Altered mechanoreceptor response in Drosophila bang-sensitive mutants

Abstract

Bang-sensitive mutants of Drosophila melanogaster (bas1, bssMW1, eas2, tko25t) display seizure followed by paralysis when subjected to mechanical shock. However, no physiological or biochemical defect has been found to be common to all of these mutants. In order to observe the effects of bang-sensitive mutations upon an identified neuron, and to study the nature of mechanically induced paralysis, we examined the response of a mechanosensory neuron in these mutants. In each single mutant and the double mutant bas1 bssMW1, the frequency of action potentials in response to a bristle displacement was reduced. This is the first demonstration of a physiological defect common to several of the bang-sensitive mutations. Adaptation of spike frequency, cumulative adaptation to repeated stimulation (fatigue) and the time course of recovery from adaptation were also examined. Recovery from adaptation to a conditioning stimulus was examined in two mutants (bas1 and bssMW1), and initial recovery from adaptation was greater in both mutants. Quantification of receptor potentials was complicated by variability inherent in extracellular recording conditions, but examination of the waveform and range of amplitudes did not indicate clear mutant defects. Therefore the differences observed in the spike response may be due to an alteration of the transfer from receptor potentials to action potential production. DNA sequence analysis of tko and eas has indicated that they encode apparently unrelated biochemical products. Our results suggest that these biochemical lesions lead to a common physiological defect in mechanoreceptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuropathology in Drosophila Mutants With Increased Seizure Susceptibility

“…Both double-mutant strains exhibited extreme bang-sensitive paralysis, severely reduced viability, and early neurodegeneration. This is consistent with summation of bang sensitivity previously reported for bas and bss mutations (Engel and Wu 1994;Lee and Wu 2002) and suggests that bang-sensitive mutations may ultimately impinge on the same processes mediating neuronal excitability and viability.…”

Mechanical and Temperature Stressor–Induced Seizure-and-Paralysis Behaviors inDrosophilaBang-Sensitive Mutants

“…In addition, a synaptic defect has been found in the bss mutation, with altered long-term facilitation at the larval neuromuscular junction (Jan & Jan, 1978), associated with multiple firing in the motor neuron (Ganetzky & Wu, 1982). Moreover, the bas , bss , eas , and tko mutations have been demonstrated to alter spike coding in mechanosensory cells (Engel & Wu, 1994). Significantly, the bang-sensitive behavior in the above mutants is suppressed by the nap ts mutation (Wu et al, 1978; Ganetzky & Wu, 1982), which acts to reduce nerve excitability by a decrease of sodium channel density (Kernan et al, 1991).…”

“…As in mammalian epilepsy, in which a large number of genes and neuronal mechanisms have been associated with seizure disorders (McNamara, 1994; Shoffner et al, 1990; Noebels, 2003; Klassen et al, 2011), several studies on Drosophila bang-sensitive mutants have documented a number of genes encoding proteins of different functional categories, including ion channels (Parker et al, 2011), mitochondrial proteins (Roydon et al, 1987; Fergestad et al, 2006) and lipid metabolism (Pavlidis & Tanouye, 1995; Pavlidis et al, 1994). The resultant cellular phenotypes induced in these mutants span from altered synaptic transmission and nerve excitability (Ganetzky & Wu, 1982; Jan & Jan, 1978; Engel & Wu, 1994; Marley & Baines, 2011), to spike frequency coding (Engel, 1995), as well as general seizure-like nerve and muscle spike discharge and neural pathway failure (Pavlidis & Tanouye, 1995; Kuebler & Tanouye, 2000; 2001; Lee & Wu, 2002; 2006). Therefore, the Drosophila bang-sensitive mutants may provide a rich source for mutational and cellular analysis to identify interacting molecular and cellular networks that are responsible for seizure phenotypes.…”

Mechanosensation and Adaptive Motor Control in Insects

“…Recordings from macrochaete bristles on the head of blowflies [24] and the notum of Drosophila [18, 21, 29, 30] have identified only slowly adapting bristles with a very low mechanical threshold of ~1° (Figure 2). These bristles are probably not sensitive to wind or sound [24], but rather respond to transient mechanical deflections such as those created by contact with external objects or during grooming behavior.…”