Modeling Williams syndrome with induced pluripotent stem cells

Area of Science:

• Neuroscience
• Genetics
• Stem Cell Biology

Background:

• Williams syndrome (WS) is a rare genetic neurodevelopmental disorder caused by deletions on chromosome 7.
• WS is characterized by unique cognitive and social profiles, but the neural effects of gene haploinsufficiency are poorly understood.
• A human cellular model is needed to study WS at the neural level.

Purpose of the Study:

• To investigate the molecular and cellular phenotypes of Williams syndrome in human neural cells.
• To establish and characterize induced pluripotent stem cell (iPSC)-derived neural progenitor cells (NPCs) and neurons from WS patients.
• To explore potential therapeutic targets for WS by examining gene complementation effects.

Main Methods:

• Generated iPSCs from Williams syndrome patients.
• Differentiated WS iPSCs into neural progenitor cells (NPCs) and neurons.
• Assessed NPC apoptosis, doubling time, and neuronal morphology (dendrites, dendritic spines).
• Measured neuronal activity, including calcium transient frequency and synchronized activity.
• Complemented WS NPCs with the FZD9 gene to assess rescue effects.

Main Results:

• WS iPSC-derived NPCs exhibited increased apoptosis and longer doubling times.
• Complementation with FZD9 partially rescued the NPC phenotype.
• WS iPSC-derived neurons displayed altered morphology, with longer dendrites and increased dendritic spine density.
• WS neurons showed increased calcium transient frequency and synchronized activity, linked to enhanced synaptic connections.
• These findings provide a cellular basis for WS neurodevelopmental and behavioral characteristics.

Conclusions:

• Williams syndrome patient-derived iPSCs and their neural derivatives reveal significant cellular and molecular alterations.
• Increased apoptosis and altered neuronal morphology/activity in WS cells provide insights into the disorder's pathophysiology.
• This study establishes a valuable human cellular model for WS research and drug discovery.
• Findings can be validated using in vivo models like MRI and postmortem brain tissue analysis.