MSH3 polymorphisms and protein levels affect CAG repeat instability in huntington's disease mice

Expansions of trinucleotide CAG/CTG repeats in somatic tissues are thought to contribute to ongoing disease progression through an affected individual's life with Huntington's disease or myotonic dystrophy. Broad ranges of repeat instability arise between individuals with expanded repeats, suggesting the existence of modifiers of repeat instability. Mice with expanded CAG/CTG repeats show variable levels of instability depending upon mouse strain. However, to date the genetic modifiers underlying these differences have not been identified. We show that in liver and striatum the R6/1 Huntington's disease (HD) (CAG)~100 transgene, when present in a congenic C57BL/6J (B6) background, incurred expansion-biased repeat mutations, whereas the repeat was stable in a congenic BALB/cByJ (CBy) background. Reciprocal congenic mice revealed the Msh3 gene as the determinant for the differences in repeat instability. Expansion bias was observed in congenic mice homozygous for the B6 Msh3 gene on a CBy background, while the CAG tract was stabilized in congenics homozygous for the CBy Msh3 gene on a B6 background. The CAG stabilization was as dramatic as genetic deficiency of Msh2. The B6 and CBy Msh3 genes had identical promoters but differed in coding regions and showed strikingly different protein levels. B6 MSH3 variant protein is highly expressed and associated with CAG expansions, while the CBy MSH3 variant protein is expressed at barely detectable levels, associating with CAG stability. The DHFR protein, which is divergently transcribed from a promoter shared by the Msh3 gene, did not show varied levels between mouse strains. Thus, naturally occurring MSH3 protein polymorphisms are modifiers of CAG repeat instability, likely through variable MSH3 protein stability. Since evidence supports that somatic CAG instability is a modifier and predictor of disease, our data are consistent with the hypothesis that variable levels of CAG instability associated with polymorphisms of DNA repair genes may have prognostic implications for various repeat-associated diseases

New quality regulations versus established nursing home practice: a qualitative study

<p>Abstract</p> <p>Background</p> <p>Western governments have initiated reforms to improve the quality of care for nursing home residents. Most of these reforms encompass the use of regulations and national quality indicators. In the Norwegian context, these regulations comprise two pages of text that are easy to read and understand. They focus particularly on residents’ rights to plan their day-to-day life in nursing homes. However, the research literature indicates that the implementation of the new regulations, particularly if they aim to change nursing practice, is extremely challenging. The aim of this study was to further explore and describe nursing practice to gain a deeper understanding of why it is so hard to implement the new regulations.</p> <p>Methods</p> <p>For this qualitative study, an ethnographic design was chosen to explore and describe nursing practice. Fieldwork was conducted in two nursing homes. In total, 45 nurses and nursing aides were included in participant observation, and 10 were interviewed at the end of the field study.</p> <p>Results</p> <p>Findings indicate that the staff knew little about the new quality regulations, and that the quality of their work was guided by other factors rooted in their nursing practice. Further analyses revealed that the staff appeared to be committed to daily routines and also that they always seemed to know what to do. Having routines and always knowing what to do mutually strengthen and enhance each other, and together they form a powerful force that makes daily nursing care a taken-for-granted activity.</p> <p>Conclusion</p> <p>New regulations are challenging to implement because nursing practices are so strongly embedded. Improving practice requires systematic and deeply rooted practical change in everyday action and thinking.</p