Profiling parvalbumin interneurons using iPSC: challenges and perspectives for Autism Spectrum Disorder (ASD).

Autism spectrum disorders (ASD) are persistent conditions resulting from disrupted/altered neurodevelopment. ASD multifactorial etiology-and its numerous comorbid conditions-heightens the difficulty in identifying its underlying causes, thus obstructing the development of effective therapies. Increasing evidence from both animal and human studies suggests an altered functioning of the parvalbumin (PV)-expressing inhibitory interneurons as a common and possibly unifying pathway for some forms of ASD. PV-expressing interneurons (short: PVALB neurons) are critically implicated in the regulation of cortical networks' activity. Their particular connectivity patterns, i.e., their preferential targeting of perisomatic regions and axon initial segments of pyramidal cells, as well as their reciprocal connections, enable PVALB neurons to exert a fine-tuned control of, e.g., spike timing, resulting in the generation and modulation of rhythms in the gamma range, which are important for sensory perception and attention.New methodologies such as induced pluripotent stem cells (iPSC) and genome-editing techniques (CRISPR/Cas9) have proven to be valuable tools to get mechanistic insight in neurodevelopmental and/or neurodegenerative and neuropsychiatric diseases. Such technological advances have enabled the generation of PVALB neurons from iPSC. Tagging of these neurons would allow following their fate during the development, from precursor cells to differentiated (and functional) PVALB neurons. Also, it would enable a better understanding of PVALB neuron function, using either iPSC from healthy donors or ASD patients with known mutations in ASD risk genes. In this concept paper, the strategies hopefully leading to a better understanding of PVALB neuron function(s) are briefly discussed. We envision that such an iPSC-based approach combined with emerging (genetic) technologies may offer the opportunity to investigate in detail the role of PVALB neurons and PV during "neurodevelopment ex vivo."