Exam 7: Wiring of the Nervous System

The loss of Numb in the Drosophila SOP lineage results in two IIa precursors and the production of extra hair and socket cells at the expense of neuron and sheath cells, while the overexpression of Numb results in extra neuron and sheath cells at the expense of hair and socket cells. Which cell type(s) does Notch activity specify?

Maxillary palp ORN axons:

All of the following are found in dendrites but not axons except for:

Alternative splicing appears to be responsible for the unique specification of a huge number of possible connections by generating many variants of:

The kinase LKB1 (Par4) was first identified in C. elegans as a factor required for asymmetric cell division/fate in the early embryo: PAR4 mutant cells divide symmetrically, resulting in early lethality. If the role of Par4 is similar in both contexts, what might you expect to observe by staining early C. elegans embryos with an antibody to this protein?

The semaphorins are highly conserved axon guidance ligands with critical roles in nervous system development in both mammals and insects. It was recently reported that Sema1A can also function as a transmembrane receptor in reverse signaling to mediate photoreceptor axon-axon attraction in the developing Drosophila visual system. What kind of experimental result would be used to support a role in reverse signaling in the visual system?

What phenotype should result from the overexpression of Sema1A in a fly projection neuron? Briefly explain your reasoning.

Which of the following would not increase the number of motor neurons or sympathetic neurons surviving in a chick explant?

What might you expect to observe if multiple neurons were experimentally manipulated to express exactly the same combination of Dscam exons? Briefly explain your reasoning.

If a mutation were to occur to disrupt the localization of ankyrinG, such that this protein became distributed throughout the Purkinje cell body and axon, what phenotype would you expect? Briefly explain your reasoning, assuming that the mutation does not disrupt interactions between ankyrinG and neurofascin.

Axon pruning in Drosophila mushroom body neurons appears to share molecular mechanisms with:

What effects would you expect to see on the sizes of various areas of the telencephalon-primary visual cortex, primary somatosensory cortex, and frontal/motor cortex-if Wnt signaling were inhibited during anteroposterior patterning of the neural tube?

Which spatial map in the brain is a discrete rather than a continuous map?

The expression of neuroligins or neurexins in cultured nonneuronal cells demonstrates that these molecules are sufficient to induce presynaptic specializations in mouse hippocampal neurons in vitro. Rare mutations in neuroglian and neurexin genes have been associated with familial autism spectrum disorders. However, even mice lacking all three neuroligin genes still have the normal number of synapses. Propose some possible explanations to reconcile these findings and suggest some experiments that could be performed to distinguish between them.