ABSTRACT
Medulloblastoma (MB) comprises a group of heterogeneous paediatric embryonal neoplasms of the hindbrain with strong links to early development of the hindbrain1-4. Mutations that activate Sonic hedgehog signalling lead to Sonic hedgehog MB in the upper rhombic lip (RL) granule cell lineage5-8. By contrast, mutations that activate WNT signalling lead to WNT MB in the lower RL9,10. However, little is known about the more commonly occurring group 4 (G4) MB, which is thought to arise in the unipolar brush cell lineage3,4. Here we demonstrate that somatic mutations that cause G4 MB converge on the core binding factor alpha (CBFA) complex and mutually exclusive alterations that affect CBFA2T2, CBFA2T3, PRDM6, UTX and OTX2. CBFA2T2 is expressed early in the progenitor cells of the cerebellar RL subventricular zone in Homo sapiens, and G4 MB transcriptionally resembles these progenitors but are stalled in developmental time. Knockdown of OTX2 in model systems relieves this differentiation blockade, which allows MB cells to spontaneously proceed along normal developmental differentiation trajectories. The specific nature of the split human RL, which is destined to generate most of the neurons in the human brain, and its high level of susceptible EOMES+KI67+ unipolar brush cell progenitor cells probably predisposes our species to the development of G4 MB.
Subject(s)
Cell Differentiation , Cerebellar Neoplasms , Medulloblastoma , Metencephalon , Cell Differentiation/genetics , Cell Lineage , Cerebellar Neoplasms/classification , Cerebellar Neoplasms/genetics , Cerebellar Neoplasms/pathology , Cerebellum/embryology , Cerebellum/pathology , Core Binding Factor alpha Subunits/genetics , Hedgehog Proteins/metabolism , Histone Demethylases , Humans , Ki-67 Antigen/metabolism , Medulloblastoma/classification , Medulloblastoma/genetics , Medulloblastoma/pathology , Metencephalon/embryology , Metencephalon/pathology , Muscle Proteins , Mutation , Otx Transcription Factors/deficiency , Otx Transcription Factors/genetics , Repressor Proteins , T-Box Domain Proteins/metabolism , Transcription FactorsABSTRACT
The objective of the study was to determine the association between AAC and neuromuscular function over 5 years. Participants in this study were ambulant women over 70 years old residing in Perth, Western Australia who participated in the Calcium Intake Fracture Outcomes Study, a randomised controlled trial of calcium supplementation. 1046 women (mean age = 74.9 ± 2.6 years; BMI = 27.1 ± 4.4 kg/m2) were included. Lateral spine images captured during bone density testing were scored for AAC (AAC24; 0-24) at baseline. Severe AAC (AACsev) was defined using established cut points (AAC24 ≥ 6). At baseline and follow-up, isometric grip strength was assessed using a dynamometer. Mobility was assessed by the Timed-Up-and-Go (TUG) test. Using pre-defined criteria, muscle weakness was considered as grip strength < 22 kg and poor mobility defined as TUG > 10.2 s. A subset of women had appendicular lean mass (ALM) determined by dual-energy X-ray absorptiometry at baseline and follow-up (n = 261). AACsev was evident in 193 (18.5%) women. Average decline in grip strength after 5 years was greater in those with AACsev than those without (3.6 ± 3.7 vs. 2.9 ± 4.2 kg; p = 0.034). This remained significant after adjustment for age, treatment allocation, diabetes, smoking history, renal function, medical record-derived prevalent vascular disease, BMI and physical activity (ß = - 0.184; 95% confidence interval: - 0.361, - 0.008; p = 0.040). AACsev was not associated with 5-year changes in TUG or ALM in univariable or multivariable analyses (all p > 0.05). In older women, severe aortic calcification was associated with greater 5-year decline in muscle strength, but not TUG or ALM. These findings support the concept that vascular disease may have an effect on the loss of muscular strength.
