Synthesis and properties of GuNA purine/pyrimidine nucleosides and oligonucleotides.

We recently designed guanidine-bridged nucleic acids (GuNA), and GuNA bearing a thymine (T) nucleobase was synthesized and successfully incorporated into oligonucleotides. The GuNA-T-modified oligonucleotides possessed high duplex-forming ability towards their complementary single-stranded RNAs and were highly stable against 3'-exonuclease. Therefore, GuNA is a promissing artificial nucleic acid for therapeutic antisense oligonucleotides. We herein report the facile synthesis of GuNA phosphoramidites bearing adenine (A), guanine (G), and 5-methylcytosine (mC) nucleobases and a robust method for the preparation of GuNA-modified oligonucleotides, even with sequences having acid-sensitive purine nucleobases. Oligonucleotides modified with GuNA-A, -G, or -mC possessed high duplex-forming ability, similar to those modified with GuNA-T. Moreover, some of the GuNA-modified oligonucleotides were revealed to have high base discriminating ability compared with that of their natural counterparts. GuNA nucleosides exhibited no genotoxicity in bacterial reverse mutation assays. Thus, all GuNAs (GuNA-T, -A, -G, and -mC) are now available to be examined in therapeutic applications.

Synthetic Method for 2'-Amino-LNA Bearing Any of the Four Nucleobases via a Transglycosylation Reaction.

A transglycosylation reaction of 2'-amino-locked nucleic acid (LNA) from thymine (T) to other nucleobases adenine (A), guanine (G), and 5-methylcytosine (mC) has been developed. This reaction proceeds in high yield and with high ß-selectivity. The mild reaction conditions enable the coexistence of acid-labile protecting groups, including a 4,4'-dimethoxytrytyl (DMTr) group. 2'-Amino-LNAs bearing any nucleobase can now be easily synthesized.

Retinitis Pigmentosa with EYS Mutations Is the Most Prevalent Inherited Retinal Dystrophy in Japanese Populations.

The aim of this study was to gain information about disease prevalence and to identify the responsible genes for inherited retinal dystrophies (IRD) in Japanese populations. Clinical and molecular evaluations were performed on 349 patients with IRD. For segregation analyses, 63 of their family members were employed. Bioinformatics data from 1,208 Japanese individuals were used as controls. Molecular diagnosis was obtained by direct sequencing in a stepwise fashion utilizing one or two panels of 15 and 27 genes for retinitis pigmentosa patients. If a specific clinical diagnosis was suspected, direct sequencing of disease-specific genes, that is, ABCA4 for Stargardt disease, was conducted. Limited availability of intrafamily information and decreasing family size hampered identifying inherited patterns. Differential disease profiles with lower prevalence of Stargardt disease from European and North American populations were obtained. We found 205 sequence variants in 159 of 349 probands with an identification rate of 45.6%. This study found 43 novel sequence variants. In silico analysis suggests that 20 of 25 novel missense variants are pathogenic. EYS mutations had the highest prevalence at 23.5%. c.4957_4958insA and c.8868C>A were the two major EYS mutations identified in this cohort. EYS mutations are the most prevalent among Japanese patients with IRD.

Exploring the length of the common channel of pancreaticobiliary maljunction on magnetic resonance cholangiopancreatography.

BACKGROUND: In the revised diagnostic criteria for pancreaticobiliary maljunction (PBM), PBM can be diagnosed from a long common channel by magnetic resonance cholangiopancreatography (MRCP). However, it is necessary to differentiate from high confluence of pancreaticobiliary ducts (HCPBD) with a relatively long common channel (≥6 mm) and effect of the sphincter in the pancreaticobiliary junction. This multicenter study aimed to explore definite value of the length of an abnormally long common channel, which enables to distinguish PBM from HCPBD on MRCP. METHODS: In 184 PBM patients and 22 HCPBD patients who were diagnosed by direct cholangiography and underwent MRCP, the length of the common channel was measured. RESULTS: The length of the common channel was 16.2 ± 6.9 mm on direct cholangiography and 13.9 ± 6.2 mm on MRCP in PBM patients, and 7.7 ± 1.5 mm and 6.6 ± 1.4 mm in HCPBD patients. The optimal cut off value of the length of the common channel to distinguish PBM from HCPBD was identified to be 9 mm. CONCLUSIONS: Pancreaticobiliary maljunction can be diagnosed from an abnormally long common channel on MRCP, but in cases of the common channel ≤9 mm on MRCP, direct cholangiography is needed to confirm PBM.

The first USH2A mutation analysis of Japanese autosomal recessive retinitis pigmentosa patients: a totally different mutation profile with the lack of frequent mutations found in Caucasian patients.

Retinitis pigmentosa (RP) is a highly heterogeneous genetic disease. The USH2A gene, which accounts for approximately 74-90% of Usher syndrome type 2 (USH2) cases, is also one of the major autosomal recessive RP (arRP) causative genes among Caucasian populations. To identify disease-causing USH2A gene mutations in Japanese RP patients, all 73 exons were screened for mutations by direct sequencing. In total, 100 unrelated Japanese RP patients with no systemic manifestations were identified, excluding families with obvious autosomal dominant inheritance. Of these 100 patients, 82 were included in this present study after 18 RP patients with very likely pathogenic EYS (eyes shut homolog) mutations were excluded. The mutation analysis of the USH2A revealed five very likely pathogenic mutations in four patients. A patient had only one very likely pathogenic mutation and the others had two of them. Caucasian frequent mutations p.C759F in arRP and p.E767fs in USH2 were not found. All the four patients exhibited typical clinical features of RP. The observed prevalence of USH2A gene mutations was approximately 4% among Japanese arRP patients, and the profile of the USH2A gene mutations differed largely between Japanese patients and previously reported Caucasian populations.

Spatially-resolved spectral image of a microwave-induced plasma with Okamoto-cavity for nitridation of steel substrate.

When a nitrogen microwave-induced plasma produced with an Okamoto-cavity was employed as a source for the nitridation of steel samples, the characteristics of the plasma were investigated by analyzing a spatially-resolved emission image of nitrogen excited species obtained with a two-dimensionally imaging spectrograph. Our previous study had reported on an excellent performance of the Okamoto-cavity microwave-induced plasma (MIP), enabling a nitrided layer having a several-micrometer-thickness to form on an iron substrate, even if the treatment is completed within 1 min, which is superior to a conventional plasma nitriding using low-pressure glow discharges requiring a prolonged treatment time. In this paper, the reason for this is discussed based on a spectrometric investigation. The emission images of band heads of nitrogen molecule and nitrogen molecule ion extended toward the axial/radial directions of the plasma at larger microwave powers supplied to the MIP, thus elevating the number density of the excited species of nitrogen, which would activate any chemical reaction on the iron substrate. However, a drastic increase in the growth rate of the nitrided layer when increasing the microwave power from 600 to 700 W, which had been observed in our previous study, could not be explained only from such a variation in the excited species of nitrogen. This result is probably because the growth process is dominantly controlled by thermal diffusion of nitrogen atom after it enters into the iron substrate, where the substrate temperature is the most important parameter concerning the mobility in the iron lattice. Therefore, the Okamoto-cavity MIP could contribute to a thermal source through radiative heating as well as a source of nitrogen excited species, especially in the growth process of the nitrided layer.

Total synthesis of hirsutellone B via Ullmann-type direct 13-membered macrocyclization.

Total synthesis of Hirsutellone B has been achieved by a convergent synthetic strategy. This synthesis features direct construction of the highly strained 13-membered macrocycle of Hirsutellone B utilizing the Ullmann-type reaction. To the best of our knowledge, this is the first application of macrocyclization utilizing an intramolecular Ullmann-type reaction between an aliphatic alcohol and aryl halide.