Prevalence of mutation associated to resistance with nucleoside analogues in a cohort of naïve HIV-1 positive subjects during the period 1984-1997

We examined samples from 98 naïve HIV-1 positive patients with the seroconversion period between 1984 and 1997, 64 of whom with a diagnosed primary infection. We observed a progressive increase in the percentage of patients harboring mutations associated with zidovudine resistance, starting from 8% during the period 1987-1994 to 20% and 36% in patients with HIV infection diagnosed during 1996 and 1997 respectively. The small number of patients analyzed in groups 3 and 4 is an important limitation to establish the real increase in the prevalence of mutations we observed during the past two years. However, it is important to underline the trend and, in our opinion, further studies to better define the relevance of such phenomenon in the clinical practice must be performed.

In vivo response of mouse liver to gamma-radiation assessed by the comet assay

The alkaline comet assay was used to measure DNA damage induced in liver cells of mice irradiated with gamma-radiation, as well as the repair competency of these cells. A simplified procedure for the isolation of nuclei from cells in solid tissues was developed. This simplified method allows nuclei to be processed into lysis only 5 min after briefly chilling the tissue to depress any enzymatic activity. The nuclei were spontaneously released by a sharp cut of the tissue and exposure of the cut to a drop of 50 mM sodium-phosphate buffer at pH 7.2, immediately before adding the low melting agarose. Thus, the procedure minimizes time-dependent modification of the endogenous level of damage by reducing additional strand breaks or repair produced during processing. The induction of DNA damage by gamma-radiation behaved as a one-hit event in the liver cells, as there was a positive linear correlation between the radiation dose and the fraction of DNA migrated into the comet tails. The level of DNA damage produced by gamma-radiation was highly significant at doses of 0.5 and 1 Gy. Based on the mean extent of DNA migration, the level of damage was not reduced following only one hour of repair time however, after two hours, there was a significant reduction in DNA migration. To increase the resolution of the statistical analysis, the nuclei of each sample were distributed in five types of comets, according to the percentage of DNA in the tail. To compare the frequency distributions of these types of comets between different experimental situations, a Pearson chi-square statistical analysis was applied. It was found, by this analysis, that the DNA repair which occurred 1 h after 1 Gy of gamma-irradiation is significant and that, after 2 h, more DNA repair occurs, but a significant residual damage still persists when comparing this sample with the control.

Comparison of clinical-radiological and molecular findings in hypochondroplasia

Hypochondroplasia is an autosomal dominant skeletal dysplasia characterized by disproportionate short stature. A mutation (N540K) in the fibroblast growth factor receptor 3 (FGFR3) gene was described in some patients with this condition. The aims of the study were to identify the frequency of the FGFR3 gene mutation, to define the salient clinical and radiological abnormalities of the affected subjects, and to verify the contribution of molecular findings to the clinical and radiological definition of hypochondroplasia. Based on the most common radiological criteria, we selected 18 patients with a phenotype compatible with hypochondroplasia. Height, sitting height, and cranial circumference were measured in all patients. Radiographs of the lumbar spine, left leg, pelvis, and left hand were also obtained. The presence of the N540K mutation was verified by restriction enzyme digestions. Half of our patients carried the N540K mutation. Although similar in phenotype to the patients without the mutation, they showed in addition relative macrocephaly. The association of the unchanged/narrow interpedicular distance with the fibula longer than the tibia was more common in patients with gene mutation. Although we did not find a firm correlation between genotype and phenotype, in our study the N540K mutation was most often associated with disproportionate short stature, macrocephaly, and with radiological findings of unchanged/narrow interpedicular distance and fibula longer than tibia.

Rapid detection of 21-hydroxylase deficiency mutations by allele-specific in vitro amplification and capillary zone electrophoresis

A quick diagnosis of the classic form of 21-hydroxylase deficiency (simple virilizing and salt wasting) is of great importance, especially for prenatal diagnosis and treatment in pregnancies at risk. A method for simultaneous detection of common point mutations in the P450c21 B gene is here proposed by combining a nested PCR amplification refractory mutation system (ARMS) with capillary zone electrophoresis (CZE) in sieving liquid polymers. In the first PCR, B genes are selectively amplified. In the nested reaction, ARMS-detected wild-type and mutated alleles are separately pooled and resolved by CZE. CZE is performed in coated capillaries in the presence of 30 g/L hydroxyethyl cellulose in the background electrolyte for size separation of the DNA analytes. For high-sensitivity detection the electrophoresis buffer contains the fluorescent dye SYBR Green I. Laser-induced fluorescence detection is obtained by excitation at 488 nm and signal collection at 520 nm. Specificity and reproducibility of the protocols were established by using samples from 75 Italian families with 21-hydroxylase deficiency already genotyped by allele-specific oligonucleotide hybridization or direct sequencing. Whereas dot-blot is time consuming because of the high number of hybridizations with radioactive probes, this present protocol is more rapid, giving sufficient separation on CZE after PCR reactions without preconcentration or desalting of samples.

Unusual clinical features and early brain MRI lesions in a family with cerebral autosomal dominant arteriopathy

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a recently described inherited disorder. The pathologic gene maps on chromosome 19. The clinical spectrum of the disease consists of recurrent strokes, migraine, transient ischemic attacks, mood changes, and dementia. We report a genetically assessed CADASIL family with atypical clinical presentations of epileptic seizures. In two asymptomatic family members there were early brain abnormalities on MRI. Our report expands the clinical spectrum of CADASIL and suggests that it is possibly an undiagnosed disorder.

A fast comet assay variant for solid tissue cells. The assessment of DNA damage in higher plants

The single-cell gel electrophoresis or comet assay, under high alkaline conditions, detects low levels of DNA damage. In it, broken DNA migrates from the nucleus to the anode providing images similar to comets. To adapt this assay to solid tissue cells, nuclei were directly obtained from Allium cepa L. roots. The surface of each single fresh sharply cut meristem was exposed to a small drop of 50 mM Sörensen buffer at pH 6.8, placed on a regular agarose-coated slide. By immediately adding low melting point agarose at 30 degrees C, nuclei resulted embedded in agarose. A final layer of this agarose ended the preparative steps. Conventionaly prepared leukocytes were used as a control. The treatment with detergent (lysis step of the conventional assay) proved to be unnecessary for the nude nuclei. A 20 min-long electrophoresis (at 0.65 V. cm-1, 230 mA and 10 degrees C) was more sensitive than a 10 min-long one for detecting the differential response of plant nuclei to 2 and 4 Gy of gamma-irradiation. A short fixation in methanol transformed the preparations into semi-permanent ones, without altering their later DNA staining by ethidium bromide. The use of instantaneously isolated nuclei simplifies and expands the use of this technique to any eukaryotic cell from solid tissues.

Ligase chain reaction assay for human mutations: the Sickle Cell by LCR assay

We can detect the beta-globin gene sickle cell mutation by using an assay based on the ligase chain reaction. The simultaneous amplification of the human growth hormone gene in the same reaction serves as a control for the amount of template DNA or amplification efficiency. Ligation products, which are biotinylated at one end and tagged with an arbitrary "tail" sequence at the other, are captured by hybridization to "tail"-complementary oligonucleotides immobilized on polystyrene microwells. The captured ligation products are detected colorimetrically by use of streptavidin-alkaline phosphatase conjugate. In a study of 24 subjects, the assay unequivocally discriminated among normal, carrier, and sickle cell genotypes.

A role for N-myristoylation in protein targeting: NADH-cytochrome b5 reductase requires myristic acid for association with outer mitochondrial but not ER membranes

N-myristoylation is a cotranslational modification involved in protein-protein interactions as well as in anchoring polypeptides to phospholipid bilayers; however, its role in targeting proteins to specific subcellular compartments has not been clearly defined. The mammalian myristoylated flavoenzyme NADH-cytochrome b5 reductase is integrated into ER and mitochondrial outer membranes via an anchor containing a stretch of 14 uncharged amino acids downstream to the NH2-terminal myristoylate glycine. Since previous studies suggested that the anchoring function could be adequately carried out by the 14 uncharged residues, we investigated a possible role for myristic acid in reductase targeting. The wild type (wt) and a nonmyristoylatable reductase mutant (gly2-->ala) were stably expressed in MDCK cells, and their localization was investigated by immunofluorescence, immuno-EM, and cell fractionation. By all three techniques, the wt protein localized to ER and mitochondria, while the nonmyristoylated mutant was found only on ER membranes. Pulse-chase experiments indicated that this altered steady state distribution was due to the mutant's inability to target to mitochondria, and not to its enhanced instability in that location. Both wt and mutant reductase were resistant to Na2CO3 extraction and partitioned into the detergent phase after treatment of a membrane fraction with Triton X-114, demonstrating that myristic acid is not required for tight anchoring of reductase to membranes. Our results indicate that myristoylated reductase localizes to ER and mitochondria by different mechanisms, and reveal a novel role for myristic acid in protein targeting.

Point mutations in Italian patients with classic, non-classic, and cryptic forms of steroid 21-hydroxylase deficiency

Seventy-three Italian patients affected by steroid 21-hydroxylase deficiency were studied by a PCR-allele-specific oligonucleotide protocol in order to evaluate the presence of eight known point mutations. The majority of chromosomes were found to carry point gene conversions normally present in the pseudogene. Within the classic form, the most common mutations were the splicing mutation A/C-655 to G in intron 2 (34.2%), the nonsense mutation C-1993 to T in exon 8 (10.8%), and the missense mutation T-999 to A in exon 4 (10%). Within the non-classic form, the missense mutation G-1683 to T was the most common (57.7%). Other mutations were either absent, such as the three clustered missense mutations T-1380, T-1383, T-1389 to A in exon 6, or very rare, like the 1761 + T in exon 7 and the C-2108 to T in exon 8. Family genotyping revealed the presence of ten asymptomatic parents carrying mutations in both chromosomes, thus identifying the gene defect in cryptic subjects. Interestingly, the same mutations were found in both symptomatic and asymptomatic forms.

Clinicopathological and genetic studies of two further Italian families with cerebral autosomal dominant arteriopathy

We report on two Italian families with an early-adult onset autosomal dominant disorder, characterized by leukoencephalopathy, migraine, psychiatric disturbances, stroke and dementia. These findings fulfill the diagnostic criteria for cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) syndrome. Moreover, to confirm the CADASIL gene location to 19p12, we performed a linkage analysis with four microsatellite markers. The results of the genetic study gave positive but not significant lod scores, indicating only weak evidence of a linkage with 19p12. In one autopsy case, we found extensive ischemic changes due to the selective involvement of the small muscular arteries of the cerebral white matter. The lesions consisted of a thickening of the media with deposition of granular eosinophilic material. Ultrastructural examination of the arterial walls showed graded damage to smooth muscle cells, mostly of the longitudinal layer, and an abnormal proliferation of basal lamina components. Immunocytochemical analysis showed strong reactivity using antibodies to collagen IV and smooth myosin proteins. The results suggest a primary involvement of the smooth muscle cells of small cerebral arteries, with a secondary alteration of basal lamina components and elastic tissue.

TBP binds the transcriptionally inactive TA5 sequence but the resulting complex is not efficiently recognised by TFIIB and TFIIA

The binding of TBP (TFIID) to the TATA box has been considered to direct promoter recognition and pre-initiation complex formation because it is the first event leading to basal transcription by RNA polymerase II. Here, we analyse the binding of yeast TBP to a consensus TATAAA box and two point mutations, TAAAAA (inactive) and TATATA (active). Despite the fact that the TAAAAA sequence does not support transcription in vitro, yeast TBP binds the three sequences showing, in this sense, only a limited sequence specificity. However, the TBP-TAAAAA complex cannot be recognised by other basal transcription factors, in particular by TFIIB. DNase I footprinting patterns of the TBP-TAAAAA complex are different from those observed in functional TBP-TATA box complexes, indicating that, most likely, it is a different spatial arrangement of the TBP-DNA complex that prevents formation of the TFIIB-TBP-TAAAAA complex, also seriously impairing entry of TFIIA to the complex. DNA deformability of the A/T-rich sequences appears to be an important determinant in the formation of a productive TBP-TATA complex. These results indicate that the transcriptional competence of A/T-rich sequences is determined not only by TBP binding, but also by the ability of other basal transcription factors to recognise the preformed TBP-DNA complexes.

Seven novel additional small mutations and a new alternative splicing in the human dystrophin gene detected by heteroduplex analysis and restricted RT-PCR heteroduplex analysis of illegitimate transcripts

Around 35% of Duchenne and Becker muscular dystrophy (DMD/BMD) patients cannot be identified by techniques which identify major DMD rearrangements in the dystrophin gene. In order to characterize the gene defect in these patients, we screened 40 exons of the dystrophin gene by heteroduplex analysis on genomic DNA in 50 affected Italian males. Using conventional heteroduplex analysis and a modified heteroduplex analysis on restricted RT-PCR products of illegitimate transcripts, restricted RT-PCR heteroduplex analysis, we were able to identify 7 novel small mutations and a new alternative splicing involving exon 25 of the dystrophin gene in peripheral blood lymphocytes and skeletal muscle transcripts.

Mutational analysis of muscle and brain specific promoter regions of dystrophin gene in DMD/BMD Italian patients by denaturing gradient gel electrophoresis (DGGE)

In order to characterize the nature of mutations occurring in non-deleted Duchenne (DMD) and Becker muscular dystrophy (BMD) affected males, a total of 40 unrelated Italian patients was studied for the presence of point mutations within the muscle-specific regulatory region of the dystrophin gene. We decided to investigate the dystrophin promoter sequences because nucleotide variations in these regions could impair the expression of the gene and be the underlying molecular defect in some forms of the disease. In four patients suffering from mental retardation, the brain promoter region was also studied. To screen for point mutations, we applied molecular analysis by parallel denaturing gradient gel electrophoresis (DGGE). No sequence alterations were found in either the muscle or the brain promoters, suggesting that mutations in these regions do not represent a common mechanism of mutation in DMD/BMD.

HLA-DQ screening for risk assessment of insulin dependent diabetes in northern Italy

Genetic markers may be used to improve the prediction of insulin-dependent diabetes mellitus (type 1) in individuals with islet autoantibodies. In order to develop a risk assessment strategy for the Lombardy region of northern Italy based on genetic and immunological markers, we analyzed HLA DQA1 and DQB1 alleles in 60 type 1 probands and their first-degree relatives and 65 unrelated control subjects from the same area using polymerase chain reaction (PCR) and oligonucleotide probes. The major risk haplotypes were DQA1 *0501-DQB1*0201 (39.1% of diabetic vs. 8.9% of non-diabetic haplotypes) and DQA1 *0301-DQB1*0302(20% of diabetic vs 7.1% of non-diabetic haplotypes). Stratified analysis showed DQA1*0102-DQB1*0502 also to be associated with type 1 susceptibility when found together with DQA1*0501-DQB1*0201 or DQA1*0301-DQB1*0302. One type 1 patient had the type 1-protective DQA1*0102-DQB1*0602 haplotype. Overall, 88% of patients and 20% of unrelated control subjects had either DQA1*0501-DQB1*0201 or DQA1*0301-DQB1*0302 in the absence of DQA1*0102-DQB1*0602. These data suggest that typing for markers identifying these three haplotypes in the Lombardy population will achieve a sensitivity of almost 90% and exclude 80% of children from subsequent islet autoantibody testing.

A nonsense mutation (Gln-673-Term) in exon 17 of the human dystrophin gene detected by heteroduplex analysis

Heteroduplex analysis was used to search for small mutations in a sample of 40 Italian DMD/BMB patients in whom large rearrangements were not found. A novel nonsense mutation in exon 17 of the dystrophin gene, consisting of a C to T transition, is described.

Amplification of 18 dystrophin gene exons in DMD/BMD patients: simultaneous resolution by capillary electrophoresis in sieving liquid polymers

Duchenne (DMD) and Becker (BMD) muscular dystrophies are the two most common myopathies described so far. In the late 80s, Chamberlain et al. and Beggs et al. proposed two PCR assays allowing detection of over 98% DMD/BMD deletions. Since each of them is based on specific co-amplification of 9 dystrophin gene exons, a method attempting simultaneous analysis of DMD/BMD should offer unambiguous resolution and identification of 18 DNA fragments ranging in size from approximately 100 to 500 bp. We have developed a novel capillary electrophoresis method that allows simultaneous analysis of the two PCR sets with full diagnostic value. It consists of (a) an ultrastable inner capillary coating based on a novel acrylamide monomer (N-acryloyl amino ethoxy ethanol); (b) a very low viscosity (barely 70 mPa) sieving polymer solution, formed by short-chain (average mol wt of 230,000, 55,000 Mn) polyacrylamides; (c) substitution of four fragments in the classical multiplex reaction (181 and 535 bp in the Beggs, 416 and 459 bp in the Chamberlain) with four new fragments of different lengths (170, 313, 154 and 88 bp, respectively). These new conditions allow resolution and unambiguous identification of all 18 PCR-amplified fragments in a single electrophoretic run. The set of 18 fragments comprises the following: 88, 113, 139, 154, 170, 196, 202, 238, 268, 271, 313, 331, 357, 360, 388, 410, 506 and 547 bp.

CAG triplet analysis in families with androgen insensitivity syndrome by capillary electrophoresis in polymer networks

The potential use of capillary zone electrophoresis in polymer networks (linear polymers above the entanglement threshold, added to the background electrolyte for sieving purposes) for analysis of DNA fragments amplified by a polymerase chain reaction, is shown. In typical runs, the capillary is filled with Tris-borate-EDTA buffer, at pH 8.3, containing 6% linear polyacrylamide as a dynamic sieving matrix. Such formulations allow replenishing the capillary with fresh sieving solution when resolution decays after prolonged use (typically > 30 injections per capillary are obtained). The DNA fragments are detected by their intrinsic absorbance at 254 nm. This system has been applied to the analysis of CAG triplet polymorphism in families carrying the androgen insensitivity syndrome. While easy separation is obtained for fragments 139 base pairs (bp) and 160 bp (in families carrying a difference of 7 CAG repeats) even more difficult cases (such as those of families exhibiting fragments of 136 and 139 bp, thus differing by only one CAG repeat) are resolved with precision and diagnostic value.

Failure to detect Glut4-Ile383 and IR-Gln1152 variants in NIDDM (non-insulin dependent diabetes mellitus) and control subjects in an Italian population

Insulin receptor (IR) and insulin-responsive glucose transporter (Glut4) represent two candidate genes involved in the development of non-insulin dependent diabetes mellitus (NIDDM); detection of molecular alterations in these genes might explain their possible contribution to NIDDM. Recently, mutations within the coding region of IR and Glut4 have identified: they include the Glut4Ile383 and IRGln1152 variants which were found at low frequencies in diabetic Caucasian populations. In this study Italian NIDDM patients and control subjects were analysed and mutated alleles were not found. Therefore in our population these variants appear to have little relevance to the genetic susceptibility to NIDDM.

Structural characterization of intrinsically curved AT-rich DNA sequences

AT-rich DNA sequences other than AnTm tracts (n + m > or = 4) are known to be intrinsically curved. The AATAT-element constitutes one known example of these sequences. In this paper, the elucidation of the structural basis of the curvature induced by this sequence element was addressed. As judged by the patterns of cleavage by the hydroxyl radical and DNase I, the AATAT sequence shows a narrow minor groove. Furthermore, the 5' adenine residue of the AA dinucleotide contained within the sequence is hyperreactive to diethylpyrocarbonate. Similar structural properties are shown by several sequences inducing intrinsic DNA curvature, such as an A5-tract or the closely related ATAAT, AATATA and TAATAT sequences, which are also shown here to induce curvature. On the other hand, other related sequences, such as TATAA and ATATA, that do not induce curvature, show different structural characteristics.

Capillary zone electrophoresis in polymer networks of polymerase chain reaction-amplified oligonucleotides: the case of congenital adrenal hyperplasia

The use of capillary zone electrophoresis (CZE) in polymer networks for the analysis of an 8 bp (base pair) deletion in congenital adrenal hyperplasia was investigated. Separations were performed in Tris-borate-EDTA buffer (pH 8.3) containing 6% liquid linear polyacrylamide as a sieving dynamic matrix and 10 microM ethidium bromide for improving DNA fragment separation. Easy analysis and detection of the 127 and 135 bp amplified fragments was accomplished. The capillary column can be used for > 50 analyses before degradation and loss of resolution. The results are comparable to those obtained by gel-slab zone electrophoresis in a 12%T, 4%C polyacrylamide matrix. The sensitivity, by simple UV absorption at 254 nm, is similar to that obtained in gel slabs by dye intercalation staining.

Substitution of Leu for Pro-193 in the insulin receptor in a patient with a genetic form of severe insulin resistance

Mutations have been identified in the insulin receptor (IR) gene in patients who are insensitive to insulin action. We studied an extremely insulin resistant patient whose insulin binding to Epstein-Barr virus (EBV) transformed lymphocytes was severely reduced. Transmembrane signalling, evaluated as insulin receptor autophosphorylation, was normal. The patient's IR was immunoprecipitated normally by AbP6, a polyclonal antibody directed to the beta subunit. However, there was an approximately 50% decrease in the affinity of IR immunoprecipitation by a monoclonal antibody (MA-10) directed against the alpha subunit. These observations suggested that there were likely to be a mutation in the patient's insulin receptor that caused misfolding of the IR alpha subunit. Analysis of gene structure by Southern blotting experiments did not reveal any major deletion in the IR gene of the proband. Northern blot analysis showed a normal level of expression of IR gene. We applied denaturing gradient gel electrophoresis (DGGE) as well as direct sequence analysis to study the 22 exons of IR gene amplified by polymerase chain reaction (PCR) using the proband's genomic DNA as a template. We identified a new missense mutation substituting leucine (CTG) for proline (CCG) in homozygous state at codon 193 in exon 3. Both parents are heterozygous for the Leu193 mutation. The Leu193 mutation was not detected in any of 75 normal subjects (150 chromosomes), indicating that it is not a common sequence variant of the insulin receptor. In addition, during the course of screening the patient's DNA with perpendicular DGGE, we identified two previously unreported silent substitutions in exon 9.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular characterization of 21-hydroxylase deficiency in 70 Italian families

Seventy Italian families affected by 21-hydroxylase deficiency were studied in order to evaluate the distribution of mutations. The coding P450c21B gene, the highly homologous P450c21A pseudogene and the linked C4A, C4B and DRB genes, mapping within the major histocompatibility complex region, were studied by multiple restriction analysis and in vitro amplification. In the affected individuals, 21.4% of the chromosomes were found to carry either gene deletions or large and small gene conversions. Our findings, consistent with previous reports in other ethnic groups, provide further evidence for the genetic heterogeneity of the disease.

A single mRNA, transcribed from an alternative, erythroid-specific, promoter, codes for two non-myristylated forms of NADH-cytochrome b5 reductase

Two forms of NADH-cytochrome b5 reductase are produced from one gene: a myristylated membrane-bound enzyme, expressed in all tissues, and a soluble, erythrocyte-specific, isoform. The two forms are identical in a large cytoplasmic domain (Mr approximately 30,000) and differ at the NH2-terminus, which, in the membrane form, is responsible for binding to the bilayer, and which contains the myristylation consensus sequence and an additional 14 uncharged amino acids. To investigate how the two differently targeted forms of the reductase are produced, we cloned a reductase transcript from reticulocytes, and studied its relationship to the previously cloned liver cDNA. The reticulocyte transcript differs from the liver transcript in the 5' non-coding portion and at the beginning of the coding portion, where the seven codons specifying the myristoylation consensus are replaced by a reticulocyte-specific sequence which codes for 13 non-charged amino acids. Analysis of genomic reductase clones indicated that the ubiquitous transcript is generated from an upstream "housekeeping" type promoter, while the reticulocyte transcript originates from a downstream, erythroid-specific, promoter. In vitro translation of the reticulocyte-specific mRNA generated two products: a minor one originating from the first AUG, and a major one starting from a downstream AUG, as indicated by mutational analysis. Both the AUGs used as initiation codons were in an unfavorable sequence context. The major, lower relative molecular mass product behaved as a soluble protein, while the NH2-terminally extended minor product interacted with microsomes in vitro. The generation of soluble reductase from a downstream AUG was confirmed in vivo, in Xenopus oocytes. Thus, differently localized products, with respect both to tissues and to subcellular compartments, are generated from the same gene by a combination of transcriptional and translational mechanisms.

A genetic linkage study of schizophrenia to chromosome 5 markers in a northern Italian population

Some recent findings report that the area 5q11.2-13.3 of chromosome 5 segregates with schizophrenia in an uncle-nephew pair (Bassett et al 1988). However, linkage studies between chromosome 5 markers loci and schizophrenia lead to different results: Sherrington et al (1988) found a positive linkage, whereas other groups of researchers found evidence against linkage (Kennedy et al 1988; St. Clair et al 1989; Detera-Wadleigh et al 1989; McGuffin et al 1990; Aschauer et al 1990; Crowe et al 1991). We have studied five Italian pedigrees segregating schizophrenia using a map of four markers for the chromosomal region 5q11.2-13.3. Linkage analyses revealed negative lod scores, and thus no evidence for linkage was obtained in our Italian families.

Identification of sequence elements contributing to the intrinsic curvature of the mouse satellite DNA repeat

In this paper, the contribution of different sequence elements to the intrisic curvature of the mouse satellite DNA repeat was investigated. This DNA fragment contains nineteen groups of three or more consecutive adenines which are only poorly phased with respect to the helical repeat. The mouse satellite DNA repeat shows a sinusoidal pattern of cleavage by the hydroxyl radical; the waves of reactivity are phased with respect to the A-tracts. Some interesting observations arise from a detailed analysis of these cleavage patterns: a) the maxima of hydroxyl radical cleavage are more periodically spaced along the DNA sequence than the A-tracts themselves. As a consequence, the position of each maximum with respect to the A-tract is variable; b) the sequence 5' TGGAATATG/AA 3' shows a sinusoidal pattern of hydroxyl radical cleavage. This sequence shows a retarded migration in polyacrylamide gels indicating that it is actually intrinsically curved. These results are discussed in view of the current models for DNA curvature.

Satellite DNAs contain sequences that induced curvature

The repeating units of mouse, rat, and alpha-monkey satellites have been cloned. All three show properties that are characteristic of curved DNA: (i) their migration in polyacrylamide gels is slower than predicted from their sequences, and (ii) they appear as curved molecules when visualized by electron microscopy. All three satellite repeats contain runs of d(A.T)n greater than or equal to 3 residues that are likely to be responsible for their curvature. From analysis of 20 different satellite DNA sequences, we conclude that, in satellite DNA, adenine residues show a high tendency to cluster in groups of three or more.

Sister chromatid exchanges in first-trimester chorionic villi after in vivo and in vitro exposure to diagnostic ultrasound

A study was done to evaluate the effects of diagnostic ultrasound on sister chromatid exchange (SCE) in first-trimester chorionic villi under controlled technical conditions. Chromosome analysis was performed by the direct method using spontaneous mitoses from the cytotrophoblast layer, and SCE visualization was accomplished by a 72 h treatment with 5-bromodeoxyuridine (BrdU) at a concentration of 10 micrograms/ml. The slides were stained with acridine orange. Immediately before first-trimester chorionic villus sampling, a group of ten pregnant women was exposed to diagnostic ultrasound for 20 min (in vivo exposure). This group of patients was compared with a control group who were not exposed. A mean value of SCE/cell frequency of 4.2 +/- 0.2 was found in the exposed pregnancies, while a value of 3.7 +/- 0.2 was observed in the control group. After in vitro exposure of chorionic villi obtained from elective abortions, the frequency of SCE/cell did not differ significantly among samples with different exposures (1, 2, and 3 h) and controls. The positive control (mitomycin C) yielded a significant increase in SCE frequency.

Cloning and nucleotide sequence of the isoamylase gene from a strain of Pseudomonas sp

A strain of Pseudomonas sp., SMP1, isolated from a soil sample collected in the Monterotondo area (Rome), secreted isoamylase activity into the culture medium. The enzyme was purified and optimal reaction and stability conditions were determined by varying pH and temperature. The chemico-physical properties of the enzyme were similar to those of the isoamylase purified in Japan more than 20 years ago from 'Pseudomonas amyloderamosa' strain SB15. A genomic library of SMP1 was prepared in Escherichia coli using pUC12 as vector. Two isoamylase-producing colonies were identified out of 6300 screened. The hybrid plasmids isolated from the two clones showed common restriction patterns. The chromosomal portion of one of these plasmids (pSM257) was completely sequenced. Comparison between the deduced amino acid sequence of the isoamylase and the published sequences of other amylolytic enzymes showed the presence of conserved domains.

Two transcripts encode rat cytochrome b5 reductase

A cDNA expression library in lambda gt11 was screened with affinity-purified polyclonal anti-rat cytochrome b5 reductase antibodies. One positive clone out of 450,000 clones was isolated and found to be incomplete. This clone was used to rescreen the library, and a second, overlapping clone that contained the entire coding sequence was isolated. RNA gel blots showed that the two overlapping clones contained approximately 90% of the reductase mRNA sequence. Sequencing data showed (i) that rat reductase has a 93% sequence similarity with bovine and human reductase and (ii) that reductase is not synthesized as a high molecular weight precursor. Results of Southern blot analysis were consistent with the hypothesis that a single gene codes for the soluble and membrane-bound (microsomal and mitochondrial) forms of the reductase, present in erythrocytes and liver, respectively. The cloned cDNA was used to study reductase transcripts in liver and reticulocytes. Two antisense RNA probes that together covered the entire coding region and part of the noncoding region of reductase mRNA were used in RNase A protection experiments. These probes detected only one transcript in liver, suggesting that endoplasmic reticulum and mitochondrial reductase are translated from the same mRNA. In contrast, two transcripts were detected in reticulocytes, one of which mismatched the liver probe approximately 30 nucleotides downstream from the initiation codon. Since the soluble and membrane form of the reductase are known to differ at the N terminus, we suggest that this second transcript encodes soluble reductase.

Computer-assisted mathematical analysis of sigmoid biological events

A program in BASIC is described which allows accurate quantification of some numerical parameters that can be objectively correlated to biological indexes in sigmoid biological events. Attention was focused on the polymerization process of actin (a muscle protein with a mol. wt of 42,000 daltons) studied as the variation in the OD360 index with time. The experimental points, if plotted, can be well approximated by a rational function of the type delta OD360 = f(t), which passes through the origin and can be represented graphically by a sigmoid curve. The program was very helpful in comparing the experimental curves and in analysing significant parameters, such as maximum velocity and asymptote, that characterize these curves and whose interpretation would otherwise be purely subjective.