Bioassaying putative RNA-binding motifs in a protein encoded by a gene that influences courtship and visually mediated behavior in Drosophila: in vitro mutagenesis of nonA.

The no-on-transient-A (nonA) gene of Drosophila melanogaster influences vision, courtship song, and viability. The nonA-encoded polypeptide is inferred to bind single-stranded nucleic acids. Although sequence-analysis of NONA implies that it belongs to a special interspecific family of this protein type, it does contain two classical RNA recognition motifs (RRM). Their behavioral significance was assayed by generating transgenic strains that were singly or multiply mutated within the relatively N-terminal motif (RRM1) or within RRM2. Neither class of mutation affected NONA binding to polytene chromosomes. The former mutations led to extremely low viability, accompanied by diminished adult longevities that were much worse than for a nonA-null mutant, implying that faulty interpolypeptide interactions might accompany the effects of the amino-acid substitutions within RRM1. All in vitro-mutated types caused optomotor blindness and an absence of transient spikes in the electroretinogram. Courtship analysis discriminated between the effects of the mutations: the RRM2-mutated type generated song pulses and trains that tended to be mildly mutant. These phenotypic abnormalities reinforce the notion that nonA's ubiquitous expression has its most important consequences in the optic lobes, the thoracic ganglia, or both, depending in part on the nonA allele.

Defects in courtship and vision caused by amino acid substitutions in a putative RNA-binding protein encoded by the no-on-transient A (nonA) gene of Drosophila.

The Drosophila no-on-transient A (nonA) gene is involved in the visual behaviors and courtship song of the fly. The NONA polypeptide contains two copies of the RNA-recognition motif (RRM), a hallmark of proteins involved in RNA binding, and an adjacent conserved charged region. This 311-amino-acid region is found in four other proteins and largely overlaps the Drosophila-Behavior/Human Splicing (or DBHS) domain. The newest family member, Drosophila nAhomo, was discovered in a database search, and encodes a protein with 80% identity to NONA. In this study, three nonA mutations generated by chemical mutagenesis were sequenced and found to fall within the conserved region. Site-directed mutagenesis of the two RRMs, and within a (conserved) charged region located C-terminal to them, was performed to determine the significance of these domains with respect to whole-organismal phenotypes. Behavior and viability were assessed in transformed flies, the genetic background of which lacks the nonA locus. Point mutations of amino acid 548 in the charged region confirmed the etiology of the nonAdiss courtship-song mutation and showed that a milder substitution at this site produced intermediate singing behavior, although it failed to rescue visual defects. Mutagenesis of the RRM1 domain resulted in effects on viability, vision, and courtship song. However, amino acid substitutions in RNP-II of RRM2 led to near-normal phenotypes, and the in vivo nonA mutations located in or near RRM2 caused visual defects only. Thus, we suggest that the first RRM could be important for all functions influenced by nonA, whereas the second RRM may be required primarily for normal vision.

Effect of response practice variables on learning spelling and sight vocabulary.

Four experiments were conducted to examine variables associated with response practice as an instructional technique for individuals with intellectual disabilities. In Experiment 1, the effect of the cover component in the "cover write" method was evaluated, as were the comparative effects of written versus oral practice of spelling words by rehabilitation clients. The results showed that the cover procedure generally did not enhance performance over and above that produced by practice alone, and written practice generally was not superior to oral practice. Experiment 2 demonstrated that less response practice (i.e., five times) was as effective as more practice (i.e., 10 and 15 times) for teaching spelling to adolescents with developmental disabilities. Experiments 3 and 4 also showed that even less response practice (i.e., one time) was as effective as more practice (five times), and irrelevant practice following errors was as effective as relevant practice for teaching spelling and sight vocabulary to adolescents with behavior disorders and developmental disabilities, respectively. The findings suggest that a parsimonious procedure of limited response practice and positive reinforcement may be effective for the tasks and populations studied.