Early suppression of the endocannabinoid degrading enzymes FAAH and MAGL alters locomotor development in zebrafish

The fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) enzymes are the predominant catabolic regulators of the major endocannabinoids (eCBs), anadamide (AEA) and 2-arachidonoylglycerol (2-AG), respectively. The expression and roles of eCBs during early embryogenesis remain to be fully investigated. Here, we inhibited FAAH and MAGL in zebrafish embryos during the first 24 hours of life and examined motor neuron and locomotor development at 2 and 5 days post fertilization (dpf). Application of the dual FAAH/MAGL inhibitor, JZL195 (2 µmol l−1) resulted in a reduction in primary motor neuron (PMN) and secondary motor neuron (SMN) axonal branching. JZL195 also reduced nicotinic acetylcholine receptor (nAChR) expression at neuromuscular junctions (NMJs). Application of URB597 (5 µmol l−1), a specific inhibitor of the FAAH enzyme also decreased primary motor neuron branching but did not affect secondary motor neuron branching and nAChR expression. Interestingly, JZL184 (5 µmol l−1), a specific inhibitor of MAGL showed no effects on motor neuron branching or nAChR expression. Co-treatment of the enzyme inhibitors with the CB1R inhibitor AM 251 confirmed the involvement of CB1R in motor neuron branching. Disruption of FAAH or MAGL reduced larval swimming activity, and AM251 attenuated the JZL195 and URB597 induced locomotor changes, but not the effects of JZL184. Together, these findings indicate that inhibition of FAAH, or augmentation of AEA acting through CB1R during early development may be responsible for locomotor deficiencies.

Mitochondria serve as axonal shuttle for Cox7c mRNA through mechanism that involves its mitochondrial targeting signal

Localized protein synthesis plays a key role in spatiotemporal regulation of the cellular proteome. Neurons, which extend axons over long distances, heavily depend on this process. However, the mechanisms by which axonal mRNAs are transported to protein target sites are not fully understood. Here, we describe a novel role for mitochondria in shuttling a nuclear encoded mRNA along axons. Fractionation analysis and smFISH revealed that the mRNA encoding Cox7c protein is preferentially associated with mitochondria from a neuronal cell line and from primary motor neuron axons. Live cell imaging of MS2-tagged Cox7c or Cryab control mRNA in primary motor neurons further confirmed the preferential colocalization of Cox7c mRNA with mitochondria. More importantly, Cox7c demonstrated substantial co-transport with mitochondria along axons. Intriguingly, the coding region, rather than the 3UTR, was found to be the key domain for the co-transport. Furthermore, we show that puromycin treatment as well as hindering the synthesis of the mitochondrial targeting signal (MTS) reduced the co-localization. Overall, our results reveal a novel mRNA transport mode which exploits mitochondria as a shuttle and translation of the MTS as a recognition feature. Thus, mitochondria may play a role in spatial regulation of the axonal transcriptome and self-sustain their own proteome at distant neuronal sites.

Cervical Spondylotic Radiculopathy Producing Motor Manifestations Mimicking Primary Muscular Atrophy

Cervical radiculopathy unaccompanied by pain or sensory disorder but manifested only by paresis, atrophy, fasciculation, and reflex loss is unusual. Three such cases are presented. Considerable diagnostic difficulty may arise in distinguishing patients presenting with these features from those who have primary motor neuron disease. Two additional case reports demonstrate that this distinction is not always possible. Diagnosis, management, and prognosis are discussed. Differentiation between motor neuron disease and spondylosis will avert needless surgery in the former group and will result in beneficial, sometimes curative surgery in the latter group.