Primary sensory neuron dysfunction underlying mechanical itch hypersensitivity in a Shank3 mouse model of autism.

Scientists studied itch sensitivity in mice that model autism. These mice scratched more when their skin was touched and were extra sensitive to itchy sensations. The researchers found problems with certain nerve fibers that detect touch, and identified changes in a protein called TAFA4. When they blocked specific nerve pathways, the extra itchiness went away. This suggests that touch and itch problems in autism might be connected to how the nervous system processes sensory information.

This preclinical study investigated mechanical itch sensitivity in Shank3 mice, a model of autism spectrum disorder. Researchers found that these mice showed heightened scratching responses to skin deformation and hypersensitivity to mechanical itch (alloknesis). Electrophysiological experiments revealed that C-fiber low-threshold mechanoreceptors were hyporesponsive, and genetic analysis showed downregulation of TAFA4 protein. Pharmacological inhibition of Aβ-LTMR eliminated itch hypersensitivity, while TAFA4 injections reduced spontaneous scratching but didn't restore normal itch sensitivity.

The findings suggest somatosensory deficits contribute to itch hypersensitivity in this autism model, with evidence for two distinct pathways regulating mechanical itch - one TAFA4-dependent and one independent.

Findings suggest sensory processing differences in autism may have identifiable neurobiological bases involving specific nerve pathways and proteins. This could inform development of targeted interventions for sensory-related challenges, particularly itch hypersensitivity and related skin behaviors in autistic individuals.

Animal model findings may not directly translate to humans. Sample size not reported. Study focuses on single autism model (Shank3) which may not represent all autism presentations. Mechanisms identified are preliminary and require validation in human studies.

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder marked by social deficits, repetitive behaviors and atypical sensory perception. The link between ASD and skin abnormalities, inducing itchiness, has never been investigated in depth. This study explores mechanical itch sensitivity in the Shank3mouse model. Key observations include heightened scratching in response to skin deformation and hypersensitivity to mechanical itch (i.e. alloknesis) in Shank3mice.

In Shank3mice, ex vivo electrophysiological experiments revealed that C-fiber low-threshold mechanoreceptors (C-LTMRs) were hyporesponsive and transcriptomic analysis showed a downregulation of TAFA4, a protein secreted by C-LMTRs. Interestingly, pharmacologically inhibiting Aβ-LTMR, important in mechanical itch initiation, abolished the itch hypersensitivity. Also, TAFA4 injections reduced the spontaneous scratching response to skin deformation but failed to restore itch sensitivity. Our data suggest that somatosensory deficits in Shank3mice lead to a hypersensitivity to itchiness and indicate that two pathways might be regulating mechanical itchiness, dependent or not on TAFA4.