A Role for Dystonia-Associated Genes in Spinal GABAergic Interneuron Circuitry.

Spinal interneurons are critical modulators of motor circuit function. In the dorsal spinal cord, a set of interneurons called GABApre presynaptically inhibits proprioceptive sensory afferent terminals, thus negatively regulating sensory-motor signaling. Although deficits in presynaptic inhibition have been inferred in human motor diseases, including dystonia, it remains unclear whether GABApre circuit components are altered in these conditions. Here, we use developmental timing to show that GABApre neurons are a late Ptf1a-expressing subclass and localize to the intermediate spinal cord. Using a microarray screen to identify genes expressed in this intermediate population, we find the kelch-like family member Klhl14, implicated in dystonia through its direct binding with torsion-dystonia-related protein Tor1a. Furthermore, in Tor1a mutant mice in which Klhl14 and Tor1a binding is disrupted, formation of GABApre sensory afferent synapses is impaired. Our findings suggest a potential contribution of GABApre neurons to the deficits in presynaptic inhibition observed in dystonia.

The disruption of Celf6, a gene identified by translational profiling of serotonergic neurons, results in autism-related behaviors.

The immense molecular diversity of neurons challenges our ability to understand the genetic and cellular etiology of neuropsychiatric disorders. Leveraging knowledge from neurobiology may help parse the genetic complexity: identifying genes important for a circuit that mediates a particular symptom of a disease may help identify polymorphisms that contribute to risk for the disease as a whole. The serotonergic system has long been suspected in disorders that have symptoms of repetitive behaviors and resistance to change, including autism. We generated a bacTRAP mouse line to permit translational profiling of serotonergic neurons. From this, we identified several thousand serotonergic-cell expressed transcripts, of which 174 were highly enriched, including all known markers of these cells. Analysis of common variants near the corresponding genes in the AGRE collection implicated the RNA binding protein CELF6 in autism risk. Screening for rare variants in CELF6 identified an inherited premature stop codon in one of the probands. Subsequent disruption of Celf6 in mice resulted in animals exhibiting resistance to change and decreased ultrasonic vocalization as well as abnormal levels of serotonin in the brain. This work provides a reproducible and accurate method to profile serotonergic neurons under a variety of conditions and suggests a novel paradigm for gaining information on the etiology of psychiatric disorders.

Mouse transgenesis in a single locus with independent regulation for multiple fluorophores.

A major barrier to complex experimental design in mouse genetics is the allele problem: combining three or more alleles is time-consuming and inefficient. Here, we solve this problem for transgenic animals with a simple modification of existing BAC transgenesis protocols, and generate triple-colored 'prism' mice in which the major cell types of the brain: neurons, astrocytes, and oligodendrocytes, are each labeled with a distinct fluorophore. All three fluorophores are expressed from the same locus, yet each fluorophore is expressed in an independent temporal and spatial pattern. All three transgenes are generally co-inherited across multiple generations with stable genomic copy number and expression patterns. This generic solution should permit more sophisticated experimental manipulations to assess functional interactions amongst populations of cell types in vivo in a more rapid and efficient manner.