We report a sensitive LC (liquid chromatography)/MS/MS assay using selected reaction monitoring to quantify RA (retinoic acid), which is applicable to biological samples of limited size (10-20 mg of tissue wet weight), requires no sample derivatization, provides mass identification and resolves atRA (all-trans-RA) from its geometric isomers. The assay quantifies over a linear range of 20 fmol to 10 pmol, and has a 10 fmol limit of detection at a signal/noise ratio of 3. Coefficients of variation are: instrumental, 0.5-2.9%; intra-assay, 5.4+/-0.4%; inter-assay 8.9+/-1.0%. An internal standard (all-trans-4,4-dimethyl-RA) improves accuracy by confirming extraction efficiency and revealing handling-induced isomerization. Tissues of 2-4-month-old C57BL/6 male mice had atRA concentrations of 7-9.6 pmol/g and serum atRA of 1.9+/-0.6 pmol/ml (+/-S.E.M.). Tissue 13-cis-RA ranged from 2.9 to 4.2 pmol/g, and serum 13-cis-RA was 1.2+/-0.3 pmol/ml. CRBP (cellular retinol-binding protein)-null mouse liver had atRA approximately 30% lower than wild-type (P<0.05), but kidney, testis, brain and serum atRA were similar to wild-type. atRA in brain areas of 12-month-old female C57BL/6 mice were (+/-S.E.M.): whole brain, 5.4+/-0.4 pmol/g; cerebellum, 10.7+/-0.3 pmol/g; cortex, 2.6+/-0.4 pmol/g; hippocampus, 8.4+/-1.2 pmol/g; striatum, 15.3+/-4.7 pmol/g. These data provide the first analytically robust quantification of atRA in animal brain and in CRBP-null mice. Direct measurements of endogenous RA should have a substantial impact on investigating target tissues of RA, mechanisms of RA action, and the relationship between RA and chronic disease.

Loss-of-function mutations in FGFR1 underlie 7% of nIHH with different degrees of impairment in vitro. These mutations act in concert with other gene defects in several cases, consistent with oligogenicity.

Background and objectiveDysferlinopathies are a group of muscle disorders caused by mutations in the DYSF gene. Previous muscle imaging studies describe a selective pattern of muscle involvement in smaller patient cohorts, but a large imaging study across the entire spectrum of the dysferlinopathies had not been performed and previous imaging findings were not correlated with functional tests.MethodsWe present cross-sectional T1-weighted muscle MRI data from 182 patients with genetically confirmed dysferlinopathies. We have analysed the pattern of muscles involved in the disease using hierarchical analysis and presented it as heatmaps. Results of the MRI scans have been correlated with relevant functional tests for each region of the body analysed.ResultsIn 181 of the 182 patients scanned, we observed muscle pathology on T1-weighted images, with the gastrocnemius medialis and the soleus being the most commonly affected muscles. A similar pattern of involvement was identified in most patients regardless of their clinical presentation. Increased muscle pathology on MRI correlated positively with disease duration and functional impairment.ConclusionsThe information generated by this study is of high diagnostic value and important for clinical trial development. We have been able to describe a pattern that can be considered as characteristic of dysferlinopathy. We have defined the natural history of the disease from a radiological point of view. These results enabled the identification of the most relevant regions of interest for quantitative MRI in longitudinal studies, such as clinical trials.Clinical trial registrationNCT01676077.

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