Pervasive Induction of Regulatory Mutation Microclones in Sun-exposed Skin.

Carcinogen-induced mutations are thought near-random, with rare cancer-driver mutations underlying clonal expansion. Using high-fidelity Duplex Sequencing to reach a mutation frequency sensitivity of 4×10 per nt, we report that sun exposure creates pervasive mutations at sites with ∼100-fold UV-sensitivity in RNA-processing gene promoters - cyclobutane pyrimidine dimer (CPD) hyperhotspots - and these mutations have a mini-driver clonal expansion phenotype. Numerically, human skin harbored 10-fold more genuine mutations than previously reported, with neonatal skin containing 90,000 per cell; UV signature mutations increased 8,000-fold in sun-exposed skin, averaging 3×10 per nt.

Chemiexcited Neurotransmitters and Hormones Create DNA Photoproducts in the Dark.

In DNA, electron excitation allows adjacent pyrimidine bases to dimerize by [2 + 2] cycloaddition, creating chemically stable but lethal and mutagenic cyclobutane pyrimidine dimers (CPDs). The usual cause is ultraviolet radiation. Alternatively, CPDs can be made in the dark (dCPDs) via chemically mediated electron excitation of the skin pigment melanin, after it is oxidized by peroxynitrite formed from the stress-induced radicals superoxide and nitric oxide.

Triplet-Energy Quenching Functions of Antioxidant Molecules.

UV-like DNA damage is created in the dark by chemiexcitation, in which UV-activated enzymes generate reactive oxygen and nitrogen species that create a dioxetane on melanin. Thermal cleavage creates an electronically excited triplet-state carbonyl whose high energy transfers to DNA. Screening natural compounds for the ability to quench this energy identified polyenes, polyphenols, mycosporine-like amino acids, and related compounds better known as antioxidants.

Genomic sites hypersensitive to ultraviolet radiation.

If the genome contains outlier sequences extraordinarily sensitive to environmental agents, these would be sentinels for monitoring personal carcinogen exposure and might drive direct changes in cell physiology rather than acting through rare mutations. New methods, adductSeq and freqSeq, provided statistical resolution to quantify rare lesions at single-base resolution across the genome. Primary human melanocytes, but not fibroblasts, carried spontaneous apurinic sites and TG sequence lesions more frequent than ultraviolet (UV)-induced cyclobutane pyrimidine dimers (CPDs).

Conservative evolution in duplicated genes of the primate Class I ADH cluster.

Humans have seven alcohol dehydrogenase genes (ADH) falling into five classes. Three out of the seven genes (ADH1A, ADH1B and ADH1C) belonging to Class I are expressed primarily in liver and code the main enzymes catalyzing ethanol oxidization. The three genes are tandemly arrayed within the ADH cluster on chromosome 4 and have very high nucleotide similarity to each other (exons: >90%; introns: >70%), suggesting the genes have been generated by duplication event(s).

Population variation in linkage disequilibrium across the COMT gene considering promoter region and coding region variation.

Catechol-O-methyl transferase (COMT) catalyzes the first step in one of the major pathways in the degradation of catecholamines. The COMT gene on chromosome 22 has been considered a candidate gene for many neuropsychiatric disorders, in part because an exon 4 single nucleotide polymorphism (SNP) in COMT causes an amino acid substitution associated with significantly altered enzyme activity. This functional variant, detected as an NlaIII restriction site polymorphism (RSP), is polymorphic in populations from around the world.

TRANSPLANTATION OF POLYMER ENCAPSULATED PC12 CELLS: USE OF CHITOSAN AS AN IMMOBILIZATION MATRIX.

Polymer capsules were fabricated to encapsulate PC12 cells within a semipermeable and immunoprotective barrier. The inclusion of precipitated chitosan as an immobilization matrix within the polymer capsules increased the survival and physiological functioning of the PC12 cells. In an initial study, HPLC analysis revealed that the inclusion of a chitosan matrix resulted in an increased output of catecholamines from the encapsulated PC12 cells under both basal conditions, and following high potassium depolarization at 2 and 4 wk following encapsulation in vitro.