A rat model of a focal mosaic expression of PCDH19 replicates human brain developmental abnormalities and behaviours.

Protocadherin 19 gene-related epilepsy or protocadherin 19 clustering epilepsy is an infantile-onset epilepsy syndrome characterized by psychiatric (including autism-related), sensory, and cognitive impairment of varying degrees. Protocadherin 19 clustering epilepsy is caused by X-linked protocadherin 19 protein loss of function. Due to random X-chromosome inactivation, protocadherin 19 clustering epilepsy-affected females present a mosaic population of healthy and protocadherin 19-mutant cells. Unfortunately, to date, no current mouse model can fully recapitulate both the brain histological and behavioural deficits present in people with protocadherin 19 clustering epilepsy. Thus, the search for a proper understanding of the disease and possible future treatment is hampered. By inducing a focal mosaicism of protocadherin 19 expression using in utero electroporation in rats, we found here that protocadherin 19 signalling in specific brain areas is implicated in neuronal migration, heat-induced epileptic seizures, core/comorbid behaviours related to autism and cognitive function.

Anders Retzius and his gyri.

Anders Retzius (1796-1860), a renowned Swedish scientist, left important contributions to human and animal anatomy. He was the first to discover, in 1856, two small bulges as part of the medial segment of the hippocampal tail. These convolutions were named "gyri Andreae Retzii" by his son, Gustaf Retzius (1842-1919), in honor of their discoverer, his father. The gyri of Anders Retzius consist of a CA1 subfield and the subiculum. These areas feature marked connections with the entorhinal cortex and other hippocampal subfields. Only assumptions can be made at present regarding the physiological role of the gyri of Anders Retzius, in conjunction with the involvement of the CA1 hippocampal field in neuropathological conditions.