset of acute myeloid leukemia characterized by this translocation.     

Partial trisomy of chromosome 21 by maternal translocation t(15;21) (q26.2; q21)]

A balanced reciprocal translocation, t(15;21) (q262;q21) was observed in the mother and maternal grandfather of two patients. The propositus, who received the abnormal chromosome 15 from his mother, is trisomic for the distal part of chromosome 21, and his phenotype is that of classical trisomy 21. His sister, who is trisomic for the proximal part of 21q, is slightly retarded but developmentally normal otherwise.     

Dosage effect of the cytoplasmic superoxide dismutase (SOD-1) gene in the erythrocytes of Down's syndrome patients]

The activity of cytoplasmic superoxydase (SOD-1) was studied in erthrocytes of 17 patients affected with Down's syndrome (trisomy 21) and in 26 healthy persons. A 1.56-fold increase of the enzyme activity was observed in the group of patients as compared with the control group. This could be explained as the dosage effect of the corresponding gene located in the chromosome 21.     

Formation of novel CENP-A domains on tandem repetitive DNA and across chromosome breakpoints on human chromosome 8q21 neocentromeres

Endogenous human centromeres form on megabase-sized arrays of tandemly repeated alpha satellite DNA. Human neocentromeres form epigenetically at ectopic sites devoid of alpha satellite DNA and permit analysis of centromeric DNA and chromatin organization. In this study, we present molecular cytogenetic and CENP-A chromatin immunoprecipitation (ChIP) on CHIP analyses of two neocentromeres that have formed in chromosome band 8q21 each with a unique DNA and CENP-A chromatin configuration. The first neocentromere was found on a neodicentric chromosome 8 with an inactivated endogenous centromere, where the centromeric activity and CENP-A domain were repositioned to band 8q21 on a large tandemly repeated DNA. This is the first example of a neocentromere forming on repetitive DNA, as all other mapped neocentromeres have formed on single copy DNA. Quantitative fluorescent in situ hybridization (FISH) analysis showed a 60% reduction in the alpha satellite array size at the inactive centromere compared to the active centromere on the normal chromosome 8. This neodicentric chromosome may provide insight into centromere inactivation and the role of tandem DNA in centromere structure. The second neocentromere was found on a neocentric ring chromosome that contained the 8q21 tandemly repeated DNA, although the neocentromere was localized to a different genomic region. Interestingly, this neocentromere is composed of two distinct CENP-A domains in bands 8q21 and 8q24, which are brought into closer proximity on the ring chromosome. This neocentromere suggests that chromosomal rearrangement and DNA breakage may be involved in neocentromere formation. These novel examples provide insight into the formation and structure of human neocentromeres.     

Purification and Partial Characterization of a Genetically-Defined Superoxide Dismutase (SOD-1) Associated with Maize Chloroplasts

The chloroplast-associated form of superoxide dismutase from maize (Zea mays L.) (SOD-1) has been purified by a stepwise procedure consisting of (NH₄)₂SO₄ fractionation, G-100 Sephadex gel filtration, DEAE-Sephacel chromatography, and hydroxylapatite chromatography. This procedure resulted in a single band on sodium dodecyl sulfate-polyacrylamide gels indicating that the preparation is homogeneous. The holoenzyme molecular weight was estimated at 31,000 to 33,000 by gel filtration. The subunit molecular weight of this dimeric protein was estimated at 14,500 on sodium dodecyl sulfate-polyacrylamide gels. Studies involving amino acid composition analysis, immunological cross-reactivity, in vitro subunit hybridizations, and H₂O₂ sensitivity indicate that SOD-1 differs significantly from SOD-2 and SOD-4, the other cupro-zinc forms of SOD from maize. The possible physiological role of SOD-1 within the chloroplast is discussed.     

Molecular evidence for true isochromosome 21q

Summary In one family a duplicated 21q was shown to be a true isochromosome, which segregates from mosaic mother to non-mosaic child with full Down syndrome phenotype. Densitometric analysis of Southern blots, using probe pPW228C for the distal long arm of chromosome 21, indicated that the 21q duplication contains two copies of the allele detected by the probe. Maternal mosaic karyotype of 45,XX,-21/46,XX/46, XX,-21,+21i(21q) also suggested transverse mitotic centromere division as the origin of the 21q isochromosomes. Morphologic analysis of chromosome heteromorphisms strengthened this interpretation because the free 21 missing in the cell line with 45 chromosomes was also missing in cells with the isochromosome. In a second family the cytogenetic data also suggested transmission of an i(21q) from mosaic mother to nonmosaic Down syndrome child but molecular evidence did not prove identity of alleles in the duplicated chromosome 21.     

Interchange trisomy 21 by t(1;21)(p22;q22)mat

Interchange trisomy 21 by t(1:21)(p22:q22)mat: Interchange trisomy 21 by t(1;21)(p22;q22)mat was identified in a sporadic patient with Down syndrome. With a 21q22 specific probe, we observed signals on both normal 21 chromosomes and on the der. We reviewed the 23 published reports of families with reciprocal translocations leading to viable offspring with interchange trisomy 21. The breakpoints in chromosome 21 were mainly located in 21q (19/24 instances, including the present report) and in 19/23 cases the other chromosome involved in the translocation was (pairs 1-12). The underlying 3:1 segregation occurred mainly in carrier mothers; only one patient presented a de novo imbalance and in another case the father was the carrier. In addition, there were 4 instances of concurrence with another unbalanced segregation (adjacent-1 or tertiary trisomy) and 3 families with recurrence of interchange trisomy 21. The mean age of 14 female carriers at birth of interchange trisomy 21 offspring (24.8 yr) was lower that the mean (28.3 yr) found in a larger sample of mothers of unbalanced offspring due to 3:1 segregation (mostly tertiary trisomics) and was not increased with respect to the general population average. Overall, these data agree with previous estimates regarding recurrence risk (9-15%) and abortion rate (about 28%) in female carriers ascertained through an interchange trisomic 21 child.     

Chromosomal localization of human endogenous retroviral element ERV1 to 18q22----q23 by in situ hybridization

From a clone containing the entire locus of human endogenous retroviral element ERV1, we have obtained a DNA probe that is specific for the 3' long terminal repeat (LTR) sequence. This probe was used to map the LTR of ERV1 by in situ hybridization to chromosomes from normal human blood lymphocytes. The LTR was found to be localized to the distal portion of the long arm of human chromosome 18, within bands q22----q23. This chromosome locus is near the constitutive fragile site at band q21.3 on chromosome 18 associated with the 14;18 translocations seen in follicular lymphomas.     

A Contiguous Physical Map of the Pericentromeric Region of Chromosome 21q between D21Z1 and D21S13E

We constructed a long range restriction map of the pericentromeric 21q region between the centromere, identified by the alphoid DNA sequence D21Z1, and D21S13E. The physical map showed the order and intermarker distances of five new loci, including two for which highly informative dinucleotide repeat polymorphisms were identified. The total distance between D21Z1 and D21S13E was 2400 kb. Comparison of genetic and physical distances indicated that there is about 400 to 500 kb per centimorgan that is not significantly different from the average 470 kb per centimorgan for the whole of chromosome 21q. Our physical mapping results do not indicate suppression of recombination in pericentromeric 21q.     

Maternal balanced translocation (4;21) leading to an offspring with partial duplication of 4q and 21q without phenotypic manifestations of Down syndrome

We describe an 8-years old female with supernumerary chromosome der(21)t(4;21)(q25;q22) resulting in partial trisomy 4q25-qter and partial trisomy 21(pter-q22). The extra material was originated from a reciprocal balanced translocation carrier mother (4q;21q). Karyotyping was confirmed by FISH using whole chromosome painting probes for 4 and 21q and using 21q22.13-q22.2 specific probe to rule out trisomy of Down syndrome critical region. Phenotypic and cytogenetic findings were compared with previously published cases of partial trisomy 4q and 21q. Our patient had the major criteria of distal trisomy 4q namely severe psychomotor retardation, growth retardation, microcephaly, hearing impairment, specific facies (broad nasal root, hypertelorism, ptosis, narrow palpebral fissures, long eye lashes, long philtrum, carp like mouth and malformed ears) and thumbs and minor feet anomalies. In spite of detection of most of the 3 copies of chromosome 21, specific features of Down syndrome (DS) were lacked in this patient, except for notable bilateral symmetrical calcification of basal ganglia. This report represents further delineation of the phenotype-genotype correlation of trisomy 4q syndrome. It also supports that DS phenotype is closely linked to 21q22. Nevertheless, presence of basal ganglia calcification in this patient may point out to a more proximal region contributing in its development in DS, or that genes outside the critical region may influence or control manifestations of DS features.