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

Prenatal findings and molecular cytogenetic analyses of partial trisomy 12q (12q24.32→qter) and partial monosomy 21q (21q22.2→qter)

OBJECTIVES

To present the prenatal findings and molecular cytogenetic analyses of partial trisomy 12q and partial monosomy 21q, and a review of the literature.

METHODS

Amniocentesis was performed at 23 gestational weeks in a 33-year-old woman because of abnormal sonographic findings. Amniocentesis revealed a derivative chromosome 21, or der(21), with a deletion on the region of 21q22.2 and an addendum of a small chromosomal segment of unknown origin. The maternal karyotype was subsequently found to be 46,XX,t(12;21)(q24.32;q22.2). Level II ultrasound showed microcephaly, micrognathia, a ventricular septal defect, and rocker-bottom feet. The pregnancy was terminated. A malformed infant was delivered without the phenotype of holoprosencephaly (HPE). Fluorescence in situ hybridization (FISH) and polymorphic DNA markers were used to investigate the involved chromosomal segments.

RESULTS

FISH study showed the absence of the signal of 21q subtelomeric probe and the presence of the signal of 12q subtelomeric probe in the der(21). The fetal karyotype was 46,XY,der(21) t(12;21)(q24.32;q22.2)mat. Genetic marker analysis showed a deletion at 21q22.2 and a breakpoint between D21S156 (present) and D21S1245 (absent). The deleted segment was measured about 4.5 Mb encompassing the HPE critical region.

CONCLUSIONS

Molecular genetic analyses help in determining the prenatally detected unbalanced cryptic translocation as well as parental balanced subtle translocation. A duplication of 12q24.32-->qter and a deletion of 21q22.2-->qter may be associated with prenatal sonographic findings of microcephaly, borderline ventriculomegaly and cerebellar hypoplasia, micrognathia, a ventricular septal defect, and rocker-bottom feet. Haploinsufficiency of the HPE critical region at 21q22.3 may not cause an HPE phenotype.

Monosomy 21q: two cases of del(21q) and review of the literature

We report on two cases of partial monosomy 21 and review cases with a partial or an apparently full monosomy 21. In situ hybridization and/or molecular studies appear to be necessary tools to study imbalance in such a small chromosome and to perform further genotype-phenotype correlations. The segregation mode in cases with a translocation is adjacent 1, adjacent 2, and 3:1 in about 1/4, 1/4 and 1/2 of the cases, respectively.

Superoxide dismutase, aging, and degenerative disease

Over 15 years of research on correlations between superoxide dismutase (SOD) activity and aging or life span have failed to provide a consistent picture of the role of SOD in aging. While genetic manipulations that increase CuZn-SOD activity have only a slight, if any, effect on maximum life span in several species, they do increase resistance to oxidative stress. However, increasing both CuZn-SOD and catalase does significantly increase maximum life span. Decreased SOD expression in a variety of species increases their vulnerability to oxidative stress, and in the case of genetically altered CuZn-SOD, leads to premature death of motor neurons in humans. Little is known about the regulation of expression of SOD and other antioxidant defense enzymes in eukaryotes. The research summarized below collectively suggest that SOD plays an important role in longevity and degenerative disease, but much remains to be learned before manipulation of SOD expression can be considered for effective intervention in either process.

Monosomy for 21pter-q21: case report and assignment of a DNA clone (Fr8-77) to the deleted segment

A 4-month-old Japanese girl with partial monosomy 21 was described. The patient has craniofacial anomalies, a short neck, wide-set nipples, anal atresia, deformed feet, hypertonia, intrauterine growth retardation, and mental deficiency. RFA- and high-resolution GTG-banding chromosome analyses, and Southern- and slot-blot analyses interpreted her karyotype as 45,XX,-2,-21, + der(2)t(2:21)(q37.3;q22.1). The origin of this de novo translocation ascertained by analyses with both QFQ-heteromorphisms and a Fr8-77/BamHI RFLP was paternal. Comparison of the patient with previously reported patients confirmed that her manifestations are consistent with those of monosomy for 21pter-q21. Based on the results of molecular analyses on the present patient, a DNA clone, Fr8-77 (D21S82), was assigned to pter-q21.

Expression of LFA-1 by a lymphoblastoid cell line from a patient with monosomy 21: effects on intercellular adhesion

Monosomy 21 (M21) is a rare aneuploid condition which in certain cases leads to reduced levels of chromosome 21 gene products. We have prepared an Epstein-Barr virus lymphoblastoid cell-line (LCL) from patient with M21 who has immunological abnormalities, and analysed the expression of lymphocyte function-associated antigen-1 (LFA-1). This heterodimeric leucocyte integrin consists of CD11a (alpha) subunits non-covalently associated with CD18 (beta) subunits coded, respectively, by genes on chromosomes 16 and 21. To determine whether monosomy 21 results in decreased expression of LFA-1, monoclonal antibodies were used to compare the expression of CD11a and CD18 on the M21 LCL with LCL from trisomy 21 (Down's syndrome, T21), normal controls and a possible case of leucocyte adhesion deficiency. In addition, phorbol-ester-induced homotypic adhesion, an LFA-1-mediated effect, was compared in these LCLs. The results are consistent with a gene dosage mediated reduction of LFA-1 expression by the M21 LCL.

A methyl viologen-sensitive mutant of the nematode Caenorhabditis elegans

A methyl viologen (paraquat)-sensitive mutant, mev-1 (LG III), in Caenorhabditis elegans was about 4 times more sensitive to methyl viologen than the wild type. This mutant was also hypersensitive to oxygen. The brood size was about 1/4 that of the wild type. The average life span was determined to be 9.3 days as compared to 14.3 days for the wild type. The activity of superoxide dismutase (SOD), a scavenging enzyme for superoxide anion, was about half the wild-type level. We suggest that oxygen radicals may be involved in the normal aging mechanism in C. elegans.

Decreased superoxide dismutase-2 activity in a patient with ring chromosome 6

Manganese superoxide dismutase (SOD-2) activity was measured in erythrocytes and leukocytes of a patient with ring chromosome 6. Compared to normal control individuals, SOD-2 activity in leukocytes of the patient was lower, whereas cuprozinc SOD (SOD-1) activity was normal. These findings suggest the cause of decreased enzyme activity is the effect of the ring form on production of the enzyme or inherent instability of ring chromosomes.

Aspects of the structure, function, and applications of superoxide dismutase

The current status of superoxide dismutase (SOD) is that it is an enzyme with diverse ramifications. This review attempts an understanding of SOD as a structural, functional, and biological entity. Accordingly, the review is in three parts. The first part discusses SOD in terms of protein structure, proceeding from primary to secondary and three-dimensional structure for the three forms of SOD: copper/zinc SOD, manganese SOD, and iron SOD. This is the order of structural knowledge of the enzyme. Iron SOD is an enzyme of prokaryotes and some higher plants. Manganese SOD is an enzyme of prokaryotes and eukaryotes. Copper/zinc SOD is an enzyme of eukaryotes and certain prokaryotes. The evolutionary relationships of the three forms of SOD, the status of the copper/zinc SOD gene in prokaryotes, and the cloning and sequencing of SOD genes are discussed. The second part of the review deals with the catalytic mechanism of SOD in the three forms of the enzyme. Structural and mechanistic conclusions from various spectroscopic studies are critically considered. A detailed picture is given of the active site of copper/zinc SOD. The third part is a review of SOD in the general context of oxygen toxicity. After consideration of the question of superoxide toxicity and superoxide pathology, several areas in which SOD has been investigated or used as a tool in a biochemical, pharmacological, or clinical context are discussed, including population genetics; trisomy 21; development and senescence; the nutritional copper, zinc, and manganese status; hemolysis and anemia; oxygen toxicity in the lung and nervous system; inflammation, autoimmune disease and chromosome breakage, ischemia and degenerative changes; radiation damage; and malignancy. A comprehensive picture is given of measurements of SOD activity in disease states, and the question of superoxide-related disease is considered at several points.

Ring chromosome 21 and SOD activity of blood cells

A female infant was found to have an abnormal karyotype with mosaicism: 45,XX,-21/46,XX,r(21) (p11.2 q22.3). She showed a slightly decreased level of superoxide dismutase (SOD) activity in erythrocytes, polymorphonuclear and mononuclear leukocytes. The cuprozinc SOD (SOD-1) activity of leukocytes was 70-80% of normal level, while their manganese SOD (SOD-2) activity was within the normal range. The relationship between the chromosomal aberration and the SOD activity is discussed in relation to the gene dosage effect.

Significance of erythrocyte lipid peroxidation and superoxide dismutase activity in a patient with idiopathic pulmonary haemosiderosis

In a patient with idiopathic pulmonary haemosiderosis, lipid peroxidation of erythrocytes and their superoxide dismutase activity were determined. The latter was found to be decreased, and the erythrocytes showed easy peroxidisability, which was shown by vulnerability to hydrogen peroxide and a marked elevation of iron-catalysed lipid peroxidation in addition to a higher basal malondialdehyde level, an end product of lipid peroxidation. These findings were correlated with haemolysis, iron-deficiency anaemia and a shortened survival of erythrocytes. Although the aetiological significance of our observations still remains to be clarified, it appears that antioxidant enzymes and the peroxidative reactivity of erythrocytes should be carefully evaluated in other patients with idiopathic pulmonary haemosiderosis.