Summary: Male and female mice carrying a human DAT mutation show distinct, region-specific effects on dopamine synapses. These differences reshape attention, reward, motivation, and other behaviors in a sex-dependent manner.
Source: FAU
Many neuropsychiatric disorders differ markedly between men and women in prevalence, age of onset, and clinical presentation. Disorders with a strong male bias include Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD), where diagnoses occur roughly four times more often in males than in females.
Whether these disparities arise from sex chromosome effects, hormone-driven development, or differences in how biological mechanisms and environmental factors shape behavior, remains an active area of research. What is clear is that altered behavior in these conditions reflects changes in key brain circuits formed during development and modulated throughout life by neurotransmitters.
Dopamine is a central neurotransmitter for many functions affected in ADHD and ASD: motor control, motivation, reward and social interaction, attention, and higher cognitive processes. Although dopamine pathways have long been studied—and are targets of common ADHD medications—the intrinsic sex-dependent differences in these circuits that could guide more precise diagnosis and treatment are only now coming into focus.
Researchers at Florida Atlantic University, in collaboration with the University of North Dakota School of Medicine and Health Sciences, have identified important sex differences in how the brain clears dopamine at synapses. Their study, published in Molecular Psychiatry and led by Randy Blakely, Ph.D., and first author Adele Stewart, Ph.D., reveals that male and female brains use distinct mechanisms to regulate dopamine transporters (DAT), producing different physiological and behavioral outcomes.
Earlier work by Blakely’s group uncovered a human DAT variant that behaves abnormally: instead of removing dopamine from the synapse, the altered transporter can run in reverse and release dopamine. When this variant was engineered into mice, male mutants displayed changes in locomotion, habit formation, and impulsivity that matched the transporter’s anomalous activity. Those initial experiments, however, involved only male animals.
In the new study the researchers examined females and discovered that the mutation does not affect the same brain regions and behaviors as in males. Instead, females exhibit mutation effects in regions that remain unchanged in males, and the reverse is also true. This divergence traces to a circuit-specific, sex-dependent switch in how a regulatory protein linked to D2-type dopamine autoreceptors (D2ARs) controls DAT behavior, amplifying the transporter’s reverse activity in different striatal regions depending on sex.
These circuit- and sex-specific differences produce distinct behavioral profiles. Female mutant mice showed increased anxiety-like behavior and impaired novelty recognition compared with wildtype females. Male mutant mice displayed reduced social interaction and greater perseverative behavior—traits not observed in female mutants. The results indicate that females are not simply protected from the mutation; they express a different set of behavioral consequences driven by an inherent sex-biased organization of dopamine circuits.
The DAT variant studied has been identified in males diagnosed with ADHD and ASD, and a clinical report also linked the same variant to bipolar disorder in a female patient—an observation consistent with the role dopamine signaling may play in mood regulation. The team has also documented impulsivity traits in a female carrier of the mutation, suggesting some behavioral overlap between sexes or differences in the specific forms of impulsivity exhibited.
A common explanation for sex differences in psychiatric diagnoses invokes a “resilience” model, where one sex is thought to mask or resist pathology. Recent evidence, including the present findings, suggests an alternative: sex-biased symptom expression and comorbidities can obscure accurate diagnosis because current clinical instruments may not capture the same disorder in both sexes.
The researchers emphasize that rodent models are not identical to humans, but they offer a valuable window into biological mechanisms that contribute to sex differences in neuropsychiatric risk. Their data show that the same molecular lesion can produce divergent physiological and behavioral outcomes depending on sex-specific circuit architecture. This has direct implications for diagnosis and treatment: therapies that work in one sex may be less effective—or even inappropriate—in the other if they fail to account for sex-dependent neuronal signaling.
Beyond this specific DAT variant, the study underscores a broader principle: genetic or molecular changes can have sex-dependent effects depending on whether co-regulatory genes are expressed in the same cells. Investigators studying other dopamine-linked disorders should consider whether similar sex- and circuit-dependent mechanisms could shape disease features and normal behavior alike.
Study co-authors from FAU’s Department of Biomedical Science include Felix P. Mayer, Ph.D.; Raajaram Gowrishankar, Ph.D.; Gwynne L. Davis, Ph.D.; Lorena B. Areal, Ph.D.; Paul J. Gresch, Ph.D.; Rania M. Katamish; Samantha E. Stilley; Keeley Spiess; Maximilian J. Rabil; and Maureen K. Hahn, Ph.D. Also contributing were Rodeania Peart and Faakhira A. Diljohn from FAU’s Harriet L. Wilkes Honors College and Roxanne A. Vaughan, Ph.D., from the University of North Dakota School of Medicine and Health Sciences.
Funding: The work was supported by the Postdoctoral Training Program in Functional Neurogenomics (MH065215), a NARSAD Young Investigator Grant from the BBRF awarded to Stewart, a Max Kade fellowship to Mayer, an NIH predoctoral fellowship (MH107132) to Davis, NIH grants (2P20GM104360 and MH086530) awarded to Vaughan and Blakely respectively, and institutional undergraduate research support for Peart and Wiggins.
About this genetics, ASD, and ADHD research news
Author: Gisele Galoustian
Source: FAU
Contact: Gisele Galoustian – FAU
Image: The image is in the public domain
Original Research: Closed access. “Behaviorally penetrant, anomalous dopamine efflux exposes sex and circuit dependent regulation of dopamine transporters” by Randy Blakely et al. Molecular Psychiatry
Abstract
Behaviorally penetrant, anomalous dopamine efflux exposes sex and circuit dependent regulation of dopamine transporters
Most neuropsychiatric disorders show sex differences in prevalence, onset, or symptoms. Although altered dopamine signaling is common across many of these conditions, sex-dependent mechanisms that selectively respond to dopamine and shape sex-specific behaviors have not been fully defined.
Previously, the team showed that anomalous dopamine efflux (ADE) is a defining property of the DAT Val559 variant identified in male-biased disorders such as ADHD and ASD. In vivo, Val559-driven ADE activates nigrostriatal D2-type autoreceptors (D2ARs), which in turn enhance inappropriate nonvesicular dopamine release by increasing phosphorylation and surface trafficking of ADE-prone DAT proteins.
The current work demonstrates that DAT Val559 mice display sex-dependent changes in responses to psychostimulants, social interactions, and cognition. Mechanistically, ADE-driven D2AR regulation of DAT is both sex- and circuit-specific: dorsal striatum D2AR/DAT coupling is seen only in males, whereas ventral striatum D2AR/DAT coupling is exclusive to females. Systemic administration of the D2R antagonist sulpiride, which blocks ADE-driven DAT trafficking, normalizes the sex-specific behavioral changes without affecting the opposite sex or wildtype animals.
These results highlight the capacity of D2ARs to regulate DAT in a sex- and circuit-dependent manner as a key determinant of sex-biased effects arising from disrupted dopamine signaling. The study provides a clear example of how a shared biological insult can lead to alternative physiological and behavioral outcomes rather than uniform resilience.