Nonsense mutations in CABC1/ADCK3 cause progressive cerebellar ataxia and atrophy

Hereditary ataxias are genetic disorders characterized by uncoordinated gait and often poor coordination of hands, speech, and eye movements. Frequently, atrophy of the cerebellum occurs. Many ataxias are autosomal dominant, but autosomal recessive (AR) disease occurs as well. Homozygosity mapping in a consanguineous family with three affected children with progressive cerebellar ataxia and atrophy revealed a candidate locus on chromosome 1, containing the CABC1/ADCK3 (the chaperone, ABC1 activity of bc1 complex homologue) gene. CABC1/ADCK3 is the homologue of the yeast Coq8 gene, which is involved in the ubiquinone biosynthesis pathway. Mutation analysis of this gene showed a homozygous nonsense mutation (c.1042C > T, p.R348X). Eight additional patients with AR cerebellar ataxia and atrophy were screened for mutations in the CABC1/ADCK3 gene. One patient was compound heterozygous for the same c.1042C > T mutation and a second nonsense mutation (c.1136T > A, p.L379X). Both mutations created a premature stop codon, triggering nonsense mediated mRNA decay as the pathogenic mechanism. We found no evidence of a Dutch founder for the c.1042C > T mutation in AR ataxia. We report here the first nonsense mutations in CABC1 that most likely lead to complete absence of a functional CABC1 protein. Our results indicate that CABC1 is an important candidate for mutation analysis in progressive cerebellar ataxia and atrophy on MRI to identify those patients, who may benefit from CoQ10 treatment.     

Effects of substituting a portion of standard physiotherapy time with virtual reality games among community-dwelling stroke survivors

Background

Evidence indicates that the continuation of therapy among community-dwelling stroke survivors improves physical function. Community rehabilitation programmes often face limitations in terms of resources. It is imperative to include new motivational interventions to encourage some level of non-clinician management. The aim of this study was to determine whether there were any changes in physical function and activities of daily living when substituting a portion of the standard physiotherapy time with virtual reality games among community-dwelling stroke survivors.

Methods

In this controlled trial, the experimental group received 30 minutes of virtual reality balance games in addition to 90 minutes of standard physiotherapy. The control group continued with their two hours of routine standard physiotherapy. Both groups received 12 therapy sessions: two-hour sessions twice per week for six continuous weeks. Changes in physical function, activities of daily living and balance ability were assessed using the Timed Up and Go test, 30-second Sit to Stand test, Timed Ten-Metre Walk test, Six-Minute Walk test and the Barthel Index, and static balance was assessed using a probalance board.

Results

Twenty-eight participants completed post-intervention assessments. The results showed a significant within-subject effect on the Timed Up and Go test: F (1, 26)?=?5.83, p?=?0.02; and the 30-second Sit to Stand test; F (1, 26)?=?13.50, p?=?0.001. The between-subject effect was not significant (p?>?0.05) for any of the outcome measurements.

Conclusion

Substituting a portion of the standard physiotherapy time with virtual reality games was equally effective in maintaining physical function outcomes and activities of daily living among community-dwelling stroke survivors.

Trial Registration

Australia and New Zealand Clinical Trials Register, ACTRN12613000478718

     

Effect of two cleaning processes for bone allografts on gentamicin impregnation and in vitro antibiotic release

Bone allografts are a useful and sometimes indispensable tool for the surgeon to repair bone defects. Microbial contamination is a major reason for discarding allografts from bone banks. To improve the number of safe allografts, we suggest chemical cleaning of the grafts followed by antibiotic impregnation. Comparison of two chemical cleaning processes for bone allografts aiming for antibiotic impregnation and consequently delivery rates in vitro. Bone chips of 5–10 mm were prepared from human femoral heads. Two cleaning methods (cleaning A and cleaning B) based on solutions containing hydrogen peroxide, paracetic acid, ethanol and biological detergent were carried out and compared. After the cleaning processes, the bone chips were impregnated with gentamicin. Bacillus subtilis bioassay was used to determine the gentamicin release after intervals of 1–7 days. Differences were compared with non-parametric Mann–Whitney U tests. The zones of inhibition obtained from the bone grafts cleaned with both cleaning processes were similar between the groups. The concentration of the released antibiotic was decreasing gradually over time, following a similar pattern for both groups. The cleaning procedure A as well as the cleaning procedure B for bone allografts allowed the impregnation with gentamicin powder in the same concentrations in both groups. The delivery of gentamicin was similar for both groups. Both cleaning procedures were easy to be carried out, making them suitable for routine use at the bone banks.     

Insulin-induced serine phosphorylation of IRS-2 via ERK1/2 and mTOR: studies on the function of Ser675 and Ser907

The identity of specific serine phosphorylation residues of insulin receptor substrate (IRS)-2 and their impact on insulin signal transduction are largely unknown. Ser(675) and Ser(907) of mouse IRS-2 are adjacent to PI 3-kinase or Grb2 binding domains, respectively. Using monoclonal phosphosite-specific antibodies, we demonstrated the phosphorylation of both serines after stimulation of Fao hepatoma cells with insulin, anisomycin, or phorbol esters. Phosphorylation of both sites was a late and prolonged event during insulin treatment and was also detected in liver tissue of insulin-treated as well as refed mice. Inhibition and siRNA-mediated knockdown of ERK1/2 indicated that the insulin-induced phosphorylation of Ser(907) was ERK dependent. Phosphorylation of Ser(907) did not prevent the insulin-induced association of IRS-2 with Grb2, but phosphorylation of the adjacent Tyr(911) was proved to be crucial in HEK 293 cells expressing IRS-2 Ala mutants. The insulin-induced phosphorylation of Ser(675) was prevented by inhibition and siRNA-mediated knockdown of mTOR but not of p70(S6K1). Mutation of Ser(675) to Ala did not affect downstream insulin signaling but increased the half-life of the protein, suggesting an involvement of phospho-Ser(675) in an accelerated degradation of IRS-2. Moreover, the insulin-induced degradation of IRS-2 was blocked by inhibition of mTOR. We conclude that the two novel insulin-dependent serine phosphorylation sites of IRS-2 were not involved in the regulation of the adjacent PI 3-kinase and Grb2 binding domains but might be implicated in the ERK- and mTOR-mediated negative feedback control.     

Identification of QTL genes for BMD variation using both linkage and gene-based association approaches

Low bone mineral density (BMD) is a risk factor for osteoporotic fracture with a high heritability. Previous large scale linkage study in Northern Chinese has identified four significant quantitative trait loci (QTL) for BMD variation on chromosome 2q24, 5q21, 7p21 and 13q21. We performed a replication study of these four QTL in 1,459 Southern Chinese from 306 pedigrees. Successful replication was observed on chromosome 5q21 for femoral neck BMD with a LOD score of 1.38 (nominal p value = 0.006). We have previously identified this locus in a genome scan meta-analysis of BMD variation in a white population. Subsequent QTL-wide gene-based association analysis in 800 subjects with extreme BMD identified CAST and ERAP1 as novel BMD candidate genes (empirical p value of 0.032 and 0.014, respectively). The associations were independently replicated in a Northern European population (empirical p value of 0.01 and 0.004 for CAST and ERAP1, respectively). These findings provide further evidence that 5q21 is a BMD QTL, and CAST and ERAP1 may be associated with femoral neck BMD variation.