Motor neuron rescue in spinal muscular atrophy mice demonstrates that sensory-motor defects are a consequence, not a cause, of motor neuron dysfunction.

The loss of motor neurons (MNs) is a hallmark of the neuromuscular disease spinal muscular atrophy (SMA); however, it is unclear whether this phenotype autonomously originates within the MN. To address this question, we developed an inducible mouse model of severe SMA that has perinatal lethality, decreased motor function, motor unit pathology, and hyperexcitable MNs. Using an Hb9-Cre allele, we increased Smn levels autonomously within MNs and demonstrate that MN rescue significantly improves all phenotypes and pathologies commonly described in SMA mice. MN rescue also corrects hyperexcitability in SMA motor neurons and prevents sensory-motor synaptic stripping. Survival in MN-rescued SMA mice is extended by only 5 d, due in part to failed autonomic innervation of the heart. Collectively, this work demonstrates that the SMA phenotype autonomously originates in MNs and that sensory-motor synapse loss is a consequence, not a cause, of MN dysfunction.

Early introduction of clinical skills improves medical student comfort at the start of third-year clerkships.

BACKGROUND: To determine whether introducing clinical skills during the second year of medical school, via a competency-based College system approach, improves comfort level for medical students entering third-year clinical rotations. METHOD: From 2003-2005, two cohorts of third-year medical students at the University of Washington were surveyed on their comfort level in the categories of history taking, physical examination, communication, and patient care. RESULTS: The cohort of students exposed to the College system reported a statistically significant greater comfort level in half of the measured areas, and in at least one area within each general category. No area of study showed a statistically significant decline. CONCLUSION: A competency-based College system improves medical student comfort in core clinical skills at the start of the third year curriculum.