Sequencing of the Hepatitis D Virus RNA WHO International Standard.

BACKGROUND: Well-characterized, stable calibration materials are essential to standardize quantitative viral reporting. The preferred calibration materials are the WHO International Standards and secondary standards derived from them. In 2013, the 1st WHO International Standard for Hepatitis D Virus (HDV) RNA became available. During the course of assay development in our laboratory, differences between the published sequence (GenBank ID: HQ005371) and sequence we generated from the WHO HDV Standard were identified. OBJECTIVES: We sought to sequence the entire genome of the WHO HDV Standard and compare the results to the published sequence. STUDY DESIGN: RNA extracted from the WHO HDV Standard was used to generate five overlapping PCR products, including one covering the entire HDV genome, which were Sanger sequenced using standard dye-terminator chemistry. Total RNA from the WHO HDV Standard was also converted to a cDNA library generating 2.1 million sequencing reads on a NextSeq500 instrument. RESULTS: Sanger sequencing produced 32 overlapping, partial sequences of the HDV genome. RNA-seq resulted in 8100 HDV sequences covering the viral genome an average of 645-fold. Sanger and RNA-seq consensus sequences had 100% agreement and showed 89.0% nucleotide identity with the published WHO HDV Standard sequence. BLAST analysis revealed HQ005369 as the closest match with 99.2% nucleotide identity. CONCLUSIONS: HQ005369 was deposited in GenBank along with HQ005371 and seven others from a study of nine Turkish patients. A sample mix-up or clerical error may have resulted in the incorrect association of identifier and sequence. The correct nucleic acid sequence for standards is critical for test accuracy, optimization, calibration, and troubleshooting.

The BRCA2 genetic variant IVS7 + 2T-->G is a mutation.

Biochemical and genetic characterizations that support the conclusion that the variant BRCA2 IVS7 + 2T --> G represents a deleterious mutation are presented. RNA analysis from a breast cancer patient with BRCA2 IVS7 + 2T --> G showed that the productive message was produced from only one chromosome. A haplotype analysis confirmed that the intronic variant resides on the chromosome that does not produce the normal mRNA. Additionally, an RNA splicing product that deletes exon 7 was produced by the chromosome that carries BRCA2 IVS7 + 2T --> G. The deletion of exon 7 from the RNA alters the open reading frame by removing residues 249-287 and incorporating 18 abnormal amino acids before terminating with an opal stop codon. The experimental approach presented produces strong evidence of the presence of a deleterious mutation, because the contribution by both chromosomes to each RNA species analyzed was tracked using a coding region polymorphism as a marker. Furthermore, a single nucleotide polymorphism (SNP) haplotype analysis that confirms the location of the intronic variant and an associated family history that shows a high incidence of cancer supported these biochemical data.

A characterization of genetic variants in BRCA1 intron 8 identifies a mutation and a polymorphism.

The biochemical and genetic characterizations of two variants that occur in BRCA1 intron 8 are presented. The variant IVS8+2T-->C induces an aberrant transcript that deletes exon 8. This exon-skipping deletion disrupts the open reading frame by juxtaposing exon 7 and exon 9 in the aberrant splice product. Theoretically, 50 abnormal residues from reading frame 2 are translated following exon 7 before a stop codon is encountered. The chromosomal contribution to the relevant RNA species was tracked using a silent polymorphism at codon 694 (serine AGC or AGT). Nucleotide sequencing of this polymorphic codon demonstrated that the aberrant transcript was derived solely from the chromosome encoding AGT. The normally spliced productive transcript also displayed loss of heterozygosity and was derived solely from the chromosome encoding AGC at codon 694. Also, a haplotype analysis using a breast cancer patient database showed that the chromosome bearing serine 694-AGT carried IVS8+2T-->C. A second more common variant, IVS8-58delT, was characterized as a polymorphism. Analysis of RNA from patient samples used the same silent polymorphism at codon 694 and showed that the normal message was derived from both chromosomes.

BRCA1 IVS16+6T-->C is a deleterious mutation that creates an aberrant transcript by activating a cryptic splice donor site.

Results and conclusions are presented that characterize BRCA1 IVS16+6T-->C as a deleterious mutation. BRCA1 transcripts from peripheral blood mononuclear cells of a breast cancer patient with the transition IVS16+6T-->C show the loss of a heterozygous base within codon 871. Additionally, an aberrant RNA splicing product which incorporates 69 bases of the 5' end of intron 16 at the junction of exons 16 and 17 is produced solely from the allele with IVS16+6T-->C. This insertion contains two in-frame stop codons and encodes a protein truncated at residue 1662 (plus 13 residues encoded by the intron). The aberrant transcript is specifically associated with the intronic variant since it was contained within the insertion. Furthermore, sequence analysis of the heterozygous base within codon 871 demonstrates that the two RNA products, productive mRNA and aberrantly spliced RNA, are contributed to exclusively by separate alleles. Finally, the aberrant transcript is produced by the activation of a cryptic splice site which has greater homology with the primate consensus splice sequence than the mutated exon 16 donor site.

Effects of captopril and propranolol on cognitive function and cerebral blood flow in aged hypertensive rats.

Chronic hypertension has been reported to produce adverse cognitive effects in elderly individuals, perhaps by altering central nervous system hemodynamics. The beneficial or adverse effects of antihypertensive drugs on these processes are not well understood. We examined the effects of captopril (90 mg/kg/day) and propranolol (80 mg/kg/day) on cognitive function and brain blood flow in hypertensive and normotensive rats. Cognitive function was assessed by the Morris water maze, and regional brain blood flow was measured by the [14C]iodoantipyrine method. Nineteen-month-old propranolol-treated hypertensive rats exhibited poorer performance (p < .05) than control rats and had lower brain blood flows, particularly in white matter regions (p < .01). Captopril-treated hypertensive rats did not differ significantly from control rats with regard to either cognitive performance or brain blood flow. In the normotensive rats, there were no effects of either drug on cognitive performance or brain blood flow. Thus, blood pressure reduction by propranolol but not captopril has an adverse effect on cognitive function and brain blood flow in hypertensive rats.