TY - JOUR T1 - A Modified Acetylcholine Receptor δ-Subunit Enables a Null Mutant to Survive Beyond Sexual Maturation JF - The Journal of Neuroscience JO - J. Neurosci. SP - 13223 LP - 13231 DO - 10.1523/JNEUROSCI.2814-08.2008 VL - 28 IS - 49 AU - Kimberly E. Epley AU - Jason M. Urban AU - Takanori Ikenaga AU - Fumihito Ono Y1 - 2008/12/03 UR - http://www.jneurosci.org/content/28/49/13223.abstract N2 - The contraction of skeletal muscle is dependent on synaptic transmission through acetylcholine receptors (AChRs) at the neuromuscular junction (NMJ). The lack of an AChR subunit causes a fetal akinesia in humans, leading to death in the first trimester and characteristic features of Fetal Akinesia Deformation Sequences (FADS). A corresponding null mutation of the δ-subunit in zebrafish (sofa potato; sop) leads to the death of embryos around 5 d postfertilization (dpf). In sop−/− mutants, we expressed modified δ-subunits, with one (δ1YFP) or two yellow fluorescent protein (δ2YFP) molecules fused at the intracellular loop, under the control of an α-actin promoter. AChRs containing these fusion proteins are fluorescent, assemble on the plasma membrane, make clusters under motor neuron endings, and generate synaptic current. We screened for germ-line transmission of the transgene and established a line of sop−/− fish stably expressing the δ2YFP. These δ2YFP/sop−/− embryos can mount escape behavior close to that of their wild-type siblings. Synaptic currents in these embryos had a smaller amplitude, slower rise time, and slower decay when compared with wild-type fish. Remarkably, these embryos grow to adulthood and display complex behaviors such as feeding and breeding. To the best of our knowledge, this is the first case of a mutant animal corresponding to first trimester lethality in human that has been rescued by a transgene and survived to adulthood. In the rescued fish, a foreign promoter drove the transgene expression and the NMJ had altered synaptic strength. The survival of the transgenic animal delineates requirements for gene therapies of NMJ. ER -