Human gene duplications

Duplicated genes expanded in the human lineage likely contributed to brain evolution, yet challenges exist in their discovery due to sequence-assembly errors. We used a complete telomere-to-telomere genome sequence to identify 213 human-specific gene families. From these, 362 paralogs were found in all modern human genomes tested and brain transcriptomes, making them top candidates contributing to human-universal brain features. Choosing a subset of paralogs, we used long-read DNA sequencing of hundreds of modern humans to reveal previously hidden signatures of selection. To understand their roles in brain development, we generated zebrafish CRISPR “knockout” models of nine orthologs and introduced mRNA-encoding paralogs, effectively “humanizing” larvae. Our findings implicate two new genes in possibly contributing to hallmark features of the human brain: GPR89B in dosage-mediated brain expansion and FRMPD2B in altered synapse signaling. Our holistic approach provides new insights and a comprehensive resource for studying gene expansion drivers of human brain evolution.