Institut für Medizinische Strahlenkunde und Zellforschung
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Keywords
- Axon guidance (1)
- Drosophila (1)
- LIN-5 (1)
- Midline (1)
- Morbus Fabry (1)
- Mud (1)
- Netrin (1)
- NuMA (1)
- late gadolinium enhancement (1)
- lysosomal storage disease (1)
Mushroom body defect is required in parallel to Netrin for midline axon guidance in Drosophila
(2016)
The outgrowth of many neurons within the central nervous system is initially directed towards or away from the cells lying at the midline. Recent genetic evidence suggests that a simple model of differential sensitivity to the conserved Netrin attractants and Slit repellents is insufficient to explain the guidance of all axons at the midline. In the Drosophila embryonic ventral nerve cord, many axons still cross the midline in the absence of the Netrin genes (NetA and NetB) or their receptor frazzled. Here we show that mutation of mushroom body defect (mud) dramatically enhances the phenotype of Netrin or frazzled mutants, resulting in many more axons failing to cross the midline, although mutations in mud alone have little effect. This suggests that mud, which encodes a microtubule-binding coiled-coil protein homologous to NuMA and LIN-5, is an essential component of a Netrin-independent pathway that acts in parallel to promote midline crossing. We demonstrate that this novel role of Mud in axon guidance is independent of its previously described role in neural precursor development. These studies identify a parallel pathway controlling midline guidance in Drosophila and highlight a novel role for Mud potentially acting downstream of Frizzled to aid axon guidance.
Background
Fabry disease is characterized by a progressive deposition of sphingolipids in different organ systems, whereby cardiac involvement leads to death. We hypothesize that lysosomal storage of sphingolipids in the heart as occurring in Fabry disease does not reflect in higher cardiac lipid concentrations detectable by \(^1\)H magnetic resonance spectroscopy (MRS) at 3 Tesla.
Methods
Myocardial lipid content was quantified in vivo by \(^1\)H-MRS in 30 patients (12 male, 18 female; 18 patients treated with enzyme replacement therapy) with genetically proven Fabry disease and in 30 healthy controls. The study protocol combined \(^1\)H-MRS with cardiac cine imaging and LGE MRI in a single examination.
Results
Myocardial lipid content was not significantly elevated in Fabry disease (p = 0.225). Left ventricular (LV) mass was significantly higher in patients suffering from Fabry disease compared to controls (p = 0.019). Comparison of patients without signs of myocardial fibrosis in MRI (LGE negative; n = 12) to patients with signs of fibrosis (LGE positive; n = 18) revealed similar myocardial lipid content in both groups (p > 0.05), while the latter showed a trend towards elevated LV mass (p = 0.076).
Conclusions
This study demonstrates the potential of lipid metabolic investigation embedded in a comprehensive examination of cardiac morphology and function in Fabry disease. There was no evidence that lysosomal storage of sphingolipids influences cardiac lipid content as measured by \(^1\)H-MRS. Finally, the authors share the opinion that a comprehensive cardiac examination including three subsections (LGE; \(^1\)H-MRS; T\(_1\) mapping), could hold the highest potential for the final assessment of early and late myocardial changes in Fabry disease.