High-resolution Gel Electrophoresis Research Articles

Identification of Amyloidogenic Light Chains Requires the Combination of Serum-Free Light Chain Assay with Immunofixation of Serum and Urine

The diagnosis of systemic immunoglobulin light-chain (AL) amyloidosis requires demonstration of amyloid deposits in a tissue biopsy and amyloidogenic monoclonal light chains. The optimal strategy to identify the amyloidogenic clone has not been established. We prospectively assessed the diagnostic sensitivity of the serum free light chain (FLC) kappa/lambda ratio, a commercial serum and urine agarose gel electrophoresis immunofixation (IFE), and the high-resolution agarose gel electrophoresis immunofixation (HR-IFE) developed at our referral center in patients with AL amyloidosis, in whom the amyloidogenic light chain was unequivocally identified in the amyloid deposits. The amyloidogenic light chain was identified in 121 consecutive patients with AL amyloidosis by immunoelectron microscopy analysis of abdominal fat aspirates and/or organ biopsies. We characterized the monoclonal light chain by using IFE and HR-IFE in serum and urine and the FLC kappa/lambda ratio in serum. We then compared the diagnostic sensitivities of the 3 assays. The HR-IFE of serum and urine identified the amyloidogenic light chain in all 115 patients with a monoclonal gammopathy. Six patients with a biclonal gammopathy were omitted from the statistical analysis. The diagnostic sensitivity of commercial serum and urine IFE was greater than that of the FLC kappa/lambda ratio (96% vs 76%). The combination of serum IFE and the FLC assay detected the amyloidogenic light chain in 96% of patients. The combination of IFE of both serum and urine with the FLC kappa/lambda ratio had a 100% sensitivity. The identification of amyloidogenic light chains cannot rely on a single test and requires the combination of a commercially available FLC assay with immunofixation of both serum and urine.

Cooperative alkylation of double-strand human telomere repeat sequences by PI polyamides with 11-base-pair recognition based on a heterotrimeric design

We designed and synthesized alkylating conjugates 5– 7 and their partner N-methylpyrrole- N-methylimidazole (PI) polyamides 8, 9. The DNA alkylating activities of conjugates 5– 7 were evaluated by high-resolution denaturing polyacrylamide gel electrophoresis with a 219 base pair (bp) DNA fragment containing the human telomere repeat sequence. Conjugate 5 efficiently alkylated the sequence, 5′-GGTTAGGGTT A-3′, in the presence of partner PI polyamide 8 or distamycin A (Dist). In contrast, the heterodimer system of 5 with 9 showed very weak alkylating activity. Accordingly, this heterotrimeric system of 5 with two short partners is an expedient way to attain improved precision and extension of the recognition of DNA sequences.

Visualization of Bacteriophage T3 Capsids with DNA Incompletely Packaged In Vivo

The tightly packaged double-stranded DNA (dsDNA) genome in the mature particles of many tailed bacteriophages has been shown to form multiple concentric rings when reconstructed from cryo-electron micrographs. However, recent single-particle DNA packaging force measurements have suggested that incompletely packaged DNA (ipDNA) is less ordered when it is shorter than ∼25% of the full genome length. The study presented here initially achieves both the isolation and the ipDNA length-based fractionation of ipDNA-containing T3 phage capsids (ipDNA-capsids) produced by DNA packaging in vivo; some ipDNA has quantized lengths, as judged by high-resolution gel electrophoresis of expelled DNA. This is the first isolation of such particles among the tailed dsDNA bacteriophages. The ipDNA-capsids are a minor component (containing ∼10−4 of packaged DNA in all particles) and are initially detected by nondenaturing gel electrophoresis after partial purification by buoyant density centrifugation. The primary contaminants are aggregates of phage particles and empty capsids. This study then investigates ipDNA conformations by the first cryo-electron microscopy of ipDNA-capsids produced in vivo. The 3-D structures of DNA-free capsids, ipDNA-capsids with various lengths of ipDNA, and mature bacteriophage are reconstructed, which reveals the typical T=7l icosahedral shell of many tailed dsDNA bacteriophages. Though the icosahedral shell structures of these capsids are indistinguishable at the current resolution for the protein shell (∼15 Å), the conformations of the DNA inside the shell are drastically different. T3 ipDNA-capsids with 10.6 kb or shorter dsDNA (<28% of total genome) have an ipDNA conformation indistinguishable from random. However, T3 ipDNA-capsids with 22 kb DNA (58% of total genome) form a single DNA ring next to the inner surface of the capsid shell. In contrast, dsDNA fully packaged (38.2 kb) in mature T3 phage particles forms multiple concentric rings such as those seen in other tailed dsDNA bacteriophages. The distance between the icosahedral shell and the outermost DNA ring decreases in the mature, fully packaged phage structure. These results suggest that, in the early stage of DNA packaging, the dsDNA genome is randomly distributed inside the capsid, not preferentially packaged against the inner surface of the capsid shell, and that the multiple concentric dsDNA rings seen later are the results of pressure-driven close-packing.

Sequence-specific alkylation of DNA by pyrrole-imiclazole polyamides through cooperative interaction

We designed and synthesized an alkylating N-methylpyrrole (Py) -N-methylimidazole (Im) polyamide and l-(chloromethyl)-5-hydroxy-l,2-dihydro-3H benz[e]indole (seco-CBI) conjugate 1. DNA alkylating activities of conjugate 1 were evaluated by high-resolution denaturing polyacrylamide gel electrophoresis with DNA fragment containing human telomere repeat sequence. These results revealed that simultaneous treatment of the DNA fragment with conjugate 1 and Distamycin A (Dist) alkylate at the 5(')-GGTTAGGGTTA-3' sequence effectively due to cooperative interaction. Moreover, this combination has achieved 11-base-pair (bp) recognition. Thus, it is suggested that the utilization of one alkylating agent possessing long Py-Im polyamide moiety and short Py-Im polyamide partner can be an expedient way to attain the extension and precision of the recognition of DNA sequence.

Late-Stage Polyribitol Phosphate Wall Teichoic Acid Biosynthesis in Staphylococcus aureus

Wall teichoic acids are cell wall polymers that maintain the integrity of the cellular envelope and contribute to the virulence of Staphylococcus aureus. Despite the central role of wall teichoic acid in S. aureus virulence, details concerning the biosynthetic pathway of the predominant wall teichoic acid polymer are lacking, and workers have relied on a presumed similarity to the putative polyribitol phosphate wall teichoic acid pathway in Bacillus subtilis. Using high-resolution polyacrylamide gel electrophoresis for analysis of wall teichoic acid extracted from gene deletion mutants, a revised assembly pathway for the late-stage ribitol phosphate-utilizing enzymes is proposed. Complementation studies show that a putative ribitol phosphate polymerase, TarL, catalyzes both the addition of the priming ribitol phosphate onto the linkage unit and the subsequent polymerization of the polyribitol chain. It is known that the putative ribitol primase, TarK, is also a bifunctional enzyme that catalyzes both ribitol phosphate priming and polymerization. TarK directs the synthesis of a second, electrophoretically distinct polyribitol-containing teichoic acid that we designate K-WTA. The biosynthesis of K-WTA in S. aureus strain NCTC8325 is repressed by the accessory gene regulator (agr) system. The demonstration of regulated wall teichoic acid biosynthesis has implications for cell envelope remodeling in relation to S. aureus adhesion and pathogenesis.

DNA cleavage and binding selectivity of a heterodinuclear Pt–Cu(3-Clip-Phen) complex

The synthesis and nuclease activity of a new bifunctional heterodinuclear platinum–copper complex are reported. The design of this ditopic coordination compound is based on the specific mode of action of each component, namely, cisplatin and Cu(3-Clip-Phen), where 3-Clip-Phen is 1-(1,10-phenanthrolin-3-yloxy)-3-(1,10-phenanthrolin-8-yloxy)propan-2-amine. Cisplatin is not only able to direct the Cu(3-Clip-Phen) part to the GG or AG site, but also acts as a kinetically inert DNA anchor. The nuclease activity of this complex has been investigated on supercoiled DNA. The dinuclear compound is not only more active than Cu(3-Clip-Phen), but is also capable of inducing direct double-strand breaks. The sequence selectivity of the mononuclear platinum complex has been investigated by primer extension experiments, which reveal that its interaction with DNA occurs at the same sites as for cisplatin. The Taq polymerase recognizes the resulting DNA damage as different from that for unmodified cisplatin. The sequence-selective cleavage has been investigated by high-resolution gel electrophoresis on a 36-bp DNA fragment. Sequence-selective cleavages are observed in the close proximity of the platinum sites for the strand exhibiting the preferential platinum binding sites. The platinum moiety also coordinates to the other DNA strand, most likely leading only to mono guanine or adenine adducts.Electronic supplementary materialThe online version of this article (doi:10.1007/s00775-008-0346-y) contains supplementary material, which is available to authorized users.

Sequence‐Specific Alkylation by Y‐Shaped and Tandem Hairpin Pyrrole–Imidazole Polyamides

To extend the target DNA sequence length of the hairpin pyrrole-imidazole (Py-Im) polyamide 1, we designed and synthesized Y-shaped and tandem hairpin Py-Im polyamides 2 and 3, which possess 1-(chloromethyl)-5-hydroxy-1,2-dihydro-3H-benz[e]indole (seco-CBI) as DNA-alkylating moieties. High-resolution denaturing polyacrylamide gel electrophoresis by using 5'-Texas-Red-labeled 465 base pair (bp) DNA fragments revealed that conjugates 2 and 3 alkylated the adenine of the target DNA sequences at nanomolar concentrations. Conjugate 2 alkylated adenine N3 at the 3' end of two 8 bp match sequences, 5'-AATAACCA-3' (site A) and 5'-AAATTCCA-3' (site C), while conjugate 3 recognized one 10 bp match sequence, 5'-AGAATAACCA-3' (site A) in the 465 bp DNA fragments. These results demonstrate that seco-CBI conjugates of Y-shaped and tandem hairpin polyamides have extended their target alkylation sequences.

Requirement of β-alanine components in sequence-specific DNA alkylation by pyrrole–imidazole conjugates with seven-base pair recognition

To investigate the effect of incorporation of β-alanine in alkylating N-methylpyrrole (Py)– N-methylimidazole (Im) polyamide, seco-CBI conjugates 2– 8 were synthesized by an Fmoc solid-phase method and subsequent coupling with an alkylating moiety. DNA-alkylating activities of conjugates 2– 8 were evaluated by high-resolution denaturing gel electrophoresis with 202-base pair (bp) DNA fragments. Alkylation by conjugates 2 and 3, which have antiparallel pairings of β-alanine (β) opposite β (β/β) and Py/β, occurred mainly at the adenine (A) of the matching sequences, 5′-AGCTCC A-3′ (site 1) and 5′-AGCACC A-3′ (site 3). However, conjugate 4, with β/Py, did not show any DNA-alkylating activities. Similarly, conjugate 5, which possessed a Py/Py pair, weakly alkylated the matching sites at micromolar concentrations. Conjugates 6 and 7, which possessed β/β and Py/β pairs, respectively, alkylated at the A of the matching sequences, 5′-ACTACC A-3′ (site 2) and 5′-ACAACC A-3′ (site 4). In contrast, conjugated 8, with a Py/Py pair, showed lower activity and less alkylated DNA at sites 2 and 4 with mismatched alkylation at site 1 at a higher concentration than that of 6 and 7. These results demonstrate that incorporation of β-alanine is required for the sequence-specific alkylation by seco-CBI Py–Im conjugates with a seven-base pair sequence.

Sequence-specific alkylation by a tandem motif of pyrrole-imidazole CBI conjugate

We have developed various types of sequence-specific alkylating agents by conjugation of Py-Im polyamides and alkylating moieties 1-(chloromethyl)-5-hydroxy-1,2-dihydro-3H-benz[e]indole (seco-CBI) with an indole linker. In order to extend the length of target DNA sequence of the hairpin Py-Im polyamide 1, we designed and synthesized Y-shaped and tandem hairpin Py-Im polyamides 2 and 3. High-resolution denaturing polyacrylamide gel electrophoresis using 5'-Texas Red-labeled 465-bp DNA fragments revealed that conjugates 2 and 3 alkylated the adenine of target DNA sequences at nanomolar concentrations. Furthermore, evaluation in human cancer cell lines revealed that these Py-Im polyamides 2 and 3 have strong cytotoxicities.

Methods for mapping of interaction networks involving membrane proteins

Nearly one-third of all genes in various organisms encode membrane-associated proteins that participate in numerous protein-protein interactions important to the processes of life. However, membrane protein interactions pose significant challenges due to the need to solubilize membranes without disrupting protein–protein interactions. Traditionally, analysis of isolated protein complexes by high-resolution 2D gel electrophoresis has been the main method used to obtain an overall picture of proteome constituents and interactions. However, this method is time consuming, labor intensive, detects only abundant proteins and is limited with respect to the coverage required to elucidate large interaction networks. In this review, we discuss the application of various methods to elucidate interactions involving membrane proteins. These techniques include methods for the direct isolation of single complexes or interactors as well as methods for characterization of entire subcellular and cellular interactomes.

Association of Pro12Ala polymorphism in the peroxisome proliferator–activated receptor γ2 gene with small dense low-density lipoprotein in the general population

The Pro12Ala polymorphism of the peroxisome proliferator–activated receptor γ2 (PPAR γ2) gene has been reported to predict a lower risk for developing type 2 diabetes mellitus. However, its effect on the lipid profile has been disputable. Among low-density lipoproteins, small dense low-density lipoprotein (sdLDL) particles have been linked to a greater risk for coronary artery disease. The purpose of this study was to investigate the genetic effect of the Pro12Ala polymorphism in the PPAR γ2 gene on the presence of sdLDL in the general Japanese population. In 379 subjects (aged 54 ± 13 years), body mass index, percentage of body fat, blood pressure, and biochemical profiles were measured. Pro12Ala polymorphism was genotyped by polymerase chain reaction–restriction fragment length polymorphism. The area of sdLDL subfractions (sdLDL4-7) was analyzed by high-resolution polyacrylamide gel electrophoresis. The frequency of the Ala12 allele in PPAR γ2 was 0.04. There was no difference in total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol levels between genotypes. However, subjects with the X/Ala genotype (Pro/Ala + Ala/Ala) had significantly higher serum triglyceride levels ( P = .001) and a larger area of sdLDL4-7 ( P = .002) than those with the Pro/Pro genotype. Multiple regression analysis revealed that the Ala12 allele was a significant variable contributing to the variance in the increased area of sdLDL4-7 ( P = .040). In conclusion, the Pro12Ala polymorphism in the PPAR γ2 gene was positively associated with an enlarged area of sdLDL4-7. This polymorphism may play a role in the genetic predisposition to increases in sdLDL4-7.

Oxidation of Guanine in Double-Stranded DNA by [Ru(bpy)2dppz]Cl2 in Cationic Reverse Micelles

DNA oxidation has been investigated in the medium of cationic reverse micelles (RMs). The oxidative chemistry is photochemically initiated using the DNA intercalator bis(bipyridine)dipyridophenazine ruthenium(II) chloride ([Ru(bpy)2dppz]Cl2) bound to duplex DNA in the RMs. High-resolution polyacrylamide gel electrophoresis (PAGE) is used to reveal and quantify guanine (G) oxidation products, including 8-oxo-7,8-dihydroguanine (8OG). In buffer solution, the addition of the oxidative quenchers potassium ferricyanide or pentaamminechlorocobalt(III) dichloride leads to an increase in the amount of piperidine-labile G oxidation products generated via one-electron oxidation. In RMs, however, the yield of oxidatively generated damage is attenuated. With or without ferricyanide quencher in the RMs, the yield of oxidatively generated products is approximately the same. Inclusion of the cationic quencher [CoCl(NH3)5]2+ in the RMs increases the amount of oxidation products generated but not to the extent that it does in buffer solution. Under anaerobic conditions, all of the samples in RMs, with or without added oxidative quenchers, show decreased levels of piperidine-labile oxidation products, suggesting that the primary oxidant in RMs is singlet oxygen. G oxidation is enhanced in D2O and deuterated heptane and is diminished in the presence of sodium azide in RMs, also supporting 1O2 as the main G oxidant in RMs. Isotopic labeling experiments show that the oxygen atom in 8OG produced in RMs is not from water. The observed change in the G oxidation mechanism from a one-electron process in buffer to mostly 1O2 in RMs illustrates the importance of both DNA structure and DNA environment on the chemistry of G oxidation.

Photosensitized Oxidative DNA Damage: From Hole Injection to Chemical Product Formation and Strand Cleavage

Oxidatively generated damage to DNA induced by a pyrenyl photosensitizer residue (Py) covalently attached to a guanine base in the DNA sequence context 5'-d(CAT[G1Py]CG2TCCTAC) in aerated solutions was monitored from the initial one-electron transfer, or hole injection step, to the formation of chemical end-products monitored by HPLC, mass spectrometry, and high-resolution gel electrophoresis. Hole injection into the DNA was initiated by two-photon excitation of the Py residue with 355 nm laser pulses, thus producing the radical cation Py*+ and hydrated electrons; the latter are trapped by O2, thus forming the superoxide anion O2*-. The decay of the Py*+ radical is correlated with the appearance of the G*+/G(-H)* radical on microsecond time scales, and O2*- combines with guanine radicals at G1 to form alkali-labile 2,5-diamino-4H-imidazolone lesions (Iz1Py). Product formation in the modified strand is smaller by a factor of 2.4 in double-stranded than in single-stranded DNA. In double-stranded DNA, hot piperidine-mediated cleavage at G2 occurs only after G1Py, an efficient hole trap, is oxidized thus generating tandem lesions. An upper limit of hole hopping rates, khh < 5 x 103 s-1 from G1*+-Py to G2 can be estimated from the known rates of the combination reaction of the G(-H)* and O2*- radicals. The formation of Iz products in the unmodified complementary strand compared to the modified strand in the duplex is approximately 10 times smaller. The formation of tandem lesions is observed even at low levels of irradiation corresponding to "single-hit" conditions when less than approximately 10% of the oligonucleotide strands are damaged. A plausible mechanism for this observation is discussed.

Inline Injection Microdevice for Attomole-Scale Sanger DNA Sequencing

A new affinity-capture-based inline purification, concentration, and injection method is developed for microchip capillary electrophoresis (CE) and used to perform efficient attomole-scale Sanger DNA sequencing separations. The microdevice comprises three axial domains for nanoliter-scale sequencing sample containment, sample plug formation, and high-resolution capillary gel electrophoresis. Purified and concentrated inline sample plugs are formed by electrophoretically driving Sanger sequencing extension fragments into an affinity-capture polymer network positioned within a CE separation channel. Extension fragments selectively hybridize and concentrate at the polymer interface while residual primer, nucleotides, and salts electrophorese out of the system. The plug is thermally released and injected into the CE channel by direct application of the separation voltage. To evaluate this system, 30 nL of sequencing sample prepared from 100 amol (60 million molecules) of human mitochondrial hypervariable region II amplicon was introduced into the microchip, purified, concentrated, and injected, generating a read length of 365 bases with 99% accuracy. This efficient inline injection system obviates the need for the excess sample that is required by cross-injection techniques, thereby enabling Sanger sequencing and other high-performance genetic analysis using DNA quantities approaching theoretical detection limits.

DNA Alkylation by Pyrrole−Imidazole seco-CBI Conjugates with an Indole Linker: Sequence-Specific DNA Alkylation with 10-Base-Pair Recognition through Heterodimer Formation

The sequence-specific DNA alkylation by conjugates 4 and 5, which consist of N-methylpyrrole (Py)-N-methylimidazole (Im) polyamides and 1-(chloromethyl)-5-hydroxy-1,2-dihydro-3H-benz[e]indole (seco-CBI) linked with an indole linker, was investigated in the absence or presence of partner Py-Im polyamide 6. High-resolution denaturing polyacrylamide gel electrophoresis revealed that conjugate 4 alkylates DNA at the sequences 5'-(A/T)GCCTA-3' through hairpin formation, and alkylates 5'-GGAAAGAAAA-3' through an extended binding mode. However, in the presence of partner Py-Im polyamide 6, conjugate 4 alkylates DNA at a completely different sequence, 5'-AGGTTGTCCA-3'. Alkylation of 4 in the presence of 6 was effectively inhibited by a competitor 7. Surface plasmon resonance (SPR) results indicated that conjugate 4 does not bind to 5'-AGGTTGTCCA-3', whereas 6 binds tightly to this sequence. The results suggest that alkylation proceeds through heterodimer formation, indicating that this is a general way to expand the recognition sequence for DNA alkylation by Py-Im seco-CBI conjugates.

High Levels of Soluble P-Selectin Are Associated with the Risk of Venous Thromboembolism and the P-Selectin Thr715 Variant.

The cell adhesion molecule P-selectin, which is found in the alpha granula of platelets and in Weibel-Palade bodies of endothelial cells, has been shown to play an important role in the pathophysiology of thrombosis. However, the meaning of soluble P-selectin (sP-selectin) in venous thromboembolism (VTE) is still uncertain because clinical data are limited. The purpose of this study was to investigate whether sP-selectin is associated with the risk for VTE and to elucidate the association of sP-selectin and the P-selectin gene variation (SELP) Thr715Pro in high risk patients with recurrent VTE. We recruited cases and control individuals between January 2005 and November 2005 for an analysis of sP-selectin plasma levels and the SELP Thr715Pro. Patients with a history of objectively confirmed recurrent VTE and at least one event of an unprovoked deep venous thrombosis or pulmonary embolism were enrolled. Plasma was obtained at least 3 months after the most recent event of VTE. Age and sex-matched healthy individuals served as controls. sP-selectin levels were measured with a high sensitive ELISA. The variant for the P-selectin gene was determined by a mutagenically separated PCR followed by high resolution gel-electrophoresis. Hundred-sixteen patients (53 female / 63 male; mean age +/−SD: 56 +/−12 yrs) and 129 controls (66 female / 63 male; mean age +/−SD: 53 +/−11 yrs) were enrolled. Mean concentration (+/−SD) of sP-selectin (ng/mL) was significantly higher in patients than in controls (47.28 +/−15.00 vs. 36.77 +/−11.00, p<0.001). The unadjusted odds ratio (OR) of elevated sP-selectin (cut-off level 55.10 ng/mL representing the 95th percentile of the controls) was 8.5 (95% confidence interval (CI): [3.7–23.3], p<0.001) and increased after adjustment for factor V Leiden, prothrombin G20210A variant, elevated factor VIII level, hyperhomocysteinemia and BMI (OR=11.1, 95% CI [4.3–33.0], p<0.001). Carriers of the SELP Pro715 were more prevalent among controls than patients (21.7% versus 14.7%), however, the difference was statistically not significant (p=0.19). The subgroup of carriers of the SELP Pro715 (n=45) had significantly lower sP-selectin levels than non-carriers (31.31+/−7.94 vs. 44.10+/−14.08, p<0.001). In conclusion, our study shows a highly significant association between elevated sP-selectin levels and VTE. Furthermore, sP-selectin levels correlate with genotype status and individuals carrying the SELP Pro715 have lower levels of sP-selectin.

Molecular design of DNA alkylating pyrrole-imidazole polyamides with longer recognition sequence

The sequence-specificity, and DNA alkylating activity of the conjugate 1, which consists of N-methylpyrrole (Py)-N-methylimidazole (Im) polyamides, 1-(chloromethyl)-5-hydroxy-1,2-dihydro-3H-benz[e]indole (seco-CBI) with indole linker, were investigated in the absence or presence of partner Py-Im polyamide 2. High-resolution denaturing polyacrylamide gel electrophoresis showed that the specificity of DNA alkylation by 1 modulated in the presence of partner 2. We found that sequence-specific DNA alkylation by 1 and 2 with 10 base pair (bp) match recognition sequence through heterodimer formation. This result indicates one possibility of DNA alkylation with longer recognition sequence by different two molecules.

The biological impact of sequence-specific DNA alkylation by pyrrole-imidazole polyamides

We have developed a series of novel DNA alkylating polyamides possessing indole linkers. Investigations using high-resolution gel electrophoresis revealed that the indole linked Py-Im polyamide alkylated at A of a targeted nine base pair matching sequence. Evaluation in human cancer cell lines revealed that the indole linked Py-Im polyamides have strong cytotoxicities. Furthermore, we showed that alkylation of the template strand of the coding region by these polyamides causes effective gene silencing.

Classification of sporadic Creutzfeldt-Jakob disease revisited

The sporadic form of Creutzfeldt-Jakob disease (sCJD) has been classified on the basis of the molecular mass of the protease-resistant scrapie prion protein (PrP(Sc)), which can be type 1 or type 2, and the genotype at the methionine (M)/valine (V) polymorphic codon 129, which can be MM, MV or VV. In one classification proposed by Parchi et al., [Parchi P, Giese A, Capellari S, Brown P, Schulz-Schaeffer W, Windl O, Zerr I , Budka H , Kopp N , Piccardo P , Poser S , Rojiani A , Streichemberger N , Julien J , Vital C , Ghetti B , Gambetti P , Kretzschmar H . Classification of sporadic Creutzfeldt-Jakob disease based on molecular and phenotypic analysis of 300 subjects. Ann Neurol 1999; 46: 224-33.] the most common subtype of sCJD, designated sCJDMM1, is viewed as a single entity. Two other classifications proposed by Collinge et al. [Collinge J, Sidle KC, Meads J, Ironside J, Hill AF. Molecular analysis of prion strain variation and the aetiology of 'new variant' CJD. Nature 1996; 383: 685-90.] and Zanusso et al., [Zanusso G, Farinazzo A, Fiorini M, Gelati M, Castagna A, Righetti PG, Rizzuto N, Monaco S . pH-dependent prion protein conformation in classical Creutzfeldt-Jakob disease. J Biol Chem 2001; 276: 40377-80.] respectively, subdivide sCJDMM1 into two subtypes on the basis of the different molecular mass and phenotypic characteristics, primarily disease duration. To resolve this discrepancy, we divided a group of 22 subjects with confirmed sCJDMM1 according to Parchi et al. into two sub-populations according to whether the disease duration was <5 months (short-duration subjects) or >7 months (long-duration subjects). We then examined the PrP(Sc) molecular mass under the conditions that allowed wide variability of the pH of the PrP(Sc) preparations as well as under stringent pH conditions, using high-resolution gel electrophoresis. We also compared the characteristics of the PrP(Sc) associated with the short- and long-duration subjects using two-dimensional immunoblot, conformational stability immunoassay and sucrose gradient fractionation. Finally, the two sub-populations were also compared with regard to their clinical and pathological features including the lesion profiles. When sample homogenization and protease digestion were performed under stringent pH conditions, the PrP(Sc) molecular mass did not differ between short- and long-duration sCJDMM1 subjects. The conformational characteristics of the protease-resistant PrP(Sc) as well as the clinical and pathological phenotypes were also homogeneous except for the more severe lesions of the long-duration cases. We therefore conclude that the variability of the PrP(Sc) molecular mass underlying the division of sCJDMM1 into two subtypes is largely due to pH variations during tissue preparation, and sCJDMM1 with short and long disease duration have similar phenotypes and PrP(Sc) characteristics. These data indicate that the differentiation of sCJDMM1 into two subgroups is not currently justified.

Familial frontotemporal dementia with neuronal intranuclear inclusions is not a polyglutamine expansion disease

BackgroundMany cases of frontotemporal dementia (FTD) are familial, often with an autosomal dominant pattern of inheritance. Some are due to a mutation in the tau- encoding gene, on chromosome 17, and show an accumulation of abnormal tau in brain tissue (FTDP-17T). Most of the remaining familial cases do not exhibit tau pathology, but display neuropathology similar to patients with dementia and motor neuron disease, characterized by the presence of ubiquitin-immunoreactive (ub-ir), dystrophic neurites and neuronal cytoplasmic inclusions in the neocortex and hippocampus (FTLD-U). Recently, we described a subset of patients with familial FTD with autopsy-proven FTLD-U pathology and with the additional finding of ub-ir neuronal intranuclear inclusions (NII). NII are a characteristic feature of several other neurodegenerative conditions for which the genetic basis is abnormal expansion of a polyglutamine-encoding trinucleotide repeat region. The genetic basis of familial FTLD-U is currently not known, however the presence of NII suggests that a subset of cases may represent a polyglutamine expansion disease.MethodsWe studied DNA and post mortem brain tissue from 5 affected members of 4 different families with NII and one affected individual with familial FTLD-U without NII. Patient DNA was screened for CAA/CAG trinucleotide expansion in a set of candidate genes identified using a genome-wide computational approach. Genes containing CAA/CAG trinucleotide repeats encoding at least five glutamines were examined (n = 63), including the nine genes currently known to be associated with human disease. CAA/CAG tract sizes were compared with published normal values (where available) and with those of healthy controls (n = 94). High-resolution agarose gel electrophoresis was used to measure allele size (number of CAA/CAG repeats). For any alleles estimated to be equal to or larger than the maximum measured in the control population, the CAA/CAG tract length was confirmed by capillary electrophoresis. In addition, immunohistochemistry using a monoclonal antibody that recognizes proteins containing expanded polyglutamines (1C2) was performed on sections of post mortem brain tissue from subjects with NII.ResultsNo significant polyglutamine-encoding repeat expansions were identified in the DNA from any of our FTLD-U patients. NII in the FTLD-U cases showed no 1C2 immunoreactivity.ConclusionWe find no evidence to suggest that autosomal dominant FTLD-U with NII is a polyglutamine expansion disease.