Optimized testing strategy for the diagnosis of GAA-FGF14 ataxia/spinocerebellar ataxia 27B

Dominantly inherited GAA repeat expansions in FGF14 are a common cause of spinocerebellar ataxia (GAA-FGF14 ataxia; spinocerebellar ataxia 27B). Molecular confirmation of FGF14 GAA repeat expansions has thus far mostly relied on long-read sequencing, a technology that is not yet widely available in clinical laboratories. We developed and validated a strategy to detect FGF14 GAA repeat expansions using long-range PCR, bidirectional repeat-primed PCRs, and Sanger sequencing. We compared this strategy to targeted nanopore sequencing in a cohort of 22 French Canadian patients and next validated it in a cohort of 53 French index patients with unsolved ataxia. Method comparison showed that capillary electrophoresis of long-range PCR amplification products significantly underestimated expansion sizes compared to nanopore sequencing (slope, 0.87 [95% CI, 0.81 to 0.93]; intercept, 14.58 [95% CI, − 2.48 to 31.12]) and gel electrophoresis (slope, 0.84 [95% CI, 0.78 to 0.97]; intercept, 21.34 [95% CI, − 27.66 to 40.22]). The latter techniques yielded similar size estimates. Following calibration with internal controls, expansion size estimates were similar between capillary electrophoresis and nanopore sequencing (slope: 0.98 [95% CI, 0.92 to 1.04]; intercept: 10.62 [95% CI, − 7.49 to 27.71]), and gel electrophoresis (slope: 0.94 [95% CI, 0.88 to 1.09]; intercept: 18.81 [95% CI, − 41.93 to 39.15]). Diagnosis was accurately confirmed for all 22 French Canadian patients using this strategy. We also identified 9 French patients (9/53; 17%) and 2 of their relatives who carried an FGF14 (GAA)≥250 expansion. This novel strategy reliably detected and sized FGF14 GAA expansions, and compared favorably to long-read sequencing

Biallelic mutations in SORD cause a common and potentially treatable hereditary neuropathy with implications for diabetes

Here we report biallelic mutations in the sorbitol dehydrogenase gene (SORD) as the most frequent recessive form of hereditary neuropathy. We identified 45 individuals from 38 families across multiple ancestries carrying the nonsense c.757delG (p.Ala253GlnfsTer27) variant in SORD, in either a homozygous or compound heterozygous state. SORD is an enzyme that converts sorbitol into fructose in the two-step polyol pathway previously implicated in diabetic neuropathy. In patient-derived fibroblasts, we found a complete loss of SORD protein and increased intracellular sorbitol. Furthermore, the serum fasting sorbitol levels in patients were dramatically increased. In Drosophila, loss of SORD orthologs caused synaptic degeneration and progressive motor impairment. Reducing the polyol influx by treatment with aldose reductase inhibitors normalized intracellular sorbitol levels in patient-derived fibroblasts and in Drosophila, and also dramatically ameliorated motor and eye phenotypes. Together, these findings establish a novel and potentially treatable cause of neuropathy and may contribute to a better understanding of the pathophysiology of diabetes

Diagnosis, management and outcome of clinically-suspected spinal infection

Objectives: Spontaneous spinal infection (SI) is a quite rare but serious entity. This study aimed to evaluate outcome and follow-up data of SI cases without a microbiological diagnosis (suspected SI). Methods: We undertook a retrospective, comparative study of 82 spontaneous SI cases in adults presenting over an 11-year period to two Italian hospitals. Results: The diagnostic yields of blood culture, percutaneous needle biopsy of spine, and surgical sample culture were 43.6%, 72.7%, and 91.6%, respectively. Overall, causative organisms were identified in 60 (73.2%) cases, the most frequently isolated pathogens being Staphylococcus aureus and Mycobacterium tuberculosis. The median diagnostic delay was similar (p = 0.39) in pyogenic (1 month) and suspected (0.5 month) SI cases, and longer in tuberculous cases (4 months) than in the other SI case groups (p = 0.069 and p = 0.062, respectively). All patients received antibiotic treatment, and 21 (25.5%) underwent surgery, that was required more frequently in tuberculous (40.7%) than in pyogenic (25.0%) and suspected SI cases (9.1%) (p = 0.028). Of 67 patients who completed a 1-year follow-up period, 24 had persisting painful disability that was more frequent in tuberculous (66.7%) cases than in pyogenic (21.7%) and suspected SI (15.0%) cases (p = 0.03). Conclusions: Although a microbiological diagnosis was not achieved in nearly a quarter of SI cases, both diagnostic delay and outcome were similar to those of pyogenic SI cases. Earlier recognition of tuberculous SI is mandatory, as this is associated with the highest long-term morbidity

Aspetti Clinici dell'infezione da HIV. Esperienza personale

The authors analyze the clinical aspects of HIV infection in light of the most recent studies. The natural history of the disease appears more definite than in the recent years, but many aspects are still unclear. Current therapy and future therapeutic trends are also discussed. A prospective study of 108 HIV-positive subjects, observed for periods ranging from 6 months to 2 years showed a cumulative probability of evolution to full-blown AIDS of 34.4%/year for subjects with immunodeficiency (WR3-WR5 groups, according to the Walter Reed classification). Finally, the authors report their clinical experience with 35 patients with full-blown AIDS from 1984 to 1987

PP4-dependent HDAC3 dephosphorylation discriminates between axonal regeneration and regenerative failure

The molecular mechanisms discriminating between regenerative failure and success remain elusive. While a regeneration‐competent peripheral nerve injury mounts a regenerative gene expression response in bipolar dorsal root ganglia (DRG) sensory neurons, a regeneration‐incompetent central spinal cord injury does not. This dichotomic response offers a unique opportunity to investigate the fundamental biological mechanisms underpinning regenerative ability. Following a pharmacological screen with small‐molecule inhibitors targeting key epigenetic enzymes in DRG neurons, we identified HDAC3 signalling as a novel candidate brake to axonal regenerative growth. In vivo, we determined that only a regenerative peripheral but not a central spinal injury induces an increase in calcium, which activates protein phosphatase 4 that in turn dephosphorylates HDAC3, thus impairing its activity and enhancing histone acetylation. Bioinformatics analysis of ex vivo H3K9ac ChIPseq and RNAseq from DRG followed by promoter acetylation and protein expression studies implicated HDAC3 in the regulation of multiple regenerative pathways. Finally, genetic or pharmacological HDAC3 inhibition overcame regenerative failure of sensory axons following spinal cord injury. Together, these data indicate that PP4‐dependent HDAC3 dephosphorylation discriminates between axonal regeneration and regenerative failure

Epigenomic signatures underpin the axonal regenerative ability of dorsal root ganglia sensory neurons

Axonal injury results in regenerative success or failure, depending on whether the axon lies in the peripheral or the CNS, respectively. The present study addresses whether epigenetic signatures in dorsal root ganglia discriminate between regenerative and non-regenerative axonal injury. Chromatin immunoprecipitation for the histone 3 (H3) post-translational modifications H3K9ac, H3K27ac and H3K27me3; an assay for transposase-accessible chromatin; and RNA sequencing were performed in dorsal root ganglia after sciatic nerve or dorsal column axotomy. Distinct histone acetylation and chromatin accessibility signatures correlated with gene expression after peripheral, but not central, axonal injury. DNA-footprinting analyses revealed new transcriptional regulators associated with regenerative ability. Machine-learning algorithms inferred the direction of most of the gene expression changes. Neuronal conditional deletion of the chromatin remodeler CCCTC-binding factor impaired nerve regeneration, implicating chromatin organization in the regenerative competence. Altogether, the present study offers the first epigenomic map providing insight into the transcriptional response to injury and the differential regenerative ability of sensory neurons