Restoration of FMRP expression in adult V1 neurons rescues visual deficits in a mouse model of fragile X syndrome

Many people affected by fragile X syndrome (FXS) and autism spectrum disorders have sensory processing deficits, such as hypersensitivity to auditory, tactile, and visual stimuli. Like FXS in humans, loss of Fmr1 in rodents also cause sensory, behavioral, and cognitive deficits. However, the neural mechanisms underlying sensory impairment, especially vision impairment, remain unclear. It remains elusive whether the visual processing deficits originate from corrupted inputs, impaired perception in the primary sensory cortex, or altered integration in the higher cortex, and there is no effective treatment. In this study, we used a genetic knockout mouse model (Fmr1KO), in vivo imaging, and behavioral measurements to show that the loss of Fmr1 impaired signal processing in the primary visual cortex (V1). Specifically, Fmr1KO mice showed enhanced responses to low-intensity stimuli but normal responses to high-intensity stimuli. This abnormality was accompanied by enhancements in local network connectivity in V1 microcircuits and increased dendritic complexity of V1 neurons. These effects were ameliorated by the acute application of GABAA receptor activators, which enhanced the activity of inhibitory neurons, or by reintroducing Fmr1 gene expression in knockout V1 neurons in both juvenile and young-adult mice. Overall, V1 plays an important role in the visual abnormalities of Fmr1KO mice and it could be possible to rescue the sensory disturbances in developed FXS and autism patients.

Experiencias técnicas en el uso de la prueba inmunohistoquímica para el diagnóstico del síndrome de frágil X / Technical experiences in the use of the immunohistochemical test for diagnosing Fragile X syndrome

Se evaluó un método inmunohistoquímico diseñado por Willemsen y otros en 1995, para detectar la presencia o ausencia de la proteína FMRP, involucrada en el síndrome de frágil X. Este proceder se fundamenta en una secuencia de reacciones antígeno-anticuerpo, que garantiza la inmunodetección de la proteína, que resulta fácil de realizar con un costo menor a las demás técnicas descritas para el diagnóstico de la afección. No obstante, se hizo una exhaustiva valoración de los posibles errores técnicos, partiendo de la experiencia acumulada durante el pesquisaje inmunohistoquímico que se aplicó a 6 615 recién nacidos y a 658 individuos varones con retraso mental de etiología no precisada. Se expusieron algunas fotos para ilustrar los errores más frecuentes