Inefficient nuclear delivery of plasmid DNA is thought to activity of apoptotic and lysosomal nucleases; (2) disposal be one of the daunting hurdles to gene transfer, utilizing a of microinjected plasmid DNA was inhibited in cytosolnonviral delivery system such as polycation-DNA complex.depleted cells or following the encapsulation of DNA in Following its internalization by endocytosis, plasmid DNA phospholipid vesicles; (3) generation and subsequent elimhas to be released into the cytosol before its nuclear entry ination of free 3Ј-OH ends could be detected by the tercan occur. However, the stability of plasmid DNA in the minal deoxynucleotidyl transferase-mediated dUTP nick cytoplasm, that may play a determinant role in the transfecend-labeling assay (TUNEL), reflecting the fragmentation tion efficiency, is not known. The turnover of plasmid DNA, of the injected DNA; and finally (4) isolated cytosol, delivered by microinjection into the cytosol, was deterobtained by selective permeabilization of the plasma memmined by fluorescence in situ hybridization (FISH) and brane, exhibits divalent cation-dependent, thermolabile quantitative single-cell fluorescence video-image analysis. nuclease activity, determined by Southern blotting and 32 PBoth single-and double-stranded circular plasmid DNA disrelease from end-labeled DNA. Collectively, these findings appeared with an apparent half-life of 50-90 min from the suggest that the metabolic instability of plasmid DNA, cytoplasm of HeLa and COS cells, while the amount of cocaused by cytosolic nuclease, may constitute a previously injected dextran (MW 70 000) remained unaltered. We prounrecognized impediment for DNA translocation into the pose that cytosolic nuclease(s) are responsible for the nucleus and a possible target to enhance the efficiency of rapid degradation of plasmid DNA, since (1) elimination of gene delivery. plasmid DNA cannot be attributed to cell division or to the Keywords: gene transfer; plasmid DNA; turnover; degradation; DNase; microinjection Introduction Liposome-mediated cellular transfer of plasmid DNA is a promising approach for gene therapy. However, despite the significant amount of lipid/DNA complexes internalized by the target cells, transgene expression remains undesirably low.1 Obstacles to nuclear accumulation of plasmid DNA include: the slow internalization process of the lipid/DNA complex in certain cells; 2 the entrapment of DNA in the endolysosomal compartment; 1,3,4 and the diffusional barrier of the nuclear envelope. 5The underlying mechanism of escape of internalized plasmid DNA from the endo-lysosomes is not fully understood. This process involves the destabilization of the limiting membrane of the endolysosomal compartment, the dissociation of the lipid/DNA complex and the release of plasmid DNA into the cytosol.6-8 Penetration of naked plasmid DNA into the cytosol was verified by using the T7 polymerase transfection system, which Correspondence: GL Lukacs, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canad...

We have identified missense mutations at conserved amino acids in the PRPS1 gene on Xq22.3 in two families with a syndromic form of inherited peripheral neuropathy, one of Asian and one of European descent. The disease is inherited in an X-linked recessive manner, and the affected male patients invariably develop sensorineural hearing loss of prelingual type followed by gating disturbance and visual loss. The family of European descent was reported in 1967 as having Rosenberg-Chutorian syndrome, and recently a Korean family with the same symptom triad was identified with a novel disease locus CMTX5 on the chromosome band Xq21.32-q24. PRPS1 (phosphoribosyl pyrophosphate synthetase 1) is an isoform of the PRPS gene family and is ubiquitously expressed in human tissues, including cochlea. The enzyme mediates the biochemical step critical for purine metabolism and nucleotide biosynthesis. The mutations identified were E43D, in patients with Rosenberg-Chutorian syndrome, and M115T, in the Korean patients with CMTX5. We also showed decreased enzyme activity in patients with M115T. PRPS1 is the first CMT gene that encodes a metabolic enzyme, shedding a new light on the understanding of peripheral nerve-specific metabolism and also suggesting the potential of PRPS1 as a target for drugs in prevention and treatment of peripheral neuropathy by antimetabolite therapy.

A molecular‐level coding method utilizing DNA base pairs as code units has been systemized. The system consists of four steps: encoding, encrypting, decrypting and decoding (see Figure), which are realized by tailor‐made nanohybrids (DNA–layered double hydroxide (LDH) and polypyrrole–maghemite). The nanohybrids give solutions to the inherent problems which hamper DNA molecular code systems; stability in encrypting and rapidity in analysis.

It has been suggested that the haplotypic relationship between microsatellite markers and single nucleotide polymorphisms (SNPs) is of considerable importance, as microsatellite markers can potentially be incorporated into haplotypes containing SNPs to increase marker density across a region of interest. However, SNPs and microsatellite markers have different mutation rates and durations, and it is conceivable that the linkage disequilibrium (LD) patterns between the genetic markers may considerably differ. We assessed the LD patterns using 1,661 SNPs and 65 microsatellite markers along chromosome 22 and investigated whether common patterns of LD between the two genetic markers are deduced from the results. The results demonstrated that the patterns of LD among microsatellite markers varied considerably and the LD runs of SNPs and microsatellite markers showed distinct patterns. Microsatellite markers have a much higher mutation rate and the evolution of microsatellite markers is a more complex process which has distinct mutation properties from those of SNPs. We consider that these might contribute to the different LD patterns between the two genetic markers. Therefore, it would seem inadvisable to make assumptions about persistence of LD across even a relatively small genetic distance among microsatellite markers and to construct mixed marker haplotypes/LD maps employing microsatellite markers.