The human gene VPS4A (Vacuolar Protein Sorting 4 Homolog A) has been identified as involved in reward anticipation and reward processing. Dysfunctional reward processing is implicated in various mental and behavioral disorders, including attention deficit hyperactivity disorder (ADHD) and addictions. VPS4A is associated with the endosomal compartments and is involved in intracellular protein trafficking. It is a member of the AAA ATPase family; in human, there is a closely related paralogous gene, VPS4B. There is a single orthologous gene in Drosophila, Dmel\Vps4, for which loss-of-function alleles, UAS constructs, and RNAi targeting constructs have been generated.
The human VPS4A gene has not been introduced into flies.
Pan-neuronal overexpression of Dmel\Vps4 results in flies with a hypoactive phenotype; flies with pan-neuronal Vps4 knockdown of ~20%, effected by RNAi, show significant hyperactivity. Higher levels of pan-neuronal RNAi-effected knockdown result in larval or pupal lethality. Genetic interactions and a large number of physical interactions have been described for Dmel\Vps4; see below and in the Vps4 gene report.
[updated Nov. 2017 by FlyBase; FBrf0222196]
Attention-deficit/hyperactivity disorder (ADHD) is a chronic condition that includes a combination of persistent problems, such as difficulty sustaining attention, hyperactivity and impulsive behavior; the condition often continues into adulthood (https://www.mayoclinic.org/diseases-conditions/adhd/symptoms-causes/syc-20350889).
Meta-regression analyses have estimated the worldwide ADHD/HKD prevalence at between 5.3% and 7.1% in children and adolescents, and at 3.4% (range 1.2-7.3%) in adults (http://adhd-institute.com/burden-of-adhd/epidemiology/).
ADHD is the most common childhood-onset behavioral disorder, affecting approximately 5 to 10% of children and adolescents (Wolraich et al., 1996; pubmed: 8714320). In this condition, persistent inattention and/or hyperactive-impulsive behavior results in impaired social and/or academic functioning. Boys are affected about 8 times more frequently than girls (Zametkin et al., 1990; pubmed:2233902). [from MIM:143465; 2017.11.21]
Many to one (2 human to 1 Drosophila); the human genes are VPS4A and VPS4B.
High-scoring ortholog of human VPS4A and VPS4B (1 Drosophila to 2 human); Dmel\Vps4 shares 75-76% identity and 86% similarity with the human genes.