Abrogation of Stem Loop Binding Protein (Slbp) function leads to a failure of cells to transition from proliferation to differentiation, retinal coloboma and midline axon guidance deficits.

Through forward genetic screening for mutations affecting visual system development, we identified prominent coloboma and cell-autonomous retinal neuron differentiation, lamination and retinal axon projection defects in eisspalte (ele) mutant zebrafish. Additional axonal deficits were present, most notably at midline axon commissures. Genetic mapping and cloning of the ele mutation showed that the affected gene is slbp, which encodes a conserved RNA stem-loop binding protein involved in replication dependent histone mRNA metabolism. Cells throughout the central nervous system remained in the cell cycle in ele mutant embryos at stages when, and locations where, post-mitotic cells have differentiated in wild-type siblings. Indeed, RNAseq analysis showed down-regulation of many genes associated with neuronal differentiation. This was coincident with changes in the levels and spatial localisation of expression of various genes implicated, for instance, in axon guidance, that likely underlie specific ele phenotypes. These results suggest that many of the cell and tissue specific phenotypes in ele mutant embryos are secondary to altered expression of modules of developmental regulatory genes that characterise, or promote transitions in, cell state and require the correct function of Slbp-dependent histone and chromatin regulatory genes.

Application of an allele-specific PCR to clinical HIV genotyping samples detects additional K103N mutations in both therapy naïve and experienced patients.

Low-level drug resistance is not detected by routine consensus sequence genotype analysis (CSA) but low levels of specific mutations, such as the non-nucleoside reverse transcriptase inhibitor (NNRTI)-resistant mutation K103N, can be quantitated by allele-specific PCR (ASP). This study has applied an ASP to quantitate low-level K103N in patients presenting for clinical HIV genotyping and assess the correlation with antiretroviral treatment history and outcomes. HIV RNA was extracted from patient plasma and subjected to PCR amplification of the reverse transcriptase (RT) region followed by genotyping by CSA and real-time ASP for K103N. When applied to samples from patients presenting for genotyping, the ASP detects K103N, not K103 nor K103R, but cross-reacts with K103S. ASP identified all samples that were K103N by CSA (10.5%) and an additional 14% by ASP only, representing patients who were therapy naïve and with NNRTI treatment history. ASP detected therapy-acquired K103N at low levels up to 6 years after cessation of NNRTI therapy. In three patients with new HIV diagnosis and K103N detected by ASP only, K103N virus declined rapidly from the circulation but persisted in PBMC DNA at >12 months post-diagnosis. Efavirenz (EFV) combination therapy in three patients with low-level K103N suppressed successfully viral load, although one patient developed failure and CSA-detectable K103N after 15 months of therapy. Thus, analysis of K103N by ASP in conjunction with CSA genotyping provides additional information that reflects K103N transmission and persistence but detection of low-level K103N does not preclude successful EFV-containing combination therapy.

Antibiotic resistance in animals.

There is currently no systematic surveillance or monitoring of antibiotic resistance in Australian animals. Registration of antibiotics for use in animals is tightly controlled and has been very conservative. Fluoroquinolones have not been registered for use in food producing animals and other products have been removed from the market because of human health concerns. In the late 1970s, the Animal Health Committee coordinated a survey of resistance in Salmonella and Escherichia coli isolates from cattle, pigs and poultry and in bovine Staphylococcus aureus. Some additional information is available from published case reports. In samples collected prior to the withdrawal of avoparcin from the market, no vancomycin resistant Enterococcus faecium or Enterococcus faecalis were detected in samples collected from pigs, whereas some vanA enterococci, including E. faecium and E. faecalis, were found in chickens. No vanB enterococci were detected in either species. Virginiamycin resistance was common in both pig and poultry isolates. Multiple resistance was common in E. coli and salmonellae isolates. No fluoroquinolone resistance was found in salmonellae, E. coli or Campylobacter. Beta-lactamase production is common in isolates from bovine mastitis, but no methicillin resistance has been detected. However, methicillin resistance has been reported in canine isolates of Staphylococcus intermedius and extended spectrum beta-lactamase producing E. coli has been found in dogs.