Olduvai domain expression downregulates mitochondrial pathways: implications for human brain evolution and neoteny

Area of Science:

• Evolutionary biology
• Neuroscience
• Genetics

Background:

• Olduvai (DUF1220) protein domains, encoded by the NBPF gene family, show significant human lineage-specific copy number expansion.
• Higher Olduvai copy number correlates with increased brain size and neuron count in primates and humans, including variations seen in microcephaly and macrocephaly.

Purpose of the Study:

• To elucidate the mechanism by which Olduvai domains influence neural stem cell proliferation and brain development.
• To investigate the functional impact of NBPF1 gene overexpression, which encodes multiple Olduvai domains.

Main Methods:

• Transcriptome (RNAseq) and proteome (mass spectrometry) analyses were performed on cells overexpressing NBPF1.
• Gene Ontology (GO) enrichment analysis was used to identify biological processes and molecular functions affected by NBPF1 overexpression.
• Live-cell imaging was employed to verify changes in mitochondrial appearance.

Main Results:

• Both RNAseq and mass spectrometry indicated a downregulation of mitochondria in NBPF1-overexpressing cells.
• GO analysis revealed significant enrichment for the mitochondrial electron transport chain among downregulated proteins, with NADH dehydrogenase activity identified as a key deregulated function.
• Live-cell imaging confirmed a reduction in apparent mitochondria.

Conclusions:

• Olduvai domains mediate a dosage-dependent reduction in cellular energy through mitochondrial downregulation.
• This energy reduction may lead to a developmental slowdown, expanding the neurogenic window and facilitating increased neuron production and larger brain size.
• The proposed mechanism may also explain neotenic features in other developmental processes.