Mitochondrial Implications Associated with 3q29 Schizophrenia Risk Copy Number Variant

Abstract

The 3q29 chromosomal region appear to have a significant role in normal neuronal development. The heterozygous deletion as well as the one copy duplication are linked to psychiatric conditions and neurodevelopmental disorders, respectively. Through genome wide studies, the 3q29 deletion has been identified as one of the greatest risk factors for Schizophrenia. The disorder is influenced by numerous genetic risk variants with unknown consequential mechanisms even after decades under scrutiny. Dysregulated mitochondria is hypothesized to play an upstream role in the pathogenesis, as this organelle generates the majority of cellular energy including that of synaptic formation and function. How 3q29 dosage alterations could implicate mitochondria is yet to be uncovered, hence the aim of this study. Isogenic embryonic stem cell lines engineered using CRISPR technology were genotyped for 3q29 copy number. Seventy five clones were screened, resulting in three possible duplication clones and eleven deletion clones. Genotyped cell lines were expanded and characterized via staining of transcription factors indicating their pluripotency and undifferentiated state. Clones could thereafter be lysed in order to quantify protein subunits of electron transport chain complexes once the protocol was established. Several iterations of adjusting the Western blot methodology eventually resulted in detection of all subunits. Two batches of previously induced neurons were also investigated to bridge different time points during development. Preliminary results indicate that edited stem cells have a lower expression of mitochondrial protein complexes, with complex V appearing the most stable. The stability of complex V and the lower expression of protein SDHA in 3q29del cells are consistent with previous literature in mice. Neuronal protein complexes show an overall high variability except for the COX4 protein being more expressed in duplication clones. To conclude, the identified stem cell lines together with the established Western blot protocol allow for further investigation targeting protein quantification of the transport chain complex subunits. The identified expression trends also motivate continuation of these experiments.